GroupDIY

Project Specific Discussions => Dynamic Processors => Topic started by: [silent:arts] on March 23, 2009, 05:15:12 AM

Title: D-LA2A Support Thread
Post by: [silent:arts] on March 23, 2009, 05:15:12 AM
since more and more people will build the [silent:arts] D-LA2A version I thought I will start this thread.
please ask your questions here, no PMs please.

the Project started at Franks Forum, and there is already a huge amount of information over there:
http://www.nrgrecording.de/nrg/viewtopic.php?t=405

D-LA2A schematic (http://www.silentarts.de/DIY/D-LA2A/D-LA2A_rev02-Schematic.pdf)
D-LA2A ground scheme (http://www.energyrecording.de/viewtopic.php?t=405&postdays=0&postorder=asc&start=3)
wiring the heaters (http://www.energyrecording.de/viewtopic.php?t=405&postdays=0&postorder=asc&start=52)
wiring the Rondo Müller PSU transformer (http://www.energyrecording.de/viewtopic.php?t=405&postdays=0&postorder=asc&start=45)
tube socket modification for 2RU cases (http://www.energyrecording.de/viewtopic.php?t=405&postdays=0&postorder=asc&start=19)

Rx25 (TBD) & Meter callibration (http://www.groupdiy.com/index.php?topic=23253.msg276178#msg276178) by SSLtech
Limiter Response Calibration (RV137/RV237) (http://www.groupdiy.com/index.php?topic=32677.msg553490#msg553490)
Stereo Balance Adjust (RV103/RV203) (http://www.groupdiy.com/index.php?topic=32677.msg553491#msg553491)
comments about Cx04 & Cx14 (aka Arco caps) (http://www.groupdiy.com/index.php?topic=32677.msg535420#msg535420) by Kingston
some very important things that all should be awared (http://www.groupdiy.com/index.php?topic=32677.msg540317#msg540317) by poctop

compiled informations from this thread in a single PDF (http://www.groupdiy.com/index.php?topic=32677.msg560982#msg560982) by sonicwarrior

BOM (https://www.dropbox.com/s/s0hrp3rxn9klrty/D-LA2A_BOM_QNS.xlsx?dl=0) by Azone with additions by QNote

 videos of a D-LA2A build and calibration (https://groupdiy.com/index.php?topic=32677.msg834024#msg834024) by QNote

FINISHED UNITS:

[silent:arts] (http://www.groupdiy.com/index.php?topic=21961.msg259356#msg259356)
waldorfcave (http://www.nrgrecording.de/nrg/viewtopic.php?t=405&postdays=0&postorder=asc&start=92)
bernbrue (http://www.groupdiy.com/index.php?topic=27522.msg330456#msg330456)
Infernal_Death (http://www.nrgrecording.de/nrg/viewtopic.php?t=405&start=145)
ChuckD (http://www.nrgrecording.de/nrg/viewtopic.php?t=405&start=192)
ChuckD (http://www.nrgrecording.de/nrg/viewtopic.php?t=405&start=200) (Numero deux) :shock:
geoff004 (http://www.groupdiy.com/index.php?topic=31014.msg376345#msg376345)
inputoutput (http://www.groupdiy.com/index.php?topic=32511.msg394870#msg394870)
stitch-o (http://www.groupdiy.com/index.php?topic=32677.msg398092#msg398092)
tskguy (http://www.groupdiy.com/index.php?topic=32677.msg417839#msg417839)
Holger (http://www.groupdiy.com/index.php?topic=32677.msg424504#msg424504)
stereokillah (http://www.groupdiy.com/index.php?topic=32677.msg431812#msg431812)
USIEL (http://www.groupdiy.com/index.php?topic=32677.msg435455#msg435455)
stereokillah (http://www.groupdiy.com/index.php?topic=32677.msg435499#msg435499)  (Numero deux)
Silvas (http://www.groupdiy.com/index.php?topic=36889.msg453338#msg453338)
crisotop (http://www.groupdiy.com/index.php?topic=29854.0) (scroll down thru all those nice builds)
Kingston (http://www.groupdiy.com/index.php?topic=39095.msg482305#msg482305)
alexc (http://www.groupdiy.com/index.php?topic=32677.msg526379#msg526379)
electrisizer (http://www.groupdiy.com/index.php?topic=32677.msg532700#msg532700)
Soeren_DK (http://www.groupdiy.com/index.php?topic=32677.msg533728#msg533728)
horvitz (http://www.groupdiy.com/index.php?topic=32677.msg539592#msg539592)
poctop (http://www.groupdiy.com/index.php?topic=32677.msg540660#msg540660)
drgrateful (http://www.groupdiy.com/index.php?topic=32677.msg542996#msg542996)
baadc0de (http://www.groupdiy.com/index.php?topic=32677.msg549542#msg549542)
Audioman (http://www.groupdiy.com/index.php?topic=32677.msg551849#msg551849)
creal (http://www.groupdiy.com/index.php?topic=32677.msg552125#msg552125)
desol (http://www.groupdiy.com/index.php?topic=32677.msg553207#msg553207)
Borja Lopez (http://www.groupdiy.com/index.php?topic=32677.msg554734#msg554734)
sea_man (http://www.groupdiy.com/index.php?topic=32677.msg562237#msg562237)
briomusic (http://www.groupdiy.com/index.php?topic=32677.msg564623#msg564623)
Cardinen (http://www.groupdiy.com/index.php?topic=32677.msg583430#msg583430)
etiefenthaler (http://www.groupdiy.com/index.php?topic=32677.msg592470#msg592470)
MicDaddy (http://www.groupdiy.com/index.php?topic=32677.msg592723#msg592723)
mrclunk (http://www.groupdiy.com/index.php?topic=32677.msg598065#msg598065)

and many many more 8)
Title: Re: D-LA2A Support Thread
Post by: MartyMart on March 23, 2009, 07:31:13 AM
Great, thanks Volker ... it"s on my list !!

Marty.
Title: Re: D-LA2A Support Thread
Post by: Kingston on March 23, 2009, 07:35:57 AM
a useful looking link from that thread about grid stoppers:

http://www.groupdiy.com/index.php?topic=258781

but it's for the old prodigy pro forum version..

how do I make that link compatible with the one today?
Title: Re: D-LA2A Support Thread
Post by: Audioman on March 23, 2009, 06:38:43 PM
Hi All ,
Anybody have a BOM for the Dual LA-2A for the european customers including where to buy tubes and T4B cells ??
And also the right type of tubes
Thank you all !!
Fabio
Title: Re: D-LA2A Support Thread
Post by: tskguy on March 23, 2009, 06:46:16 PM
I would be interested in a USA bom as well.

Eric
Title: Re: D-LA2A Support Thread
Post by: kazper on March 23, 2009, 06:55:03 PM
What happened to the build thread from S.A. first build?

I just looked for it a couple weeks ago referencing the PCB I have from that buy.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 24, 2009, 04:00:24 AM
What happened to the build thread from S.A. first build?
I just looked for it a couple weeks ago referencing the PCB I have from that buy.
there never was a build thread except the one at Franks place.

Anybody have a BOM for the Dual LA-2A for the european customers including where to buy tubes and T4B cells ??
And also the right type of tubes
here (http://www.nrgrecording.de/nrg/viewtopic.php?t=405) you find some links for the caps I used, and a BOM bernbrue once did.
T4Bs:
http://www.dripelectronics.com/t4b.html
http://www.studioelectronics.biz/sunshop/index.php?l=product_detail&p=1142
Title: Re: D-LA2A Support Thread
Post by: tskguy on March 24, 2009, 02:18:26 PM
Would any la2a bom work for most of this build? I have found some US friendly BOM's for diffrent layouts and was wondering if most of it would be the same?

Eric
Title: Re: D-LA2A Support Thread
Post by: RAM on March 24, 2009, 03:38:38 PM
It'll probably work for the resistors at least. But most of the electrolytic caps may not fit on the board. Plus the PSU is different.

Rob
Title: Re: D-LA2A Support Thread
Post by: tskguy on March 24, 2009, 05:58:13 PM
Thanks,

I actually orderd the PSU from the group buy so Im good to go there. As for caps I can figure that out pretty easily.

Im just being lazy Im sure I can get together a BOM onmy own pretty quickly.

Eric
Title: Re: D-LA2A Support Thread
Post by: tskguy on March 24, 2009, 09:07:59 PM
Hi all,

Will this work for the relays??

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=Z767-ND

Eric
Title: Re: D-LA2A Support Thread
Post by: Silvas on March 24, 2009, 09:28:08 PM
This thread is great news !!!

Now, to the questions :

Will the antek 1T250 work here?

Seems like an economical option...i think the voltages and VA´s are right
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 25, 2009, 06:08:31 AM
Will the antek 1T250 work here?
looks good to me, but you won't have any relay power for the bypass (actually those are "compressor in" relays.

Eric, your relays are fine.
Title: Re: D-LA2A Support Thread
Post by: deuce42 on March 25, 2009, 06:43:32 AM
Great thread idea Silent Arts.

To everyone else, Silent Arts has been so helpful in my experience at the "Franks Place" forum for this project and I am glad the thread can continue here at groupdiy.

Now for my question, since these things put out huge amounts of gain, can I substitute input transformers and use 1:1 ratio transformers rather than the normal 1:4 to lower the amount of gain? Besides substituting the 100k gain pot for a the 25kpot/75k resistor as discussed at Franks Place , could I substitute 1:1 input transformers instead?  I have these Sowters lying around which are 600/600 ohms 1:1  and I would love to make use of them.

Thanks
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 25, 2009, 07:01:27 AM
Now for my question, since these things put out huge amounts of gain, can I substitute input transformers and use 1:1 ratio transformers rather than the normal 1:4 to lower the amount of gain?
yes you can ;)
Title: Re: D-LA2A Support Thread
Post by: tskguy on March 25, 2009, 08:30:17 AM
Thanks,

I was wondering about the input iron also. Im considering using Lundhal transformers and Talked with Kevin the US distribitor and he suggested using 1:1 on the input as well.
Im working on a USA Bom and noticed I cant find the silver Mica caps. Does anybody have a usa source for those?

Eric
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 25, 2009, 09:40:37 AM
Eric, I doesn't have to be Silver Micas
Title: Re: D-LA2A Support Thread
Post by: tskguy on March 25, 2009, 09:54:41 AM
Thats what I figured but I thought that I would try and stay true to your original design.

Eric
Title: Re: D-LA2A Support Thread
Post by: deuce42 on March 25, 2009, 10:14:33 AM
Awesome - thanks! These are special 4757 Sowters made for the BBC. Will givem them a go and then report back:)
Title: Re: D-LA2A Support Thread
Post by: Silvas on March 25, 2009, 11:20:26 AM
Will the antek 1T250 work here?
looks good to me, but you won't have any relay power for the bypass (actually those are "compressor in" relays.

Eric, your relays are fine.

But it is possible to steal some voltage from the heaters secondary to do this right? running the relays at 5v ? or i can use a second toroid (have lots of 10va anteks lying around).

Thanks !
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 25, 2009, 11:43:57 AM
But it is possible to steal some voltage from the heaters secondary to do this right? running the relays at 5v ? or i can use a second toroid (have lots of 10va anteks lying around).
I wouldn't feel comfortable with AC heaters and a rectifier / voltage regulator next to it (but what do I know) ::)
a second transformer would do the job for sure (but you won't need 10VA)
you could wire a switch instead of the realays.
you could skip the "In" (or bypass) and solder bridges at the relays too.
many ways ...
Title: Re: D-LA2A Support Thread
Post by: Kingston on March 25, 2009, 12:34:46 PM
I will probably do DC heaters, and steal 5V from there with a L7805.
Title: Re: D-LA2A Support Thread
Post by: Silvas on March 25, 2009, 01:53:16 PM
Thanks for the replies guys, surely i´ll try many ways to do it and see which is best.
Title: Re: D-LA2A Support Thread
Post by: stitch-o on March 25, 2009, 07:11:43 PM
Its Alive!!  (almost)

Just finished wiring up the transformers (UTC A-10 and A-24) and the XLR I/O.
T4B's from Drip and a tasty assortment of NOS vintage tubes complete the circuits 'flavors'.

I've only done power-up so far but will be doing some troubleshooting and more testing in the next few days. Nothing smoked, everything lights up...phew!
I think I might have wired the gain pots backward as when I switch the VU from G.R. to Level, the needles on both VU's pin all the way...until I turn the gain ALL the way up and then the needles fall all the way down.
Also, I plan on dropping in a couple of LED indicators for the IN/BYPASS as I like to be able to see basically whats going on (or off, as the case may be) from across the room.
BIG ups to Geoff004 for double checking my wiring mess and (of course) Volker aka [Silent:arts] for the boards...there were a couple others who helped early on too but names are escaping me (someone gave me a great relay wiring tip)
Anyways, I thought a few pics might inspire some to get to work, round these parts:::
Cheers!
(http://img102.imageshack.us/img102/9383/dscf1473.jpg)
(http://img102.imageshack.us/img102/5351/dscf1472.jpg)
(http://img102.imageshack.us/img102/751/dscf1471.jpg)
Title: Re: D-LA2A Support Thread
Post by: FerrariT on March 25, 2009, 09:05:50 PM
Is everyone using the custom Xfrmrs [silentarts] had made
or
???

just curious ...
Title: Re: D-LA2A Support Thread
Post by: stitch-o on March 26, 2009, 11:29:30 AM
I re-wired the gain and PR pots: yup, they were wired backwards.
Now everything seems to work on first glance.

The only thing I have noticed now,
when I turn the gain pot up past 65 (2 o'clock) when the meter is on 'level', the meter
jumps up and pins. This happens on both channels and, surprisingly, will happen on both meters
when only one gain pot is cranked and the other gain sits anywhere near 65.
Some sort of feedback maybe but its registering in both channels....hmmmm

Still haven't gotten' it on the bench to pass audio, measure voltage, and calibrate and such but that should happen tonight.

Cheers!
Title: Re: D-LA2A Support Thread
Post by: rob_gould on March 26, 2009, 04:51:54 PM
Hi [silent-arts],

I want to use Elma 24 position rotary switches for gain and peak reduction.  Is it just a simple case of calculating 0 - 100k log values and 0 - 25k log values on a spreadsheet and picking the nearest values like you did for the PM 660?

Thanks,

Rob
Title: Re: D-LA2A Support Thread
Post by: tskguy on March 26, 2009, 05:39:06 PM
Hey all,


What is ds101 and ds201 it says NE2 under the Semicunducter. I cant figure out what it is..
Any help would be great!!
Eric
Title: Re: D-LA2A Support Thread
Post by: RedNoise on March 26, 2009, 06:34:23 PM
Ne2 are Neon lamps , avaible @ conrad IIRC.

.:EDIT:.

http://www1.conrad.de/scripts/wgate/zcop_b2c/~flN0YXRlPTE3MzQwMDEwNDc=?~template=PCAT_AREA_S_BROWSE&glb_user_js=Y&shop=B2C&zhmmh_lfo=&zhmmh_area_kz=&product_show_id=725200&gvlon=&p_init_ipc=X&p_page_to_display=fromoutside&~cookies=1&cookie_n[1]=b2c_insert&cookie_v[1]=62&cookie_d[1]=&cookie_p[1]=%2f&cookie_e[1]=Mon%2c+27-Apr-2009+22%3a36%3a36+GMT&scrwidth=1280
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 26, 2009, 07:16:55 PM
I want to use Elma 24 position rotary switches for gain and peak reduction.  Is it just a simple case of calculating 0 - 100k log values and 0 - 25k log values on a spreadsheet and picking the nearest values like you did for the PM 660?
me too  ;D ;D ;D
on my second one, but no time to build it :-[ :-[ :-[
(will have Haufe 1:1 iron at the input, V74 iron for the output, Drips "Mastering T4Bs") ;D ;D ;D
the PM spreadsheet will work, yes

What is ds101 and ds201 it says NE2 under the Semicunducter. I cant figure out what it is..
yes, what RedNoise said: neon lamps.
it was hard to figure out what to use in europe, since NE2 is an american part number ...

Title: Re: D-LA2A Support Thread
Post by: tskguy on March 26, 2009, 08:22:32 PM
Very cool!! 
Thanks guys,

P.S. I should have a US friendly BOM with Digikey and Mouser part numbers for most all parts very soon.

Eric
Title: Re: D-LA2A Support Thread
Post by: geoff004 on March 27, 2009, 08:15:31 AM
What is ds101 and ds201 it says NE2 under the Semicunducter. I cant figure out what it is..

here's a mouser # for the neon:  36NE002

For the power I think there are a couple options.  I used the transformer from Antek and it was pretty cheap - like $30 shipped.  It'll power the whole thing fine.
There's a ton of information at the nrgrecording site - enough to complete this project.

Congrats Stitch - looks great.
I use mine every time my DAW puts out audio.
Title: Re: D-LA2A Support Thread
Post by: stitch-o on March 27, 2009, 11:40:41 PM
thanks bro! Like I said, I owe you a pint or three  ;D

So, I finally passed audio through this sucker and here's my troubleshooting list:
-Ridiculous amounts of gain. I matched levels with bypass and I had the gain knob not even on 1.
I have some 12AU7's around here so I'll try those first and the 22K log w/75k resistor in series trick second.
-Left channel doesn't compress. Also, I'm not sure the stereo link does anything yet either...probably a connected issue.
-There is some distortion and LF loss somewhere. Very well might be connected to the extensive gain issue.

edit: it just struck me that, quite possibly, the relay on the left channel is not getting any power.
That would explain the problem...I'll check that out first.

Once I sort out these little blips, I'll throw it on my friends bench.

Any tips for calibration?

Cheers!
Title: Re: D-LA2A Support Thread
Post by: creal on March 28, 2009, 09:32:54 AM
Quote
since more and more people will build the [silent:arts] D-LA2A version I thought I will start this thread.
please ask your questions here, no PMs please.

thx for this thread
i will start mine soon
Title: Re: D-LA2A Support Thread
Post by: kazper on March 28, 2009, 12:23:04 PM
Thanks,

I was wondering about the input iron also. Im considering using Lundhal transformers and Talked with Kevin the US distribitor and he suggested using 1:1 on the input as well.
Im working on a USA Bom and noticed I cant find the silver Mica caps. Does anybody have a usa source for those?

Eric

Mouser
Tubedepot (also a good spot for the big 10uf's)
Small bear electronics
Title: Re: D-LA2A Support Thread
Post by: phatmateo on March 28, 2009, 02:23:02 PM
Thanks for the US BOM!  Good to know someone else is out there in Chicago with a diy addiction :)
Title: Re: D-LA2A Support Thread
Post by: tskguy on March 28, 2009, 03:04:40 PM
Your welcome,


We should try and get a bunch of the Chicago guys together some time. Its always fun to meet guys that share the same obsession!
Ive met with Shabtek before he is in chi town as well.

Eric
Title: Re: D-LA2A Support Thread
Post by: tskguy on March 29, 2009, 05:45:50 PM
Hi all,

Im trying to decide what type of transformers to use and to save money I think I may try the edcore transformer for output. Ive looked at there web site and with my limited knowledge cant figure out what one would be best. Anyone have an idea what to use?

Eric
Title: Re: D-LA2A Support Thread
Post by: deuce42 on March 29, 2009, 10:59:40 PM
This may be obvious but my experience is that the input transformers in these comps have profound effects on sound but output transformers don't seem to me to make the same degree of difference. Others here with far more knowledge than me may disagree and that is cool - we all have views on things.

I would maybe look at the Edcor WSM15k/600 for outputs. They're super cheap (approx $10). You can try the XSM15k/600 instead but the extra wattage that the XSM series give over the WSM series may not really be needed for this project.

Input transformers are another story - I am sure each reputable transformer (sowter, cinemag, jensen, actual UTC's etc) will give the DLA2A a completely different flavour.
Title: Re: D-LA2A Support Thread
Post by: RedNoise on March 30, 2009, 09:58:00 AM
Hi ,
Do you think UTC A25 would work fine in the DLA2A???
IIRC they're 15K/600 correct???
thanks.
Title: Re: D-LA2A Support Thread
Post by: stitch-o on March 30, 2009, 10:47:46 AM
Hi ,
Do you think UTC A25 would work fine in the DLA2A???
IIRC they're 15K/600 correct???
thanks.

This is a handy list:::
http://www.groupdiy.com/index.php?topic=6518.0

EDIT:
and this would be handy too:::
http://www.waltzingbear.com/Schematics/UTC.html
Title: Re: D-LA2A Support Thread
Post by: RedNoise on March 30, 2009, 11:32:10 AM
thanks stitch'o!
Title: Re: D-LA2A Support Thread
Post by: tskguy on March 31, 2009, 11:20:40 AM
Hi all,

So I think Ive decided to go with the edcor wsm15k/600 for the output tx. Now Im still trying to decide about the input. Ive read that a 1:1 tx is nice because of the reduced gain sensitivity but Im really having a hard time deciding on the brand. Jenson Sowter or Lundahl. Ive used Lundahl's on all my builds so far and really like the sound but I havent seen many guys use them in this circuit.
Looking for some help!!
Title: Re: D-LA2A Support Thread
Post by: deuce42 on March 31, 2009, 10:28:12 PM
I have stuck Edcor WSM's 600/15k inputs in mine for starters on the basis that once I had the DL2A up and running smoothly I would look towards new input transformers. Am about to replace them with Sowters I just purchased.

Am happy to report back results as soon as I am done.

Title: Re: D-LA2A Support Thread
Post by: diyfanatic on April 01, 2009, 03:51:14 AM
is it ok to use 500v cap for the big 10uf?
I would like to use Sprague instead of Solen Fasten.

and second question:
for starter I will use only one channel cause money running low.
no problem to leave the second channel empty?

cheers!
Jr.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 01, 2009, 04:04:11 AM
is it ok to use 500v cap for the big 10uf?
I would like to use Sprague instead of Solen Fasten.
no problem, but watch the polarization.

for starter I will use only one channel cause money running low.
no problem to leave the second channel empty?
this is no problem either
Title: Re: D-LA2A Support Thread
Post by: diyfanatic on April 01, 2009, 04:41:31 AM
great news!!
Title: Re: D-LA2A Support Thread
Post by: ermetiko on April 01, 2009, 01:31:03 PM
hi....i want to know if i can replace the sowter 4383 and 8940 with the sowter 1009 and 1010 that are the replacements of the original UTC....i have the original t4b optical cell from universal audio....


thanks
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 01, 2009, 01:44:25 PM
Hi thanks  :)

the transformers do not interact with the t4b.
put in whatever you want to try.
(which doesn't mean I tell you to order those specific parts for this PCB)
Title: Re: D-LA2A Support Thread
Post by: ermetiko on April 01, 2009, 02:02:18 PM
i have still some doubts......the 1009 and 1010 have very different ratios and impedance......have i to mod something to put in these transformers....?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 01, 2009, 02:59:03 PM
without being an LA2A guru:
if those are replicas of the original transformers they should work without any modification.
(once upon a time I always though the 4383 and 8940 are the correct replicas, but what do I know)
Title: Re: D-LA2A Support Thread
Post by: Audioman on April 03, 2009, 06:43:36 AM
Hi All,
I'm looking for the right power trafo for the Dual -LA2A anyone have the farnell code or other
Let me know
Thank you All
Fabio
Title: Re: D-LA2A Support Thread
Post by: diyfanatic on April 03, 2009, 07:17:12 AM
Hi Audioman.

the power Tx is a custom one.
Here the specs.
(http://www.twin-x.com/groupdiy/albums/userpics/RKT_f%C3%BCr_Dual_LA2A_no_price.JPG)

http://www.mueller-rondo.com/

cheers.
Jr.
Title: Re: D-LA2A Support Thread
Post by: deuce42 on April 03, 2009, 08:03:27 AM
And whilst we are recommending stuff - anyone know where I could get a 2ru case made for this project?  I know perusha sells DLA2A cases but they are 3RU and my rack case is running out of precious spaces. If not a full case, maybe even just a front panel????

Thanks
Title: Re: D-LA2A Support Thread
Post by: stitch-o on April 03, 2009, 08:13:01 AM
i have still some doubts......the 1009 and 1010 have very different ratios and impedance......have i to mod something to put in these transformers....?

the 1009 (replacement for the A-10, which has a turns of 1:10) has a ratio of 1:9 which is closer to the A-10 than the 4383 which has a ratio of 1:4. The inputs are all 600:50K, so that isn't the problem.
I have encountered this issue as the symptom of massive amounts of gain.
So far may edit list to do is the 25k gain pot mod and using 12AU7s in the first stage instead of 12AX7s.
If anyone has any similar issues or suggestions, I'm all ears....
When I get to this mod, I'll report back.

Cheers!
Title: Re: D-LA2A Support Thread
Post by: diyfanatic on April 03, 2009, 08:16:27 AM
to deuce42

Do It Yourself...

http://www.frontpanelexpress.com/

I will do mine in a 2u format, same issue...space...and I want only one channel fo now!
but the drilling will be made by myself, easy, only 2 pots and 2 switch.
lettering with stickers.

cheers.
Jr.
Title: Re: D-LA2A Support Thread
Post by: RedNoise on April 03, 2009, 12:26:56 PM
Deuce42:
IIRC 2U is tight regardin to the tubes.You'll have to "Dremel" your tubes standoff.
Have a look @ nrg , mentionned thread in the first post.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 03, 2009, 04:13:52 PM
Deuce42:
IIRC 2U is tight regardin to the tubes.You'll have to "Dremel" your tubes standoff.
Have a look @ nrg , mentionned thread in the first post.
it is tight but can be done. we have seen some 2U D-LA2As, not only mine.
but do something for ventilation.
and yes, the 6AQ5 is a higher tube ...
(all others will fit well in a 2U rack)
Title: Re: D-LA2A Support Thread
Post by: Audioman on April 03, 2009, 04:35:00 PM

Hi diyfanatic,
The web site is only in german language !! and unfortunately i'm not speak german language ...
Did you have ordered from that company the toroid and if yes how much it cost build one ??
Let me know
Thank you
Fabio

Hi Audioman.

the power Tx is a custom one.
Here the specs.
(http://www.twin-x.com/groupdiy/albums/userpics/RKT_f%C3%BCr_Dual_LA2A_no_price.JPG)

http://www.mueller-rondo.com/

cheers.
Jr.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 03, 2009, 04:41:01 PM
The web site is only in german language !! and unfortunately i'm not speak german language ...
wrong:
Quote
DIY Projects
This section is for registered users to discussspecific projects and troubleshooting.
the thread is in english. navigation might be in german, I don't know how to test this.
(I'm not afflicted to this website in any way)
however, shouldn't be a problem
Title: Re: D-LA2A Support Thread
Post by: diyfanatic on April 03, 2009, 05:38:41 PM
some nice french dudes made a group buy a month ago
you can have all the info about the tx
http://www.groupdiy.com/index.php?topic=32314.0

I have not bought it for now, still working on a 1176 and a D-aoc.

there's an email on the first page, try to shoot in english and ask for the ref of the tx (in the pict)
Title: Re: D-LA2A Support Thread
Post by: stitch-o on April 03, 2009, 08:55:45 PM
the saga continues:::
so the relays are getting power, thats not the reason why the left channel isn't working....
but I think the 6AQ5 on the left channel isn't getting juice.
what are the voltages I should be reading there?

all the tubes are now getting power. Still no compression in the right channel.
The funny thing is I know the signal is in the channel because the gain knob does its job and the bypass works as well.
now Im searching for bad solderpoints...

EDIT pt2: looks like I cooked a trace on the gridstopper 1k resistor on the 12bh7a.
so my question is: where do either end of the gridstoppers for the 12bh7 go?

the 5814a and 12AT7s are reigning the gain in a lot but I'll be ordering 25k pots and 75k resistors on Monday.

cheers!
Title: Re: D-LA2A Support Thread
Post by: stitch-o on April 04, 2009, 07:38:06 AM
so my question is: where do either end of the gridstoppers for the 12bh7 go?


So I traced the paths on the other channel's gridstopper 1k resistor, then jumped the shorted connection on the problem channel and.......
still no compression on the left channel.

When the Peak Reduction pot is turned ALL the way up, there is slight distortion so I know the pot is in the circuit. All tubes are lit up.

Maybe I missed a connection somewhere in the sidechain/control voltage circuit?
Where in the circuit is that located?

Any ideas of where to troubleshoot from here would be greatly appreciated   :-\


Cheers!
Title: Re: D-LA2A Support Thread
Post by: deuce42 on April 04, 2009, 10:28:15 AM
Diy Fanatic and Red Noise - thanks for your posts regarding the 2u spaces. I understand that there is a need to lower the tube socket mounts if using a 2ru case, but my TB4's from drip seem even taller than the to height of the 6005 valve. Anybody else notice this? My guess is it may still be possible but very tight indeed.  3ru seems like just such a waste of space!!!! Am I overdoing this?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 04, 2009, 10:35:40 AM
2U D-LA2A with UREI T4Bs:
http://www.silentarts.de/DIY/D-LA2A/IMG_3980.jpg

2U D-LA2A with Drip T4Bs:
http://www.nrgrecording.de/nrg/viewtopic.php?t=405&postdays=0&postorder=asc&start=92

it is doable, depends on the inner hight of your case
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 04, 2009, 10:38:10 AM
When the Peak Reduction pot is turned ALL the way up, there is slight distortion so I know the pot is in the circuit. All tubes are lit up.

Maybe I missed a connection somewhere in the sidechain/control voltage circuit?
Where in the circuit is that located?

you already swapped your T4Bs between the left and the right channel ?
Title: Re: D-LA2A Support Thread
Post by: stitch-o on April 04, 2009, 11:38:52 AM
When the Peak Reduction pot is turned ALL the way up, there is slight distortion so I know the pot is in the circuit. All tubes are lit up.

Maybe I missed a connection somewhere in the sidechain/control voltage circuit?
Where in the circuit is that located?

you already swapped your T4Bs between the left and the right channel ?

Late last night I did swaps of tubes and T4Bs with same no compression problem.
So I know the problem isn't the tubes, transformers, relays, frontpanel switches or pots or T4Bs.
Its really weird cause the channel bypasses normally, and when "IN" will gain properly....just no compression.

I'll double check all the tubes and T4Bs later today but if you, or anyone, has a suggestion as to what else I can focus on while the hood is up, I'd be muchly appreciative  ;D
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 04, 2009, 12:02:05 PM
schematic (http://www.silentarts.de/DIY/D-LA2A/D-LA2A_rev02-Schematic.pdf)
if you have wired the gain & threshold pot with the suggested molex connectors swap them for a test.
compare voltage on pin3 of the T4B on both channels with the same signal applied.
Title: Re: D-LA2A Support Thread
Post by: stitch-o on April 04, 2009, 12:09:11 PM
schematic (http://www.silentarts.de/DIY/D-LA2A/D-LA2A_rev02-Schematic.pdf)
if you have wired the gain & threshold pot with the suggested molex connectors swap them for a test.
compare voltage on pin3 of the T4B on both channels with the same signal applied.


Perfect I will do all of that! (tho I use no molex)
+ thank you for your schematic. I have many versions of the La2a floating around here....

Cheers!
Title: Re: D-LA2A Support Thread
Post by: stitch-o on April 05, 2009, 12:12:15 PM
I'm starting with some continuity testing (thanks again for the schematic, it makes it much easier):
I'm not quite finished but I did find a descrepancy between the working channel and the non-compressing channel.
Reading the schemo:
Resistor R132/R232 says it is to go to, on the V103/V203of the 12ax7, one leg to pin 2 and one leg to pin 7 on the tube socket.
On the non-working channel I have connectivity between R132 and pins 2 and 7 of V103 only.
On the working channel, I am getting one leg of r232 is connected to pin 2 of V203 but the other leg shows connectivity on 4,5, 7 AND 9. Can this be right?

Edit: The only thing I can think of is that there is a short to the heater run on channel 2 but it works fine and why pin 9 getting signal?

Back to beeping...


EDIT 2:: After some focused critical evaluation and re-soldering a few points (this seems to be the issue specifically C181 and C182), the left channel works!!

Now, my issue seems to be that I'm not really seeing any gain reduction (on both channels) til its up near 7.5 (out of ten) on the PR pot. I still have so much gain as to incur distortion in the signal so I'll be ordering the pots tomorrow for the gain mod and will go from there.

BTW: this thing is dead quiet...

Edit 3::: ooops, the 12AU7 and 12AT7 were switched between 101/203 and 103/203....back to sounding almost excellent.

EDIT 4:::: I had 12AU7s in the V101/V201 position.
I now know it REQUIRES a 12AX7 or equivalent to drive the compressor stage. heh heh....uh.... :P
 I also now know I had a bum tube.
Found a spare seet of cheapo 12AX7s and Everything is as it should be til I do the pot mod.

pheew and Cheers!
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 05, 2009, 02:52:01 PM
sounds like good news ;D
Title: Re: D-LA2A Support Thread
Post by: deuce42 on April 06, 2009, 12:32:43 AM
Stitcho - sounds like your almost there:)

I have a question which I hope isn't too stupid. Since these things put out huge amounts of gain the alternatives seem to be subbing a 12au7 instead of a 12ax7 at v1 and the Volker 22k/7k resistor pot mod. But why not just keep the gain pot very low - like on 1 or 2? Does it matter keeping the low settings on the gain knob instead? Am I missing something obvious?
Title: Re: D-LA2A Support Thread
Post by: crisotop on April 06, 2009, 05:25:03 AM
I think Volkers gain mod uses a 75k resistor in series with a ~25k Pot (but I guess your 7k was just a typo). The only big advantage you get is better gain control - if you have a full ~300° range for ~26dB or about 10° makes a huge difference, the latter is nearly impossible to recall and you need a calm hand to set makeup gain ;)

cheers
christoph
Title: Re: D-LA2A Support Thread
Post by: Kingston on April 06, 2009, 05:36:00 AM
What about another option for the make up gain? People seem content with the 25k pot + 75k resistor trick.


How about a simple balanced pad on the output *after* the transformer? Common sense would dictate it would "sound better" since the output transformer and last gain stage are driven a lot harder. The 25k pot + 75k resistor trick makes all the standard (and very expensive) LA-2A output options pretty pointless, for example those sowter replicas.
Title: Re: D-LA2A Support Thread
Post by: deuce42 on April 06, 2009, 07:59:35 AM
Yes my apologies - meant 75k not my 7k typo. I am thinking too that the pad switch makes more sense in terms of driving the transformers.

Anyone got any views on doing this?
Title: Re: D-LA2A Support Thread
Post by: stitch-o on April 06, 2009, 08:11:06 AM
Stitcho - sounds like your almost there:)

I have a question which I hope isn't too stupid. Since these things put out huge amounts of gain the alternatives seem to be subbing a 12au7 instead of a 12ax7 at v1 and the Volker 22k/7k resistor pot mod. But why not just keep the gain pot very low - like on 1 or 2? Does it matter keeping the low settings on the gain knob instead? Am I missing something obvious?
Thanks bro! Yeah, ALMOST is the operative word. Its that last 5% that will mean the world to me. ;D

The biggest part of my problem was that I had a 5814a in the V1 pos (a 12AU7 variant).
This did not generate enough signal to drive the compression. As soon as I stuck a higher MU tube in the V1, all of my non-compression issues were solved: so from what I gather, V1 NEEDS a 12AX7/ECC83/7025/etc to drive the compression circuit (I believe this was the crux of my problems)
In my comp, V3 now has the 5814a and I am ordering2 x 12AX7 RCA long greyplates. Also, 2 x 25k log pots and 75k resistors today as I still have MASSIVE amounts of gain.

The solution of just leaving the gain on 1 or 2 doesn't quite work for me. There has to be some flexibility for me in the process of dialing in proper gain staging between this piece, the one before it, and the one after it. I, seriously, can't get the gain past .75-1.25 before it redlights out.
For you, maybe this isn't important...dunno
Title: Re: D-LA2A Support Thread
Post by: diyfanatic on April 06, 2009, 08:27:27 AM
noob question to myself about the gain...

if we use a 600/600 input tx, the gain should be decreased?

and in the case of the 600/10k input tx, why not taking a 100K pot or upper value instead of 25k pot?
Title: Re: D-LA2A Support Thread
Post by: stitch-o on April 06, 2009, 08:38:47 AM
noob question to myself about the gain...

if we use a 600/600 input tx, the gain should be decreased?

and in the case of the 600/10k input tx, why not taking a 100K pot or upper value instead of 25k pot?

You need to impedance match the input to the circuit that's why the 600-10k value transformer.

My question is tho: if the original La2a had input trunnies that were 50k secondaries (UTC A10 or HA100x are 10:1 600-50k-->maybe my info on the UTCs is not accurate?) and this design is exactly an original La2a, why the 10k secondary sowter 4383 trunnies? I need to look over some schematics...

Edit: ...which I just did. This project is identical to the original design from what I can see, tho I might have missed something as I was focusing on the input network.
Title: Re: D-LA2A Support Thread
Post by: stitch-o on April 06, 2009, 08:57:57 AM
Common sense would dictate it would "sound better" since the output transformer and last gain stage are driven a lot harder.

But in this case WAY to hard, IMVHO.
Mine was getting not-so-nice distortion and loss of all bass because of too much drive.
The tube mu downgrade ended 95% of distortion and gave me back low end.
and my gain setting still isn't past 1.5!!!!
I'm going to mouser now for the pots and resistors...

Try the different things out and see what works.

Cheers!
Title: Re: D-LA2A Support Thread
Post by: deuce42 on April 06, 2009, 09:32:32 AM
Actually I had wondered similarly about the input tranformers secondary 10k when the schematic seems to want 50k. Guess it is just a matter of trying it and finding what works best for your ears.

I note that there was a post somewhere else on this board where SSL Tech or someone else seemed to be of the view that the best tranny for LA2A was a 600/15k set up becuase it was easier to dig into signals that were less "hot sounding". It appeared as though there was consensus on this board that numerous permutations had been tried and in the end the 600/15k was the best.

Wish I could find it here.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 06, 2009, 11:26:11 AM
for all this questions I would suggest doing a search in the LAB for LA2 and author SSLtech.
you can learn many things reading this posts.

a 1:1 transformer at the input will work fine and reduces some gain.
a PAD at the output works only if you want to have some 50% of THD.
the LA2a has loads of gain, which doesn't mean it has high headroom.
Title: Re: D-LA2A Support Thread
Post by: Kingston on April 07, 2009, 06:21:16 AM
Quote from: [silent:arts
a PAD at the output works only if you want to have some 50% of THD.
the LA2a has loads of gain, which doesn't mean it has high headroom.

Oh. I have always been under the impression it had a severely oversized headroom. Didn't know it is basically a glorified guitar amp. And of course I now have to hear this distortion in action, so pad it is.

I had also been wondering how people are able to use the 10k/600 "small" edcors as outputs. The low clean gain explains it: you won't saturate the trafo (or the gain stage) at any sensible "modern" gain values.
Title: Re: D-LA2A Support Thread
Post by: deuce42 on April 07, 2009, 10:32:16 PM
On another note - anybody notice that the compress/limit switch seems to have almost no effect? - In fact I wondered whether I had a solder short somewhere because I could barely perceive the difference.

My thinking is that this may be because the comp/ limit comes at the input stage which might be a bit crude and unsophisticated. Guess it doesn't matter because the LA2A is most often used to add some vibe or mojo during tracking rather than as an exact scientific audio instrument and adding vibe and mojo is certainly what it does magnificantly!
Title: Re: D-LA2A Support Thread
Post by: stitch-o on April 20, 2009, 05:04:53 PM
I think I found the solution to my problem:
I had the A-10's dual secondaries wired in series.

A quick change of the jumpers on the A-10 and I think I have everything sorted...

just got an oscilloscope so tonight is the real test!
Title: Re: D-LA2A Support Thread
Post by: Silvas on April 20, 2009, 09:19:26 PM
Actually I had wondered similarly about the input tranformers secondary 10k when the schematic seems to want 50k. Guess it is just a matter of trying it and finding what works best for your ears.

I note that there was a post somewhere else on this board where SSL Tech or someone else seemed to be of the view that the best tranny for LA2A was a 600/15k set up becuase it was easier to dig into signals that were less "hot sounding". It appeared as though there was consensus on this board that numerous permutations had been tried and in the end the 600/15k was the best.

Wish I could find it here.

This post?
http://www.groupdiy.com/index.php?topic=26119.40

I ordered 600:15k and 15k:600 edcors following ssltech´s advice on that topic...hope they work great !
Title: Re: D-LA2A Support Thread
Post by: deuce42 on April 21, 2009, 04:09:13 AM
Yep that was the post I meant!

You did order the "wsm" rather than "xsm" versions though right????

There has been a lot of slander about the edcors screwing up the top end frequencies in the LA2A circuit (including slander on that thread). I read and read as much as I could about them and some other member (I am good at recounting threads without remembering who said them:) queried whether the high end loss could be due to the XSM version being 2.5 watts. This may mean capacitance loss resulting in the high end being muffled.  Generally people rush out and by the XSM version rather than the 0.5watt WSM versions which are cheaper. Actually the LA2A doesn't need that extra 2 watts and this may as described above even result in frequency loss.

Whilst I talk from such authority on this- based only upon hearsay (or readsay if there is such a word:), - it may or may not be true. Regardless of whether this theory is correct, I used the WSM's 600/10ks in my build. For what its worth I heard no high frequency loss whatsoever.

Even more so, I seem to not have found the time lately, but I was hoping to post samples of both the Edcor WSM's and some BBC custom wound Sowters. I heard barely any difference between the pricey Sowters and the $9.90 Edcor's. The Sowters maybe had a little more bass end but the Edcors were really nice and actually found them even slightly clearer than the Sowters.  Now it is true that these are line Sowters (i.e. 600/600 ohm) and the Ecdors are 1:4's so they are not entirely identical but the ten buck Edcors really satisfy me as much as the Sowters.

Will post soundclips soon I promise and you guys can decide for yourself.

Title: Re: D-LA2A Support Thread
Post by: crisotop on April 21, 2009, 04:35:52 AM
I try to post soundclips of my D-AOC (very similar input stage to a La-2a) which uses XSM 10k/10k on the input - and I absolutely love the sound! The top end gets softened like you would image a sweet tapemachine to sound - it's beautiful and not 'dull' in any way. On the paper (measured with rhode&schwartz upv) I have slight dip (-1dB @ 20kHz) before the spectrum rises again, but it sounds nowhere like that. As said, I try to post clips soon... I would highly recommend the 1:1 XSM on the input, it may look wrong theoretically, but it sounds mighty fine, at least I like the character (otherwise just use somehting clinical as a Lundahl and compare the sound to your UAD emulation  ;D)

cheers
christoph
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 21, 2009, 04:39:22 AM
nice to see so many happy D-LA2A users ;D ;D ;D
Title: Re: D-LA2A Support Thread
Post by: stitch-o on April 21, 2009, 12:53:47 PM
I think I found the solution to my problem:
I had the A-10's dual secondaries wired in series.

A quick change of the jumpers on the A-10 and I think I have everything sorted...

just got an oscilloscope so tonight is the real test!

jumping 7&8 and 9&10 on the A-10 did the trick!!
Using the jumpers to wire the transformer as a voltage divider, I think I have it down to 12.5k
coming form the input transformers secondaries.
Any which way, it sounds GREAT!

fat and buttery on first quick test passing signal.
A pair of 1958 RCA 12AX7's showed today for
the V3 and I have a pair of 5star 6072s coming for the V1.
Left to do is add some LED IN/Bypass indicators.

Has anyone contemplated a 10 or 20db pad on input?

Cheers and thanks!
Title: Re: D-LA2A Support Thread
Post by: Kingston on April 22, 2009, 10:50:33 AM
I was thinking of doing a slightly more optimal PSU solution than the dual 6,3 VAC + 5VDC for heaters and relays/lights, but there are a few things I don't quite get.

First of all, why is the d-la2a original PSU transformer suggestion (as already bought by many people here) with dual VAC heater windings? (2X 6,3 2VAC)

Dual LA2A only needs 3.3VAC for the heaters. Hum prevention with dual windings?


So instead I was thinking of using one of these generic 6.3VDC regulators (by moby) with a single 9V 4A winding for both of the channels. Sure needs a big heat sink but so what. Then steal another 5VDC from there with a few caps and a 7805 for lights and relays.

Anything wrong with that? I can't foresee any hum troubles provided the 6.3VDC is already regulated super-clean, but what else might there be.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 22, 2009, 11:00:12 AM
First of all, why is the d-la2a original PSU transformer suggestion (as already bought by many people here) with dual VAC heater windings? (2X 6,3 2VAC)
I always round up, and it might change only in an Euro.

Dual LA2A only needs 3.3VAC for the heaters. Hum prevention with dual windings?
the dual windings are just there since it is a dual LA2A. and since I had to order a custom wound transformer, why not. heater wiring is easier in my opinion. haven't thought about hum etc.

So instead I was thinking of using one of these generic 6.3VDC regulators (by moby) with a single 9V 4A winding for both of the channels. Sure needs a big heat sink but so what. Then steal another 5VDC from there with a few caps and a 7805 for lights and relays.

Anything wrong with that? I can't foresee any hum troubles provided the 6.3VDC is already regulated super-clean, but what else might there be.
try it, why not ?
can't see any problem.
but let us know in the end :)
Title: Re: D-LA2A Support Thread
Post by: Kingston on April 22, 2009, 11:19:36 AM
I'm also ordering a custom transformer (for several projects) so I thought about simplifying things a bit. I would have thought dual heater wiring would be less easy. I guess another man's simple is another man's complicated.  ;)

I'll post experiences here when it's done.
Title: Re: D-LA2A Support Thread
Post by: deuce42 on April 23, 2009, 09:56:45 AM
It seems clear that all the mojo in this project is in V1 besides obviously the trannies.

I have experimented with a few 12ax7 valves for V1. So far the JJ Electronic's ECC83s (direct equivalent of 12ax7) is doing it for me.
Title: Re: D-LA2A Support Thread
Post by: Kingston on May 06, 2009, 12:37:05 PM
[silent:arts],

how did you come up with the 150pF value for the cap in C4? (C104 in your schematic)

In every single LA-2A schematic I've seen to date this is marked as 50-380pF, ie. the Arco 465 trimmer cap.


Also, the C114 (T4 response trim) is probably too important to set into "stone" with the marked 330pF. Arco 465 is traditionally used here as well, and it has a strong effect on the compression response, from "flat" to almost "de-esser" like characteristics. Some have even made it into a switch on the front panel.
Title: Re: D-LA2A Support Thread
Post by: stereokillah on May 09, 2009, 10:56:23 AM
hello every body,

I tried to make a wiring guide  with all information on this thread and techtalk thread.
i don't know if it's good.

"Pictures erased cause was wrong will posted in next page"
 
i'm not sure about me don't hesitate to says me if there is some error

Other thing need i stuffed like this pictures ?
Cause some people tell me i need to do and some other idon't need cause i have the REv2.
So i don't see track on this 6volt and i think i need to but i prefer have a confirmation.
 ???

I'm beginer for sure.

Thank you


(http://www.silentarts.de/DIY/D-LA2A/IMG_3945.jpg)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 09, 2009, 11:13:38 AM
cool, will look for some errors / improvements.

Other thing need i stuffed like this pictures ?
Cause some people tell me i need to do and some other idon't need cause i have the REv2.

you are meaning the heater wiring at the bottom of the PCB ?
yes, this is the same in rev01 and rev02.
Title: Re: D-LA2A Support Thread
Post by: stereokillah on May 09, 2009, 03:14:30 PM
Quote
you are meaning the heater wiring at the bottom of the PCB ?
yes, this is the same in rev01 and rev02.

Thank you [silent:arts]
i was thinking about it. It's stuffed.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 09, 2009, 03:29:02 PM
few other things after a first look:

the stereo link won't work like drawn. the red wires need to be switched together, the black ones are only for using shielded cables. the shield should only be connected at the molex connectors, not at the switch (if you switch them together you will get a nice ground loop)

for the potentiometers you should use shielded cables too. shield is pin 1 at the molex
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 09, 2009, 03:32:22 PM
Volker - is the stereo link like the D-AOC .... only needs one wire ?   ;)

Marty.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 09, 2009, 03:47:52 PM
Volker - is the stereo link like the D-AOC .... only needs one wire ?   ;)
Marty - for sure yes. the D-AOC is based on the LA2A ;D
Title: Re: D-LA2A Support Thread
Post by: stereokillah on May 09, 2009, 04:44:14 PM
ok thank you, after much  reflection i find what you mean.

Just blocked on the shield translation. " Bouclier" in french
But i think would be cable Blindé
SO could  be like this

Picture erase cause wrong

I hope i had the good translation, Very soory i'm beginer in english too.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 09, 2009, 04:53:37 PM
Looks fine with the stereo switch now.
for the Pots: shield must be connected to pin1 of the pots too.
Title: Re: D-LA2A Support Thread
Post by: stereokillah on May 09, 2009, 05:25:58 PM
Thank's again [silent:arts] for the time according.

(http://i296.photobucket.com/albums/mm171/renbis/TARGET__LA2_rev01_Platinenl-1.gif)

Title: Re: D-LA2A Support Thread
Post by: tskguy on May 18, 2009, 12:14:57 PM
Hi all,

Just started stuffing my board and I noticed that I purchased 300pf for c114 and c214. Not the 330pf. Will that be a problem? I think I did this by looking at the links for caps that Silent Arts had on the original thread.

Eric
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 18, 2009, 12:27:19 PM
Hi all,
Just started stuffing my board and I noticed that I purchased 300pf for c114 and c214. Not the 330pf. Will that be a problem? I think I did this by looking at the links for caps that Silent Arts had on the original thread.
Eric
Eric, should be fine - try it. won't blow anything.
Title: Re: D-LA2A Support Thread
Post by: tskguy on May 18, 2009, 02:55:01 PM
Very cool,


Thanks for such a quick response!!!

Eric
Title: Re: D-LA2A Support Thread
Post by: rob_gould on May 20, 2009, 08:46:54 AM

Hi All,

Does anyone have a couple of neons (part NE2 on the board) they'd be willing to throw in the post to me for this? My La2a is finished now except for these lamps, and I don't realy want to put a Conrad order in just for these.

If anyone has spares, I'd appreciate the favour.  I can put a couple of £ or € in the post for anyone in the UK / europe...

Cheers,

Rob
Title: Re: D-LA2A Support Thread
Post by: RedNoise on May 22, 2009, 12:09:28 PM
Hi guyz!
Could someone confirm these pots will suite DLA2A please??

http://www.banzaieffects.com/Bourns-AP-FS-100k-log-pr-31141.html

Sorry for dumb question , I just want to void wastin money...
Thanks.
Title: Re: D-LA2A Support Thread
Post by: Kingston on May 22, 2009, 12:18:05 PM
Of course they will work, but since you're browsing banzai, I would recommend Piher instead. We all have our knob "feel" preferences, but I've found the banzai pihers really consistent.

check these out:

http://www.banzaieffects.com/Mono-c-470.html
Title: Re: D-LA2A Support Thread
Post by: RedNoise on May 22, 2009, 12:20:02 PM
Many thanks Kingston , fast answer , greattly appreciated!Cheers!
Title: Re: D-LA2A Support Thread
Post by: tskguy on May 22, 2009, 03:35:42 PM
Hey all,

Im getting close to finishing this thing and I have a few questions.

1. Are all of the voltages after the power transformer DC?

2. If I choose to not use the gridstopper mod do I need to short that spot on the board?

THANKS!!

Eric

Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 22, 2009, 03:39:35 PM
1. Are all of the voltages after the power transformer DC?
after the rectifier diodes

2. If I choose to not use the gridstopper mod do I need to short that spot on the board?
yes
Title: Re: D-LA2A Support Thread
Post by: tskguy on May 22, 2009, 04:41:50 PM
Thanks again!!!

Eric
Title: Re: D-LA2A Support Thread
Post by: Kingston on May 22, 2009, 06:26:38 PM
[silent:arts],

how did you come up with the 150pF value for the cap in C4? (C104 in your schematic)

In every single LA-2A schematic I've seen to date this is marked as 50-380pF, ie. the Arco 465 trimmer cap.


Also, the C114 (T4 response trim) is probably too important to set into "stone" with the marked 330pF. Arco 465 is traditionally used here as well, and it has a strong effect on the compression response, from "flat" to almost "de-esser" like characteristics. Some have even made it into a switch on the front panel.

sorry, but I have to bump this. I'd like to know.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 23, 2009, 03:48:06 AM
how did you come up with the 150pF value for the cap in C4? (C104 in your schematic)

In every single LA-2A schematic I've seen to date this is marked as 50-380pF, ie. the Arco 465 trimmer cap.


Also, the C114 (T4 response trim) is probably too important to set into "stone" with the marked 330pF. Arco 465 is traditionally used here as well, and it has a strong effect on the compression response, from "flat" to almost "de-esser" like characteristics. Some have even made it into a switch on the front panel.

if I recall correctly I searched every LA2A thread, and those have been suggested values if you can't find the Arco 465 (which is nearly impossible in europe).
feel free to try different values, but let us know  ;)
Title: Re: D-LA2A Support Thread
Post by: Kingston on May 23, 2009, 08:03:12 AM
I searched through the big threads also and found some suggested values. Just wanted to make sure how you landed on yours.

the "compression character/de-esser" switch came up somewhere by SSLtech if I recall correctly. I'll try Arcos for one channel to test a good range, but I was going to do the actual front panel switch with silver micas. We'll see.

If I recall correctly the other variable cap actually had little or no effect on anything at all. I have it on my notes somewhere...

Anyway, I'll report back when there's progress.
Title: Re: D-LA2A Support Thread
Post by: tskguy on May 23, 2009, 10:20:16 AM
Hi all,

I found one more question that i cant seem to figure out...There is a spot next to c8 that doesnt seem to be labled and doesnt look like a extension of the 100n cap that is next to it. Here is a pic of what im talking about.

(http://i280.photobucket.com/albums/kk187/tskguy/question.jpg)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 23, 2009, 10:26:06 AM
just put a jumper there
Title: Re: D-LA2A Support Thread
Post by: tskguy on May 23, 2009, 10:59:09 AM
Very cool....
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 06, 2009, 11:35:05 AM
Hey all,

Stumped again....I went with Cinemag 9589 output TX and Lundahl LL1527xl for the input.
Im having a hard time finding out the sowter tx data sheets so I can figure out the way to wire these guys in. Any insite would be great!!!


Eric
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 06, 2009, 11:46:33 AM
Eric, the colored leads can be seen here:
http://www.sowter.co.uk/schematics/la2adiy.jpg
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 06, 2009, 12:16:46 PM
Thanks again!!

Now I just need to figure out wich colors the cinemag 9589 mean. I dont understand there wiring diagram.

Eric
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 06, 2009, 12:22:50 PM
8940 yellow = CM9589 red
8940 green = CM9589 brown
8940 grey = CM9589 yellow
8940 pink = CM9589 orange
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 06, 2009, 12:44:04 PM
WOW

Again I cant thank you enough!!

Eric



Title: Re: D-LA2A Support Thread
Post by: canidoit on June 06, 2009, 09:57:48 PM
If you buy an IEC socket with a built in fuse for 240 volts. What fuse do you get, like how many amps or milliamps and is it slow blow or fast blow?
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 07, 2009, 12:17:37 AM
Well after a long days work I powerd this bad boy up....and nothing blew up! Thats always good. But I am having some issues. So.... It passes audio but no gain, I do not have the VU meters hooked up yet and Im wondering if that would be part of the problem. The starange part is that it passes audio even powerd off??  I also blew some fuses during testing. they are only 250v 250ma slow blow and Ive read I need larger amp rating. So I hope thats it. One a good note the audio is very clean. Also it looks like all the tubes are heating up ok.

Thanks in advance,

Eric
Title: Re: D-LA2A Support Thread
Post by: canidoit on June 07, 2009, 01:31:06 AM
Well after a long days work I powerd this bad boy up....and nothing blew up! Thats always good. But I am having some issues. So.... It passes audio but no gain, I do not have the VU meters hooked up yet and Im wondering if that would be part of the problem. The starange part is that it passes audio even powerd off??  I also blew some fuses during testing. they are only 250v 250ma slow blow and Ive read I need larger amp rating. So I hope thats it. One a good note the audio is very clean. Also it looks like all the tubes are heating up ok.

Thanks in advance,

Eric
Where is this fuse that blows that you talk about? Is this in your IEC power socket? If not then do you have a fuse in your IEC power socket and if so, is it slow blow or fast blow and how many milliamps. Are you using 240 or 115 volts to power up your unit from the mains socket?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 07, 2009, 03:49:53 AM
.... It passes audio but no gain, I do not have the VU meters hooked up yet and Im wondering if that would be part of the problem. The starange part is that it passes audio even powerd off??  ...
sounds like you are testing the bypass  ;D ;D ;D
the relays need power for operation mode, no power = bypass.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 07, 2009, 03:51:20 AM
If you buy an IEC socket with a built in fuse for 240 volts. What fuse do you get, like how many amps or milliamps and is it slow blow or fast blow?
500mA slow blow. doesn't matter if your fuse is in the IEC socket or if you have an extra fuse holder.
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 07, 2009, 10:19:16 AM
ok I figured that out!! Thanks for the help...Now I get audio through with some noise wich im not to worried about..

I just need to hook up the VU's I thought I had an issue with the T4 but turned out I wasnt feeding the unit enough gain. Now all looks good.

Still some holes to drill but Im pretty stoked...

E
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 09, 2009, 11:20:17 PM

Hello again...

So everything seems to be working well. I do have a question regarding the steroe adjust and limit adjust pots on the board. What exactly does it adjust?  Cant seem to figure it out.

Thanks in advance
E
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 10, 2009, 03:29:00 AM
...the two pots that are mounted back there should be turned fully counter clockwise.
make sure both of them are...
ok, you don't have them mounted at the back ...
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 10, 2009, 02:11:01 PM
No I chose to use the two pots mounted on the board. They dont seem to have a stop to them so turning them counter clockwise isnt very logical.  Just trying to understand the best way to adjust this thang :)

Eric
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 10, 2009, 03:10:12 PM
No I chose to use the two pots mounted on the board. They dont seem to have a stop to them so turning them counter clockwise isnt very logical.  Just trying to understand the best way to adjust this thang :)
Eric
Eric, they have a stop (you will hear a "click")
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 10, 2009, 04:46:29 PM
Ok cool,

I was being a little careful I was worried they would break.....I wil do that, Thanks again.

Eric
Title: Re: D-LA2A Support Thread
Post by: stereokillah on June 14, 2009, 04:46:34 PM
hello , for the first try,
i would put edcor transformer inside the dla2a, for input and output.
i tryed to check the data to know how to link it, this my result:

INPUT edcor XSM 600/10k
edcor pin 1 = 4383 brown
edcor pin 2 = 4383 pink
edcor pin 4 = 4383 green
edcor pin 5 = 4383 blue
edcor pin 8 = 4383 grey
edcor ground= 4383 black

OUTPUT edcor XSM10k/600
edcor pin 1 = 8940 yellow
edcor pin 4 = 8940 green
edcor pin 5 = 8940 grey
edcor pin 8 = 8940 pink
edcor ground= 8940 black

the question is: Is it right and need i used the grip like the sowter pin or need i wired it direct on the xlr ?

Thank you
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 14, 2009, 04:55:34 PM
the question is: Is it right and need i used the grip like the sowter pin or need i wired it direct on the xlr ?
1st: haven't checked (yet)
2nd: it is possible to connect the transformers directly to the XLRs, with the disadvantage of not using the bypass circuit located on the PCB
Title: Re: D-LA2A Support Thread
Post by: stereokillah on June 14, 2009, 05:54:25 PM
thank you [silent:arts] , i will do with the pin to have the bypass .

there is not problem with this edcor on input, cause i've already seen  on the output of the DLa2a finish but never input.
Title: Re: D-LA2A Support Thread
Post by: bernbrue on June 15, 2009, 04:28:51 AM
thank you [silent:arts] , i will do with the pin to have the bypass .

there is not problem with this edcor on input, cause i've already seen  on the output of the DLa2a finish but never input.

I tried the Edcors 10k/10k as input tx and had a strange frequency response. I finally used the recommended Sowters for input and the Edcors for output.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: crisotop on June 15, 2009, 04:47:05 AM
On the papeer I assume - I have a 10k/10k in my D-AOC (similar input stage) and it sounds beautiful, but looks strange as well ;)

cheers
christoph
Title: Re: D-LA2A Support Thread
Post by: stereokillah on June 15, 2009, 07:56:43 AM
thank you bernbrue and Crisotop
i think i will take swoter for the input, but for the output is it edcor xsm 10k/600 or other please?
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 15, 2009, 09:15:42 PM
Ok boys I have something very strange happening. So far everything seems to working great. It does a great job compressing and works very well. I was trying to listen to the noise floor so I cranked the gain and at past 5 it made a click and then it blew both my tweeters!!  crap!!!

Very strange...What could cause this?

I am using a strange combo of transformers but I dont think that would be the problem. Im also not using the gridstoppers, any ideas??

Eric
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 16, 2009, 12:41:28 PM
HF oscillation. sorry for the tweeters :o
try the gridstoppers, or reduce the gain range (what I did).
you will never need gain past 5.
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 16, 2009, 01:38:16 PM
Cool thanks again,

I will try thos fixes this evening and let you know. Atleast It seems like a probleam that has a known fix. The gain range fix is the 25 ohm pot with a 75 resistor correct?? I plan on the grid stoppers first though. I also am running the input at 1:2 I may try 1:1 and see if that helps as well.


Eric
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 16, 2009, 02:06:20 PM
I don't think a change to a 1:1 transformer will change the oscillation, since it is input level independent.
and I don't know if it is tube or (PCB) layout dependent. some people have it, some not.
with my PCBs, with Drip PCBs, and I have read from P2P units too.

gain range fix in my unit is the 25K ohm pot with the 75K ohm resistor, yes.
(and I still never moved the gain over the middle).
if you need more gain you could try a 50K ohm pot with a 50K ohm resistor.
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 16, 2009, 02:16:28 PM
Thats good to know... I will leave the transformer the same. I really dont have any issues with the amount of gain. It has plenty!!!
And I would never really need to go past five my testing usually has it around 2 or 3 for makeup gain. I really just want to fix it in case someone pumps it past five again and blows my overly sensitive tweeters!! Im just glad Im not in the middle of a project!
They dont sound very nice without tweeters..

Eric

Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 16, 2009, 02:27:00 PM
in this case try the "gain mod".
better adjusting range as a benefit too.
(but before testing with your loudspeakers do with a meter)
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 16, 2009, 02:35:44 PM
Very cool,

Thanks again for your help.

Eric
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 16, 2009, 08:52:44 PM
Ok
I did the grid stopper and it didnt do anything...Bummer. Oh well I guess I wil try the gain mode.
Did the original do this? Or is it a issue related to tube diffrences? It seems strange that I couldnt fix the real cause not just bandaid it.

Eric

Title: Re: D-LA2A Support Thread
Post by: tskguy on June 16, 2009, 10:12:10 PM
Ok,

If I unplug my output transformers from the board my strange gain issue goes away??? I am using cinemag tx's and I wonder if I have it wired wrong.

I also have a pair of the edcor wsm tx's maybe I should give them a try? 

Eric
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 16, 2009, 11:17:48 PM
So I double checked my wiring on the output and it seems fine. The only real diff is that the cinemag doesnt have a black wire so I just left it out. I guess its for ground. Is that ok??

Eric
Title: Re: D-LA2A Support Thread
Post by: crisotop on June 17, 2009, 04:11:41 AM
Jens or Bernd once noticed that the oscillation depends how close the output tranny is to the I/O XLRs. Try moving the trannies around until the hf oscillation dissapears.

hth, christoph
Title: Re: D-LA2A Support Thread
Post by: bernbrue on June 17, 2009, 05:25:13 AM
Jens or Bernd once noticed that the oscillation depends how close the output tranny is to the I/O XLRs. Try moving the trannies around until the hf oscillation dissapears.

hth, christoph

Thx Chrisoph for mentioning this. Indeed, I found out that the transformers shouldn´t be too close to the XLR inputs/outputs. I moved them a bit and the oscillation problem was solved.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 17, 2009, 05:28:06 AM
ah yes, I remember:
http://www.nrgrecording.de/nrg/viewtopic.php?t=405&postdays=0&postorder=asc&start=225
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 17, 2009, 08:25:26 AM
Well that didnt make any diffrence... :-\ Well I guess I will get some 50k pots and see if that works. Im sure it will fix it. But I would love to fix the heart of this issue. One thing I wanted to mention is that it doesnt mateer if anything is plugged in or if its in bypass or not. If you watch the output gain when it does this it gets slammed hard to the right at just above 50% gain. The exact same behavior is happening on either channel as well.

I have been doing a ton of searching as well and havent seen anything like it....

Eric
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 18, 2009, 09:54:40 AM
Ok I finally figured this out!! It was a combo of unshielded wires and and wire placement. Things are good now! Silent:arts, thanks for all your help!

Here it is....
(http://i280.photobucket.com/albums/kk187/tskguy/Mic%20Stuff/d-la2a004.jpg)
(http://i280.photobucket.com/albums/kk187/tskguy/Mic%20Stuff/d-la2a007.jpg)
(http://i280.photobucket.com/albums/kk187/tskguy/Mic%20Stuff/d-la2a001.jpg)
(http://i280.photobucket.com/albums/kk187/tskguy/Mic%20Stuff/d-la2a003.jpg)

And Yes I know the T4 cells are huge!! But they fit and sound great!!!!

E
Title: Re: D-LA2A Support Thread
Post by: crisotop on June 18, 2009, 10:06:27 AM
wohoo! congrats!
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 18, 2009, 10:13:44 AM
Thanks man!

It is a big project its nice to have it finished!

E
Title: Re: D-LA2A Support Thread
Post by: rob_gould on June 18, 2009, 10:27:58 AM

Nice work - looking good :)

Can't wait to get my one of these up and running...
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 18, 2009, 10:32:35 AM
congrats  ;D
great you featured out the oscillation  :) :) :)
is this a Gustav PCB ?
Title: Re: D-LA2A Support Thread
Post by: tskguy on June 18, 2009, 11:15:18 AM
Yes it is....

The board itself looked great Gustav did a fine job reproducing your PCB.

Thanks again!!!

E
Title: Re: D-LA2A Support Thread
Post by: shabtek on June 18, 2009, 03:03:00 PM
nice!
Title: Re: D-LA2A Support Thread
Post by: mrvision on July 18, 2009, 01:19:10 PM
Hi,

Does anybody know where can I get a PCB for a DLA2A?

Best Regards,
Title: Re: D-LA2A Support Thread
Post by: stereokillah on July 18, 2009, 02:34:57 PM
Hello mrvision,

you could find it on the black marcket if someone need to sold  it

or waiting the webshop from Silent Art in a few time.
Title: Re: D-LA2A Support Thread
Post by: Holger on July 22, 2009, 03:03:12 PM
My version:


(http://audiofor.tv/diy/ProjectFotoFolder/LA-2A/Front2.jpg)

Built around an old Simpson meter in a 3 RU Modutec case.
The front panel has the same color than Emre's PM 666...
http://www.groupdiy.com/index.php?topic=28274.msg422722#msg422722

(http://audiofor.tv/diy/ProjectFotoFolder/LA-2A/LeftDetail1.jpg)

Meter shows GR only, no output. I used the Edcor WSM here, maybe I'll change to Sowters when I have a some extra money.

(http://audiofor.tv/diy/ProjectFotoFolder/LA-2A/Edcors.jpg)

I had one little problem introduced by too much solder on one octal socket pin, no other problems. The compressor is matched perfectly
for stereo operation.

(http://audiofor.tv/diy/ProjectFotoFolder/LA-2A/TopRear1.jpg)
(http://audiofor.tv/diy/ProjectFotoFolder/LA-2A/LeftSide1.jpg)
(http://audiofor.tv/diy/ProjectFotoFolder/LA-2A/Top1.jpg)


Thanks to Volker for the PCB.

And thanks to the community for support and information.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on July 22, 2009, 04:36:47 PM
Holger, congrats - great looking as always :) :) :)

this one is for you:

(http://www.51xaudio.com/images/DLA2A-Holger.gif)

 ;D ;D ;D
Title: Re: D-LA2A Support Thread
Post by: stereokillah on July 23, 2009, 01:16:52 PM
Nice work Hogler,

and good idea for the vu meter,
have you used this edcor transformer mode please?
INPUT edcor XSM 600/10k
edcor pin 1 = 4383 brown
edcor pin 2 = 4383 pink
edcor pin 4 = 4383 green
edcor pin 5 = 4383 blue
edcor pin 8 = 4383 grey
edcor ground= 4383 black

OUTPUT edcor XSM10k/600
edcor pin 1 = 8940 yellow
edcor pin 4 = 8940 green
edcor pin 5 = 8940 grey
edcor pin 8 = 8940 pink
edcor ground= 8940 black
Title: Re: D-LA2A Support Thread
Post by: tcaylor on July 23, 2009, 02:37:12 PM
I too am looking for a PCB for the D-LA2A.  Reading the above posts, is the only hope of getting a pcb from the black market?  Seems there are plenty of single LA2A's but no D-2LA pcbs :(
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on July 23, 2009, 02:49:16 PM
the PCBs will be available again, let us say: mid september
Title: Re: D-LA2A Support Thread
Post by: tcaylor on July 23, 2009, 03:23:53 PM
thanks Silent Arts, may I ask what the projected price will be?  In the meantime, I have your parts list and I'll go ahead and pick up the other parts.  This will be my first audio project DIY and I am looking forward to it. 
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on July 23, 2009, 03:45:56 PM
thanks Silent Arts, may I ask what the projected price will be?  In the meantime, I have your parts list and I'll go ahead and pick up the other parts.  This will be my first audio project DIY and I am looking forward to it. 
project price I don't know, but the PCB should stay the same (I think it was EUR 22,- plus shipping).
be aware you need a special PSU transformer - don't think I will have them in stock that time.
and you need those T4Bs. all other parts are easy to get.

if this will be your first project, be aware of the high voltage. this can be killer (I mean: kill you)
Title: Re: D-LA2A Support Thread
Post by: Holger on July 25, 2009, 08:53:55 AM
Stereokillah,
I used 600/15k, 15k/600 WSMs for my build.
My fault: after opening the device I found out that I used the 10k version...
I did not connect the center taps.
Today I did the 75k resistor/25k pot mod which gives me uni-gain at 11 o'clock rather than 9 o'clock gain knob position.

So:
INPUT edcor XSM 600/10k
edcor pin 1 = 4383 brown
NC = 4383 pink
edcor pin 4 = 4383 green
edcor pin 5 = 4383 blue
edcor pin 8 = 4383 grey
NC= 4383 black

OUTPUT edcor XSM10k/600
edcor pin 1 = 8940 yellow
edcor pin 4 = 8940 green
edcor pin 5 = 8940 grey
edcor pin 8 = 8940 pink
NC= 8940 black

(Volker, kriegt jetzt jeder ein Sternchen (Banner) nach Fertigstellung von Dir? ;D)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on July 25, 2009, 09:07:40 AM
(Volker, kriegt jetzt jeder ein Sternchen (Banner) nach Fertigstellung von Dir? ;D)
mhm, muss ich noch darüber nachdenken :D :D :D
also alle mit eigener Frontplatte bisher schon  ;D ;D ;D
Title: Re: D-LA2A Support Thread
Post by: stereokillah on July 25, 2009, 09:20:54 AM
thank you very much for this answer Hogler.
Title: Re: D-LA2A Support Thread
Post by: rob_gould on July 28, 2009, 07:04:45 AM

Hi Volker,

The final components I need for this project are the neon lamps, but I don't want to order these only from Conrad. 

So annoying when the thing you forget is only a few cents and postage is €€€  ::)

Will the 68V Zener that you see here be an OK substitute for the neon?

http://www.rapidonline.com/Electronic-Components/Discrete-Semiconductors/Zener-Diodes/1.3W-BZX85C-Zener-diodes/66242

Thanks
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on July 28, 2009, 01:40:35 PM
the Zener should work
Title: Re: D-LA2A Support Thread
Post by: pilot on July 28, 2009, 01:58:01 PM
Quick question regarding the TBD resistor on the DLA2A...   I am using the UA T4B's What value should I put in that hole if any?  Many Thanks.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on July 28, 2009, 02:04:54 PM
Hi Pilot,

welcome to the board :)

try this link:
http://www.nrgrecording.de/nrg/viewtopic.php?t=405&postdays=0&postorder=asc&start=27
Title: Re: D-LA2A Support Thread
Post by: stereokillah on August 02, 2009, 05:35:19 PM
hello guys this is my first big projects, i'm a beginer;

(http://i296.photobucket.com/albums/mm171/renbis/dla2a-face.gif)

(http://i296.photobucket.com/albums/mm171/renbis/dla2a-inside.gif)

(http://i296.photobucket.com/albums/mm171/renbis/dla2a-back.gif)


I try to test the voltage of tx  psu ,it work fine.

But when i put all the wire on the pcb the fuse break ,

when just the 250 x2 are plugged it's fine , i add the 5v always fine but when i plugg the 6.3v all my fuse break.

Perhaps it's only bad fuse reference , i don't know if it's slow jsut know it's 0.5A 250v i hope it's just bad fuse reference cause all my pwire under the board seems to be fine, and the resitor too.

This problem is with oand without tube.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on August 02, 2009, 05:46:42 PM
nice build ;D
give me a pic with the tubes installed once it is up and running.

check your heater wiring for shorts again again - it is not the fuse if it blows without the tubes inside.
you should measure 100 ohm between each tube sockets heater connection to ground.
Title: Re: D-LA2A Support Thread
Post by: stereokillah on August 02, 2009, 05:49:14 PM
Thanx again Silent arts for yours fast reply i will recheck it,
Title: Re: D-LA2A Support Thread
Post by: stereokillah on August 02, 2009, 07:21:12 PM
ok ,
it's good now, don't why perhaps a bad stuff, i had 100 ohm on the 4 heater to ground i have stuffed all the wire H1 and H2 and all seems work .


i will do audio test tomorow if i can.
i 've forgoten to put the resistor before the + of vu meter and i need to take 5v for all my led.

i will sleep bester now thanx Silent arts
Title: Re: D-LA2A Support Thread
Post by: stereokillah on August 03, 2009, 04:17:34 PM
I'm happy to test it , even i have problems it's only small probelem.

First the sound crack on bypass mode when i put the volume  above the 0db perhaps it's normal
 and same on compressor mode .
second i have a hi cut around 15khz and low cut around 120hz  i think it's edcor transfomer problem as i read before about the Bernbrue unit.
and i need to calibratre the VU.

SO i think i wil  change the gain pot like a lot a guys and tehe audio transformer.
Title: Re: D-LA2A Support Thread
Post by: rob_gould on August 04, 2009, 12:30:11 PM

Hi All,

I'm confused by all the different transformer information that's floating round for this project.

I was thinking about getting Sowter to do a custom version of the 4383 but with 1:1 ratio, just to control the input gain a bit more. 

All the input trannys for this project seem to be 600/10k which makes sense, but over at Frank's place Volker recommends using a 1:1 input tranny with 10k/10k impedance.

I did not think that changing ratio would make a difference to the impedance that should be used, because the impedance depends on the circuit connected to the input on one side of the tranny, and the input stage of the LA2A circuit connected to the other side of the input tranny?

Aaargh  ???  Can anyone help me out on this?!

Thanks  :)

Rob
Title: Re: D-LA2A Support Thread
Post by: stereokillah on August 04, 2009, 06:05:01 PM
i think you can choise your transformer yourself to have the sound as you like but this projects be more sure and adapted with the swoter input and output like you can see on the board.

For me , it's a cheaper price choise but i think i will take input sowter .

Second thing the 4383 seems to be 600/10k check it http://www.sowter.co.uk/specs/4383.htm (http://www.sowter.co.uk/specs/4383.htm)
Title: Re: D-LA2A Support Thread
Post by: rob_gould on August 04, 2009, 06:10:52 PM

Yeah it's Sowter that I intend to go for, but the impedances are the part that confuses me.

Top of the page you linked to says this by the way : 600/10K Line Input Transformer.

Have I got it wrong that this means 600 on the primary side and 10k on the secondary side?
Title: Re: D-LA2A Support Thread
Post by: stereokillah on August 04, 2009, 06:31:31 PM
yes soory 600 to 10k input
Title: Re: D-LA2A Support Thread
Post by: Silvas on August 12, 2009, 06:35:43 PM
Hello

It is safe to use a lower voltage rated poly cap for the 0.1 c102, c202, c103, c203 ? according to CJ's voltage chart, there's around 100 volts DC to block...and i'm short of 0.1/400v caps, but have lots of nice ERO mkp1840 which i would like to use if their 160v rating isn't a problem here. What do you think guys?

Also : i'm having some trouble locally sourcing the silver mica caps (i forgot to put them on my big parts order from USA), it is possible to substitute them with other types ? what about their influence in the sound of the unit? But maybe i'll just do a small order from Small Bear...

Thanks so much !
Title: Re: D-LA2A Support Thread
Post by: MartyMart on August 13, 2009, 04:05:26 AM
Hi Silvas, I have to do a similar thing with those caps so I think that you'll be OK
I have several 250v in those sizes though.
Smallbear are quick and fairly cheap for the mica's
A few years ago on evilbay, I got a HUGE bag of mica's in lots of values for $50
wish I had bought more as they seem expensive these days !!!

MM
Title: Re: D-LA2A Support Thread
Post by: stereokillah on August 13, 2009, 01:59:47 PM
hello guys,
like i'm a beginer , i would to know weach fuse i need to use in this unit please, or simple how to know.
thanx
Title: Re: D-LA2A Support Thread
Post by: Silvas on August 13, 2009, 11:23:17 PM
Hello

It is safe to use a lower voltage rated poly cap for the 0.1 c102, c202, c103, c203 ? according to CJ's voltage chart, there's around 100 volts DC to block...and i'm short of 0.1/400v caps, but have lots of nice ERO mkp1840 which i would like to use if their 160v rating isn't a problem here. What do you think guys?

Also : i'm having some trouble locally sourcing the silver mica caps (i forgot to put them on my big parts order from USA), it is possible to substitute them with other types ? what about their influence in the sound of the unit? But maybe i'll just do a small order from Small Bear...

Thanks so much !


I figured it out....i can use the 160v polypropylene on c102, c202 (around 90 volts dc) but not on c103, c203. Anyway, i was only 2 caps short (c102 and c202). Still not sure about using other types for the silver micas.

Title: Re: D-LA2A Support Thread
Post by: Silvas on August 29, 2009, 03:54:52 PM
Hello

It is safe to use a lower voltage rated poly cap for the 0.1 c102, c202, c103, c203 ? according to CJ's voltage chart, there's around 100 volts DC to block...and i'm short of 0.1/400v caps, but have lots of nice ERO mkp1840 which i would like to use if their 160v rating isn't a problem here. What do you think guys?

Also : i'm having some trouble locally sourcing the silver mica caps (i forgot to put them on my big parts order from USA), it is possible to substitute them with other types ? what about their influence in the sound of the unit? But maybe i'll just do a small order from Small Bear...

Thanks so much !


I figured it out....i can use the 160v polypropylene on c102, c202 (around 90 volts dc) but not on c103, c203. Anyway, i was only 2 caps short (c102 and c202). Still not sure about using other types for the silver micas.




I ended up ordering the silver micas from small bear anyway....now, i´m waiting for the antek power trafos (one for the HT/heater and a small one for relays) to turn the D-LA2A on...
Title: Re: D-LA2A Support Thread
Post by: stereokillah on September 01, 2009, 04:55:11 PM
Great GReat GREat GREAt GREAT!!!

I 've put the swoter input and all work fine , i've tried  Tung sol 12AX7A and Sovtek 12AXLPS

Definitively i keep the sovtek the tungsol give me a bad noise about -65 db  but sovtek -80

Just have some difference between the two vu meter don't know why.

So thank you for all th help .
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 01, 2009, 05:17:01 PM
cool 8) 8) 8)

what is the difference between the two meters?

and don't forget some pics with the tubes inside - looks much better in your banner ;D
Title: Re: D-LA2A Support Thread
Post by: stereokillah on September 01, 2009, 06:18:55 PM
Hi SIlent arts

for my vu meter , with the same signal one give me -7 and second -8 same thing in GR for same zero depart
it's JLM meter like sifam al 19
the R 3k9 seemed not to be enought strong i 've put oe trimer on the + to

Thank you

(http://i296.photobucket.com/albums/mm171/renbis/DIY/Dla2aface.jpg)

(http://i296.photobucket.com/albums/mm171/renbis/DIY/100_0501.jpg)




Title: Re: D-LA2A Support Thread
Post by: SIXTYNINER on September 02, 2009, 12:52:26 PM
"photo cells" are custom T4b ?
 8)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 02, 2009, 12:58:25 PM
"photo cells" are custom T4b ?
 8)
yes, you won't buy them at mouser, digikey, farnell etc
Title: Re: D-LA2A Support Thread
Post by: RedNoise on September 02, 2009, 04:49:07 PM
congrats StK ! Very nice DLA2A...Too fast for me bro! ;D

Did you finally screwed the Sowter?(or did you rubber them?)
Title: Re: D-LA2A Support Thread
Post by: stereokillah on September 02, 2009, 05:42:38 PM
thanx Rednoise!

it's screwed to the support plate
Title: Re: D-LA2A Support Thread
Post by: stereokillah on September 04, 2009, 08:24:31 PM
"photo cells" are custom T4b ?
 8)

sorry
come from Drip electronic
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 05, 2009, 04:05:15 AM
sorry for the delay ;D ;D ;D

(http://www.51xaudio.com/banner/DLA2A-stereokillah.gif)
Title: Re: D-LA2A Support Thread
Post by: bernbrue on September 05, 2009, 09:10:44 AM
Hi stereokillah,
congrats!!! A really pro looking unit. You´ll will be amazed by the superb sound, unbeatable and very unique. I recommend to do the pot mod to tame the immense amount of gain. There are trimpots to modify the compression/limiter response and another trimpot for stereo adjust. Tweak them until the meters show identical values. Readjust the meter zero trimmers.
A bientot
Bernd

@ Volker: really nice banners. For my personal taste the pictures change too fast. We want to enjoy them, don´t we?

regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: stereokillah on September 05, 2009, 10:49:34 AM
Again Thank you Silent arts for this porjects  and thanx for the banner,

Thank you Bernbrue i will try the pot mod instead the trimmer just need to have some idea to block it o the front panel.
Title: Re: D-LA2A Support Thread
Post by: USIEL on September 20, 2009, 02:56:26 PM
Hi  guys ,

Yesss    finally finished my  D LA2A  .....my 3rd diy project    ;D
Sowter transformers  ,Sifam VU  meters , RCA  12bh7 a ,  telefunken 12ax7 tubes ,bakelite knobs verrrrrry nice   , verrryy nice.....BUT... :(

.....When i  powered it up  nothing happened , well almost nothing , the only tubes glowing are the NE 2 's and not the other tubes .....no sound  no action on the vu meters ......nothing

I've checked some of the voltages on the tubes  ,12 ax7  pin 4 and 9 - 350V        ...6aq5 pin 3 - 360V        ...12BH7 A  pin 4 - 360V
I dont know if this  is normal but im affraid that they are  to high

I hope one of you guys can help me .....you probably need more information (so please ask ),but i was afraid to damage the tubes so switched it out as soon i saw the  high voltages... 

thanks  ,
Usiel

Title: Re: D-LA2A Support Thread
Post by: USIEL on September 20, 2009, 02:57:37 PM
and the inside
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 20, 2009, 03:01:48 PM
Usiel,

nice build ;D

to your problems my 1st guess is:
you didn't wire the heaters ;)
Title: Re: D-LA2A Support Thread
Post by: Kingston on September 20, 2009, 03:02:01 PM
I've checked some of the voltages on the tubes  ,12 ax7  pin 4 and 9 - 350V        ...6aq5 pin 3 - 360V        ...12BH7 A  pin 4 - 360V
I dont know if this  is normal but im affraid that they are  to high

Sounds to me like you have not connected heaters, or something is wrong in this area.

What's your heater voltage, and do they measure correctly at the tube sockets?

[edit]

hah, silent:arts beat me to it
Title: Re: D-LA2A Support Thread
Post by: USIEL on September 20, 2009, 04:37:11 PM
wow  you guys are fast  ..and woowww do i feel stupid hahaha    i didn't wire the heaters at all !!!  :o

..thanks for your time guys  !! i appreciate it very much

Title: Re: D-LA2A Support Thread
Post by: stereokillah on September 20, 2009, 08:42:45 PM
Hi
this my second DLa2a, i love this unit and how it work.

for gain i put pot 47k log plus resitor 47k i kepp the 100k log for the gain reduction

Just have some difference on the vu gain reduction when it's on stereo and when it's on dual.

Thanx again guys
(http://i296.photobucket.com/albums/mm171/renbis/DIY/dla2a-face.gif)

(http://i296.photobucket.com/albums/mm171/renbis/DIY/dla2a-inside.gif)
Title: Re: D-LA2A Support Thread
Post by: deuce42 on September 21, 2009, 02:11:58 AM
Stereokillah - build looks great man!
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 21, 2009, 03:48:19 AM
Nice work gentlemen. Keep them coming ;D

(http://www.51xaudio.com/banner/DLA2A-USIEL.gif)

(http://www.51xaudio.com/banner/DLA2A-stereokillah2.gif)
Title: Re: D-LA2A Support Thread
Post by: canidoit on September 21, 2009, 05:27:56 AM
and the inside
Nice work!

I noticed you used shielded cable instead of twisting wires?

If you have two wires running, is it usually better to use shielded cable with the shield grounded on one end or just use two wires twisted?

If you have one wire running, is it better to use shielded cable with the shield grounded on one end or just use one wire?

If shielded cables are the way to go, Il put it into practice to use shielded cables for all my wire runs.
Title: Re: D-LA2A Support Thread
Post by: USIEL on September 21, 2009, 06:13:34 PM
 Yes !  its working and sounding great now, thanks again guys ..
...And  i've got  my own banner   :D  

Thank you canidoit !    i always use schielded wire when audio passes
I dont think you can go wrong with shielded cable , but  its not always necessary



Title: Re: D-LA2A Support Thread
Post by: stereokillah on September 21, 2009, 06:18:59 PM
Canidoit, like on this link http://www.groupdiy.com/index.php?topic=32677.msg408770#msg408770 (http://www.groupdiy.com/index.php?topic=32677.msg408770#msg408770)
the shielded are needed for pot stereo switch and xlr, for the other it's jsut cosmetics.
Title: Re: D-LA2A Support Thread
Post by: stereokillah on September 29, 2009, 03:51:12 PM
hello, someone could give me the good method calibrated the stereo way please,

Cause when i calibrate it the stereo seems good and when i give more reductionthere is diffence between the two channel, i calibrate a new time and if i change the ain reduction the two channel seems differnets again.

Title: Re: D-LA2A Support Thread
Post by: USIEL on October 01, 2009, 02:09:24 PM
Hi stereokillah... maybe this will help you

www.uaudio.com/products/.../la2a/_docs/LA-2A_manual.pdf (http://www.uaudio.com/products/.../la2a/_docs/LA-2A_manual.pdf)

Title: Re: D-LA2A Support Thread
Post by: stereokillah on October 01, 2009, 02:24:10 PM
Thank you USIEL i've tryed this but seem to be caused by the 6aq5a , there is not matched for one paire .

At time i ve calibrated and insversed he tube after and work fine in stereo, it's just the time to hav matched pair.
Title: Re: D-LA2A Support Thread
Post by: SIXTYNINER on October 02, 2009, 09:48:41 AM
hi silent arts
sent you pm,
it is arrived there?
 :)
Title: Re: D-LA2A Support Thread
Post by: stereokillah on October 16, 2009, 08:45:45 AM
hello,
who could tell me wich tubes need realy to be matched paire for the stereo way please?

thank you
Title: Re: D-LA2A Support Thread
Post by: stereokillah on October 16, 2009, 05:47:32 PM
I M VERY LOST WITH THE SETREO CALIBRATION?


If the calibration is good when the potentiometer peak reduction it's on 12 o'clock it's different when this pot is full and same thing if i calbrate it on full pot when it is on 12 oclock the compression is differents.
that with same signal input 1khz.
there is something wrong with my method or with my conpenets.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on October 16, 2009, 05:59:43 PM
Hi stereokillah,

remember one thing: the potentiometer have a tolerance of up to 20%.
there is no way to calibrate it exactly for full and half of the scale.

when using in stereo I always calibrate it like this:
- mono sine wave to both channels
- set desired gain equally watching my external RTW (Meter)
- set the desired gain reduction equally watching my external RTW (Meter)
Title: Re: D-LA2A Support Thread
Post by: stereokillah on October 16, 2009, 07:22:31 PM
hi Silent arts and thanx,

i'm beginer but not crazy, perhaps will be better i i put switch 24 positions instead of the pot.
Title: Re: D-LA2A Support Thread
Post by: ChrioN on October 21, 2009, 07:51:33 AM
would the tracking between channels be much off if using stepped rotary switches on both channels? thinking about the tollerance of the drip T4B's..
Title: Re: D-LA2A Support Thread
Post by: Audioman on November 12, 2009, 02:38:44 PM
Hi all ,
I need your advice about the case of the D-LA2A :
If i make the Project with a 2U case there is a problem of too much temparature inside the case ??
Or i s better to choose an 3U case ?
Please let me know
Thank you
Fabio
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 12, 2009, 02:50:01 PM
Fabio,

while mine is a 2U case (with ventilation holes) I have 1U free space on top ...
Title: Re: D-LA2A Support Thread
Post by: ermetiko on November 14, 2009, 01:26:02 PM
hi.....i'm calibrating my unit.....for having a flat frequency response the limiter response trimmer must be 0R and C112-212 in short circuit.....?
Title: Re: D-LA2A Support Thread
Post by: Audioman on November 17, 2009, 11:42:12 AM
HI ALL,
I RECEIVED AN E-MAIL FROM DRIPELECTRONICS
THAT ASK ME IF I WANT THE T4Bs SLOW OR FAST
CAN YOU HELP ME ABOUT IT ??
LET ME KNOW
THANK YOU
FABIO
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 17, 2009, 11:54:44 AM
Audioman, you should unlock your caps lock.

slow = classical
fast = might be better for mastering

just make sure they are stereo matched.
Title: Re: D-LA2A Support Thread
Post by: Audioman on November 17, 2009, 12:46:42 PM
Now i unlock the caps lock .... ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D
Thank you for the info !!!
Fabio
Title: Re: D-LA2A Support Thread
Post by: baadc0de on November 18, 2009, 03:53:15 AM
silent:arts, your inbox is full so I can't PM you; sorry for hijacking this thread a bit, but do you have any estimate on when the D-LA2A PCBs will be available again?

Best Regards,
B.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 18, 2009, 09:54:51 AM
silent:arts, your inbox is full so I can't PM you; sorry for hijacking this thread a bit, but do you have any estimate on when the D-LA2A PCBs will be available again?

Best Regards,
B.

once I have written the terms of condition and all product descriptions I will open the web store.
the sooner the better, but I will need at least two more weeks ::)
Title: Re: D-LA2A Support Thread
Post by: Audioman on November 21, 2009, 01:29:26 PM
Hi All,
Where i can find the component placement for the revision 02
I find only the version 01
Soldering iron was burning  ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D
Let me know
Thank you
Fabio
Title: Re: D-LA2A Support Thread
Post by: Audioman on November 23, 2009, 06:25:54 AM
Hi all
Anyone can tell me the value of the resistor namad TBO ??
Let me know
Thank you
Fab
Title: Re: D-LA2A Support Thread
Post by: crisotop on November 23, 2009, 06:35:24 AM
R125, 225 = 33k
Title: Re: D-LA2A Support Thread
Post by: Kingston on November 23, 2009, 07:01:31 AM
That's not entirely correct.

from elsewhere in the forum, regarding T4B matching and calibration:

(from my notes, probably originally posted by SSLTech)

Quote
You adjust R25 until it matches. Without calibrating R25, they don't track accuratley on ANY LA-2a. Replace R25 with a trimpot of about 1.5 or 2 times the stated value of R25 then start it halfway and NEVER take it all the way to either extreme. Somewhere in there will be a setting which makes the meter agree when switching between GR and +4, after setting a tone to 0VU output in +4 mode with no GR present. Increase the GR and set it so that it matches at around -5dB (5dB gain reduction). It will be maybe a little off at -3dB, maybe a little off at -8dB... a little off all over the scale, but I find that matching the meter at-5dB is usually an excellent compromise. The only way to get them to track correctly is to MATCH the optos in your T4b. Then you re-adjust R25 and try again.

elsewhere in the forum there's lots of info. Please use the search.

Same applies to C4 and C14. There's a lot more to them than the stone set values of D-LA2A Rev2 schematics...
Title: Re: D-LA2A Support Thread
Post by: Audioman on November 23, 2009, 07:38:17 AM
Wolker can you clarify this ????
Please let me know
Thank you !!!
Fab
Title: Re: D-LA2A Support Thread
Post by: crisotop on November 23, 2009, 07:43:11 AM
What's wrong with Kingstons (thanks btw  ;)) explanation? either use the default value of 33k, or match the resistor to "perfect" specs.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 23, 2009, 07:56:53 AM
33K is fine. the original T4Bs came with a resistor, but I don't know anybody who haven't received another value than 33K.

the nice description Kingston posted is indeed from SSLTech (can't find the thread now ...)
btw, this resistor is part of the gainreduction metering - the only thing what happens without calibration is:
your meter shows a gain reduction of 5dB, but in reality it might be 4 or 6dB.
Title: Re: D-LA2A Support Thread
Post by: stereokillah on November 23, 2009, 03:51:53 PM
i ve read this last message and i would to know.
my twwo dla2a have the same problem with Gr meter, after  all the calibration, the u + 4 is the same on the 2 vumeter but for the same compression on protools vu , the dla2a gr meter give me differents result , for exemple ine give -3 and the other -7 with stereo and dula mono.

if i put trimmer istead of TBD could i modified this problem
Title: Re: D-LA2A Support Thread
Post by: stereokillah on November 24, 2009, 05:52:28 PM
ok now on right channel there is a trimmer instead of the 33k TBD and after some calibration i've the same signal in the two vumeter in GR mode , buut now the pointer go to +2 some second before return to zerowhen i back the reduction to 0
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 24, 2009, 06:00:11 PM
you might work too fast for slow vintage circuits  ;)
Title: Re: D-LA2A Support Thread
Post by: stereokillah on November 24, 2009, 06:48:04 PM
in fact i'm happy to resolved this small problem, i'm building a third unit at time.

Great project.
Title: Re: D-LA2A Support Thread
Post by: Audioman on November 30, 2009, 10:00:09 AM
Hi All,
I'm looking for some tubes 6AQ5 for The D-LA2A but i have some difficult to find it
Can you please help me to find it ??
Let me know
Thank you
Fabio
Title: Re: D-LA2A Support Thread
Post by: rob_gould on November 30, 2009, 10:16:47 AM

There are lots on ebay

http://electronics.shop.ebay.co.uk/Vintage-Electronics-/14998/i.html?_nkw=6aq5&_catref=1&_fln=1&_trksid=p3286.c0.m282
Title: Re: D-LA2A Support Thread
Post by: pilot on December 04, 2009, 10:18:42 AM
Another is alive!

(http://img410.imageshack.us/img410/5618/front1ig.jpg)
(http://img146.imageshack.us/img146/7109/inside1r.jpg)
(http://img410.imageshack.us/img410/8289/inside2zy.jpg)
Title: Re: D-LA2A Support Thread
Post by: rob_gould on December 04, 2009, 11:41:13 AM


Good work!  Pretty neat :)

Can you tell us which transfomer combo you used? 
How is the gain on the unit?
Did you do do the 75k resistor / 25k pot mod?
Title: Re: D-LA2A Support Thread
Post by: bernbrue on December 04, 2009, 12:50:41 PM
Hi,
very nice built. You won´t be dissappointed in terms of sound, that´s for shure. Congrats!!
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on December 04, 2009, 01:08:34 PM
cool, have fun with it.
where did you get those T4Bs?
Title: Re: D-LA2A Support Thread
Post by: Kingston on December 04, 2009, 11:12:43 PM
a bit of info about the grid stoppers (those optional 1k resistors around 12BH7). I was asking about them long a go, but now I have all the info there is to them.

It has been said in the past one should use the grid stoppers when using Sowter 8940 output transformer, for example. It would otherwise oscillate.

It's not as simple as that. One can use those sowter outputs - even the more accurate utc A24 clone "sowter 1010" without grid stoppers.

You just have to calibrate C4 (feedback network high cut) accordingly. It should be replaced with a trimmer like Arco 465 (used in the originals as well). You get to tweak output high frequency response this way too.

The 300pF value might be too high for many builds, and too little low cut in the feedback network would result to oscillation. C4 to the rescue, tweak it down a notch.

Another choice is to knock down B+ some 10-20 volts. or use grid stoppers.

or do all of the above for bomb proof output gain stage.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on December 05, 2009, 04:53:23 AM
thanks for the explanation Kingston.

fyi, my first build (no grid stoppers on rev01 PCBs) works fine without grid stoppers and sowter output transformer.
it oscillated only at stupid high gain settings I would never need / use.
the "gain pot mod" solved it while bringing a better adjustable gain range.

the grid stoppers have been added to rev02 since they are hard to implement to rev01 builds, but are easily bypassed if you don't want to use them.

the reason why there is no C4 trimmer is: I didn't find any easily available in europe. the 300pF is a guessed estimate I read somewhere in the long LA2A threads, but can easily exchanged to other values.
Title: Re: D-LA2A Support Thread
Post by: Kingston on December 05, 2009, 05:31:34 PM
it oscillated only at stupid high gain settings I would never need / use.
the "gain pot mod" solved it while bringing a better adjustable gain range.

I suppose that's fine if you only ever want to use it as a compressor.

But LA2A is a great preamp/lineamp as well, with some 40-50dB of gain, depending on transformer choices. Full pot range needed for this obviously. Actually the 68k input series resistor can be bypassed for some 5-6dB of extra gain.
Title: Re: D-LA2A Support Thread
Post by: Silvas on December 05, 2009, 08:09:35 PM
it oscillated only at stupid high gain settings I would never need / use.
the "gain pot mod" solved it while bringing a better adjustable gain range.

I suppose that's fine if you only ever want to use it as a compressor.

But LA2A is a great preamp/lineamp as well, with some 40-50dB of gain, depending on transformer choices. Full pot range needed for this obviously. Actually the 68k input series resistor can be bypassed for some 5-6dB of extra gain.

For a while, i wanted to add switchable +48v to the inputs for that purpose....but nah, not now. Maybe later when i´m finished and the baby is running smoothly.

Title: Elma 24 step switch as Gain/Peak red alternative - need help to calculate
Post by: mjproc on January 08, 2010, 08:02:34 PM
Hi.  I have some Elma's, and see some builds with these...

The Elma's I've got is "break before make"...  I'm not shure if "make before break" is better

http://www.elma.com/Admin/ProductionFiles1/ProductTypeFile/371/English/13%20Selector%20Switch%20Type%2004.pdf 

I'm trying to understand and calculate the different values for each step... 
Can the list below be used ?  Adding 4kOhm in series pr step

Target value   100   kOhm
Numer of steps   24   
Value pr step   4,2   
      
step   kOhm   Result
1   4   4
2   4   8
3   4   12
4   4   16
5   4   20
6   4   24
7   4   28
8   4   32
9   4   36
10   4   40
11   4   44
12   4   48
13   4   52
14   4   56
15   4   60
16   4   64
17   4   68
18   4   72
19   4   76
20   4   80
21   4   84
22   4   88
23   4   92
24   4   96


Hope someone can help my head with this, and suggest prper values pr step

Brgds
Ole Peder
Title: Re: D-LA2A Support Thread
Post by: stereokillah on January 08, 2010, 08:57:21 PM
hello,
in Pm670 thread there is a link where you can calculate if log linear or rev log, this how many step you search and give you the good value.
Title: Re: D-LA2A Support Thread
Post by: mjproc on January 09, 2010, 04:59:41 AM
Exxelent !!! I very much would like it log  ;D

Thnx for the link, and thnx to the author of the excelsheet!!!
Title: What are GS101,102,201,202 ?
Post by: mjproc on January 24, 2010, 05:46:24 PM
Hi.

Stuffing my dla2a cards and wonder what these components are.. GS101,GS102,GS201,GS202

Not mentioned in the bom, so I just want to make sure if they are "normal" 0,6W MF resistors

Brgds
Ole Peder
Title: Re: What are GS101,102,201,202 ?
Post by: Kingston on January 24, 2010, 05:56:02 PM
Stuffing my dla2a cards and wonder what these components are.. GS101,GS102,GS201,GS202

They are the grid stoppers.

Read my posts above for a detailed explanation.
Title: Re: D-LA2A Support Thread
Post by: mjproc on January 27, 2010, 06:01:33 AM
Tried to PM you [silent:arts], but your inbox is full ....  Have you received the power trafo's for DLA2A yet?  Still interested in purchasing one or two.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 27, 2010, 07:07:10 AM
Tried to PM you [silent:arts], but your inbox is full ....  Have you received the power trafo's for DLA2A yet?  Still interested in purchasing one or two.
full again ...
yes, I have received 85 kg of transformers last friday. due to the weight my wife didn't want to bring them in the house. but they over-lived 10 hours on the street ;D ;D ;D

will send you a mail later.
Title: Re: D-LA2A Support Thread
Post by: bongolijus on February 05, 2010, 02:20:18 PM
Hi there,

I have few questions regarding this beuty. The first one, what actually the limiter response and stereo adjust trimpots do? I have plan to move these on the faceplate to make more useful. The other one, will the ecc802s tube will fit the 12ax7 situation?

Thanks!
Title: Re: D-LA2A Support Thread
Post by: Silvas on February 05, 2010, 10:32:42 PM
Hi there,

I have few questions regarding this beuty. The first one, what actually the limiter response and stereo adjust trimpots do? I have plan to move these on the faceplate to make more useful. The other one, will the ecc802s tube will fit the 12ax7 situation?

Thanks!

No need to move the stereo adj. to the front. There´s a calibration procedure somewhere.

RE the limiter response pot, i put those on the front panel on my DLA2A, and i love it !

Good luck !
Title: Re: D-LA2A Support Thread
Post by: bongolijus on February 06, 2010, 04:08:46 AM
Thanks Silvas.  Ok, I'll leave the stereo adj in the calmness :) But what it does? adds stereo wideness or what? What about ecc802s tube? any ideas?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on February 06, 2010, 04:39:32 AM
... What about ecc802s tube? any ideas?
I use ECC803s
Title: Re: D-LA2A Support Thread
Post by: flight on February 14, 2010, 08:06:59 AM
Hi All ,

Hey is this normal the T4B from dripelectronics do not fit on the Pcb ??
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on February 14, 2010, 08:17:44 AM
Hi All ,

Hey is this normal the T4B from dripelectronics do not fit on the Pcb ??

most people used Drips T4B, in an octal socket ;)
Title: Re: D-LA2A Support Thread
Post by: rob_gould on February 14, 2010, 09:42:48 AM
Hi All ,

Hey is this normal the T4B from dripelectronics do not fit on the Pcb ??

You might find Bernbrue's post on this page useful :

http://www.nrgrecording.de/nrg/viewtopic.php?t=405&postdays=0&postorder=asc&start=255

Title: Re: D-LA2A Support Thread
Post by: mjproc on February 16, 2010, 01:46:31 PM
Hi

Is the 6AQ5A the same as EL90 and 6005 ?  Is it direct replacements?  Tubetown has the el90..

(I've searched the forum for this...but couldn't fint the answer :) )
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on February 16, 2010, 03:06:07 PM
as far as I remember I use EL90
Title: Re: D-LA2A Support Thread
Post by: MJFTech on February 19, 2010, 05:54:05 PM
silent:arts, do you have any estimate on when the D-LA2A PCBs will be available again?

Best Regards,
B.

once I have written the terms of condition and all product descriptions I will open the web store.
the sooner the better, but I will need at least two more weeks ::)

I would also like to buy a couple dual-LA2A PCBs!  I have a two nice Purusha dual LA2A cases & have been waiting to find PCBs...
Marc
Title: Re: D-LA2A Support Thread
Post by: mjproc on March 02, 2010, 04:08:46 PM
NE-2 question...

I received the neon lamp from Elfa today: partno: 33-665-07

Neon lamp with wire ends.
Size: Ø4×11 mm For 110 V series resistor 56 kΩ
For 220 V series resistor 100 kΩ

Current rating: 0,25 mA
Voltage rating: 65 V ac

Will this do?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 02, 2010, 05:32:05 PM
looks fine to me
Title: Re: D-LA2A Support Thread
Post by: mjproc on March 02, 2010, 06:22:39 PM
Great!! Thnx for great support!!
Title: Re: D-LA2A Support Thread
Post by: Soeren_DK on March 19, 2010, 08:56:53 AM
Can I use any of the Hairball transformeres for the project?
http://hairballaudio.com/shop/index.php?cPath=24

Cheers
Soeren
Title: Re: D-LA2A Support Thread
Post by: mjproc on March 25, 2010, 08:47:58 AM
What's the best(safest) procedure to power on for the first time.....

I'm only missing the VU's to complete my 1st dla2a...what is the safest way to power on the first time?

Is it ok to power up with only pcb + powertrafo connected?  no tubes, xformers og T4B's, then measure the voltages (even tho it's without any load)

Don't want this baby to blow up with all the expencive parts attacked....(yeah I know.... no risk no fun)

Title: Re: D-LA2A Support Thread
Post by: kazper on March 25, 2010, 11:26:10 AM
You can always use a veristat and slowly bring up the power... But typically I check, check again and recheck and then plug it in.

Title: Re: D-LA2A Support Thread
Post by: Soeren_DK on March 29, 2010, 03:22:44 PM
Can I use 22UF/400V instead of 22UF/450V for the C1, C2, C3, C4, C171, C271, C172, C272, C173, C273, C174, C274

Cheers
Soren
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 29, 2010, 03:30:13 PM
Can I use 22UF/400V instead of 22UF/450V for the C1, C2, C3, C4, C171, C271, C172, C272, C173, C273, C174, C274
yes
Title: Re: D-LA2A Support Thread
Post by: crisotop on April 06, 2010, 08:49:46 AM
How critical is the "tubes touching the case lid in 2HE units"? Could I use a bit of insulating ribbon or similar on the case lid to prevent the 6aq5 from accidentally touching the lid? I already shortened the solder legs of the socket, but it's still a very tight fit?

Thanks!
Christoph
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 07, 2010, 05:36:02 AM
use lower stand offs ;)

there is no electronically problem if the tube touches the lid.
if you have it safe in your rack nothing will happen.
but if you have it outside the rack, someone smashing another piece of gear on top it could break.
Title: Re: D-LA2A Support Thread
Post by: crisotop on April 07, 2010, 06:23:31 AM
5mm standoffs + 250V Anode Voltage = Problem? But I get your point, will try to build a suspension ring for the upper part of the tube.

Thanks!
Christoph
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 07, 2010, 08:51:15 AM
5mm standoffs + 250V Anode Voltage = Problem? But I get your point, will try to build a suspension ring for the upper part of the tube.
if I recall correctly I used 5mm standoffs.
add some insulation material between the case an PCB (some plastic or cardboard stuff, like you find it in some commercial units to prevent you to touch PSU parts)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 07, 2010, 08:56:14 AM
Hi all,

Here is a link to my mostly complete BOM for US guys.

ftp://ftp.tradingtechnologies.com/tam/eric/BOM/USABOMLA2ASilentArt.xls

If anything is cheaper someplace other than in the new file let me know and I can get it changed.

ops link don't work   :(
any new link somwhere?

regards
with your amount of posts you should know how the internet works  ;D ;D ;D
this forum adds http:// to any uncoded link. http://ftp:// will never work :D
but this will work:
ftp://ftp.tradingtechnologies.com/tam/eric/BOM/USABOMLA2ASilentArt.xls (ftp://ftp.tradingtechnologies.com/tam/eric/BOM/USABOMLA2ASilentArt.xls)
Title: Re: D-LA2A Support Thread
Post by: mjproc on April 07, 2010, 09:16:12 AM
After final wiring last night, 4 times checking everything looks visual ok...... I finally fired up my dla2a !!! nothing blew, no smell, bulbs glows :-)

Have some small puzles to solve, but this is the fun part....  Sooooo nice to seee them tubes glow :-)

I have to read the theory of operation now......

(I'll post some pictures when I move it to the new 3U case (it's still inside the behringer case, with the behringer frontpanel) I tell you,,,, this behringer is heavily modded :-)
Title: Re: D-LA2A Support Thread
Post by: SIXTYNINER on April 07, 2010, 01:37:27 PM
with your amount of posts you should know how the internet works  ;D ;D ;D
this forum adds http:// to any uncoded link. http://ftp:// will never work :D
but this will work:
ftp://ftp.tradingtechnologies.com/tam/eric/BOM/USABOMLA2ASilentArt.xls (ftp://ftp.tradingtechnologies.com/tam/eric/BOM/USABOMLA2ASilentArt.xls)

thanks so much for the link,
also http://www.nrgrecording.de/nrg/viewtopic.php?t=405
and many others links of nrg site
don't "run" properly
....probably updating site
regards
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 07, 2010, 01:48:49 PM
non working links can always happen in this internet.
might be someone used a time-limited host for pics,
the domain went down (most of my older broken links are down since I gave up silentarts.net)
and this project (and most of the links etc) is more than 4 years old ;)

if you need any missing link previous hosted by me just ask.
nobody will go thru all those pages fixing links :D
(while I did exactly that once I moved my host ...)
Title: Re: D-LA2A Support Thread
Post by: mjproc on April 08, 2010, 06:33:53 AM
I have some problems I hope someone can help me with..

My dla2a dosn't seem to compress correctly.  I set the gain knob to approx the same gain as under bypass, then turn the peak red know clockwise.  Near full clockwise I can hear distorbtion applied and gives a rather nasty fuzzy output.  This applies to both channels.

Same thing happens when running the dla2a without T4B's.  So my unit works as an amplifier.

I've wired the heaters, measured the voltages on the tubes (tho a bit higher than the reference voltages from Silentarts)

Any1 seen this before?
Title: Re: D-LA2A Support Thread
Post by: mjproc on April 08, 2010, 02:10:47 PM
checked if the T4B received any signals (mounted the T4B without cover)

The T4B leds seem to work, at least the light "pumped" in sync with the signal and were influenced by the pots.

Tried to use a flashlight to see if there were any respobse on the vu in GR mode.  the VU moved "a bit" when lit upon.

Still fuzzy output.

I've tries several different tubes for V1 and V2, from Behringer to Telefunken.  Differs in gain, but no combinations seem to resolve the "fuzz"

Ahhh my head implodes
Title: Re: D-LA2A Support Thread
Post by: mjproc on April 12, 2010, 03:30:24 AM
Hope someone who knows the nature of la2a can help me...

Is it "normal" to have small amounts of "fuzz" / "hiss" when GR is full CW?  I've tried to turn Limit/response CCW and it seem to quiet up a bit the more ccw I get.

When I run signal through with small amount of gain, 45-50% GR it sounds quite good, and does compress.

Running drums through can be from nice warm -> hard, pumpin "trashy" sound.

What I fear is that I'm trying to tame the nature of this beast, thinking this and that is too much...
(I've never tried/heard an Original LA2A)

Brgds
Ole Peder
Title: Re: D-LA2A Support Thread
Post by: RedNoise on April 16, 2010, 03:29:04 PM
Hi all !
Cannot remember if this question's already been asked but :
Would 2W 5% Carbon resistors (ie : A.Bradley) sub 3W 1% metal film resistors???
Thanks!
Title: Re: D-LA2A Support Thread
Post by: oilcanstudios on April 18, 2010, 09:29:28 AM
its a drip, but she came out nice

Big KNOBS

(http://i275.photobucket.com/albums/jj320/fireinthefield/Picture003.jpg)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 18, 2010, 09:35:06 AM
nice, but mono & needs too much rack-space ;D ;D ;D
Title: Re: D-LA2A Support Thread
Post by: Soeren_DK on April 20, 2010, 12:05:53 PM
Anybody know if these tubes? Will they be a good choice for this project?

NEW Electro Harmonix 12bh7 Gold pins
Balanced Tungsol 12AX7 used readings 91/91
NOS Procomm 6aq5a


Cheers
Soren
Title: Re: D-LA2A Support Thread
Post by: Soeren_DK on May 01, 2010, 08:18:44 AM
Can I use this trafo?

Cheers
Soren
Title: Re: D-LA2A Support Thread
Post by: stereokillah on May 01, 2010, 11:38:50 AM
hi Soeren_DK , i've used Electro Harmonix 12bh7 in my 3 units , i 've tried Tungsol 12AX7 , sovtek 12ax7lps and 12ax7 JJ,
after some test i keep sovtek and JJ and let tungsol that give me a noise more important,

i don't know Procomm 6aq5a but like it's the good reference it's fine

Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 03, 2010, 09:06:07 AM
another one is born, look here[/quote]

(http://www.garage27.com/files/music/studio/DIY/d-la2a/d-la2a_frontSmall.jpg)

(http://www.garage27.com/files/music/studio/DIY/d-la2a/d-la2a_topSmall.jpg)

 (http://www.groupdiy.com/index.php?topic=29854.0)
Quote from: crisotop
Volkers infamous d-la2a design (building was a breeze + works perfectly after 1st power up). Used "original" Sowter clones (1009 + 1010) and stepped Elma switches for easier recall. (25k pot + 75k resistor is a must on these things and brings the gain in a useful range). Matched tubes, matched T4 cells = close to perfect stereo tracking. This unit is also quieter and has less hum than my mono 3RU La2a build (what a waste of rackspace). It's tough to fit the tubes in a 2U case, but it can be done.

(http://www.51xaudio.com/images/DLA2A-crisotop.gif)
 ;D ;D ;D
Title: Re: D-LA2A Support Thread
Post by: Soeren_DK on May 03, 2010, 04:30:20 PM
hi Soeren_DK , i've used Electro Harmonix 12bh7 in my 3 units , i 've tried Tungsol 12AX7 , sovtek 12ax7lps and 12ax7 JJ,
after some test i keep sovtek and JJ and let tungsol that give me a noise more important,

i don't know Procomm 6aq5a but like it's the good reference it's fine


Thanks...  :D :D :) ;) ;)

Cheers
Soren
Title: Re: D-LA2A Support Thread
Post by: crisotop on May 04, 2010, 12:50:01 PM
In my case it's the opposite, Tungsols give me the best noise performance, they have slightly more 50/100Hz hum, but "beatiful" with noise in the upper spectrum, whereas the JJs (regular + gold) tend to buzz in the higher frequencies (especially the higher priced gold edition).

My power trafo gets hand-warm (safe to touch), hope this is normal (probably already addressed somewhere in the thread)

cheers
christoph
Title: Re: D-LA2A Support Thread
Post by: mjproc on May 04, 2010, 04:01:26 PM
I'm having a problem with phase error ???
I initially thought it was related to my mixer setup, but after assembling some insert cables last night I still have phase error.  When inverting the return on my mixer, it seems to be "normal".  I've tripple checked my wiring and cables, measures and looks ok.

Could it be a faulty trafo wiring?  I use sowters, and in mono all seems fine, phase problem is only under stereo operation.

I'm soooo close now, please help me some1.....

Ole P
Title: Re: D-LA2A Support Thread
Post by: crisotop on May 04, 2010, 04:11:51 PM
Can't quite follow your problem? You've got phase cancellation between your left and right channel? Let's say you send a 1k sine into both channels they null out on your (equally loud) mixer return channels?
Title: Re: D-LA2A Support Thread
Post by: pacemaker on May 22, 2010, 05:21:02 AM
Hi Guys,
might be a dumb question ,
but is there a BOM for Volker D-LA2A ?
regards,
Francois
Title: Re: D-LA2A Support Thread
Post by: crisotop on May 22, 2010, 05:47:39 AM
write me a pm, I might be able to help. The "standard" components (resistors, pots, caps, etc..) aren't hard to find. It's tricky to get the t4bs and suitable tubes (the circuit is a bit picky about the tubes in the amp section).

cheers,
christoph
Title: Re: D-LA2A Support Thread
Post by: pacemaker on May 22, 2010, 06:20:34 AM
Hi Crisotop,
i allready have quite all parts,
just missing the resistors, they all seems to be 1/4w except a few 3w
and diodes, from D3 to D6, wich i haven't identified yet,
also the R125 "TBD" resistor ?
Title: Re: D-LA2A Support Thread
Post by: crisotop on May 22, 2010, 06:28:49 AM
For the Diodes 1-6 I used 1N4007, R125 is roughly 33K (but should be "to be determined" in circuit - I used the suggested 33k value, and my unit works without any noticable problems)

hth, christoph
Title: Re: D-LA2A Support Thread
Post by: pacemaker on May 22, 2010, 06:33:01 AM
Ok perfect,
i was studying at volker schematics and got the answer for D3 to D6,
but was missing the TBD resistor,
can you confirm me resistor wattage ?
cause a saw some partlists for LA2A with 1/2w resistor
I allready have quite all values but only in 1/4w ,
Title: Re: D-LA2A Support Thread
Post by: crisotop on May 22, 2010, 06:47:04 AM
I'm using "modern" 0.6W types - but as far as I recall Volker mostly used 0.25W types - maybe someone else can chime in on this?

christoph
Title: Re: D-LA2A Support Thread
Post by: Kingston on May 22, 2010, 06:55:29 AM
1/4 watt is fine, but it should really be a 50-100k trimmer instead. It's used to fine tune the T4B's. Keith (SSLTech) wrote about it extensively. Search the forum.

33k value was used by default on most original LA2A's, contributing to the "no LA2A sounds the same" myth.
Title: Re: D-LA2A Support Thread
Post by: pacemaker on May 22, 2010, 11:47:54 AM
thank you guys for the advices,
will use a trimpot in place of r125,
Volker if you can confirm that 1/4w resistors are ok,
i couldstart soldering instead of making a new mouser order.
Volker are you here ?
Regards
Francois
Title: Re: D-LA2A Support Thread
Post by: bkbirge on May 22, 2010, 04:11:20 PM
Hey guys, hope this is the right place, apologies if not. I just picked up a completed D-La2a that has silentarts rev 2.0 board in it from a guy in France (I'm in USA). Build looks good and he switched it over for 110v before he shipped. When I turned it on it immediately blew the 0.5a fuses so I replaced 'em with what I had which is 3a and I reseated the tubes. Now it turns on, looks fine (haven't listened yet) and I checked the voltage on the board: the 6v taps read 7v and the 250v taps read 300v, am I going to run into problems running this hot? I don't want to burn out the filaments and my mains voltage is actually higher than 110, more like 120-130v. I didn't see any adjustment on the boards so I assume it's down to having the right transformer. I've asked the seller but I don't think he's the guy who built it. Advice please?

Oh also wanted to ask, I've got Purusha's dual enclosure and on the back are punchouts for a selectable HPF sidechain but I didn't see anyplace on the PCB's, is this a separate board or a feature that was never implemented? It'd be fun to have that.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 24, 2010, 08:22:37 AM
Volker if you can confirm that 1/4w resistors are ok,
i couldstart soldering instead of making a new mouser order.
except of the 2W resistors I used 1/4W with no problems.

Volker are you here ?
sometimes - have been very busy the last few weeks :o
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 24, 2010, 08:38:47 AM
Hey guys, hope this is the right place, apologies if not. I just picked up a completed D-La2a that has silentarts rev 2.0 board in it from a guy in France (I'm in USA). Build looks good and he switched it over for 110v before he shipped. When I turned it on it immediately blew the 0.5a fuses ...
0.5A is fine with 230V, but needs to be doubled for 115V. use a 1.0A slow blow.

... the 6v taps read 7v and the 250v taps read 300v, am I going to run into problems running this hot? I don't want to burn out the filaments and my mains voltage is actually higher than 110, more like 120-130v. I didn't see any adjustment on the boards so I assume it's down to having the right transformer.
there is no adjustment, the schematic is exactly like the original. your problem is the non-standard 120-130V mains. you could try some high wattage resistors between the transformer and the PCB, like Kubi did in his D-AOC (http://www.groupdiy.com/index.php?topic=26585.msg322677#msg322677)

Oh also wanted to ask, I've got Purusha's dual enclosure and on the back are punchouts for a selectable HPF sidechain but I didn't see anyplace on the PCB's, is this a separate board or a feature that was never implemented? It'd be fun to have that.
I have never had any plans for such a feature. Might be his standard stereo 3U backplane.
Title: Re: D-LA2A Support Thread
Post by: Kingston on May 24, 2010, 09:25:23 AM
I have never had any plans for such a feature.

you already implemented it...

Oh also wanted to ask, I've got Purusha's dual enclosure and on the back are punchouts for a selectable HPF sidechain but I didn't see anyplace on the PCB's, is this a separate board or a feature that was never implemented? It'd be fun to have that.

That's just the 1meg trimmer/rheostat of the sidechain (R37), right next to C12.

You can play with the values in any way you like, try 0k, 500k and 1meg for starters...
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 24, 2010, 10:50:34 AM
I have never had any plans for such a feature.
you already implemented it...

that wasn't me ;) :D ;D
Title: Re: D-LA2A Support Thread
Post by: bkbirge on May 25, 2010, 12:54:57 AM
Thanks for the info and advice guys!
Title: Re: D-LA2A Support Thread
Post by: pacemaker on May 25, 2010, 06:43:38 AM
Thank you very much for confirming resistance wattage Volker !
let's solder this beast !
Title: Re: D-LA2A Support Thread, partlist needed for a mouser project file
Post by: pacemaker on May 25, 2010, 08:55:52 AM
I am preparing a mouser projet for D-LA2A;
it can helpfull for future builders,
does abyone has a partlist ?
regards,
Francois
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 25, 2010, 10:32:40 AM
Francois,

here you find bernbrues parts-list (http://www.nrgrecording.de/nrg/viewtopic.php?t=405&postdays=0&postorder=asc&start=8)
Title: Re: D-LA2A Support Thread
Post by: pacemaker on May 25, 2010, 02:15:59 PM
link is not working for me  :'(
Title: Re: D-LA2A Support Thread
Post by: bernbrue on May 25, 2010, 02:29:12 PM
Hi,
here it goes.

http://www.twin-x.com/groupdiy/albums/userpics/Part_List_LA2_rev01_Platinenlayout_Silent_Art.xls

regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: pacemaker on May 26, 2010, 09:06:58 AM
ok guys i got everything,
Frank's forum is not allways reachable for me,
don't know why.....
i was able to save the first page of the D-LA2A thread
wich contains all the info i needed.
Thank very much !!!
Title: Re: D-LA2A Support Thread
Post by: Soeren_DK on June 03, 2010, 02:05:52 PM
Is there any Lundahl trafos there will fit this project?

Cheers
Soren
Title: Re: D-LA2A Support Thread
Post by: Soeren_DK on June 14, 2010, 03:00:09 AM
Should I change any thing if I use Sowter 1010 output tranny?

Cheers
Søren
Title: Re: D-LA2A Support Thread
Post by: baadc0de on July 19, 2010, 08:53:21 AM
Assuming this thread isn't dead yet :)

I've seen it mentioned in the transformer meta, that an UTC a16 could be used for a la2a input. I see it has a very different impedance ratio as opposed to the a10. What I find asking myself is how would one wire these as la2a inputs? Do we need to change anything onboard to accomodate the UTCs?

Thanks,
B.
Title: Re: D-LA2A Support Thread
Post by: azone on July 28, 2010, 05:56:40 PM
I'm getting started on a build and I have a few simple questions.

1. I'm looking to use Hairball VU meters. I see there are (3) kinds on the website. They seem to be spec'd pretty much the same with the exception of some mechanical differences and LED versus lamps etc... I'm going to be building mine into a 2U case. Is there an advantage of any of the meters over the others other than looks? Will the lamps in the 3rd version run bright enough with the stock supply voltage?

The choices are
a) 8027-B VU Meter   
b) 027-WF VU Meter
c) Custom Hairball Audio FET Compressor VU Meter

http://hairballaudio.com/shop/index.php?cPath=25

2. I'd like to use a torroidal power transformer. I've seen a couple people using them. Where are you getting them? I assume they are custom wound because of the multiple/non-standard windings?

3. I'm putting together a US BOM as I go. There was a link but it doesn't work. Does anybody know the manufacturer/part # for all the connectors, I haven't found anything in my searches. I'd be happy to cross-reference to other manufacturers/Mouser part#'s if I could get the specs.

Cheers, Brian.
Title: Re: D-LA2A Support Thread
Post by: Silvas on July 28, 2010, 06:45:54 PM
I used an Antek 1T250 for the heaters and HT. Had to use a second small toroid for the other PSU, but i think you can use a 12v one, and a 7812 regulator and 12v relays, so you can run the VU lamps.

 
Title: Re: D-LA2A Support Thread
Post by: azone on July 28, 2010, 07:26:34 PM
Quote
I used an Antek 1T250 for the heaters and HT. Had to use a second small toroid for the other PSU, but i think you can use a 12v one, and a 7812 regulator and 12v relays, so you can run the VU lamps
got it. thanks.
Title: Re: D-LA2A Support Thread
Post by: azone on July 28, 2010, 10:54:30 PM
I have a couple more questions

1. Tube sockets. I've read through all the threads here an the one on nrgrecording forum and I can't figure out what tube sockets are required. I'm stuffing it into a 2U rack so it may be important choice for the lowest profile. Anyone got any idea on part #'s? I tried to figure it out from the german BOM but no luck. 

2. Is a socket needed for the T4B?
Title: Re: D-LA2A Support Thread
Post by: azone on August 11, 2010, 02:59:53 AM
--------------------------------------------------------------------------------------------------------------------------------------------------
August 11 2010 [Note: I rearranged this thread for oldest-post-first, makes more sense to newcomers]

I'm going to start a mini-blog of my build here. I think maybe it will some other people who are trying to get all the pieces together and get one built. Especially for the guys in the US I will be putting together a BOM.
Aside from this forum thread I found most of the parts list by cross referencing the PCB layout with the LA2A schematic and the Drip Audio BOM. The most difficult part is double checking the PCB footprints of all parts so that they fit silent:arts PCB. I will be adding notes in detail as I go along.

Things I haven't ordered yet

1. Power transformer [undecided]
2. 0.1uF polypropylene caps
3. 12BH7A & 6AQ5A tubes [undecided]

Things that haven't arrived yet

1. (2) 24-position switches [diypartssupply.com / part #Elma 24 position rotary]
2. 2U Enclosure [par-metal.com / part #10-19113B]
3. (2) input transformer [edcorsa.com / part #WSM600/15k]
4. (2) output transformer [edcorusa.com / part #WSM15k/600]
5. (4) Arco 46-series Trimmer Capacitor [surplussales.com / part #(CTM)465]

Parts on-hand
1. T4B [acquired pair of NOS for decent price]
2. Resistors, caps, connectors, relays [most already on-hand, rest from Mouser, BOM to come]
3. (2) 100k potentiometers [Digikey]
4. Tube sockets [tubedepot.com]
5. (2) VU meters [hairballaudio.com / part #HB-8037]

Things I still need to complete the main PCB
1. 0.1uF polypropylene caps. I still need four. I have various mallory, vishay etc.., but most are >20mm long and don't fit the footprint which is meant for a Solen.
2. Install sockets for the 6AQ5A's. I am going to have to trim the leads on these. I'm going to wait until the enclosure arrives to determine exactly how much I need to.  
3. Install heater wires. I will do this last, before the last time I clean the PCB.

Thanks everyone for sharing all the knowledge here on the forums, I've been able to pick around and find most of what I need. Also thanks to crisotop for answering my PM's regarding some specific details.
As probably everyone who has completed one of these already knows the hard part of this clone is not actually building it, it's ordering all the correct parts, options, etc.. and managing the build!  
As I mentioned above I will be uploading a US BOM shortly as I get all the info together.   click on images for link to large versions

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-1sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-1.jpg)

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-2sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-2.jpg)

--------------------------------------------------------------------------------------------------------------------------------------------------
August 12 2010

A few notes on stuffing the PCB.

1. I used 1/2W resistors throughout (except where 3W required). The board was laid out for 1/4W so it can be a tight fit in some cases. I used 1/2W because I had them and the original used them, although I didn't simulate the circuit or anything so it's very likely 1/4W is ok as has been used by many. Just be careful if using 1/2W it'll be tight, see pics below.
2. The PCB footprint for the 3W resistors is short for most 3W resistors you will find. No problem, you'll just need to stand them up on one end as you can see below (and in many other peoples builds).
3. About the front panel I'm having one made by front panel express. I'll share it when I'm done.

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-3.jpg)

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-4.jpg)

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-5.jpg)

--------------------------------------------------------------------------------------------------------------------------------------------------
August 13 2010

I ordered the power transformer(s) today. I'm using two to avoid having to have a custom made.
1. Antek AN-IT250, 100VA, 250V @ 0.20A + 6.3V @ 3A. This will power the main circuit and the heaters.
2. Antek AN-0012, 5VA, 12V @ 0.20A. This will power the relays (12V version) and the VU meter lamps which are also 12V.  

I also finally ordered the 0.1uF Solen caps while placing another order from tubedepot.com, as well as some of those nice antique style knobs they have.
I also bought some NOS RCA tubes for the 12BH7A and 6AQ5's.

--------------------------------------------------------------------------------------------------------------------------------------------------
August 21 2010

1. power transformers came in. Not crazy about the big 100VA torroid, way overkill for the application, might try to find one lying around at work that'll give me more space and help me keep it out of the way from the PCB.
2. audio transformers are due early next week, they are the Edcor 2x WSM600/15k, 2x WSM15k/600.
3. Elma 24 position rotary's are also due next week. I decided to use them for all four controls.
4. last of the caps and other remaining parts came this week.
5. Par-metal enclosure came this week, www.par-metal.com, part #10-19113x, price is good and has vents.

I was able to test the height of the setup in the 2U enclosure. Even with generous 1/4" standoff's I still have a good 1/4" space at the top of the enclosure. The Par-metal enclosure is a six-sided type, and typically gives the most height from top & bottom since the top & bottom panels screw over the end panels so there is no wasted height. I have not tested whether the top panel can deflect enough to touch the T4B's and the 12BH7's (they are at about exactly the same height). I trimmed both sides of each lead on the 6AQ5 sockets as shown in the picture below but I didn't trim the leads for the 12BH7's. The second picture below shows the clearance looking from the front of the enclosure (click for larger image).

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-6sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-6.jpg)

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-7sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-7.jpg)

I also soldered the heater wires. One of the 6AQ5 sockets is not soldered in yet so you can see there's a few wires not connected there yet.

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-8sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-8.jpg)

--------------------------------------------------------------------------------------------------------------------------------------------------
August 27 2010

1. Still waiting for a lot of parts to come in. No problem though, still a lot to do.
2. A few changes have come up. I want to make a point to point out any changes or troubles that come about. It's not all as easy at it can look sometimes. The toroid power transformer from Antek was huge, 100VA huge, and I didn't want to deal with it and have to have the smaller toroid in there as well. It would be an unnecessary pain. It occurred to me that Volker may have some custom Toroids still, and he does! so I ordered one. The price is very fair for a custom wind that's perfect for the application. Also, I ordered another enclosure. I found the Par-Metal 10-19113 was a little short at 11" depth, making things tight. I purchased the next larger model, part# 10-19143. It's 14" deep. I was very happy with the quality of the par-metal part, and the service I've been getting from the Par-Metal/Antek guys has been good. Now I'll have to do another project with the original case ;)
3. Here's what the Edcor transformers look like. Yeah I know, boring, but size, shape, layout may help someone out who's planning a D-LA2A in the future. (click for larger image)

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-9sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-9.jpg)

4. I'm working on the first-pass front panel. Here's what the rough 1:1 layout looks like right now. I'm going to implement an active wet/dry mix control so that's what the middle knob is for.
Those big knobs are from Eagle plastics, I bought them at Mouser, part# 45KN014-GRX.
The smaller knob and pilot light is from www.tubedepot.com part#'s P-SAK, P-PL-JEWEL, & P-PL-FENDER-STYLE

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-10sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-10.jpg)

--------------------------------------------------------------------------------------------------------------------------------------------------
September 1 2010

1. VU Meter LED retrofit
At the time I bought the meters from www.hairballaudio.com they were only available with 12V lamp. Since the D-LA2A has an auxiliary 5V supply for the meter back-lighting and mechanical relays it makes more sense to go with something powered by 5V. Using LED's seemed the best bet since you can get any color variation and you'll never have to worry about replacing lamps. I emailed Mike @ Hairball to inquire about how the manufacturer retrofits LED's into the meters. The ones they sell have two LED's wired in series as shown below:

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-15sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-15.jpg)

Since the D-LA2A supplies 5V to the meter back-light (fairly low voltage) you may want wire the LED's in parallel so they can reach desired brightness. Since most LED's have ~2V forward voltage, two in series would be ~4V and the brightness would not be enough even with no series resistor. Basically, either wire two typical LED's in parallel and calculate the appropriate series resistor, or use specific 5V LED's with low reverse breakdown voltage with an appropriate series resistor and they will work. I used two 5mm clear amber LED's for each lamp housing and it worked very well, the brightness is uniform over the whole meter. For best uniform coverage of the VU meter it's best to use clear LED's (not diffuse) and to angle them at 90 degrees towards the back of the VU Meter as you can see in the pics:

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-14sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-14.jpg)


(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-13sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-13.jpg)

2. Elma 24-position switches [edited]
I installed the resistors to the Elma switches. Two of them are set for 100k log and two for 33k log (to be used in series with 68K resistor for less gain).
If you haven't used switches like this before where you add your own resistors etc.. it can be confusing.
a) Look at it as a potentiometer, a voltage divider, since this is what it is anyway, a stepped attenuator. Check out this Elma schematic from the Goldpoint Level controls website http://www.goldpt.com/schm_ser.html

(http://alphazone1.com/x0xi0/web_images/la2a/elma_rotary_schematic.gif)

b) Realize that the end-stop is before position 0, and the first resistor R1 should go at position 0.
c) The marking on the Elma part shows 0 to 22. These marking fall between switch positions and can be thought of as resistor numbers. There will be (23) resistors total when completely fitted.
d) Use silent:arts log-pot-to-switch excel document to calculate the resistor values.. http://www.silentarts.de/DIY/PM660/LogPotToSwitch.xls

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-12sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-12.jpg)

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-11sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-11.jpg)

--------------------------------------------------------------------------------------------------------------------------------------------------
September 12 2010
Just a quick update, no pictures.
1. I've got everything hooked up and have done some quick tests. everything is working.
2. I will be adding some details and pictures soon.
3. currently I am using a temporary front panel and the Edcor transformers.
4. I am sending out to have a custom panel made. It will be a good 3-4 weeks before it comes back.
5. I got a hold of a UTC HA-100x, A-24, and A-25. All were in a cinema preamp & effects switcher I found while scouring Ebay. I picked up the whole thing for relatively cheap, I'll most likely sell the A-25 and compare the original HA-100/A-24 versus the Edcors. When the time comes I'll take a bunch of audio samples and measurements on my Audio Precision system to compare them.
6. I'm almost complete with a very detailed US BOM. I'll upload it and to link to it very soon.

--------------------------------------------------------------------------------------------------------------------------------------------------
September 14 2010
I posted the US BOM further down in this thread but here it is again...
D-LA2A US BOM (XLS) (http://alphazone1.com/web_links/d-la2a_bom.xls)
D-LA2A US BOM (PDF) (http://alphazone1.com/web_links/d-la2a_bom.pdf)


--------------------------------------------------------------------------------------------------------------------------------------------------
September 26 2010
Just a quick update. no new news yet, still a lot of updates, finished details to update soon.
Title: Re: D-LA2A Support Thread
Post by: rob_gould on August 11, 2010, 04:38:14 AM

Good work.  I really need to get cracking with this too.  I have case, transformers, meters and PCB fully stuffed too so there are no excuses really.

Looking forward to see how your build progresses.  What are your plans for a front panel?
Title: Re: D-LA2A Support Thread
Post by: baadc0de on August 26, 2010, 03:03:25 AM
I have obtained the custom power transformer for dla2a quite some time ago..

Connecting it like this:

yellow        -> 220v (mains)
white         -> link to other yellow
other white -> 220v (mains)

I get 0.2V AC on the 250V taps and ~0.04V AC on others. Is the transformer dead? Or have I just miswired it?

Cheers,
B.
Title: Re: D-LA2A Support Thread
Post by: stereokillah on August 26, 2010, 08:25:46 PM
is your transformer conected to the board? if yes try disconected, if not your wiring seems to be fine check a new time.
Title: Re: D-LA2A Support Thread
Post by: baadc0de on August 27, 2010, 04:58:43 AM
Ugh! Cold solder joint on the voltage switcher.. didn't actually connect the two sides together, oops. Works now, I get proper voltages on the terminals. When connected for the first time, I heard a faint pop, but the neeons and first row of tubes have lit up. The other row has shields, so I didn't see with all the reflections if they really lit up and i'll check that in the dark today.

Incidentally, how do you bypass this unit (I have the white PCBs)? There seem to be relays on board, what are they switched with? I found no bypass switch pads.. do you switch the 5V  to the relays?

Cheers,
B.
Title: Re: D-LA2A Support Thread
Post by: stereokillah on August 27, 2010, 06:54:06 AM
(http://i296.photobucket.com/albums/mm171/renbis/DIY/TARGET__LA2_rev01_Platinenl-1.gif)
should be help you

Title: Re: D-LA2A Support Thread
Post by: baadc0de on August 27, 2010, 08:19:42 AM
should be help you



Thanks! yes, it's clear now..
Title: Re: D-LA2A Support Thread
Post by: baadc0de on August 27, 2010, 04:40:05 PM
I'm wiring UTC A-16 as inputs and A-24 as output (I have only one though).

The A-16 is a 15k : 60k transformer, with P and B pins on the primary and 60k G and F pins on the secondary and a pin that has the ground symbol. That said, how should I wire it in a DLA2A?

 - P to Brown
 - B to Green
 - G to Blue
 - F to Grey
 - Ground to Black

The A-24 is more complex, with pins numbered 1 through 10 and a ground symbol pin. It's primary is 15k on pins 7 and 10, when pins 8 and 9 are joined. The join has a "CT" annotation with it.

For 500Ohm secondary operation (probably what I want, right) the pins 1 and 6 carry the signal when 3 and 4 are joined. This join has "CT" as well. So this gets a bit more tricky for me..

 - join 8 and 9
 - yellow to 7
 - green to 10
 - join 3 and 4
 - grey to 1
 - pink to 6
 - black to ground

This is a bit confusing... thanks in advance to someone who can help!

Also, since I have no output transformer yet for one channel, can I just not run that channel by not having tubes and t4b populated in that half?

Cheers,
B.
Title: Re: D-LA2A Support Thread
Post by: baadc0de on August 28, 2010, 06:05:42 PM
It works... now I need one more A-24, cut the front and back panels and shield the audio cables that I didn't care to for this "wiring" experiment.

The photos:
(http://farm5.static.flickr.com/4098/4936076434_4c3deaee8a_b.jpg)

(http://farm5.static.flickr.com/4077/4936076650_b1f874e22a_b.jpg)

EDIT: this things rocks on vocals and bass and guitars ... but you know that already :P
Title: Re: D-LA2A Support Thread
Post by: buschfsu on August 29, 2010, 04:43:14 PM
guys i only want to build one channel with this board.  do i have to modify the psu for the reduced current load or will it be fine.
thanks
Title: Re: D-LA2A Support Thread
Post by: baadc0de on August 29, 2010, 05:39:39 PM
guys i only want to build one channel with this board.  do i have to modify the psu for the reduced current load or will it be fine.
thanks


works fine with one channel populated here (no tubes or t4b on the left channel)... the regulator gets really hot though, but it's been running well for 2 days, several hours per day.. don't know if this is a permanent solution, but it works for me. I'll be populating the rest though when I get another output transformer.
Title: Re: D-LA2A Support Thread
Post by: baadc0de on September 01, 2010, 09:16:52 AM
I haven't done any sweeping yet (have to get rightmark..) but with an a-24 at the output do I need termination?

EDIT: Well, actually...

(http://farm5.static.flickr.com/4133/4949095881_69c0dd622c_b.jpg)

This looks pretty good, no? I get a good bit of 50cycle hum, but that's just my sloppy experimental wiring.
Title: Re: D-LA2A Support Thread
Post by: tomcat on September 03, 2010, 02:53:44 PM
What makes me wonder. Somewhere (i believe old drip docs) it was recommended to use for the pots and trimmers 2watt types!?

So just overkill there or budget/underkill here?
Title: Re: D-LA2A Support Thread
Post by: benlindell on September 11, 2010, 02:35:48 PM
Hey guys, I'm starting to wire my first unit up. Couple Questions before I get too far:

1. The Gain and Peak pots, I assume the wiper is in the middle on the board, I usually use the shield for the wiper.

2. The Stereo Link switch, I just connect the left pin of each one together with a switch, and the right straight to each other?

3. the GAIN RED switch toggles Gain Reduction and Output I assume

I think that's it for now, thanks for all the help guys.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 11, 2010, 02:44:58 PM
1. The Gain and Peak pots, I assume the wiper is in the middle on the board, I usually use the shield for the wiper.
the Molex connectors have the same pin numbers like a potentiometer in that place.
use the shield for pin one, it is connected to ground anyway.

2. The Stereo Link switch, I just connect the left pin of each one together with a switch, and the right straight to each other?
yes - the right pin is ground

3. the GAIN RED switch toggles Gain Reduction and Output I assume
true
Title: Re: D-LA2A Support Thread
Post by: EHOFFA007 on September 11, 2010, 02:50:44 PM
Does anybody have the US builders BOM that was put together for this?
Also, what's the best place to source a prefab case in the US?
Thanks all
Title: Re: D-LA2A Support Thread
Post by: benlindell on September 11, 2010, 03:32:47 PM
1. The Gain and Peak pots, I assume the wiper is in the middle on the board, I usually use the shield for the wiper.
the Molex connectors have the same pin numbers like a potentiometer in that place.
use the shield for pin one, it is connected to ground anyway.

2. The Stereo Link switch, I just connect the left pin of each one together with a switch, and the right straight to each other?
yes - the right pin is ground

3. the GAIN RED switch toggles Gain Reduction and Output I assume
true

Cool, Thanks, I'm a little confused with the pin numbering, my boards don't have any numbers on them.
Title: Re: D-LA2A Support Thread
Post by: tomcat on September 11, 2010, 04:24:48 PM
What makes me wonder. Somewhere (i believe old drip docs) it was recommended to use for the pots and trimmers 2watt types!?

So just overkill there or budget/underkill here?

Volker, can you enlighten me? ;)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 11, 2010, 04:33:32 PM
Cool, Thanks, I'm a little confused with the pin numbering, my boards don't have any numbers on them.
true, no pin numberings on the PCB. left side is one, middle is two, right side is three.
if you are unsure, ohm out pin 1 with your meter.

Volker, can you enlighten me? ;)
sure. 2W is overkill. my unit (1/4W resistors, 1/2W potentiometers) works with no problems for years now.
the potentiometers carry just standard audio line-level signal.
Title: Re: D-LA2A Support Thread
Post by: benlindell on September 11, 2010, 10:06:59 PM
I think I got it, right?
Title: Re: D-LA2A Support Thread
Post by: benlindell on September 11, 2010, 10:08:04 PM
and
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 12, 2010, 02:34:51 AM
Ben, it is the correct numbering for the Molex connector, but the potentiometer should be the other way around.
Title: Re: D-LA2A Support Thread
Post by: stereokillah on September 12, 2010, 06:07:31 AM
benlindell check it, on the draw for the shielded wire the black is the shield so the 1
http://www.groupdiy.com/index.php?topic=32677.msg503869#msg503869 (http://www.groupdiy.com/index.php?topic=32677.msg503869#msg503869)
Title: Re: D-LA2A Support Thread
Post by: azone on September 12, 2010, 06:32:10 AM
Quote
Does anybody have the US builders BOM that was put together for this?
I have a very detailed US BOM I will be uploading shortly. I won't get to finishing it this weekend - most likely monday it will be posted here...
Title: Re: D-LA2A Support Thread
Post by: benlindell on September 12, 2010, 11:20:40 AM
benlindell check it, on the draw for the shielded wire the black is the shield so the 1
http://www.groupdiy.com/index.php?topic=32677.msg503869#msg503869 (http://www.groupdiy.com/index.php?topic=32677.msg503869#msg503869)
awesome, I forgot that you'd posted that, that's super helpful
Title: D-LA2A Support Thread
Post by: azone on September 13, 2010, 08:11:55 PM
D-LA2A US BOM (XLS) (http://alphazone1.com/web_links/d-la2a_bom.xls)
D-LA2A US BOM (PDF) (http://alphazone1.com/web_links/d-la2a_bom.pdf)
Title: Re: D-LA2A Support Thread
Post by: JamesW on September 13, 2010, 09:20:40 PM
Thanks for this azone the D-la2a is on my to do list
Title: Re: D-LA2A Support Thread
Post by: EHOFFA007 on September 13, 2010, 09:40:05 PM
AZONE=The MAN!!!
Thx
Title: Re: D-LA2A Support Thread
Post by: benlindell on September 16, 2010, 08:52:34 PM
I finished wiring up one side of my D-La2a and I'm not getting any signal. I traced the signal around and it's getting to the peak reduction pot, the gain pot and the t4b. the 12bh7 and 6aq5a are glowing but the 12ax7s are not. I checked and they are getting 6.7V at the heaters, Any ideas? I am using NOS russian 6n2p's which are supposed to be 12ax7 replacements.
Title: Re: D-LA2A Support Thread
Post by: benlindell on September 16, 2010, 09:58:16 PM
ahh... looking deeper, the 6n2p tubes have a different heater pins.
Title: Re: D-LA2A Support Thread
Post by: benlindell on September 16, 2010, 10:15:33 PM
And I found a pair of 12AX7s. this thing sounds awesome!!! Trying both the fast and slow drip cells, I can't decide, they are both great.

So troubleshooting, I thought I wired my gain pot for 75k+25k pot but I can get past 1 with it, I must have messed something up. I put the 75k between the wiper and the wire that goes to pin 2 on the PCB
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 17, 2010, 02:10:53 AM
Ben, put the resistor to Pin 3, not the wiper
Title: Re: D-LA2A Support Thread
Post by: pH on October 03, 2010, 02:33:46 PM
Transformer question here:
I'm using a transformer that has one 6.3v heater winding at 3A and a 12.6vct winding at 2A. If I only use half of the 12.6v winding (for just the 6AQ5s) is the rating then only 1A?
Title: Re: D-LA2A Support Thread
Post by: shabtek on October 03, 2010, 04:14:36 PM
pH, no it should still be 2A
Title: Re: D-LA2A Support Thread
Post by: pH on October 03, 2010, 05:10:39 PM
Thanks!
Title: Re: D-LA2A Support Thread
Post by: tomcat on October 04, 2010, 03:05:24 PM
And I found a pair of 12AX7s. this thing sounds awesome!!! Trying both the fast and slow drip cells, I can't decide, they are both great.

Both, make them switchable
Title: Re: D-LA2A Support Thread
Post by: pablobolche on October 06, 2010, 12:47:16 PM
Hi I am looking for the power transformer for my DLA2A. I have gone through the thread and can`t find the characteristics for this trafo, on the great azone us BOM it states only the primary specs 2x110v. Somebody please give me the rest.
thanks
Title: Re: D-LA2A Support Thread
Post by: pacemaker on October 24, 2010, 12:06:23 PM
Hi guys,
i am finishing a D-LA2A with sowter inputs and edcor wsm 10k/600 output,
i'm trying to calibrate the vu meter but when i send a 1V 0DBV from my generator,
and when i set the gain so as i get 0db on the vu meter, i got 2,80v output
is this the normal behaviour of the LA2A, ie can't get unity gain ?
or do i have a problem ?
if there's no problem, is there a way i can increase the meter resistor to get 0db in 0db out on the meter ?
regards,
Francois
Title: Re: D-LA2A Support Thread
Post by: pacemaker on October 26, 2010, 08:49:27 AM
bump
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on October 26, 2010, 11:02:51 AM
...
i'm trying to calibrate the vu meter but when i send a 1V 0DBV from my generator,
and when i set the gain so as i get 0db on the vu meter, i got 2,80v output
is this the normal behaviour of the LA2A, ie can't get unity gain ?
or do i have a problem ?
if there's no problem, is there a way i can increase the meter resistor to get 0db in 0db out on the meter ?

Francois, this is a standard VU meter. with a standard (external) 3k6 resistor it will read 0VU = 1,2277V(rms).
the D-LA2A can get set to unity gain:
feed it with +4dBu, set the gain to read 0VU at the meter, and you will get +4dBu at the output (with gain reduction set to zero for sure)
Title: Re: D-LA2A Support Thread
Post by: pacemaker on October 26, 2010, 11:22:44 AM
Hi Volker,
thanks for your answer,
i've just tried again, and with a 1.22V signal sent to pin 2 ( unbalanced )
with my generator  to the LA2A
if i adjust gain pot to get 1.22V output at pin 2
my meter, wich is an hairball audio, is reading -6VU,
is that a problem caused by the unbalance connection,
is it just a meter resistance adjustment,
or do i have a problem elsewhere and should investigate further ?
Thanks for your help,
Francois
Title: Re: D-LA2A Support Thread
Post by: creal on October 26, 2010, 11:38:24 AM
I have a stupid question. i' just started my DLA2A and i saw the PCB is printed from each side. I don't know if the component need to be soldering from each side??

When i soldering a component on a side,  i don't saw a solder everytime from the other side. Some hole stay white? it's normal or it need to sodering the side too?

Thx for your help
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on October 26, 2010, 12:18:21 PM
Francois,

this is transformer balanced, and the missing 6dB indicates one leg is missing ;)
connect your unbalanced generator between pin 2 & 3, measure the output between pin 2 & 3, nothing shorted to GND (or pin 1)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on October 26, 2010, 12:20:47 PM
When i soldering a component on a side,  i don't saw a solder everytime from the other side. Some hole stay white? it's normal or it need to sodering the side too?
soldering one side is fine (but with a good soldering technique the solder flows up to the other side ;))
Title: Re: D-LA2A Support Thread
Post by: creal on October 26, 2010, 12:49:28 PM
thx Volker, it's my first double side release ;)
Title: Re: D-LA2A Support Thread
Post by: pacemaker on October 26, 2010, 12:52:15 PM
It works, amazing volker !
i love this forum,
you can learn everyday !!
thank you very much for your help
and for bringing us this awesome project
Best regards
Francois
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on October 27, 2010, 04:11:45 AM
Francois, now we want to see some pics ;) :D ;D
Title: Re: D-LA2A Support Thread
Post by: pacemaker on October 27, 2010, 05:32:25 AM
Yeah !!
for now it's in use for a recording session,
but i will do that when it will be available,
( after cleaning the messy wiring ;-)
I would also like to put some TVA atom or mallory TC72 in place of the solen MKP,
and try to make a gain mod to get line level and mic level on a switch,
was thinking of using 25K pot and a switch to add a 75k resistor,
i have to calculate how much gain rannge i will have with only the 25k pot,
thanks for this project and all the others Volker !!
Regards,
Francois
Title: Re: D-LA2A Support Thread
Post by: AMZ-FX on November 18, 2010, 06:56:14 PM
Since the D-LA2A supplies 5V to the meter back-light (fairly low voltage) you may want wire the LED's in parallel so they can reach desired brightness. Since most LED's have ~2V forward voltage, two in series would be ~4V and the brightness would not be enough even with no series resistor.

No, the current through the LEDs determines brightness...  most LEDs can only handle 20ma max, so if we are using 5v power and put the two LEDs in series, a 62 ohms resistor would do the job, giving us around 17ma through the indicators.  You could go as low as 56 ohms for the current limiting resistor but any lower will shorten the life of the LEDs.

The backlight connection would be: +5v --> LED1 --> LED2 --> 62 ohm resistor --> Ground.

LED resistor calculator (http://www.muzique.com/schem/led.htm)

regards, Jack
Title: Re: D-LA2A Support Thread
Post by: ruckus328 on November 18, 2010, 09:04:31 PM
Hey guys, wondering if someone can help me here, having the same problem as pablobolche.  Some info on a power transformer would be much apppreciated, BOM doesn't really give anything useful.  Looks like something like this would kinda work:

http://www.antekinc.com/details.php?p=47

but doesn't get me the 5 volts for the relays.

Other thing I'm a little fuzzy on but think I've figured out ia the grounding scheme on this thing.  Looks like both of the 5V 2 pin headers on the L&R channels get jumped over to the 5V 2 pin header by the 5V regulator.  OK, good there.

Then there there's a set of 2 nonlabeled ground holes with a silkscreened line on them on the Left & Right channels in between the sowder 4383 connector and relay.  There's also a 3rd one over by the 3300uF cap by the 5V regulator.  I'm assuming each of these points wire to the star ground.  Why 2 ground holes in each one of these though?  Just want to make sure I'm not missing something here.
Title: Re: D-LA2A Support Thread
Post by: pH on November 18, 2010, 10:54:50 PM
Oops, sorry there Ruckus, forgot about those relays. I never use bypass relays so the Antek worked well for me.

-Paul
Title: Re: D-LA2A Support Thread
Post by: kazper on November 18, 2010, 11:50:11 PM
Hey guys, wondering if someone can help me here, having the same problem as pablobolche.  Some info on a power transformer would be much apppreciated, BOM doesn't really give anything useful.  Looks like something like this would kinda work:

http://www.antekinc.com/details.php?p=47

but doesn't get me the 5 volts for the relays.

Other thing I'm a little fuzzy on but think I've figured out ia the grounding scheme on this thing.  Looks like both of the 5V 2 pin headers on the L&R channels get jumped over to the 5V 2 pin header by the 5V regulator.  OK, good there.

Then there there's a set of 2 nonlabeled ground holes with a silkscreened line on them on the Left & Right channels in between the sowder 4383 connector and relay.  There's also a 3rd one over by the 3300uF cap by the 5V regulator.  I'm assuming each of these points wire to the star ground.  Why 2 ground holes in each one of these though?  Just want to make sure I'm not missing something here.


I'm sure that Antek will work, and you could use one of there smaller VA transformers to cover the 5V.
http://www.antekinc.com/details.php?p=7

As far as the grounds,  they were each made to use a spade type connector that exited towards the back. I think the design is that of a single PSU and 2x la2a circuits hence the 3 grounds as you discussed.If your flying leads use either.. but you probably know that...
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 19, 2010, 07:37:18 AM
grounding (http://www.nrgrecording.de/nrg/viewtopic.php?t=405&postdays=0&postorder=asc&start=3)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 19, 2010, 11:38:10 AM
My PSU transformer specs:

Prim:   2x115V   60VA
Sec1:   250V   0.05A
Sec2:   250V   0.05A
Sec3:   6.3V   2.00A
Sec4:   6.3V   2.00A
Sec5:   9V   1.00A
Screen:   Cu Foil
Dimensions:   85mm x 39mm
Weight:   0.95 kg
ta 40/E 50/60Hz n. EN 61558

I have them in stock (EUR 36,60 + VAT if necessary),
but shipping costs to the US would be EUR 26,05 :o
Title: Re: D-LA2A Support Thread
Post by: electrisizer on November 22, 2010, 06:02:54 AM
hi volker,
i have some edcors wsm 15k/600 for the output - do you have a european source for some input trafos? tonydb does not distrtibute edcors any more...

so... have you tried with your haufe 1:1 like mentioned earlier in the thread?

i have the original pot/resistor values so 1:1 would perhaps be good anyway  :)
Title: Re: D-LA2A Support Thread
Post by: EHOFFA007 on November 29, 2010, 05:24:36 PM
Hey,
Trying to wire four UTC A-26's as input and output transformers. This is my first build ever and I'm sure the info is on the the thread somewhere just can't seem to find it>
I found this a few pages back for output wiring of a A-24:

- join 8 and 9
 - yellow to 7
 - green to 10
 - join 3 and 4
 - grey to 1
 - pink to 6
 - black to ground

Not sure if this would apply to the A-26 as well and if it does how would I "reverse" it for input.
Any help would be appreciated! All the tubes are a glow'in and the voltages seem correct so i'm almost there!!!!
Title: Re: D-LA2A Support Thread
Post by: stereokillah on November 29, 2010, 08:01:29 PM
hi volker,
i have some edcors wsm 15k/600 for the output - do you have a european source for some input trafos? tonydb does not distrtibute edcors any more...

so... have you tried with your haufe 1:1 like mentioned earlier in the thread?

i have the original pot/resistor values so 1:1 would perhaps be good anyway  :)

buy it directly from edcor usa, we did it
Title: Re: D-LA2A Support Thread
Post by: audiophreak on December 03, 2010, 10:45:18 AM
Hi All,
       Just starting out with this project, and already have a question... I have a large stock for Carbon film resistors ( got from an Electronics shop that closed ) and was wondering if they would be good to use in this Project as the U.S. BOM listed resistors as metal film.
    Thanks
               Chip
Title: Re: D-LA2A Support Thread
Post by: tomcat on December 03, 2010, 02:42:26 PM
when the original LA2 was released there where just carbon resistors on the market. So make a guess ;)
Title: Re: D-LA2A Support Thread
Post by: audiophreak on December 03, 2010, 08:51:39 PM
Thanks tomcat  !

    I kinda thought so, but wanted to ask here to possibly get a different perspective.  I found this article - http://www.geofex.com/Article_Folders/carbon_comp/carboncomp.htm -  and found it interesting, I try to take in as many opinions as possible, then try what I feel makes science to me    ;D
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on December 04, 2010, 02:55:42 AM
just make sure they fit physically - most older carbon resistors are bigger than 0207
Title: Re: D-LA2A Support Thread
Post by: EHOFFA007 on December 06, 2010, 12:17:51 AM
I wired the a-26's and the unit is passing signal but very low level. I wired the input a-26 as follows:

brown=pin 1
Pins 3&4 jumped
green=pin 6
Blue=pin  7
pins 8&9 jumped
grey= pin 10
Black=ground
Not sure what to do with the center tap (Pink)???

I'm a noob so I just tried reversing the in and out signals on the transformer and left the jumpers in the same position as the output transformer.
Any help would awesome!!!

Title: Re: D-LA2A Support Thread
Post by: drgrateful on December 09, 2010, 10:05:01 AM
Hi,

should the 3k6 resistor be connected to the positive or negative side of the VU meter? I found inconsistent info about this and therefore I would greatly appreciate it, if someone could clarify this point for me...

Cheers,

Matteo
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on December 09, 2010, 11:02:05 AM
I always wire mine to the positive side.
Title: Re: D-LA2A Support Thread
Post by: pH on December 09, 2010, 11:29:25 AM
The UREI manual schematic shows the negative side, but I've seen no difference between the two in practice.

Title: Re: D-LA2A Support Thread
Post by: EHOFFA007 on December 10, 2010, 02:43:01 PM
So I didn't jump the grid stoppers, that was my issue with the no signal flow.
Right channel is passing audio now but not the left.
Making some progress!
Title: Re: D-LA2A Support Thread
Post by: thestudio on December 10, 2010, 08:26:51 PM
Where can I purchase the D-la2a pcb.......????
Title: Re: D-LA2A Support Thread
Post by: benlindell on December 10, 2010, 09:04:16 PM
Where can I purchase the D-la2a pcb.......????
http://www.groupdiy.com/index.php?topic=39570.0
Title: Re: D-LA2A Support Thread
Post by: EHOFFA007 on December 11, 2010, 03:57:37 AM
Getting 182.2v on both sides of the 250V legs of the Rondo trafo. What would cause this?
Not sure if under voltage would cause audio not to pass on channel 1.
I swapped all tubes,t4b & i/o transformers w/ channel 2 (passing audio at least) and still no audio.
I can hear the gain working and getting the HF OSC but no audio passing.
I could use some advise......Pretty Please  ;D
Title: Re: D-LA2A Support Thread
Post by: thestudio on December 11, 2010, 11:31:30 AM
I've been to that thread but is there a email address or site to purchase these pcb's.......?
Title: Re: D-LA2A Support Thread
Post by: bernbrue on December 11, 2010, 11:56:39 AM
Getting 182.2v on both sides of the 250V legs of the Rondo trafo. What would cause this?
Not sure if under voltage would cause audio not to pass on channel 1.
I swapped all tubes,t4b & i/o transformers w/ channel 2 (passing audio at least) and still no audio.
I can hear the gain working and getting the HF OSC but no audio passing.
I could use some advise......Pretty Please  ;D

Hi,
did you wire the primary for 115V?
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: benlindell on December 11, 2010, 01:43:47 PM
I've been to that thread but is there a email address or site to purchase these pcb's.......?

Gotta read it all the way down:

Quote
contact sales[at]51xAudio.com if you have any interest.
please always include your forum name and location for a quote.

best
Volker
[silent:arts]
Title: Re: D-LA2A Support Thread
Post by: EHOFFA007 on December 11, 2010, 06:40:59 PM
Getting 182.2v on both sides of the 250V legs of the Rondo trafo. What would cause this?
Not sure if under voltage would cause audio not to pass on channel 1.
I swapped all tubes,t4b & i/o transformers w/ channel 2 (passing audio at least) and still no audio.
I can hear the gain working and getting the HF OSC but no audio passing.
I could use some advise......Pretty Please  ;D

Hi,
did you wire the primary for 115V?
regards
Bernd



I'm pretty sure I do?

2x 115 ge-ws/ge-ws (ge = Yellow ws=white?)

Tied yellow's together to hot pin of the IEC
Tied white's together, switched and tied to Negative of IEC.
Title: Re: D-LA2A Support Thread
Post by: stereokillah on December 11, 2010, 09:43:57 PM


which voltage do you have if the 250v wires are not connected on boardif it's 250v you have a problem on board

swap tubes t4 put out the 250v wires of the left side and mesure if it's good you have a prloblem on left side,
if not  replace it and put out the right side and mesure if it's good it's a problem on right side,
 
check if there is not a bad contact with the wires under the board and check your resistor
Title: Re: D-LA2A Support Thread
Post by: EHOFFA007 on December 13, 2010, 02:17:38 PM
Thanks for the help man!
So the bench multimeter I bought off evilbay was acting wonky. In the trash it went!
Got a new meter that works and this is what is actually happening.
Power traffo totally offboard is giving me 277V ac on the mains.
when connected i'm getting the same AC voltage and 362v DC on both D1 and D2
On the right channel tube sockets,getting 350V DC
On the Left channel tube sockets getting  277v DC
I flipped the board and checked for shorts with the continuity tester=OK
Maybe a bad Cap on the left channel? What would cause the DC voltage to get knocked down?
This is my first real troubleshoot so bear with me  ::)
Title: Re: D-LA2A Support Thread
Post by: alexc on December 16, 2010, 04:04:17 AM
Here's my DLA2A just finished and now tweaking and listening...

Using Jensen 1:4 inputs and Carnhill 4:1 outs, Drip T4Bs and mci/triplett meters.

(http://www.users.on.net/~alexc/res/pics/dla2a_pic1.jpg)

(http://www.users.on.net/~alexc/res/pics/dla2a_pic2.jpg)

All good, went together easy and sounding superb. Getting familiar with it
and how it sounds compared to the other la2a style units I have.

Thanks Volker for the great pcb!
Title: Re: D-LA2A Support Thread
Post by: baadc0de on December 16, 2010, 05:53:11 AM
Here's my DLA2A just finished and now tweaking and listening...

Using Jensen 1:4 inputs and Carnhill 4:1 outs, Drip T4Bs and mci/triplett meters.
 
All good, went together easy and sounding superb. Getting familiar with it
and how it sounds compared to the other la2a style units I have.

Thanks Volker for the great pcb!

Looking great. This four-Vus plus reminiscent-of-La3a layout of yours is very appealing to me. It will probably serve as a main inspiration when I do my second dual unit lol. I only don't dig different VU lights. A bit distracting to me. Be sure to tell us how it compares to other LA2A-like stuff ;)

Cheers,
B.
Title: Re: D-LA2A Support Thread
Post by: alexc on December 17, 2010, 02:57:19 AM
Thanks!

Well I have to say this is a great result - unity gain noise floor of -79dBu for the first channel
and -79dbU for the channel closest to psu traffo on my RTA which is calibrated to the dBu standard.

My Motu converter noise floor is -83dBu.

Outstandingly quiet build - equal best for the units I've built, alongside the Poorman 670.

Significantly quieter than my Drip v1 build, which came in at about -72dBu (from memory).
Massively quieter than my ADL CL1 which is around -65dBu or so. (It prolly needs caps change - it is an early one)

I'm finding those Carnhill outputs a little thicker sounding with some more crunch than the Sowter
but not a lot in it really. No question - it sounds fantastic and all works as expected.

Certainly the Carnhill 600:9600 are great in this application, especially for the price which is a lot less than Sowters.
The Jensens seem very transparent as one would expect. Can't really say there's much diff to the Sowter.
Cost a lot less tho. All in all, not much in it between them - compared to the Edcor, the Edcor is somewhat
grainier. Not a bad thing for a guitar, tho.

Well - this one is closed up now and into the studio to become a bus compressor, one of a bunch of different
ones.

Anyway - highly recommended DLA2A pcb from Silent:Arts
Title: Re: D-LA2A Support Thread
Post by: audiophreak on December 18, 2010, 09:27:46 PM
Thanks tomcat  !

    I kinda thought so, but wanted to ask here to possibly get a different perspective.  I found this article - http://www.geofex.com/Article_Folders/carbon_comp/carboncomp.htm -  and found it interesting, I try to take in as many opinions as possible, then try what I feel makes science to me    ;D

 from that article - " The place to use CC's is where there's big signal - plate resistors, and ideally the stage just before the phase inverter. The phase inverter would otherwise be ideal, with plate resistors carrying the highest signal voltage in the amp, but phase inverters are often enclosed in a feedback loop. The feedback minimizes the distortion  the resistor generates.  "

Hi All,
         ( quoting myself is kinda weird  ;D   )  anyway,  after reading that article, and still being a newbee    ;D  I guess my question is... would R117, 118, 113, 109, 133, 134  , be the optimum places for CC resistors ?
 
   ... if not, would someone be kind enough to make some suggestions ?   

  Thanks All
Title: Re: D-LA2A Support Thread
Post by: herrmann on December 26, 2010, 05:40:25 AM
What's the carnhill ref ?
Title: Re: D-LA2A Support Thread
Post by: baadc0de on December 26, 2010, 05:14:59 PM
Sorry if this has been addressed before, but what would be the most elegant way to have two opto cells per channel and make them individually switchable. I see in the schematic that the board connects 7 wires to the opto cell, so to switch them, I would need..?
Title: Re: D-LA2A Support Thread
Post by: alexc on December 26, 2010, 06:26:48 PM
>What's the carnhill ref ?

Carnhill VTB2291 : ungapped, 9600:600

http://www.audiomaintenance.com/acatalog/info_312.html (http://www.audiomaintenance.com/acatalog/info_312.html)

A fine traffo at a reasonable price - an alternative to Edcor (on the cheaper side) or Sowter (on the tres expensive side)
A little 'thicker' sounding than the Edcor ('grainier' sort of hifi) or Sowter ('clean' and hifi).

Not much in it - I could maybe tell them apart in a blind test. With a couple of tries.

Definately makes a small oep or a lundahl seem like a light, girly traffo.  :)

One thing tho - makes the output a little hotter. May want to mod the output pot to be a fixed resistance in series with
a smaller value pot, as has been previously suggested.

I plan to do that as well as experiment with a lower gain signal tube than the 12AX7 in position 1.

My unit has the output gain pot at "1" or "2" most of the time, instead of the more usual "3" or "4" on my other units.
Anything over 5 is like a battleship PA.

Cheers
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on December 26, 2010, 10:53:12 PM
Sorry if this has been addressed before, but what would be the most elegant way to have two opto cells per channel and make them individually switchable. I see in the schematic that the board connects 7 wires to the opto cell, so to switch them, I would need..?

Pin 2, 4, 6 and 8 are connected to ground - no need to switch them.
you only need to switch Pin 3, 5 and 7.
My guess: switching Pin 3 only should work too.

[note1: Pin 3 contains high voltage]
[note2: I haven't tested any T4B switching]
Title: Re: D-LA2A Support Thread
Post by: Sredna on December 26, 2010, 11:36:27 PM
And pin 5?  ;)

Quote
My guess: switching Pin 3 only should work too.
Do you mean that the internal resistance of the LDRs is so large when dark
that its no problem having two T4Bs in parallel?

Quote
[note1: Pin 3 contains high voltage]
aprox. 30 Volts AC
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on December 26, 2010, 11:59:05 PM
And pin 5?  ;)
pin 5 is overrated ;D
thanks, corrected

Quote
My guess: switching Pin 3 only should work too.
Do you mean that the internal resistance of the LDRs is so large when dark
that its no problem having two T4Bs in parallel?
yes. meter might need to be re-adjusted, audio has too much gain anyway.
but again: not tested by me

Quote
[note1: Pin 3 contains high voltage]
aprox. 30 Volts AC
like I said, high voltage 8) :D ;) :o
Title: Re: D-LA2A Support Thread
Post by: baadc0de on December 27, 2010, 01:07:32 AM
Thanks guys.. I'll report back once I implement this scheme.
Title: Re: D-LA2A Support Thread
Post by: drgrateful on December 27, 2010, 10:39:31 AM
Hi, I am planning to use this small heatsink for the 7805:

http://www.conrad-international.com/Heatsink-for-plastic-transistor-25x15x18.htm?websale7=conrad-int&pi=188115

Will this be fine? Do I need a larger one, or maybe is it better to attach the 7805 to the case, as I have seen in some builds?

Thanks for the suggestions.

Matteo
Title: Re: D-LA2A Support Thread
Post by: audiophreak on December 28, 2010, 08:21:27 PM
Hi All,
     Just starting out on this, ordering parts, Mouser is out of stock on the relays, - would this one due ?  the only diff I see is that the max currect rating is 1A instead of 2A  

Thanks,
            Chip

EDIT :  forgot the link  ::)    - http://www.mouser.com/ProductDetail/Omron-Electronics/G6K-2P-DC5/?qs=sGAEpiMZZMs3UE%252bXNiFaVBrMwKMEuUpxYUmZBiw8UvA%3d
Title: Re: D-LA2A Support Thread
Post by: Randyman... on December 28, 2010, 09:39:24 PM
Same here!  I ordered these and am also curious if they will work:

http://www.mouser.com/ProductDetail/Omron/G6A-274P-ST40-US-DC5/?qs=ISjK4nnpKfFgGVuxsXPgBw%3d%3d

They have an 80ma coil current and 400ma consumption rating instead of 100ma coil current and 500ma consumption like the ones on azone's BOM - but are both 5V, seem to have the same 2A switching capability and same footprint.

Anyone know if they will work properly?

Thanks :cool:
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on December 29, 2010, 04:06:37 AM
Hi, I am planning to use this small heatsink for the 7805:

http://www.conrad-international.com/Heatsink-for-plastic-transistor-25x15x18.htm?websale7=conrad-int&pi=188115

Will this be fine? Do I need a larger one, or maybe is it better to attach the 7805 to the case, as I have seen in some builds?

it really depends on your build. might be enough for the relays only, but if you have illuminated switches and meters ...
mount the 7805 to the case (isolated!) doesn't hurt.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on December 29, 2010, 04:15:04 AM
Just starting out on this, ordering parts, Mouser is out of stock on the relays, - would this one due ?  the only diff I see is that the max currect rating is 1A instead of 2A
- http://www.mouser.com/ProductDetail/Omron-Electronics/G6K-2P-DC5/?qs=sGAEpiMZZMs3UE%252bXNiFaVBrMwKMEuUpxYUmZBiw8UvA%3d
Chip, those have a wrong pinout

http://www.mouser.com/ProductDetail/Omron/G6A-274P-ST40-US-DC5/?qs=ISjK4nnpKfFgGVuxsXPgBw%3d%3d
Randy, they should work fine
Title: Re: D-LA2A Support Thread
Post by: audiophreak on December 29, 2010, 08:32:05 AM
Thanks [silent:arts] ,
 
       Duh.... I was looking at coil current and power consumption, pinouts were further down the spec sheet ;D

  how about this one - http://www.mouser.com/Search/ProductDetail.aspx?R=G6A-234P-ST15-US-DC5virtualkey65300000virtualkey653-G6A-234P-ST-DC5

... 30ma coil current and 150mw power consumption.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on December 29, 2010, 08:40:32 AM
Looks good.
coil current and power consumption is a matter of your PSU transformer and what else you want to drive from the 5V rail. lesser = better, the more = hotter :D

max. switching current etc: we are switching line audio level ...
Title: Re: D-LA2A Support Thread
Post by: audiophreak on December 29, 2010, 08:49:07 AM

[silent:arts] Thanks so much,
                                       I have now read the whole thread, I still have a few questions, but will try and figure them out first. as you can see, still ordering parts.

     From what I have read, cant wait to hear this  :)
Title: Re: D-LA2A Support Thread
Post by: drgrateful on January 01, 2011, 09:54:18 AM
Hi Volker,

Happy New Year and thanks for your help!

I am about to wire the xlr connectors to the board. From the pictures posted, I see that people use different solutions here: some use three wires twisted together, others use shielded two-conductor wire, with shield going to pin 1 and connected both to the XLR connector and the PCB. You seem to have used a three-conductor wire (at least this is what I think from the pictures of your build). Is there a preferred way to go here?

Thanks, Matteo
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 01, 2011, 10:34:10 AM
Hi Matteo,

yes, I used shielded cable and connected the shield at the XLR and PCB side.
not the way I do it normally.

each audio channel on the PCB has its own ground connector,
directly located next to the "input" Molex.
Title: Re: D-LA2A Support Thread
Post by: telefunk on January 06, 2011, 02:45:20 PM
Hi everybody.

Just finished my D-La2a. Used Edcor 600:15k and 15k:600 transformers and Kenetek T4b's. Everything worked really nicely immediately but there is only one problem: I NEED MORE INPUT GAIN! It works nicely when i put both channels in series, then i get fantastic compression.

What can i do to increase the input gain? Other than change the input transformer...And yes, i already adjusted the Lim Resp to full.

And other thing: why isnt everybody taking the power for the 12v VU lamps directly from the 10v AC of the Rondo Transformer?

Oh, and btw, thanks Volker! You get my full respect for doing this! Thanks!

Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 06, 2011, 02:52:47 PM
there must something wrong.
you are the first person ever asked for more input gain ...
Title: Re: D-LA2A Support Thread
Post by: Randyman... on January 06, 2011, 02:54:07 PM
What are you driving the LA2A with?  (What's the preamp sending out level-wise?).  

My Edcors should be here soon (same ones as yours) - so I hope this isn't an issue with these particular transformers in the D-LA2A (seems to work fine for others - including Azone and his fantastic BOM  :D ).  Do you have the taps wired correctly?  I know all of my pre's can spit out +26dBu to +30dBu or more - so I don't think level will be an issue on my side  ;)


8)
Title: Re: D-LA2A Support Thread
Post by: telefunk on January 06, 2011, 03:01:00 PM

I do have HUGE amounts of output gain but not enough input gain to get enough compression.

I feed the La2a inserted to my Harrison console that has nominal level of -6dBm. (channel insert point)

Can the Rondo Transformers 10Vac take also two 12v VU lamps?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 06, 2011, 03:10:14 PM
my first guess: compression potentiometer is wired wrong.

Can the Rondo Transformers 10Vac take also two 12v VU lamps?

if the "In/Bypass" works everything is fine on this side.
it is 9V btw, feeding the 5V "utility PSU".
however, it is not in the audio path.
Title: Re: D-LA2A Support Thread
Post by: telefunk on January 06, 2011, 03:13:18 PM
When i turn the gain pot i get more output gain, not input gain!

I other words, turning the Gain pot I do not get more compression...

is there something wrong?

EDIT: sorry did you mean the peak reduction pot?
Title: Re: D-LA2A Support Thread
Post by: telefunk on January 06, 2011, 03:29:28 PM

Here's how I've wired it:

http://www.solmu.fi/roni.martin/DLA2A.JPG
Title: Re: D-LA2A Support Thread
Post by: Biasrocks on January 06, 2011, 03:51:08 PM
I'm not familiar with this build, but the High Frequency compensation and Stereo Balance pots will affect the threshold.

Make sure they are fully clockwise to start.

Mark
Title: Re: D-LA2A Support Thread
Post by: telefunk on January 06, 2011, 05:01:42 PM
SOLVED!

I had my stereo adj trim pot wrong way around. So, when i turned it fully counter-clockwise, it started to work.But it seems to make difference even when not in stereo link mode?!?!
Title: Re: D-LA2A Support Thread
Post by: Biasrocks on January 06, 2011, 06:52:19 PM
Cool beans.  8)

Yes, it makes a difference even when not linked.

Glad you got it working.

Mark
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 07, 2011, 05:40:26 AM
now show us more pics ;D
Title: Re: D-LA2A Support Thread
Post by: drgrateful on January 07, 2011, 09:01:58 AM
Hi everybody.

In my Rondo transformer I also have a yellow-green wire coming out of the transformer. I can't see it in other people's builds (the other wires are exactly as those in Volker's build: see http://www.silentarts.de/DIY/D-LA2A/IMG_3981.jpg). Should this yellow-green wire be connected to the star ground?

Thank you, Matteo
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 07, 2011, 10:28:29 AM
I have that wire too (you just can't see it in that pic).
It is the screening shield.

Mine is connected directly to the IEC safety earth pin,
but star ground will be fine too.
Title: Re: D-LA2A Support Thread
Post by: electrisizer on January 07, 2011, 12:35:33 PM
hey there  :)

one question... im in wiring action right now...

do you have original shilded molex pin cables (the grey ones in pic above) or do you cut the original molex and solder them with shilded cables together?

if there are some original shilded molex cables please give me an (german) ordering source...
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 07, 2011, 01:00:20 PM
the Molex cables are DIY :o
Title: Re: D-LA2A Support Thread
Post by: electrisizer on January 07, 2011, 02:27:08 PM
thanks volker!

and another question i fired the unit up and voltages are ok but i dont find a source for t4 voltages...

the only thing i found says pin 5 is 7.5v - when i trim this value with RV 104/204 the NE2 glimmer goes out - is that right?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 07, 2011, 02:42:02 PM
no need to adjust T4 voltages.
RVX04 is your Meter zero adjustment for gain reduction.
adjust it to see 0VU on the meter with no gain reduction.
Title: Re: D-LA2A Support Thread
Post by: helterbelter on January 07, 2011, 05:55:39 PM
Hi all,

I "finished" my La2a about 6, 7, maybe more months ago. (yes, a D-LA2a board, but just one channel populated).

Back then I've tested it and it works, but it doesn't pass low frequencies. At that time I didn't have much time to continue searching for the mistake, and I kinda thought the Edcors (15k/600 and 600/15k) were to blame for the lowcut, but by now I think this isn't the reason.

I've read the whole thread again, looking for similar problems, but I didn't find any. Does anybody here have a clue what might be wrong ? I'm 99-100% sure there's no short somewhere, and all voltages measure fine. (I had another problem to solve earlier, so I already checked this stuff).
Title: Re: D-LA2A Support Thread
Post by: herrmann on January 08, 2011, 12:53:23 PM
Quote
Carnhill VTB2291 : ungapped, 9600:600
Ok, I guess it will work for the input too ? (reversed)
Title: Re: D-LA2A Support Thread
Post by: Randyman... on January 08, 2011, 06:59:25 PM
I've got 4 of the original LA2A Arco 465 Trimmer Caps on the way for C104/C204 and C114/C214.  Will these fit directly into the PCB - or will I need to get creative to mount them properly?  I also planned on using a bournes 50K trimmer resistor for R25 (or whatever the resistor is that needs to be set for the T4B - most people use a 33K IIRC) to get this thing as tweaked out as possible.

Is there a calibration procedure somewhere?

I've got the main PCB stuffed (heaters wired, too) - so just waiting on the transformers and chassis before I power her up for the first time!  Any suggestions before I slam HV into it for the first time?

Thanks!  8)
Title: Re: D-LA2A Support Thread
Post by: audiophreak on January 08, 2011, 07:08:19 PM
Hi,
     were did you get the Arco 465 Trimmer Caps ?   I've been looking for any trimmer cap, but cant seem to find any in the pf range needed - ( 1-120pf to 330-500pf )  I.ve found a couple part numbers from Data sheets, but when I call or send email, they don't have them in stock and 3-5 MONTHS to get them .
Title: Re: D-LA2A Support Thread
Post by: Randyman... on January 08, 2011, 07:35:59 PM
Azone's BOM has them listed in the "Substitution/Upgrade" part from surplussales.com :

http://www.surplussales.com/Variables/Compression/CompCap1.html  (scroll down)

It's the Arco 465 #CTM-465 according to Azone and a few others...

Any tips on a calibration procedure?

8)
Title: Re: D-LA2A Support Thread
Post by: alexc on January 08, 2011, 07:43:25 PM
Carnhill 9600:600 reversed would 'work' for the input - sure
But it is not really meant for the role of an input transformer, being unshielded, quite large
and of a power rating more suited to an output. There's probably other reasons too  :)

I think it would be preferable to find a shielded input transformer of 600:10K or 600:15K
or even 600:50K as I have seen. My pref would be 600:15K.

But it would work. As do the Edcor open frame unshielded transformers.
Title: Re: D-LA2A Support Thread
Post by: audiophreak on January 08, 2011, 08:17:07 PM
Thanks Randyman,
                              I did check those last week, but they listed them as " Out of Stock "   -  as for calibration ..   check pages 12 , 13 of this thread, I'm sure there's more but that was all I could find right now. hopeing to get mine together over the next month or so ...   good luck with yours, keep us updated   :)
Title: Re: D-LA2A Support Thread
Post by: helterbelter on January 08, 2011, 08:18:15 PM
I'm pretty much interested in buying the carnhill for the output too.

Which inputtransformer do you use ?



And a shameless bump for the question I asked earlier today ! I have checked my build again today, but didn't find the cause.

Hi all,

I "finished" my La2a about 6, 7, maybe more months ago. (yes, a D-LA2a board, but just one channel populated).

Back then I've tested it and it works, but it doesn't pass low frequencies. At that time I didn't have much time to continue searching for the mistake, and I kinda thought the Edcors (WSM 15k/600 and 600/15k) were to blame for the lowcut, but by now I think this isn't the reason.

I've read the whole thread again, looking for similar problems, but I didn't find any. Does anybody here have a clue what might be wrong ? I'm 99-100% sure there's no short somewhere, and all voltages measure fine. (I had another problem to solve earlier, so I already checked this stuff).
Title: Re: D-LA2A Support Thread
Post by: Randyman... on January 08, 2011, 09:11:46 PM
Thanks Randyman,
                              I did check those last week, but they listed them as " Out of Stock "   -  as for calibration ..   check pages 12 , 13 of this thread, I'm sure there's more but that was all I could find right now. hopeing to get mine together over the next month or so ...   good luck with yours, keep us updated   :)

I'm not sure if they got more in (I think these are old stock) - but I know I have (4) on the way to me (in transit).  I believe they still have some left...

Re-Reading the calibration stuff on Page 12-13 - but still don't see many specifics.  Some links are dead (like the UA link!).  I'll keep searching...

8)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 09, 2011, 04:16:16 AM
I've got 4 of the original LA2A Arco 465 Trimmer Caps on the way for C104/C204 and C114/C214.  Will these fit directly into the PCB - or will I need to get creative to mount them properly?
You need to go the creative way :D
I used fixed values, since those Arco trimmers were impossible to source.

I also planned on using a bournes 50K trimmer resistor for R25 (or whatever the resistor is that needs to be set for the T4B - most people use a 33K IIRC) to get this thing as tweaked out as possible.
Is there a calibration procedure somewhere?
SSLtech wrote an excellent LA2A calibration procedure somewhere in another thread.

I've got the main PCB stuffed (heaters wired, too) - so just waiting on the transformers and chassis before I power her up for the first time!  Any suggestions before I slam HV into it for the first time?
if you are worried leave the T4Bs out the first time.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 09, 2011, 04:34:54 AM
...
Back then I've tested it and it works, but it doesn't pass low frequencies. At that time I didn't have much time to continue searching for the mistake, and I kinda thought the Edcors (15k/600 and 600/15k) were to blame for the lowcut, but by now I think this isn't the reason.
http://www.groupdiy.com/index.php?topic=26119.msg429195#msg429195
Title: Re: D-LA2A Support Thread
Post by: alexc on January 09, 2011, 06:18:14 AM
I used Jensen 1:4 inputs  37.5K:2.3K wired backwards if I remember correctly.
They were a deal from a forum member. Very transparent and very quiet.

My other one uses a Sowter 4383 600:10K 1:4. It's also very clean and quiet.

If I was doing another, I'd probably use the Sowter again.
Or try and find an Altec or UTC maybe.

I like Edcor but not for inputs  - they can pickup a little too much RFI for my liking.
You can move them away from the psu and all that, but even so - haven't had to do this with
shielded input traffos.

I started the DLA2A and also DOAC with Edcors but changed them to the Jensens for that reason.
Depends on how much money you want to part with :)
Title: Re: D-LA2A Support Thread
Post by: alexc on January 09, 2011, 06:29:56 AM
To track down why and where you are losing low-freq, I would try and trace the signal
with a cro and a signal gen set to a low frequency. If it is noticable by ear, it should be
visible on the cro.

The LA2A is not all that complex. Excluding the sidechain
     input traffo -> attenuator  -> gain pot -> 12AX7 gain stage x2 -> white cathode follower stage -> OP traffo

You could also rig up a cheap audio probe going to cheap computer powered speakers and follow the chain,
making sure you probe the low DC voltage points ie. *after* DC blocking caps.

Listen for where the low freqs disappear. Do some searching for a suitable audio probe.

*** As always - be very careful probing High Voltage circuits. If in doubt, don't do it. ***

My guess is the usual suspects : wiring errors - check the wiring of the input and output transformers,
component values - check caps and resistors. Also try tube swapping. Faulty tubes do occur, particularly
in the first 12AX7.

Another thing to do - use a soundcard with a spectrum analyser that can do a frequency sweep

Good luck!
Title: Re: D-LA2A Support Thread
Post by: helterbelter on January 09, 2011, 01:20:33 PM
http://www.groupdiy.com/index.php?topic=26119.msg429195#msg429195

Yes, that's why I suspected the trannies.  However, mine are not the XSM, but are WSM, as recommended by SSLTech. I will follow Alexc's lead first, after that, it'll be transformer swapping time.

AlexC :
 
I'll swap the first 12AX7 to begin with, if that doesn't work,  probing it will be the next step. Not really looking forward to it with these high voltages, hence the question where the cause might be. So, thanks for your suggestions,

Thanks for the replies !
Title: Re: D-LA2A Support Thread
Post by: herrmann on January 09, 2011, 01:25:41 PM
The VTB9071 10k:10k may be more adequate ? Then why not adding a 3PDT to lower the input impedance at 2k5 ? Maybe it's a stupid idea, don't know...
Title: Re: D-LA2A Support Thread
Post by: alexc on January 10, 2011, 05:15:00 AM
10K:10K may work - I haven't tried it.

I think the step up in voltage provided by a 600:10K  or 600:15K is neccessary in order to ensure sufficient signal level to drive the T4B into compression.

I wouldn't recommend it, but I seem to recall reading about it somewhere.
Title: Re: D-LA2A Support Thread
Post by: alexc on January 10, 2011, 05:27:18 AM
I used the XSM  Edcors in this build and didn;t notice any excessive low end roll off.

it does help to do a sweep to determine how rolled off and at what freq.

-3dB at 20Hz is a standard measure of the low freq cutoff.

I would regard anything more than -3db at 40Hz to be an issue, usually meaning the
transformer is not well matched to the application.

I don't think you would hear it until it was > -3dB rolloff  at 80Hz or so.

Some points regarding probing tube circuits - never hurts to reiterate!

With respect to probing, take your time, know in advance which point your are going to examine,
then  power up, do the measure and power down.

Always keep one hand in pocket to avoid the possibility of an across-the-chest shock.

Aa always, make sure the main PSU capacitors are drained EVERY time you power down.
It's a discipline - a power down 'make safe' routine.

It is useful to keep a multimeter attached to the psu caps always on indicating the voltage.
I use a second one as a 'double check' every time I'm probing.

You may need a grounding probe with resistor for the purpose of draining the psu caps.

That aside, probing should show you very quickly where the loss of bass occurs.
There's only a couple of points to check :

- farside of C1/grid of 12AX7 #1 (V1 pin7)
- farside of C2/grid of 12BH7 (V2 pin 7)
- farside of C5/primary of Output traffo

If it's not at any of the points above, it's in the input side of the tubes - the input traffo or T4B.


Let us know if you have questions and good luck :)
Title: Re: D-LA2A Support Thread
Post by: herrmann on January 11, 2011, 05:19:46 AM
Quote
10K:10K may work - I haven't tried it.
I think the step up in voltage provided by a 600:10K  or 600:15K is neccessary in order to ensure sufficient signal level to drive the T4B into compression.
This is actually the "jensen mod", but I can't find any comparaison review. Also on ebay there's some cinemag 15k:15k that are selling as LA2a input transformer.
Title: Re: D-LA2A Support Thread
Post by: drgrateful on January 11, 2011, 08:28:59 AM
Hi all,

I would like to wire two 12v VU lamps and one 6.3v on/off bulb. If I got it right, I see that it is OK to wire the VU lamps to the fifth secondary of the Rondo transformer (9vAC), as long as the in/bypass relays keep working, since this secondary is not in the audio path: is this correct?

Now, what is the best way to wire the 6.3v on/off bulb? I don't think it should be wired directly to the third or fourth secondary (both 6.3vAC) of the Rondo transformer, correct?

Thanks, Matteo
Title: Re: D-LA2A Support Thread
Post by: Soeren_DK on January 21, 2011, 05:37:51 AM
Ready for take off

Anything I should be aware of before power up it up?
Should i leave the T4 out at first? and what about tubes?

Anybody have some voltages around the board the I can compare to?

Cheers
Soren
Title: Re: D-LA2A Support Thread
Post by: alexc on January 21, 2011, 07:00:30 AM
I usually check the basic voltages of heater, B+ at the tube sockets and t4b socket before adding tubes and t4b.

Then power up briefly - look for smoke release. Check those basic voltages.

I like to wear some eye and ear protection when I first power up a tube unit. And don't lean over it until
you think it's all clear :)

If all seems (smells)  OK, add tubes and t4b and repeat. Check for voltage drops on those places as you go.

When you power on without smoke for a couple of minutes, should be all good.

Then do detail checks of voltages as per the schematic.

There's only a couple of places where it may smoke if you made errors.

Good luck!
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 21, 2011, 07:06:00 AM
check heaters & B+ without any tubes T4Bs.
insert the tubes, check again (still no T4B).
listen to it (still no T4B) with and without audio.
all fine?
plug in your T4B and enjoy.
Title: Re: D-LA2A Support Thread
Post by: electrisizer on January 21, 2011, 01:47:47 PM
nearly finished  ;D


(http://img707.imageshack.us/img707/3564/la2a2.jpg)

(http://img830.imageshack.us/img830/8653/la2a1.jpg)
Title: Re: D-LA2A Support Thread
Post by: electrisizer on January 21, 2011, 03:03:39 PM
problems:

i had a bit distortion + low cut on channel B when peak red. was going on. the v203 dosent like the JJ ecc83!

i changed to a vintage telefunken -> distortion gone. the crazy thing: v103 dosent distort with the JJ  ::)

second thing: at high gain level i have oscillation on both channels , but this gain ill never need. perhaps ill change to 100k pots/resistors.

input trafos are the haufe rk310, output edcors...

this thing smashes sounds in the front :)
Title: Re: D-LA2A Support Thread
Post by: electrisizer on January 24, 2011, 02:10:57 PM
ah - im going crazy, theres still a bug...

first question: does audio pass even if theres no power on? (mine does)

second question: days before i had really nice compression now theres nearly nothing...even if i have full limit resp.

i suspect the relays but cant measure any voltages right now...
Title: Re: D-LA2A Support Thread
Post by: tomcat on January 24, 2011, 06:26:42 PM
1: Yes, these are hw bypass relays, no power: bypass
Title: Re: D-LA2A Support Thread
Post by: thestudio on January 24, 2011, 06:30:16 PM
Question: Is there a reason that heater runs couldn't of been put on the pcb instead of using separate wire runs?  Did UA on their dual La2a use the pcb for heater runs???
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 25, 2011, 03:44:55 AM
Question: Is there a reason that heater runs couldn't of been put on the pcb instead of using separate wire runs?  Did UA on their dual La2a use the pcb for heater runs???
You can't twist PCB traces, and we are talking about AC heaters, 2 x 2A ...
I'm not aware of a UA dual LA2A, any link?
Title: Re: D-LA2A Support Thread
Post by: Soeren_DK on January 25, 2011, 08:04:40 AM
the reason why there is no C4 trimmer is: I didn't find any easily available in europe. the 300pF is a guessed estimate I read somewhere in the long LA2A threads, but can easily exchanged to other values.

On my pcb c104/c204 is marked with 150pf and I bought 150pf?

Cheers
Soren
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 25, 2011, 08:30:29 AM
... On my pcb c104/c204 is marked with 150pf and I bought 150pf?
and me (and most others) used 150pF ;D
Title: Re: D-LA2A Support Thread
Post by: drgrateful on January 25, 2011, 01:19:59 PM
I am almost done...

I fired up the D-LA2A without the T4B's. I measured the following voltages:

After D1: 340v
After R129: 250v
V101: pin1 105v, pin6 108v
V102: pin1 106v, pin7 112v
V103: pin1 81v, pin6 81v
V104: pin5 126v, pin6 114v

Voltages for the other channel are similar, except for v204: pin5 142v, pin6 98v.

Am I in the ballpark? Can I plug in the T4B's confidently?

The NE2 neon lamps don't light up: is this OK without the T4B's plugged in?
Title: Re: D-LA2A Support Thread
Post by: Soeren_DK on January 25, 2011, 04:19:05 PM
... On my pcb c104/c204 is marked with 150pf and I bought 150pf?
and me (and most others) used 150pF ;D
Thanks Volker.
I'm almost done but I need to adjust the unit. Anyone have guide other the little section in the manual?

Cheers
Soren
Title: Re: D-LA2A Support Thread
Post by: Randyman... on January 25, 2011, 08:59:13 PM
... On my pcb c104/c204 is marked with 150pf and I bought 150pf?
and me (and most others) used 150pF ;D
Thanks Volker.
I'm almost done but I need to adjust the unit. Anyone have guide other the little section in the manual?

Cheers
Soren

Ditto - Same boat.  Did you use the Arco trimmer caps?  How did you mount them to the PCB?  Or for that matter - if anyone has any handy tips for mounting the Arco trimmer caps - that would be great!  PCB is stuffed, just waiting on the chassis (any day now!).  I have a perfect project lined up to break this beast in, too!  :D

 8)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 26, 2011, 02:16:35 AM
I'm almost done but I need to adjust the unit. Anyone have guide other the little section in the manual?
do you think it is mis-adjusted?
Title: Re: D-LA2A Support Thread
Post by: Soeren_DK on January 26, 2011, 02:48:27 AM
No not really. But maybe there was a guide to adjust the RV137 and RV103?

Cheers
Soren
Title: Re: D-LA2A Support Thread
Post by: Soeren_DK on January 26, 2011, 12:20:34 PM
Finished :)
(almost, only need some knobs but I couldn't wait)


(http://www.doctorsclub.dk/diy/d-la2/thumb/LA2-1.jpg) (http://www.doctorsclub.dk/diy/d-la2/LA2-1.jpg)

(http://www.doctorsclub.dk/diy/d-la2/thumb/LA2-2.jpg) (http://www.doctorsclub.dk/diy/d-la2/LA2-2.jpg)

(http://www.doctorsclub.dk/diy/d-la2/thumb/LA2-3.jpg) (http://www.doctorsclub.dk/diy/d-la2/LA2-3.jpg)

(http://www.doctorsclub.dk/diy/d-la2/thumb/LA2-4.jpg) (http://www.doctorsclub.dk/diy/d-la2/LA2-4.jpg)

(http://www.doctorsclub.dk/diy/d-la2/thumb/LA2-5.jpg) (http://www.doctorsclub.dk/diy/d-la2/LA2-5.jpg)

(http://www.doctorsclub.dk/diy/d-la2/thumb/LA2-6.jpg) (http://www.doctorsclub.dk/diy/d-la2/LA2-6.jpg)

Cheers
Soren
Title: Re: D-LA2A Support Thread
Post by: ilfungo on January 26, 2011, 12:50:31 PM
great job!!! ;)
I saw that you used for Sowter in and out
how do they sound?
thanks
Title: Re: D-LA2A Support Thread
Post by: Soeren_DK on January 26, 2011, 04:30:38 PM
great job!!! ;)
I saw that you used for Sowter in and out
how do they sound?
thanks

Thanks..  :)
We are relocating so I don't have the right fatalities to test this beast right now. I'm listening through a ghetto blaster with AUX IN but it sound great... ;) ;)

Cheers
Soren
Title: Re: D-LA2A Support Thread
Post by: jrfred453 on January 26, 2011, 04:48:56 PM
Hey guys,
Just firing one of these up.
Right away with all the tubes in the fuse blows :o
I'm in the US and using a 1amp fuse. The Antec power transformer I'm using has 3.6v and 5 amps for the heaters. So I should use a bigger fuse????
I continued on to find the problem...
Inserted one tube at a time into the first channel. The 12BH7A blew the fuse, so I used the one from the other channel. No blown fuse and continued to check voltages.
after D1-340v
after R129-250.6v
V101 #1-92.1v #6-104.1v
V102 #1-85.1v #7-65.1v
V103 #1-78.8v #6-78.8v
V104 #5-116v #6-112.3v
Where should I look for the cause of the low voltage at V102

I also tried to insert tubes in channel 2..... but the fuse blew (1 amp fuse??)
all points without tubes show 340v on channel 2
Title: Re: D-LA2A Support Thread
Post by: drgrateful on January 27, 2011, 10:14:21 AM
The NE2 neon lamps don't light up: is this OK without the T4B's plugged in?

I will answer myself: I needed to adjust RV104 and RV204: now the neon lamps light up as they should.
Title: Re: D-LA2A Support Thread
Post by: thestudio on January 27, 2011, 08:49:38 PM
"You can't twist PCB traces, and we are talking about AC heaters, 2 x 2A ...I'm not aware of a UA dual LA2A, any link?"

How about using different layers within the pcb?  ????
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 28, 2011, 02:25:14 AM
How about using different layers within the pcb?  ????
a four layer PCB for a small tube project :o 8)
but you can't twist PCB layers either ;) ;) ;)
Title: Re: D-LA2A Support Thread
Post by: electrisizer on January 28, 2011, 07:50:54 AM
hey there im in troubleshooting process but need some help

as described before theres nearly no compression (about poor 0.5 db) at max limit resp. + peak red.

i figured out that theres no difference if the drip T4 is build in or not  :o its the same on both channels...
the VU needle jerks sometimes a very little bit when i crank the PR pot up thats all.

i hope to isolate the problem with it. gain stage is working really good...

even if im not a beatle:
Help! I need somebody.
Help! Not just anybody.
Help! You know, I need someone, help!
Title: Re: D-LA2A Support Thread
Post by: toffifee on January 29, 2011, 06:30:19 AM
Which ratios do those RK310 have? If they are near 1:1 or even 2:1  (and you wired them as step down), it will be hard to get compression at all. So first try to crank up the level of your input source, and adjust the "stereo adj" trimpots so that the 6AQ5 gets max level.
Could be that you have a functioning unit, but not enough gain into the sidechain.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 29, 2011, 06:36:57 AM
the RK310 is 1:1
RVX03 needs to be "full open"
Title: Re: D-LA2A Support Thread
Post by: electrisizer on January 29, 2011, 07:19:30 AM
hey thank you!!!

thats it!

the stereo adj was the problem  ;D  i crank it up -> now it works with nice full scale compression...

i tested the unit this morning. the noise floor is around -75-80db thats really good.
like the others i have too much gain. even if i use the grid stoppers i have oscillation when i crank gain pot to much...


theres a question left:

do i still need the 3k9 resistor for the VU? (like it wa said at nrgrecording)


Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 29, 2011, 07:23:19 AM
do i still need the 3k9 resistor for the VU? (like it wa said at nrgrecording)
yes, it is not on the PCB and needs to be added at the VU meter
Title: Re: D-LA2A Support Thread
Post by: Randyman... on February 01, 2011, 09:05:05 PM
So, since most everyone seems to "get by" w/o the Arco Trimmer Caps and w/o trimmer resistors for the T4B's (33K IIRC) - do you reckon I should just scrap them and see what happens w/o them (used fixed value components)?  I'm having a hard time figuring out how to mount the Arco Trimmer Caps, if I'd need to use shielded wire from PCB to Trimmer Cap, and then how in the heck to properly calibrate them once they are wired up.  I saw a small blurb on how to get the 33K T4B resistor spec'd, but I can't find anything concrete about the trimmer caps.

My Chassis should be here any day now, and the PCB's are stuffed with the exception of the Trimmer Caps.  Since they obviously had a reason for calibrating the original units, I can't help but assume these Arco Trimmer Caps and trimmer resistors for the T4B's should be installed and calibrated to have an "in spec" unit?  I have 4 of the Arco's staring me in the face (seem to be hard to find abroad) - so I'd like to use them.

Thanks for any further info.  I'm hoping to get this done very soon (once the chassis arrives), and I have a project that would benefit immensely with this compressor squashing away "in spec"  :D !

Thanks!  8)
Title: Re: D-LA2A Support Thread
Post by: drgrateful on February 02, 2011, 06:02:12 AM
I just finished my D-LA2A!  ;D

Everything seems to be working fine, but I can't figure out how to do the stereo adjustment. Maybe it's something simple that I don't understand (I am not an expert by any means) and hopefully someone will be able to help me out. I will detail the steps I followed (essentially, I followed the manual), hoping they will be useful to someone else in this thread:

1) I sent a 700Hz, 1.5Vpp sine wave to both channels.
2) I adjusted the two gain controls for equal output (by checking the VU meters), with peak reduction fully counterclockwise.
3) I made sure that RV103 and RV203 ("stereo adj") were set to  fully counterclockwise (I can here that click).
4) I placed the VU meter selectors in "gain reduction" position.
5) I advanced the gain reduction control of the left channel until about 5 db of reduction were shown on the meters.
6) As expected, the gain reduction was not the same for both channels. Then, I noted for which channel there was more reduction (for me it was the right channel) and turned clockwise RVX03 for that channel  (for me it was RV203), until both meters showed equal reduction.

Now, I would expect that the output levels for the two channels should be the same. For me, the are way different!
If the input levels are the same, and the gain reduction shown by the VU meters is the same, why are the output levels so different?  ??? ???

Thanks for any hint!!!  :)
Title: Re: D-LA2A Support Thread
Post by: herrmann on February 02, 2011, 10:45:03 AM
I don't know about stereo calibration, but are your T4b's matched ?
Title: Re: D-LA2A Support Thread
Post by: drgrateful on February 02, 2011, 10:59:03 AM
They are from Drip Electronics, and I asked for them to be matched.
Title: Re: D-LA2A Support Thread
Post by: thestudio on February 02, 2011, 11:45:05 AM
Seems to be a diffence is price in terms of power transformers Antek totals up to $44 but I see that there's one offered for $66? What's everyone using, prefered? 

Title: Re: D-LA2A Support Thread
Post by: horvitz on February 02, 2011, 03:34:38 PM
I just placed an order for this one:

http://www.antekinc.com/details.php?p=671

What are you looking at for $66?  As far as I can tell, there are only two choices for 250V.  The one with the single secondaries is $29 (and out of stock), the one with the doubles which I bought is $34.50.  Haven't actually received mine yet though so I can't comment on it.
Title: Re: D-LA2A Support Thread
Post by: Biasrocks on February 02, 2011, 06:32:19 PM
My Chassis should be here any day now, and the PCB's are stuffed with the exception of the Trimmer Caps.  Since they obviously had a reason for calibrating the original units, I can't help but assume these Arco Trimmer Caps and trimmer resistors for the T4B's should be installed and calibrated to have an "in spec" unit?  I have 4 of the Arco's staring me in the face (seem to be hard to find abroad) - so I'd like to use them.

Thanks for any further info.  I'm hoping to get this done very soon (once the chassis arrives), and I have a project that would benefit immensely with this compressor squashing away "in spec"  :D !

Thanks!  8)

Haven't tried it yet, but will because I've got a few Arco's sitting in front of me as well, from what I understand at least one of the trimmers affect the overall frequency response of the limiter (C4), the other is there for the sidechain eq iirc. Try using your measurement software and adjusting one of them for the flatest response without gain reduction. The other one you could probably get away with a fixed (recommended) value.

More info here

http://www.groupdiy.com/index.php?topic=254.msg2750#msg2750

and here

http://www.groupdiy.com/index.php?topic=3278.msg145013#msg145013

Mark
Title: Re: D-LA2A Support Thread
Post by: Randyman... on February 03, 2011, 10:29:50 PM
Wow - Good info there - thanks Mark!  Do you know if the Edcor transformers in Azone's BOM will "want" to be flat to 20K, or do they have some natural roll-off that shouldn't be over-compensated for in the primary frequency-response trimmer-cap calibration?  I liked the thought of switchable values in the sidechain - maybe once I get it all tweaked out I can select some fixed values that sound good and go from there.  Or optimize one sidechain for Vox and one for Room or Kick?

Also - How did you mount the Arco Trimmer Caps?  I'm assuming you ran some wires from the PCB pads and mounted them off-board somewhere?  Do these wires need to be shielded?  Does anyone have any pics of Arco Trimmer Caps installed in a D-LA2A build by chance?  I'm still a little unsure how I'm going to place/mount/wire them in my build.

Still waiting on customs to get me my chassis!!!  :D  The tracking info shows it's been sitting still in Customs for close to a month now.  Customs must be a very laid-back "get to it when you can" type job  ::)

Thanks again - Hope to have this baby up and running soon for an important project (important to me  ;) )

8)
Title: Re: D-LA2A Support Thread
Post by: benlindell on February 03, 2011, 10:52:49 PM
I just placed an order for this one:

http://www.antekinc.com/details.php?p=671

What are you looking at for $66?  As far as I can tell, there are only two choices for 250V.  The one with the single secondaries is $29 (and out of stock), the one with the doubles which I bought is $34.50.  Haven't actually received mine yet though so I can't comment on it.

Thats the one I got, it works great, I added a little 5Volt one with it for the relays.
Title: Re: D-LA2A Support Thread
Post by: drgrateful on February 04, 2011, 04:02:31 AM
Also - How did you mount the Arco Trimmer Caps?

just look at pp. 18-19 of this document:

http://www.kiwistudio.gr/pcb_manual1.pdf
Title: Re: D-LA2A Support Thread
Post by: Hank Dussen on February 04, 2011, 04:55:16 AM
Instead of these expensive Arco Trimmer Caps, why not mount two sockets in which you can insert different caps?
Title: Re: D-LA2A Support Thread
Post by: Kingston on February 04, 2011, 05:12:06 AM
I won't comment on mounting the Arco caps because that part takes only a little bit of imagination, but a word of advice on them nevertheless:

C4 acts very much like a high shelf filter above something like 10khz. It's in the feedback loop of the make up gain amp, and is used to set a flat response with your choice of output transformer. But this cap is such a central part of the amp it has a great effect on sound. And those Arcos are Sh*te! They do horrible things to the top end. I ended up getting a selection of silver mica caps in the range of the arco (something like 150-500pF if I remember correctly), then tested for the one that gave the flattest frequency response. (the socket idea above is great!)

But also remember that this horrible Arco is the LA2A sound like your grandma used to make. Great for those period perfect clones.

The similar Arco in the sidechain has barely any effect on sound. I had heard that it might have some effect on the compressors high frequency response like a "de-esser", but no matter what material I tried the trimmer had no effect on anything. You can even leave it out, or just use the recommended value. Won't make a difference. The very first LA2A's did not have it either.

The 1meg high-pass filter trimmer in the sidechain on the other hand, that belongs to the front panel of every LA2A. rotary as a 0-250k-500k-750k-1M selector would also work great, maybe on-off-on switch with settings of 0-500k-1M. This controls how much the compressor bites your bass.
Title: Re: D-LA2A Support Thread
Post by: pacemaker on February 04, 2011, 07:03:53 AM
mmm nice idea for the sidechain filter Kingston !
is that R37 on the L2A2 schematics ?
I also came across a CJ suggestion in the original LA2A thread
"If you really wanna have some fun, put a pot in place of R11 68 k feedback resistor"
My D-LA2A is in use now so i can't test this "mod"
and i'm trying to understand which effect it will have on sound,
add some nice harmonic distortion ? increase gain ?
do you ahve any idea kingston ?
Title: Re: D-LA2A Support Thread
Post by: Kingston on February 04, 2011, 08:14:51 AM
Yes, R37 is the high-pass filter. Has rather extreme effect on sound so like I said, put it on the front panel.

R11 is the global feedback resistor. LA2A make up gain amp is absolutely swimming in negative feedback with that 68k. It's a very linear amp, complete devoid of any recognizable tube distortion. You won't know it's tubes until someone tells you because the excess feedback removes all distortion.

R11 as a pot is basically an extra gain control. Try 50k in series with a 470k pot maybe. It will give you a lot of extra gain (and control), and you will be able make those 12AX7's sound distorted by removing feedback. But 12AX7 distortion sounds like crap and now you have a stupid amount of gain, so you probably don't want that. Harmonic distortion, yes, but not nice.

Solution: replace 12AX7 with 12AY7. You will lose some gain, but will be able to take it back by removing some of the excess feedback. Now the distortion sounds much better.

and NOW you have a tube amp!
Title: Re: D-LA2A Support Thread
Post by: pacemaker on February 04, 2011, 09:58:43 AM
yes ,i found it on another CJ's post :
"I subbed in an 12AY7 for the AX7a first stage amplifier. Less gain which helped the oscillation, plus you are  likely to find a 12AY7 that sounds better than your typical AX7a. More of a vintage sounding tube."
or :
"Drop a 6072 in for V1 and then tell us how you like it."
and agin  :
"Do you have a 12AY7 laying around? This tube makes a much better input stage than the 12AX7 for two reasons:
1) On the average it will sound nicer than the harsh 12AX7
2) It will reduce your gain so you can turn up the Gain pot above 1 with a CD type level input."

seems worth a try and maybe he's suggestion about R11 is with a 12AY7,
i also found this post from another member about changing 2 resistors :
"I also went ahead and replaced R9 and R13 with 100k resistors
(had a 12ay7 in for V1 for a while, just hadn't changed the resistors)."
and another :
"If you want to tame it even more, replace R9 and R13 with 100k.  This also has the effect of making clipping more symmetrical by biasing the tube closer to the mid-point.  I haven't tried these yet, but maybe one day..."
did you tried this tube change kingston ?
the R9 R13 100K and 12AY7 seems to be the perfect companion
for a R11 50k in series with a 470k pot mod, ;-)
can't wait to get my D-LA2A back and try this.
thank you so much for your explanation !!
regards,
francois



Title: Re: D-LA2A Support Thread
Post by: Biasrocks on February 04, 2011, 10:11:20 AM
Yes, R37 is the high-pass filter. Has rather extreme effect on sound so like I said, put it on the front panel.

R11 is the global feedback resistor. LA2A make up gain amp is absolutely swimming in negative feedback with that 68k. It's a very linear amp, complete devoid of any recognizable tube distortion. You won't know it's tubes until someone tells you because the excess feedback removes all distortion.

Really, no distortion??

My LA2 is set up with original UTC transformers. I can get a ton of distortion out of my LA2A. In fact when I first hooked it up I thought it was broken because the distortion was so high when I cranked the gain knob. I don't think I can get the gain knob past 70 without distortion in most cases.

I have used my LA2 as a distortion device from time to time, in fact did it on a vocal track just the other day. It can get very dirty and overdriven.  Why you'd want to increase the distortion is beyond me unless your using different ratios for transformers which may in fact help to clean up the distortion on the audio path vs the stock transformers A10/HA100X, A24.

Agreed with the SC HP on the front panel, very useful.

Regarding ARCO's, I haven't put them into my PTP build yet which is currently using Silver Micas in those positions. So no comment on how they compare soundwise. It doesn't seem like a big deal to mount them, no idea how you go about that on a PCB. Perhaps mount them temporarily to determine the correct value and them solder in a silver mica and call it done.

Mark
Title: Re: D-LA2A Support Thread
Post by: Kingston on February 04, 2011, 10:42:47 AM
Really, no distortion??

Not in the normal use case with even blast out mastering limited levels (10'oclock in the LA2A like they say). THD is below maybe 0.1%. That's in the linear region before you run out of headroom, no tubes to be heard, only transformers. With the amp swimming in negative feedback the roof of the headroom is very sharp, and since 12AX7 even without NFB sounds pretty bad, it's really the door to nasty-land. A great effect sometimes, that's why I have a switchable 15dB pad on the output transformer to really abuse it.

But I mostly like amps that budge out softer.

With less NFB and something like 12AY7, maybe even 12AU7/6SN7 we have more THD at lower levels but the distribution of harmonics is nicer. There might be 1% THD and everybody just says it's "more 3D", you know what I mean. And the roof of headroom is more forgiving. Easier sound shaping.

"If you want to tame it even more, replace R9 and R13 with 100k.  This also has the effect of making clipping more symmetrical by biasing the tube closer to the mid-point.  I haven't tried these yet, but maybe one day..."
did you tried this tube change kingston ?

Yes, but with several russian alternative tubes. I wanted to "break this horse" so to speak. I have another big tube experiment going but after that I might even go back and mod some more. The line amp of LA2A is ripe for it.

Changing those 220k plate resistors to something lower is indeed a good idea. The 220k are only good for the really high mu 12AX7's. You could even go and check the tube datasheet if you really want to optimise them (and the cathode bias resistors) to a certain tube. Making the distortion more symmetrical is not automatically better of course. Ears will tell, and since you can mod two channels at a time the D-LA2A is a good testbed for it.
Title: Re: D-LA2A Support Thread
Post by: audiophreak on February 04, 2011, 11:29:07 AM

  Kingston and All, thanks so much for this recent conversation, I am in the early stages of a D-LA2A and am acting like a sponge and soaking it all in    ;D
Title: Re: D-LA2A Support Thread
Post by: pacemaker on February 04, 2011, 01:00:13 PM
mmm output pad ?
very nice idea kingston,
do you have a rough schematic ?
Is it a T-pad, H-pad or other ?
for example 2 x 419R and a 220R resisotrs ?
thanks for the allreadygiven help
regards,
Francois
Title: Re: D-LA2A Support Thread
Post by: Kingston on February 04, 2011, 01:04:30 PM
Make it a 600in 600out ohm H-pad, http://www.nu9n.com/tpad-calculator.html

attenuation of 10-20dB works. Don't bother with accurate values from that calculator, just pick the closest resistor you have. 1dB here 2dB there, we're not fussy.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on February 04, 2011, 02:44:08 PM
nice explanations Kingston!

however, like with every project around here I would suggest:
build it stock first, mod it later if it doesn't fit your needs / expectation.

if you are planing any mods use sockets etc for the parts in question.
but build it stock first.

any possible trouble shooting will be easier if you started with a working stock unit.
Title: Re: D-LA2A Support Thread
Post by: pacemaker on February 04, 2011, 07:15:34 PM
yes you"re right volker ,
but as i've built 2 D-LA2A,
i wanted to add mods to the second one,
in order to explore all the aspect of this wonderful piece of gear ,
have two different units, listen to them
and if possible , learn a few things about electronics
 ;-)
Thanks to Volker for this amazing boards,
and thanks to all the brain around, CJ ,Kingston,SSLtech
who helps beginner like me ,
regards,
francois
Title: Re: D-LA2A Support Thread
Post by: Randyman... on February 04, 2011, 09:24:38 PM
Indeed - Thanks for the continued input!  It's a goldmine of info.

I think I will include the Arco caps in my build and possibly consider swapping out to a fixed value once I hear exactly what the differences are with the rolloff and my Edcor transformers.  I guess I can just find some type of plastic standoff and use a dab of silicone to mount the trimmer caps for now?  They look like they have a strange PCB mounting scheme - but they obviously won't fit on the D-LA2A PCB - and they don't have any mounting provisions aside from the leads that I can tell - but I haven't scrutinized them to the ends of the earth just yet.

I'll heed Volker's advice and start stock with the 12AX7 (already have them) - and ponder a 12AY7 and resistor mods after I finish the session I'm hoping to use the D-LA2A on!  The switchable front-panel Sidechain High-Pass will likely make it into the initial build.

Now, If I could just get my frigging case already and get to wiring!  :o

Thanks again for the wealth of info!  8)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on February 11, 2011, 03:29:25 AM
did some search for you and updated the first post (http://www.groupdiy.com/index.php?topic=32677.msg397252#msg397252) with some additional support links 8)
hope this helps to answer some FAQs.


and for sure I have to add the last two builds to our family  ;D
nice & unique work, gentlemen ;D ;D ;D

(http://www.51xaudio.com/images/DLA2A-electrisizer.gif)

(http://www.51xaudio.com/images/DLA2A-Soeren_DK.gif)
Title: Re: D-LA2A Support Thread
Post by: nielsk on February 11, 2011, 08:19:21 AM
Can someone explain for my benefit what the 100 ohm resistors to ground do on the 6vac inputs to the heaters?
Title: Re: D-LA2A Support Thread
Post by: thestudio on February 11, 2011, 12:02:10 PM
Is there any links or companies other than Par Metal, Hammond, Bud... for custom chassis/cases ???

Also, where could I get Vu meters that are angled 90 degree's opposed from each other. ><
Title: Re: D-LA2A Support Thread
Post by: electrisizer on February 11, 2011, 01:11:23 PM
@ volker thank you  :)

Is there any links or companies other than Par Metal, Hammond, Bud... for custom chassis/cases ???

Also, where could I get Vu meters that are angled 90 degree's opposed from each other. ><

i got my case from (german) ebay. there are some black 2 HEs around 27 euro... quite cheap but ok for custom things.
also cheap but very nice VUS can you get at hairball audio
Title: Re: D-LA2A Support Thread
Post by: pH on February 11, 2011, 01:47:32 PM
Quote
Can someone explain for my benefit what the 100 ohm resistors to ground do on the 6vac inputs to the heaters?

For transformers without a center tap on the heater winding a pair of well matched 100 ohm resistors to ground creates an artificial center tap. Without this you'll get a lot of hum.

-pH
Title: Re: D-LA2A Support Thread
Post by: herrmann on February 15, 2011, 10:01:26 AM
Hi
I'm about to finish mine. Just a quick question : is it ok to have about 90V DC on the output of C5 ? (i'm using sprague polarized).
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on February 15, 2011, 10:39:58 AM
C5 should block all DC - if you have 90V in front of the transformer there is something wrong.
Title: Re: D-LA2A Support Thread
Post by: herrmann on February 15, 2011, 11:06:23 AM
That's what I thought... In fact, yesterday I had Solen caps, and one channel was working, but on the other, I had 50v dc on the out of the cap (wich has burnt one of my carnhill  :-\). That's why I change both caps.
Title: Re: D-LA2A Support Thread
Post by: herrmann on February 15, 2011, 01:14:33 PM
Well, I really don't know what happens. All my voltages are good, I have 90V into that cap from the 12BH7, but they simply won't block this DC. Both.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on February 15, 2011, 01:54:12 PM
did you connect all grounds (correctly)?
could be just a measuring error - you are measuring in relation to where?
Title: Re: D-LA2A Support Thread
Post by: herrmann on February 15, 2011, 03:20:58 PM
All grounds are connected together to the case (3 pins on pcb + jumper). I'm measuring from this star ground. I maybe retry with the good Solen, as this is the only thing I've change since yesterday.
Title: Re: D-LA2A Support Thread
Post by: herrmann on February 16, 2011, 04:47:58 AM
Output cap needs to be loaded with the transformer to actually measure no DC... So, I guess in the beginning all my Solen caps were ok, and that was just the carnhill who was already faulty. Looking for problems, I have actually created them !
Title: Re: D-LA2A Support Thread
Post by: Randyman... on February 17, 2011, 10:22:59 PM
I have a troubleshooting inquiry:

I just finished my D-LA2A, and both channels pass audio.  CH1 works and compresses fine.  CH2's gain works fine but it doesn't show any gain reduction, and sounds a tiny bit distorted when I crank the Peak Reduction knob.

If I engage Stereo Link, I can tell CH2's detector is feeding a signal to CH1 (CH1 shows gain reduction from CH2 when linked).  So CH2's detector appears to be working fine, just no actual GR happening on CH2.

I already swapped T4's and tubes with the "good" channel, but the problem remains on CH2.

Any pointers on where to start looking?


Thanks to Volker and the DIY Forums!   ;D
Title: Re: D-LA2A Support Thread
Post by: Randyman... on February 18, 2011, 08:56:10 PM
Bump for any tips on my above issue (CH2 passes audio, but no GR).  I know the CH2 Sidechain is getting audio because CH1 responds to CH2's Gain Reduction when "Stereo Linked".  CH2 just doesn't do any GR, and sounds a little distorted when I crank the Peak Reduction control.

Tubes and T4B's were swapped between channels and the problem remained on CH2.  I'm a bit hesitant to start poking around with the unit powered on - so I'd LOVE to get a shove in the right direction before I go poking around the 250V hazards that lurk inside...

Thanks so much!  8)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on February 19, 2011, 03:55:02 AM
Randy:
- check if RV203 & RV213 are fully open
- look for bad solder joints at V201, C211, T4B
Title: Re: D-LA2A Support Thread
Post by: Randyman... on February 19, 2011, 07:21:25 PM
Will do.  I'll have some time on Sunday.  I'll take a peek and get back to you.

Thanks for your input, kind sir!!!  8)
Title: Re: D-LA2A Support Thread
Post by: electrisizer on February 20, 2011, 04:16:35 PM
hi,
im still having a fault: theres too much gain in my sidechain. especially on percussive sounds im getting distortion on both chanels as soon as im cranking up the peak red. pot.

my first idea it is that theres something special with the impedance of the 1:1 input tranny...

what do you think about changing the R105 to an lower and the R106 to an higher resistor value?
Title: Re: D-LA2A Support Thread
Post by: Randyman... on February 20, 2011, 11:03:08 PM
Randy:
- check if RV203 & RV213 are fully open
- look for bad solder joints at V201, C211, T4B

Hello again,

I checked RV203 & RV237 (I don't see a RV213), and they seem OK.  Adjusting them has no impact on CH2's lack of GR.  Solder joints look good at the other points mentioned as far as I can tell.

Any thing else I can try?  I might just have to use the one channel for a while as I have a Vocal session coming up and I was planning on using this box for obvious reasons :)


Also - Would the Limiter Response trim-pot be the one that would be moved to the "Side-Chain HP Filter" located on the rear of Tat's D-LA2A case?



Thanks for your continued help - I do appreciate it.   8)
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on February 21, 2011, 08:53:17 AM
Mouser is all out of Molex: 97-00-0445   or   538-97-00-0445   what is a suitable substitute that will work with the connectors?

Thanks! 
Title: Re: D-LA2A Support Thread
Post by: electrisizer on February 25, 2011, 08:32:49 AM
hey there,
still dont have a glue to get rid of distortion in sidechain...

description:

on both channels i have an high frequencey distortion as soon as peak red. is cranked up

it sounds similar to overdrive with line levels. example: one hit in bypass on hit in sidechain http://snd.sc/faxgXg (http://snd.sc/faxgXg)

so it seems to be an simple overdrive in the path. the only things that are not like in the stock build: 1:1 input trannys (haufe rk310-2)
datasheet: http://www.mikrocontroller.net/attachment/70260/www.kubarth.de_54_.pdf

the distortion exists before the stereo adj. (RV103). even at lowest RV103 and so with nearly no compression i have a distorted signal in the sidechain. my guess is that perhaps the T4 is driven too hard...

has someone an idea  ???
Title: Re: D-LA2A Support Thread
Post by: Randyman... on February 25, 2011, 10:07:59 PM
Your problem sounds oddly familiar to my CH#2 issue mentioned above (no GR, and slight distortion as the Peak Reduction is cranked up).  On mine, CH#1 works fine, and CH1 responds to CH2's Peak Reduction control when stereo linked - so I know I'm getting good sidechain audio out of CH#2 (just no GR on CH#2).  Very similar to your issue from what I can tell...

I'm hesitant to go poking around a powered D-LA2A (I was fearless with my 1176's and a "Poor Man's Scope"!) - so I'm kind of stuck ATM.  Watching your progress closely :)

I wish I would have fitted my chassis with the PCB Rails like Hairball's 1176 enclosure.  Then you can easily remove the bottom for troubleshooting w/o yanking wires out and ruining the nice wiring job (I'm not a fan of terminal blocks - I hard wire most everything)!  I guess I'm over-confident in my builds  :P

Best of luck to us both  :D
Title: Re: D-LA2A Support Thread
Post by: horvitz on February 26, 2011, 12:13:15 PM
All done.  Porn to share   :D

(http://nehpc.com/diy/D-LA2A1_sm.jpg)

(http://nehpc.com/diy/D-LA2A3_sm.jpg)

Best friends!!  ;D ;D

(http://nehpc.com/diy/group2_sm.jpg)
Title: Re: D-LA2A Support Thread
Post by: Randyman... on February 26, 2011, 06:49:43 PM
Small update on this older post of mine from Page 21:

Same here!  I ordered these and am also curious if they will work:

http://www.mouser.com/ProductDetail/Omron/G6A-274P-ST40-US-DC5/?qs=ISjK4nnpKfFgGVuxsXPgBw%3d%3d

They have an 80ma coil current and 400ma consumption rating instead of 100ma coil current and 500ma consumption like the ones on azone's BOM - but are both 5V, seem to have the same 2A switching capability and same footprint.

Anyone know if they will work properly?


The substitute relays I used had the +/- swapped (they are polarized) - so they didn't work at first.  I swapped the +/- 5v wires feeding the relays, but then the 4 small Diodes were shorting out the +5V regulator  :o .  So I snipped the diodes out, and it works fine minus some popping when switching the bypass in/out.  So if anyone uses these relays based on my previous post - make sure you are aware of this fact!


Question - Is the point of these diodes by the relays to prevent the relays from discharging back into the +5v path (pretty much back-EMF off the coil, correct?)?  Any harm in leaving them out - or should I replace them but install them "backwards" for my backwards relays?


PS - electrisizer - Any luck with your problem?  I'm hoping your solution will be very similar to mine for my CH2 issue...

horvitz - Purdy!  Hope to get some pics of mine up soon, but I want to wait until it's 100% "in the can".  I didn't use any headers, only the terminal blocks for the power transformer connection.  I like the cleaner look w/o headers, but it is making troubleshooting a PITA  ;)

PPS - I also saw drgrateful's post on how to mount the Arco's - makes sense!  Just add some makeshift leads and make them fit directly on the PCB.  I don't know why I couldn't see that w/o someone poking me with a stick.  I was about to mount them off-baord with some shielded wire and some silicone adhesive!  :o

Thanks  8)
Title: Re: D-LA2A Support Thread
Post by: poctop on February 27, 2011, 02:16:44 PM
Hello All,  I have this problem where the audio signal is always bypassed,  but the wierd thing is that i did make sure my ground was connected and there actually a pretty normal 5V on the really and the diode is reversed biased like it should, no wrong connection or bad solder  i checked evrything i could think of and everything should be working so i removed the relay and wired it manually and it works,  so my question here since i cannot put the 5VDC relay backwards and it is connected with 5Volt on it , why both relay on both channel are doing the same thing wich is with 5VDC on it its seems that the thing is bypassed anyway,  logically 4 realy cannot be bad, 

is this happened to anybody else ,  this should logically work and it is not,
is there something stupid i am missing , 

Thanks all,
Title: Re: D-LA2A Support Thread
Post by: poctop on February 27, 2011, 02:19:28 PM
Oh btw this is the realy is have been using
653-G6A-274P40-DC5

there must be an answer for this , seems so simple 5DC on the relay will put the unit in operating mode and 0VDC will bypass the unit ,
this is so wierd,
Dany,
Title: Re: D-LA2A Support Thread
Post by: electrisizer on February 27, 2011, 02:30:22 PM
hi randy

no luck here  :-\

i changed the r105 to 11k as mentioned at jensen site for 10k:10k input transformers. theres no difference to my ears (havent looked at scope, but distortion always there).

perhaps the input tranny is my fault because its on both channels. and there was another thread times ago with someones impedance problem about 10k input trannys.

i have still an oscillation when gain rises too much (i never need that gain but the gain pot mod dosent change that behavior). so this indicates perhaps the trannys.

ive checked audio signal at several points in the circuit and hear that the signal on T4s pin 3 is very loud and distorted. same at r133. but this musent be a fault...

next weeks i visit my fahter as he is a real "vintage man". building things since the 70s. not studio gear but hifi... has a scope and signal processors  perhaps he finds a solution.
Title: Re: D-LA2A Support Thread
Post by: Randyman... on February 27, 2011, 03:14:38 PM
Oh btw this is the realy is have been using
653-G6A-274P40-DC5

there must be an answer for this , seems so simple 5DC on the relay will put the unit in operating mode and 0VDC will bypass the unit ,
this is so wierd,
Dany,


Sounds like the EXACT same issue I posted about above yours!  I also had to substitute my relays from Mouser (see my above post for the ones I used).  My relays' +/- 5VDC connections are backwards from the D-LA2A PCB.  Compare the Relays in Azone's BOM to yours and see if they are also "backwards".

I had to swap the +/- that feeds each channel's relay traces.  Then the problem is that the diodes are backwards and cause a direct short on the +5 regulator.  You'll need to snip out the diodes above the relays and install them backwards (or leave them out like I did so far).

hi randy

no luck here  :-\

I'll keep my fingers crossed for you.  Sorry I'm not of any help...

 8)
Title: Re: D-LA2A Support Thread
Post by: poctop on February 27, 2011, 05:50:08 PM
thanks Randy Man i will triple check again ,  after a trace fix festival i will keep you posted ,
for sure because i wont sleep well tonight ,
Dan
Title: Re: D-LA2A Support Thread
Post by: alexc on February 28, 2011, 12:06:54 AM
Horvitz, that's some beautifully built unit(s) there.

I'd be very well proud of such high assembly quality.

Well done!
Title: Re: D-LA2A Support Thread
Post by: horvitz on February 28, 2011, 06:35:59 AM
Thank you very much, Alex!  I was hoping to get more than just test tones through the box this weekend, but the snow messed that up.  It does work fantastically though, and was a good fun build.

Randy/Dan - I assume you are looking at that relay due to the fact that the proper relay for the build is out of stock just about everywhere?  In mine, I wound up building the 5V section as 12V since the 12V version is in stock and my meters also have 12V lamps.  Maybe that would be easier than jamming that other one in there?

  Brian
Title: Re: D-LA2A Support Thread
Post by: poctop on March 01, 2011, 05:17:57 PM
Hi all,   some very important things that all should be awared,
1) C8 on the board is not on the Bom make sure you order C8 as well, think it is 0.1uf wima,
2) the use of polarized relay will not work on the board well depend on the convention i had an omron relay PN
653-G6A-274P40-DC5  and he did not work cause had the 5Volt backward to the polarity of my relay ,  it can be mounted backwards to the bottom of the board i guess,
3) i had a problem where compression would not occur before very too much gain and the reason was that i turned the stereolink fully clockwise and it should have been turn fully counter clockwise,  so depends on how you mount the trimmer there !,
4) i strongly suggest that you put some dip socket for the relay as well , just cut the pin you dont use on the sip,  so if you have a bad luck with those relay you will save the board and a lot of time been there done that got the T-shirt,
5) at some point in the developpement i had a channel noisier than the other one and i tried swapping 12ax7 arround the noise dissapaered,
6) make sure you put the jumper to the board to make your 5V relay gnd. this one pretty obvious but still !,
7) the zero GR meter adjustment and the GR tracking adjust are interrelated so you need to do it a couple of time to satisfy both condition,
8) please use a 100K trimmer on the board to replace the tracking resistor R125 and R225 so you can proceed to the GR tracking adjusments so easy,   


Well so far so good both channel compress and respond like they should more testing to come Zapppppsssss

Sincererly
 Dany,
Title: Re: D-LA2A Support Thread
Post by: AMaziad on March 02, 2011, 03:43:53 AM

(http://nehpc.com/diy/D-LA2A3_sm.jpg)



Horvitz, what power transformers are you using in your build?  I'm about to order my parts finally, and that is just about the last thing I need to source.

Thanks,

Ali
Title: Re: D-LA2A Support Thread
Post by: horvitz on March 02, 2011, 08:02:06 AM
Ali,

That's the Antek AS-1T250.  On the small one, I'm not home right now so I don't have my notes but it's the smallest Triad 15V (I think) I could find.. just do a search on Mouser.  You can see on the previous page that I built that out 12V rather than 5V, so if you're doing 5V this will not be appropriate for you.  Good luck!

  Brian
Title: Re: D-LA2A Support Thread
Post by: poctop on March 02, 2011, 11:24:51 PM
Here it is fully calibrated unit 100% functionnal thanks to silent arts,

Please Note than when performing stereo clibration unit on the right is the master unit, so peak red on left side is off,

Cheers ears,  i tought i attached all my testing so far with the unit,

Sincerly
Dan,
Title: Re: D-LA2A Support Thread
Post by: poctop on March 02, 2011, 11:27:05 PM
1
Title: Re: D-LA2A Support Thread
Post by: poctop on March 02, 2011, 11:28:15 PM
2
Title: Re: D-LA2A Support Thread
Post by: poctop on March 02, 2011, 11:28:53 PM
3
Title: Re: D-LA2A Support Thread
Post by: poctop on March 02, 2011, 11:29:34 PM
4
Title: Re: D-LA2A Support Thread
Post by: poctop on March 02, 2011, 11:30:03 PM
5
Title: Re: D-LA2A Support Thread
Post by: poctop on March 02, 2011, 11:43:46 PM
Hi All,

Now here a little explanation the title of the picture is wrong,  the 2 first picture represent the response under no compression but the unit is in operation mode,  we notice i slight bump in the high for the 2 channel,  Channel 2 has a slighlty more accentuous high, the only diffence is that C4 C14 are 390pf maybe a bit too much but this is for a test purpose,  the channel 1 has slighlt less high end    c4 c14 are 240pf so this will have to be tweaked,
The last two picture are the compression 100% curve before and after the limiter response adjustments you can notice how the high is flatter after the adjustments,

Well this is it maybe it is time to enjoy the baby now,

Sincerly Dan,
hope this helps,
Title: Re: D-LA2A Support Thread
Post by: poctop on March 02, 2011, 11:46:32 PM
Channel 2 example
Title: Re: D-LA2A Support Thread
Post by: poctop on March 02, 2011, 11:47:40 PM
Channel 1 example 240pf
Title: Re: D-LA2A Support Thread
Post by: poctop on March 02, 2011, 11:49:03 PM
just to mention Those curves were produce with DLa2A with Jensen in and out,
regards,
Dany,
Title: Re: D-LA2A Support Thread
Post by: poctop on March 03, 2011, 12:06:18 AM
a quick suggestions for any lighting solution with the 5V make sure your heatsink is big enough with this guy get about 45degC on the chip i installed a small one first and changed my mind.

Dany,
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 03, 2011, 02:56:26 AM
Aaahhh, I love seeing new finished D-LA2As  ;D ;D ;D

Mr. horvitz, you did a very nice and clean job, congratulations.
The design fits perfectly to the PM670 friend, you found your own design :) :) :)

(http://www.51xaudio.com/images/DLA2A-horvitz.gif)

Mr. poctop,
thanks for your tips and observations. I added a link in the first post.
Nice and neat job too!
BUT I'm missing a unique poctop front panel ;) ;) ;)

(http://www.51xaudio.com/images/DLA2A-poctop.gif)

now, keep them coming  ;D ;D ;D
Title: Re: D-LA2A Support Thread
Post by: electrisizer on March 03, 2011, 06:16:09 AM
just to mention Those curves were produce with DLa2A with Jensen in and out,
regards,
Dany,


hi poctop,
are this 10k:10k jensen?
 
have you done the jensen mod?

http://www.jensen-transformers.com/as/as091.pdf
Title: Re: D-LA2A Support Thread
Post by: poctop on March 03, 2011, 06:07:51 PM
No Just the zobel 11K mod,  my board was already stuffed when i saw that apps, any feedback as if the full mod is worthed now,  only 3 Resistor and 1 extra cap,  i felt that i did want to set my mallory cap at 30$ for the one i received form jensen a 22uf 450,  i dont know my top end positive slope is caused by that or my c4 that not where it should be,  i will try C4 first and do some more sweeps.

Kepp ya posted,
Title: Re: D-LA2A Support Thread
Post by: poctop on March 03, 2011, 08:35:00 PM
Problem with that wierd top end with Jensen Solved tweaked C4 to obtain this flat curve for the makup gain circuit,
1) final picture gain response
2) final picture gain reduction response

finally a value of c14 300pf and C4 = 100pf did the trick for the jensen out,

cheers,
 2 picture in the next post,

Title: Re: D-LA2A Support Thread
Post by: poctop on March 03, 2011, 08:35:46 PM
Gain Reduction response,
Title: Re: D-LA2A Support Thread
Post by: poctop on March 03, 2011, 08:41:48 PM
Thanks to everyone,

...............Next Project...............................................
Dan,
Title: Re: D-LA2A Support Thread
Post by: Randyman... on March 03, 2011, 09:25:43 PM
Hello,

Sorry to keep bombarding the forum with troubleshooting inquiries - but does anyone have any more generous "hand-outs" for me on my below issues?


Bump for any tips on my above issue (CH2 passes audio, but no GR).  I know the CH2 Sidechain is getting audio because CH1 responds to CH2's Gain Reduction when "Stereo Linked".  CH2 just doesn't do any GR, and sounds a little distorted when I crank the Peak Reduction control.

Tubes and T4B's were swapped between channels and the problem remained on CH2.  I'm a bit hesitant to start poking around with the unit powered on - so I'd LOVE to get a shove in the right direction before I go poking around the 250V hazards that lurk inside...

Thanks so much!  8)

Randy:
- check if RV203 & RV213 are fully open
- look for bad solder joints at V201, C211, T4B

Hello again,

I checked RV203 & RV237 (I don't see a RV213), and they seem OK.  Adjusting them has no impact on CH2's lack of GR.  Solder joints look good at the other points mentioned as far as I can tell.

Any thing else I can try? 

Thanks for all of the gracious people's efforts that made this wonderful project possible.  I'll post pics as soon as it's 100% working (I think it looks great :) )...  I've got plenty of other projects to keep me busy for months (5 more compressors waiting on assembly  ;D ), but I'd really like to get this nipped in the bud before moving on...

 8)
Title: Re: D-LA2A Support Thread
Post by: poctop on March 03, 2011, 11:08:21 PM
Hi Randy, try to chart the voltage you have on the working channel and compare them with the original schematic and the la2a deconstructed,
there is specific voltage point on the schemo, and also on the la2a deconstructed that will  help you summarize what is going on in the la2a,
i am still working on it to fully understand it fully.

http://www.twin-x.com/groupdiy/albums/userpics/LA2A-deconstructed.jpg

http://www.waltzingbear.com/Schematics/Urei/Urei_LA-2A.JPG

once you chart everything point that is normal ( workiung channel)  i would suggest to make a table and compare them with the non working channel maybe it will point in some directions,  dont forget also about that neon lamp or zener diode on the board it is related to the t4cell.

hope this helps ,

Dany,
Title: Re: D-LA2A Support Thread
Post by: college101 on March 08, 2011, 10:50:38 PM
OK GUYS! I just completed my La-2a and it wont pass signal...needle is stuck at 20 instead of dropping to zero? where should I go..I set it up with the sowter replacement 1968 transformers and recproaudio style turret board set up!  AC voltage at heaters is 262
Title: Re: D-LA2A Support Thread
Post by: poctop on March 09, 2011, 03:48:18 PM
there is a slight possibility you wired the pot Gain pot Wrong then it is in complete oscillation when the pots is off, , if you have signal to the meter you are almost there, hang in there, the heater voltage should arround 6-7V maybe there is something wrong in your wiring to the tube,  check the heater wiring
refer to the schemo for proper voltage test points to start with.
hope this helps ,

Dany,

Title: Re: D-LA2A Support Thread
Post by: college101 on March 09, 2011, 06:23:16 PM
NO signal to the meter...I did use the sowter transformers...Ive been reading around on the net and people have been saying that you need to use "grid stoppers" with the sowters? Im lost on that one  Can someone explain what the grid stoppers are to me?

Next..Do I need to put in the two 100k res on the green heater lines?  The 100k res are then linked back into one of the caps negative sides

The light NE-1 is working with the zero adjust...and it does discharge the caps in a timely manner

I plug'd in a tube mic with a power supply, and attempted to get signal threw the input...nothing, meter wont even budge...Im going over it again tonight to try and figure it out...

I set it up just like cayacosta turret board build( only difference is that I used the sowter trannys) but theoretically, they are set up the same...

For reference...I used the sowter 1009 input and 1010 output... Help guys..Im so close yet so far away!
Title: Re: D-LA2A Support Thread
Post by: college101 on March 09, 2011, 10:44:55 PM
OK..so I changed the input wiring...reversed what I had set up previously...no signal to vu meter...and wiring looks correct

BUT when I turned off the unit this time...caps discarged in like 2 seconds...

for real though...no signal in? as of right now ??? :o
Title: Re: D-LA2A Support Thread
Post by: college101 on March 10, 2011, 06:19:58 AM
anybody reading this thread anymore??
Title: Re: D-LA2A Support Thread
Post by: tmuikku on March 10, 2011, 06:30:30 AM
anybody reading this thread anymore??

Yes, even if I'm not building one, patience is a virtue ;). Here is general advice: Perhaps you should triple check your wiring and do homework about things you don't understand. Try to look at the schematics and really understand what things do and where signale goes and what it should look like and compare to what it actually looks like if you have an oscilloscope. At least confirm voltages on tubesockets etc. Basic troubleshooting.

People will answer when you've got more definitive questions. For example gridstoppers, first hit with Google: http://www.freewebs.com/valvewizard/gridstopper.html

Hopefully you'll get answers and the thing working soon!:)
-T
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 10, 2011, 06:43:40 AM
anybody reading this thread anymore??

yes, but this thread is about a different beast called D-LA2A.

questions about cayacostas turret board build should be asked in the main LA2A thread:
http://www.groupdiy.com/index.php?topic=3278.0
Title: Re: D-LA2A Support Thread
Post by: poctop on March 10, 2011, 03:37:58 PM
I have a question here while experimenting with my new D-La2A i notice something and i am not sure if this can be adressed or not,
i have the universal audio plug in to compare with this one,  so my observation were that i could not get more than arround 7 db of compression and my attempt to use it to reamp a drum buss were really cool but i noticed that it was kind a difficult to squash the thing like with the plug-in, i have to put the gain reg a mostly 100% to start getting a full squash and could not get the GR more than 6-7db at 100% reduction,  my unit is equipped with the jensen and i found the gain with a 100K very enjoyable but it seems that i have a hard time reaching the squashing zone with the GR at 100%,  is there something i could do about this,  when reamping i had my in and out at +4db line,  and it seems that i had better results with the seeting on my RME set at Hi gain a bit more juice than the +4db, So the question is there a way of driving this cell more to obtain a results more comparable to the UA plugin or it is just a question that the signal at the input would be higher gain to feed the compression circuit, 

well if anyone has a comments on this this will be appreciated very much,
Regards,
Dan,
Title: Re: D-LA2A Support Thread
Post by: poctop on March 10, 2011, 03:41:39 PM
Please let me clarify a single details here i have the T4B from studioelectronics these are OEM universal audio.
D
Title: Re: D-LA2A Support Thread
Post by: electrisizer on March 11, 2011, 06:00:04 AM
i have to put the gain reg a mostly 100% to start getting a full squash and could not get the GR more than 6-7db at 100% reduction, 

thats strange!
 
like said before i have 1:1 transformers too on input - but - tons of gain (still with the 25k pot) and full scale compression about 12db. unfortunatly little distortion.

for sure the la2a needs to be driven hard but i never use the high gain on my RME to feed the la2a. but when im putting the audio signal in without input tranny i nearly have no compression (max 2db) in a +4 line enviroment.

whats your r105?

Title: Re: D-LA2A Support Thread
Post by: poctop on March 11, 2011, 09:39:10 AM
Thanks for your reply here very appreciated,  so this is the thing i cannot drive more than 6-7db compression at 100 GR with a lot of signal to come in i would like it to squash to death but its not,   the only modification i have done for the Jensen is the R105 wich is 11K instead of 68K,  do you think if i applied the remainer of the La2A mod in the region of the 12BH7 itcould help my problem,  well the thing is working but i was expecting the ability to squezze it more than 6-7db at full GR,  Let me me know if i should put it back to 68K and will it help my case, 

thanks for you comments ,

Dan,
Title: Re: D-LA2A Support Thread
Post by: poctop on March 11, 2011, 09:43:13 AM
I also made sure that my tracking was calibrated properly with the R125 used a (100Kpot) they were pretty close at arround 30-40K  and the Zero adjust,  even by hear i could hear more like it should squash more than this ,   i have a 100K pot on GR is this correct,
Dan,

Title: Re: D-LA2A Support Thread
Post by: poctop on March 11, 2011, 09:54:45 AM
I was thinking about that limiter response pot that i ajdusted to get a flattest response as possible ( picture in the previous page ) maybe i should give it a shot with a maximum rolloff in the highs to see if it will increase the squash

what would you think of this ?

Any other stuff i could try,

thanks all,
dan.
Title: Re: D-LA2A Support Thread
Post by: Biasrocks on March 11, 2011, 10:33:03 AM
I was thinking about that limiter response pot that i ajdusted to get a flattest response as possible ( picture in the previous page ) maybe i should give it a shot with a maximum rolloff in the highs to see if it will increase the squash

Yes, this will solve your problem. In most cases that control should be maxed.

Mark
Title: Re: D-LA2A Support Thread
Post by: poctop on March 11, 2011, 11:55:17 AM
Thanks all, For all our help on this,

I readjusted the limiter response to get the control to get max compression and Voila,  got -12db compression with a signal of 0 db at input this will lead me where i want to go,

this is fantastic,   i need to mention that this build is dead quiet and sounds fantastic,

thanks Again for your help and figures to compare with ,

sincerly Dany,

Title: Re: D-LA2A Support Thread
Post by: poctop on March 11, 2011, 05:29:36 PM
Just want to add that i finally tried my dla2a in recording mode and my SM57 sounds like a U87,

No Kidding,

Attention everyone,  please build one of those thing as soon as possible, or you will regret it the rest of your life.

Silent:arts Rocks..................................................
Title: Re: D-LA2A Support Thread
Post by: telefunk on March 12, 2011, 08:43:10 AM
First of all i'd like to say HUGE THANKS to Volker!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I built my D-LA2A already few months ago and we've already made two albums worth of material with it and lots of mixes and all i can say that it's one of the finest pieces of gear i've used.

Mine was done with T4b's by Kenetek, absolute perfection I must say.

But there's one tiny little issue i'd like to fix:

When i crank the Gainpot to around 3 o'clock, there is HUGE amount of gain which is great BUT just before the pot is at full, the signal drops out and the VU meters at the console where the la2a is inserted, start to read FULL, but no sound.

It doesnt really matter that much since i wont ever need that much gain but i'm just interested if this can be fixed and why is it happening.

Title: Re: D-LA2A Support Thread
Post by: Biasrocks on March 12, 2011, 10:21:47 AM
When i crank the Gainpot to around 3 o'clock, there is HUGE amount of gain which is great BUT just before the pot is at full, the signal drops out and the VU meters at the console where the la2a is inserted, start to read FULL, but no sound.

To the Carly Simon tune Anticipation - "Oscillations are making me crazy, are getting me down."

Try re-orienting your off board wiring to see if it goes away.

Mark
Title: Re: D-LA2A Support Thread
Post by: drgrateful on March 13, 2011, 05:20:12 AM
Here's my new D-LA2A!

Unfortunately, while the left channel is dead quiet, on the right channel I get quite a lot of hum. I tried swapping tubes between the two channels, but the problem persists. I guess this excludes the problem source is in the tubes (am I correct?) Thanks for any suggestions!
Title: Re: D-LA2A Support Thread
Post by: drgrateful on March 13, 2011, 05:21:34 AM
Another picture...
Title: Re: D-LA2A Support Thread
Post by: drgrateful on March 13, 2011, 05:22:11 AM
And another one...
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 13, 2011, 08:42:59 AM
Here's my new D-LA2A!
no front panel pics ???
inside looks good, congrats!

Unfortunately, while the left channel is dead quiet, on the right channel I get quite a lot of hum. I tried swapping tubes between the two channels, but the problem persists. I guess this excludes the problem source is in the tubes (am I correct?) Thanks for any suggestions!
disconnect the pilot lamp and the power switch (in the middle, I guess?) first ...
Title: Re: D-LA2A Support Thread
Post by: drgrateful on March 13, 2011, 02:35:50 PM
There you go... Here's a picture of the front panel...

Thanks for the suggestions on the pilot lamp and the power switch: I will try and let you know how it works...
Title: Re: D-LA2A Support Thread
Post by: creal on March 14, 2011, 09:43:29 AM
My DLA2A(ugly frontpanel), is alive.  ;D
I love this unit, just needed to finish the layout for the definitive frontpanel. i'll replace the VU switchs by the ITT switchs like others for a 'UREI LOOK' and make a clean wiring to void the ground noise.
Except this points all works perfectly
I'll post others the picture when i recieved the definitve front panel by Frank.
I hope close the box soon ;)
Many thanks Volker for this great project.
PS: Thanks to all, for the precious infos i've found in the thread
Title: Re: D-LA2A Support Thread
Post by: drgrateful on March 14, 2011, 11:54:15 AM
disconnect the pilot lamp and the power switch (in the middle, I guess?) first ...
It was the power switch! More precisely, the wires going to the power switch needed to stay away from the wires going to the limit/comp switch. Now everything is good (no more hum)! Thanks for all the useful info!  :D :D
Title: Re: D-LA2A Support Thread
Post by: drgrateful on March 14, 2011, 11:59:22 AM
But there's one tiny little issue i'd like to fix:

When i crank the Gainpot to around 3 o'clock, there is HUGE amount of gain which is great BUT just before the pot is at full, the signal drops out and the VU meters at the console where the la2a is inserted, start to read FULL, but no sound.

It doesnt really matter that much since i wont ever need that much gain but i'm just interested if this can be fixed and why is it happening.
Telefunk: I am experiencing your same (very minor) issue. Only on one channel, just before the gain reaches 100%, I here a small pop and the VU meter starts to read full (without sound). On the other channel this does not happen. Let me know if you find out what causes this...
Title: Re: D-LA2A Support Thread
Post by: Borja Lopez on March 14, 2011, 03:06:38 PM
First, thanks to all the members of this forum and especially to Volker the master of the creature...
After one week solving problems in my project, finally partially works.

It works well with a mono unbalanced signal but when I try with a balanced signal a lot of hum appears. The problem is the same in both channels. I have tried to move and shield cables, but nothing changes.

And also I have the same problem as Telefunk and Drgrateful, when the gain pass 3 o'clock the signal drops and the VU meter read full.

Thanks for all suggestions.

Borja
Title: Re: D-LA2A Support Thread
Post by: timmygrimm on March 14, 2011, 03:58:00 PM


Is there a wiring diagram which shows how all the pots / switches should be wired, or are people just going off the schematic?

I'm assuming that the 5v relay pin by the power supply should go to both the bypass switches, switching power to the other relay pins to take the unit out of bypass?

forgive the dumb questions

thx

tim
Title: Re: D-LA2A Support Thread
Post by: creal on March 14, 2011, 04:07:02 PM
@ timmygrimm,
Check the good wiring by stereokilla  ;)

(http://i296.photobucket.com/albums/mm171/renbis/DIY/TARGET__LA2_rev01_Platinenl-1.gif)
should be help you


Title: Re: D-LA2A Support Thread
Post by: timmygrimm on March 15, 2011, 01:10:11 AM

rad... thank you
Title: Re: D-LA2A Support Thread
Post by: Borja Lopez on March 20, 2011, 12:47:55 PM
But there's one tiny little issue i'd like to fix:

When i crank the Gainpot to around 3 o'clock, there is HUGE amount of gain which is great BUT just before the pot is at full, the signal drops out and the VU meters at the console where the la2a is inserted, start to read FULL, but no sound.

It doesnt really matter that much since i wont ever need that much gain but i'm just interested if this can be fixed and why is it happening.
Telefunk: I am experiencing your same (very minor) issue. Only on one channel, just before the gain reaches 100%, I here a small pop and the VU meter starts to read full (without sound). On the other channel this does not happen. Let me know if you find out what causes this...

I have solved the problem with the distortion in the gain, passing 3 o'clock, using tubes 12at7 instead of the 12ax7. I think the lower mu factor could aid. I'm using edcor 600/15k 1:5 for the input, but I don't know at the moment the origin of the problem.
I have also solved the hum problem, a bad resistor in both chanells...
Title: C105, C205
Post by: dandeurloo on March 24, 2011, 02:51:52 PM
Hey guys I have looked through the thread and haven't really seen an answer to the sound of different caps here.  I am planning on building a High End version that I can use on the mix buss.  stepped switches and a few mods.  I am now ordering parts and wondering if anyone has any suggestions for these caps for a Mixbuss/mastering version of this comp.

Also, anyone else have any part suggestions for this kind of build?

Note:  I don't care it sounds like an original I just want it to sound great!
Title: Re: D-LA2A Support Thread
Post by: Hank Dussen on March 24, 2011, 03:39:13 PM
I suggested this already in the main LA2A threat but think it's such a great idea I'll post it again  ;)
Install sockets so you can try different caps!
Title: Re: C105, C205
Post by: telefunk on March 24, 2011, 03:40:03 PM
Hey guys I have looked through the thread and haven't really seen an answer to the sound of different caps here.  I am planning on building a High End version that I can use on the mix buss.  stepped switches and a few mods.  I am now ordering parts and wondering if anyone has any suggestions for these caps for a Mixbuss/mastering version of this comp.

Also, anyone else have any part suggestions for this kind of build?

Note:  I don't care it sounds like an original I just want it to sound great!

What caps are you exactly talking about?
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on March 24, 2011, 03:59:26 PM
I saw that and i ordered a few extras.  so think i will try that!  Any thoughts on transformers.

I suggested this already in the main LA2A threat but think it's such a great idea I'll post it again  ;)
Install sockets so you can try different caps!
Title: Re: C105, C205
Post by: dandeurloo on March 24, 2011, 04:01:32 PM

C105 and C205.  these are the pricey ones.  The mallory is $27.25 for one.  So I though I would ask before buy those plus the others.



Hey guys I have looked through the thread and haven't really seen an answer to the sound of different caps here.  I am planning on building a High End version that I can use on the mix buss.  stepped switches and a few mods.  I am now ordering parts and wondering if anyone has any suggestions for these caps for a Mixbuss/mastering version of this comp.

Also, anyone else have any part suggestions for this kind of build?

Note:  I don't care it sounds like an original I just want it to sound great!

What caps are you exactly talking about?
Title: Re: D-LA2A Support Thread
Post by: tmuikku on March 24, 2011, 04:30:06 PM
russian PIO caps seem to get votes around here. They are very large in physical size, but are still reasonably priced in ebay ;)
Title: Re: D-LA2A Support Thread
Post by: telefunk on March 24, 2011, 04:30:25 PM
c105 & c205. If you want high-end, get Solens. Around 14€ in europe, not a big deal if you consider using them for decades.

I bought Edcor WSM 600/15K & 15K/600, they work like charm.
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on March 24, 2011, 04:52:29 PM
These? 
http://www.tubedepot.com/cp-so-1000-630v.html
Title: Re: D-LA2A Support Thread
Post by: telefunk on March 24, 2011, 07:22:28 PM
Exactly.

dont you have the Azone BOM? It's all there.
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on March 24, 2011, 07:46:28 PM
yep, I'm going off of that.  I just was wondering about High End Mastering build.  That BOM is very helpful just checking on a few of the "options".


Title: Re: D-LA2A Support Thread
Post by: dandeurloo on March 24, 2011, 09:30:04 PM
Also, does anyone have an answer to what are the proper relays to be using?  Seems the 653-G5V-2-DC5 are not working properly for some guys and they are also on back order from mouser.  Any ideas of a different part that will work fine?


EDIT:  How about this one from mouser? G6A-274P-ST40-US-DC5 or Digi Key has the 653-G5V-2-DC5's. 
Title: Re: D-LA2A Support Thread
Post by: Kingston on March 25, 2011, 05:37:47 AM
Those original 5V Omrons are perfect. They are just about the most trustworthy part on this whole layout. If you can't find them, any other small signal 5VDC relay that has the same layout can be used as a replacement. They are nothing but DPDT switches afterall.

If they are not working it's always a user error. Error in the 5V supply, or possibly diodes soldered the wrong way around. Besides, you don't actually need the diodes in this circuit.

If you are interested in the sound of different caps, see the original LA2A help thread. There was plenty of discussion just some months back. To recap, use cheap/standard electrolytics for LA2A like your grandma used to make or use PIO caps (russians are cheap) for the very high end.
Title: Re: D-LA2A Support Thread
Post by: poctop on March 30, 2011, 11:23:56 PM
All you have to know about those relay if you read my comments on the first page is that the ideal is to have an unpolarized realy that will work no matter how and you dont have to change the diode, if you do have polarized relay check the polarity the 5V + side will be fed by the right side of the board if looking at the normal position in the chassis,  i had the experience with the the substitue relay by mouser had the + side on the left side ( watch the fine prints on the realy it says bottom view so it is actually inverted as you see it),  so i did not work at all,  you can mount the relay to the bottom of the boards wich will correct the polarity and no change in the diode but not very esthetic or simply make sure that your relay will work whatever the polarity ( unpolarized relay) I also recommend that you mount the relay on a dip socket so if you make a mistake or had the bad relay in there it will be magic to put another one,  this pretty covers it,  let me know if it works for you
sincerly,
Dany,
 
Title: Re: D-LA2A Support Thread
Post by: desol on April 01, 2011, 11:53:00 AM
I am wondering how i can place a switch like Kingston's in place of a 1m pot for the limiter response.
I'd like something switchable rather than variable. The way i understand it is, that at a value of 1m the limiter passes full bandwidth, but with trimmer at fully counter clockwise (no resistance) the limiter doesn't respond to lower frequencies(100hz and down)...is this correct?

So, i'm thinking I would just hang a 1mohm resistor off one side of a spdt switch and nothing off the other side(wire) to get a switchable sidechain effect..
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on April 01, 2011, 11:07:41 PM
hey guys, i'm getting close! 

I plan on ordering this for the main power:

http://www.antekinc.com/cart.php?redirect=http://www.antekinc.com%2Fdetails.php%3Fp%3D671

Does anyone have a suggested 5v transformer for the relays?



Thanks
Title: Re: D-LA2A Support Thread
Post by: desol on April 02, 2011, 09:25:40 AM
Well, on my power transformer i have 9v at 1amp on the relay secondary. So, i'd probably say that anything from an-0106 up to an-0109 would be fine. One member took his 5v from the heaters, although i'm not sure how good that would be to do, probably better with a dedicated transformer. Also had a look at your power transformer, as-1t250 looks right rather than the 350. 250 has 4 x outputs and the correct output voltage, whereas 350 only has 2x outputs at a higher voltage.
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on April 02, 2011, 11:40:33 AM
Desol thanks.  That link should be for the AS-1T250.  I have it in my cart!

As far as the relays I think I'll grab the An-0005.  Seems simple enough.

Let me know if I should be looking someplace else.

The only thing left to get are transformers and Optos from Drip!  I can't wait to use this baby.
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on April 03, 2011, 04:38:07 PM
The relays on the BOM our out of stock everywhere for months.  Does anyone know if this is a good alternative?

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=19022E2U0-ND
Title: Re: D-LA2A Support Thread
Post by: band_master on April 07, 2011, 04:44:40 PM
hey guys,
i just finished my build, been reading up a ton on this thread. feels good to make my first post! I fired up the unit last night and have a couple issues...

1. I don't seem too have much gain. I have to set the pot to 7 or 8 to match the level when bypassed. this is for both channels.

2. if i set the gain on channel 2 above 8 the needle is buried and i get distortion.

3. i have to turn the gain and peak red knobs all the way up to meter any GR at all. I assume this is related to low input gain?

I am using Edcor WSM 600/15K input and 15K/600 output and following the wiring below. Is this correct? Pin 2 and Ground are both the center tap, yes?

INPUT edcor XSM 600/10k
edcor pin 1 = 4383 brown
edcor pin 2 = 4383 pink
edcor pin 4 = 4383 green
edcor pin 5 = 4383 blue
edcor pin 8 = 4383 grey
edcor ground= 4383 black

OUTPUT edcor XSM10k/600
edcor pin 1 = 8940 yellow
edcor pin 4 = 8940 green
edcor pin 5 = 8940 grey
edcor pin 8 = 8940 pink
edcor ground= 8940 black

I am wondering if perhaps i damaged the 12BH7A tubes? I had them swapped out with the AX7 in VX03 in both channels. When I first installed the meters I was reading some GR but then I used the Zero adjust RVX04 pots to set them to zero as per the La2a manual.

I also installed a 100K pot at RX27, do I need to ground that or no?

I also tried turning RVX37 and RVX03 all the way counter clockwise. This had no effect. Stereo link mode also seems to not be working, but I figure first thing is to figure out what is wrong in dual mode. here are some pics, the nice faceplate was made by Dan at Collective Cases. Thanks Dan and Thanks Volker for the wonderful PCB!!!

BD

(http://farm6.static.flickr.com/5183/5598952380_d0691be8d9.jpg)
(http://farm6.static.flickr.com/5303/5598952226_2c5b3fe75b.jpg)
(http://farm6.static.flickr.com/5230/5598371025_e6bb423278.jpg)

Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 08, 2011, 01:51:45 AM
Hi BD,

nice your registration to the forum finally did happen :)

first, wire your Edcors correct, without any center taps


INPUT edcor XSM 600/10k
edcor pin 1 = 4383 brown
edcor pin 4 = 4383 green
edcor pin 5 = 4383 blue
edcor pin 8 = 4383 grey
ignore pink and black

OUTPUT edcor XSM10k/600
edcor pin 1 = 8940 yellow
edcor pin 4 = 8940 green
edcor pin 5 = 8940 grey
edcor pin 8 = 8940 pink
ignore black
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on April 15, 2011, 01:44:14 PM
Ok, before I solder all these resistors in I want to make sure I am 100%.  So according to the BOM for a 100K switch I place the 10.5k resistor at position 0 not position 1 on the ELMA?

Does this mean that position 22 has no resistor?







2. Elma 24-position switches [edited]
I installed the resistors to the Elma switches. Two of them are set for 100k log and two for 33k log (to be used in series with 68K resistor for less gain).
If you haven't used switches like this before where you add your own resistors etc.. it can be confusing.
a) Look at it as a potentiometer, a voltage divider, since this is what it is anyway, a stepped attenuator. Check out this Elma schematic from the Goldpoint Level controls website http://www.goldpt.com/schm_ser.html

(http://alphazone1.com/x0xi0/web_images/la2a/elma_rotary_schematic.gif)

b) Realize that the end-stop is before position 0, and the first resistor R1 should go at position 0.
c) The marking on the Elma part shows 0 to 22. These marking fall between switch positions and can be thought of as resistor numbers. There will be (23) resistors total when completely fitted.
d) Use silent:arts log-pot-to-switch excel document to calculate the resistor values.. http://www.silentarts.de/DIY/PM660/LogPotToSwitch.xls

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-12sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-12.jpg)

(http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-11sm.jpg) (http://alphazone1.com/x0xi0/web_images/la2a/azone-dla2a-11.jpg)

Title: Re: D-LA2A Support Thread
Post by: band_master on April 15, 2011, 02:41:04 PM
thanks volker! just got a chance to fix the i/o xformers last night and now i am getting HUGE gain. also, it seems like the link mode is working properly as well. I will do some more calibration and testing over the weekend. quick question though, what is the best way to wire power to the jeweled power lamp and meter LEDs?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 15, 2011, 03:06:46 PM
Ok, before I solder all these resistors in I want to make sure I am 100%.  So according to the BOM for a 100K switch ...
first make sure (with a cheap pot) if you really want a 100k switch.
at least for "gain" I doubt this.
would be a pain to unsolder all resistors and replace it with new ones ...
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 15, 2011, 03:07:50 PM
thanks volker! just got a chance to fix the i/o xformers last night and now i am getting HUGE gain. also, it seems like the link mode is working properly as well. I will do some more calibration and testing over the weekend. quick question though, what is the best way to wire power to the jeweled power lamp and meter LEDs?
good news !!!

best way to power up meter lamps etc is to use the relay switch PSU
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on April 15, 2011, 03:09:51 PM
Ok, before I solder all these resistors in I want to make sure I am 100%.  So according to the BOM for a 100K switch ...
first make sure (with a cheap pot) if you really want a 100k switch.
at least for "gain" I doubt this.
would be a pain to unsolder all resistors and replace it with new ones ...

No for the gain I will be using the 25k resistors BOM.  The 100K is for the gain reduction.  I'm going according to the BOM.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 15, 2011, 03:14:36 PM
fine.

for your question we need to know:
- do we start counting at 0 or 1
- do you want 23 or 24 steps

the picture shown starts counting at 1, and has 24 steps
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on April 15, 2011, 03:23:51 PM
Thanks for your guidance here!

I honestly am just wondering what the Azone USA BOM is for.  I am fine with 23 or 24 positions.  I mainly just want to make sure I have it right according to the parts in the USA BOM.

I currently have them all starting from position one because when I check the switch with a continuity meter in the most left position (volume all the way down) it started at position 1.  So I thought I had it right until I read the post from Azone where he said to start from the zero position.   

I also have the resistance in the position starting at the highest value (10.5k) for the most resistance which makes sense to me for the most left position.

Maybe now that I think of it, it should start on 0.  That way with the attenuator all the way to the right (volume up) then it would be just straight wire.  Current I have straight wire at position 0.


Ok, I hope someone can help me make sense of it.

Thanks
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 15, 2011, 03:41:53 PM
if we start counting from position 1,
type in (at the LogPotToSwitch Excell file)
Lowest Switch Nr is: 1
type in
Desired Impedance: 25000 (for 25k)
type in your switch positions:
23 or 24

connect "GND" to switch position 1
connect resistor 1 from pin one to two
repeat ...
for a 23 position switch you will end at position 23, connect pin 23 to "In"
(no resistor between position 23 and 24, no connection to position 24)
for a 24 position switch you will end at position 24, connect pin 24 to "In"

hope this helps
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on April 15, 2011, 03:47:51 PM
Ok that does help.  I think I have it right then. Just a triple check.

Position one should be the highest resistance value correct?  So for the 100k switches it should be the 10.5k.


Thanks
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 15, 2011, 03:55:28 PM
... Position one should be the highest resistance value correct?  So for the 100k switches it should be the 10.5k
this would make a reverse log pot :o
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on April 15, 2011, 04:02:09 PM
good thing I asked!

so position 1 should be 1.18k for the 100k version.

Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 15, 2011, 04:06:20 PM
yes - the numbers from the excel file reflect the numbers of the elmas
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on April 15, 2011, 04:08:29 PM
I always seem to make things harder then they need to be!  ugh


Thanks for the help.
Title: Re: D-LA2A Support Thread
Post by: band_master on April 16, 2011, 08:31:03 PM
thanks volker! just got a chance to fix the i/o xformers last night and now i am getting HUGE gain. also, it seems like the link mode is working properly as well. I will do some more calibration and testing over the weekend. quick question though, what is the best way to wire power to the jeweled power lamp and meter LEDs?
good news !!!

best way to power up meter lamps etc is to use the relay switch PSU


There are 2 LEDs in series in each of my meters, so I used a 47 ohm resistor for each meter. Is it best to tap the 5v before or after the regulator? Right now I have 5v from the terminal block before the regulator going to the power indicator lamp. From there I jumped either side of the lamp assembly to the positive side of each meter LED assembly. The - sides of the LED assemblies are jumped to star ground.

Does that seem right? I am getting power now to both LED assemblies as well as the power indicator lamp. Thanks for the help!!!

BD
Title: Re: D-LA2A Support Thread
Post by: baadc0de on April 19, 2011, 03:07:26 AM
Aahhh, finally... a case, front panel, knobs, lots of switches :)

(http://farm6.static.flickr.com/5222/5634114996_03871cb7be.jpg) (http://www.flickr.com/photos/[email protected]/5634114996/)

I'm very happy with the sound. This thing really kicks. Thanks Volker for the PCBs!

Now to correct a lifted pad on the output transformer connector, sigh..
Title: Re: D-LA2A Support Thread
Post by: Hank Dussen on April 19, 2011, 06:43:57 AM
Nice one!
What are the Filter and Response knob/switch?
Title: Re: D-LA2A Support Thread
Post by: baadc0de on April 19, 2011, 08:00:57 AM
Filter is the sidechain filter. Response changes the T4B cell that is in use. Do you see the 3 big holes on the back? Each channel could get 3 different T4B optos, and you could switch between them. So, vintage are the NOS T4Bs I have, Fast would be drip's fast version and modern would be IGS T4Bs.. when I get enough $$ I will implement this feature, currently it's a no-op that just looks cool :D

Let's call it the producer's knob? :)

"WOW this Modern response is so cool, you engineers have no idea, keeping it on Vintage all the time, I mean seriously, I should get mixing credit for this!"
Title: Re: D-LA2A Support Thread
Post by: zayance on April 19, 2011, 08:14:12 AM
Nice one, fooled my eyes on first sight, tought it was upside down  :D
Title: Re: D-LA2A Support Thread
Post by: baadc0de on April 19, 2011, 08:16:43 AM
Yeah, I totally should have put the knobbies under the VUs.. don't know what I was thinking really. This way you have to be more at an angle when adjusting knobs and looking at VU. But ooh well, it's a DIY piece and I made it through so who cares. It's also the best La2a that I have heard yet.

It's using a peculiar trafo combo too, UTC A16 and A26
Title: Re: D-LA2A Support Thread
Post by: zayance on April 19, 2011, 09:01:30 AM
Wasn't a criticism, i actually tought that it was pretty original.

Quote
This way you have to be more at an angle when adjusting knobs and looking at VU. But ooh well, it's a DIY piece and I made it through so who cares. It's also the best La2a that I have heard yet.

I guess should be the first one in the rack then.....
Title: Re: D-LA2A Support Thread
Post by: baadc0de on April 24, 2011, 08:23:48 AM
Well, it seems there is more to it than a lifted junction on the PCB... let's take this slow in a timeline

-- I first made this board to use with molex-like connectors
-- then since I had to wait so much time for molex tool and case front panel, I wired one channel directly, just to hear how it sounds
-- I enjoyed that channel for some time, until finally the case and tools arrived
-- I stripped the wires out and that killed one of the output transformer pads next to the relay - marked PNK
-- I pupulated the other channel and placed molexes into previously populated channel, making sure the lifted pad was soldered to the molex receiver before I soldered the other pins
-- On power up the new (previously unpopulated) channel works and the old one doesn't - the output is very highpassed
-- I trace this around, at it seems the signal is healthy after the 10uF solen
-- hooking up the trafo directly to the 10uF output + gnd and getting that to XLR produces a nice, clean signal, however since the VU connection is bypassed, but I have no VU movement for output (and I need that)
-- so I remove the molex completely and solder the trafo outs to the lower pads of the output relay (which are linked to the VU by the PCB and to the XLR out with the relay)
-- the sound is still highpassed (?!?!?!?)
-- also, measuring resistance between pin2 of input and output on that channel gives me some resistance that rises as if measuring a capacitor in circuit and that doesn't happen on the healthy channel

any ideas?? I've tried a lot of things, maybe the input XLR is shorted to gnd somehwere? Or the input trafo?
Title: Re: D-LA2A Support Thread
Post by: EHOFFA007 on April 24, 2011, 04:06:55 PM
I used a-26's for both in and out.I had the same issue with one channel. I resolved it by taking a jump from the star ground and tying it directly to one of the pins( can't remember right now) of the output traffo on the affected channel. Not sure why it worked it just did. Sorry for the non-tech tip but worth a shot!
Run a signal through the channel and probe around the utc's with a ground wire and see what happens.
Title: Re: D-LA2A Support Thread
Post by: baadc0de on April 24, 2011, 04:12:57 PM
Hmm, now that you mention it... that channel used to have an A-24! I changed over to A-26 becuase I have a pair of them. Hmm, will try, probably one of the centertaps, geez..
Title: Re: D-LA2A Support Thread
Post by: baadc0de on April 25, 2011, 08:24:10 AM
You were right! The left channel suddenly works great after A-26 pin 1 is grounded. Including the VU meter and all.. now, if only I did this while I still had the molex instead of all these wires everywhere..

Thanks mate,  I owe you a fancy beer :)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 25, 2011, 08:45:23 AM
Congrats.

now give us some insight photos of your beauty ;)
Title: Re: D-LA2A Support Thread
Post by: baadc0de on April 25, 2011, 10:12:02 AM
Well, it's not quite as nice as it was before, but still...

(http://farm6.static.flickr.com/5265/5653876032_c61c9ae40b_z.jpg) (http://www.flickr.com/photos/[email protected]/5653876032/)

(http://farm6.static.flickr.com/5150/5653305451_9d8cbbc6dc_z.jpg) (http://www.flickr.com/photos/[email protected]/5653305451/)

(http://farm6.static.flickr.com/5304/5653304451_ff6424d68e_z.jpg) (http://www.flickr.com/photos/[email protected]/5653304451/)
Title: Re: D-LA2A Support Thread
Post by: baadc0de on April 25, 2011, 03:59:20 PM
Also, she's in quite good company.. the rack itself is DIY ofcourse

(http://farm6.static.flickr.com/5189/5655019374_1d891c9833_z.jpg) (http://www.flickr.com/photos/[email protected]/5655019374/)
Title: Re: D-LA2A Support Thread
Post by: EHOFFA007 on April 26, 2011, 01:45:47 AM
You were right! The left channel suddenly works great after A-26 pin 1 is grounded. Including the VU meter and all.. now, if only I did this while I still had the molex instead of all these wires everywhere..

Thanks mate,  I owe you a fancy beer :)

Nice! I could use a beer after today :-)
I have to clean up the wiring in mine too. Sound wicked good though!
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 26, 2011, 05:12:24 AM
Also, she's in quite good company.. the rack itself is DIY ofcourse

now this is a nice collection of DIY gear 8)
BUT you will soon need to build another rack ;D

enjoy the family (http://www.51xaudio.com/)! ;D ;D ;D

(http://www.51xaudio.com/images/DLA2A-baadc0de.gif)
Title: Re: D-LA2A Support Thread
Post by: baadc0de on April 26, 2011, 05:25:16 AM
Thanks for the banner, the PCBs and the advice, this dual la2a sounds awesome, really proud of it :)

Also, yeah, the second rack is already in the works.. since this one is getting filled up really soon
Title: Re: D-LA2A Support Thread
Post by: EHOFFA007 on April 26, 2011, 02:15:49 PM
I'm in a heated competition with myself to get my rack filled up by the end of the year!
I keep telling myself I need empty rack spaces in between each piece of gear for ventilation (Cheating):-)
(https://www.me.com/ro/elliotjhoffman/Galleries/100008/My%20Photo/web.jpg?ver=13038414790001)
Title: Re: D-LA2A Support Thread
Post by: thestudio on April 27, 2011, 09:35:27 PM
Where can I purchase a very case/chassis other than Bud, Par Metal.....????
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 28, 2011, 02:48:22 AM
Where can I purchase a very case/chassis other than Bud, Par Metal.....????
Collective Cases (http://www.groupdiy.com/index.php?topic=41963.0)
Title: Re: D-LA2A Support Thread
Post by: thestudio on April 29, 2011, 04:35:38 PM
Anyone else other then Collective???
Title: Re: D-LA2A Support Thread
Post by: EHOFFA007 on April 30, 2011, 12:26:50 AM
I've gotten several cases from:
Www.diy-racked.com
Good service and prices, located in the EU so I've been getting my cases from dan at collective since he opened up.
Title: Re: D-LA2A Support Thread
Post by: desol on April 30, 2011, 09:22:55 PM
Hey guys

Couple questions. I just got everything together today. I first powered it up without tubes/t4b. The left side neon didn't light but right did....then a little smoke from right side down by 3 watt resistor and HV capacitor. Quickly shut off. Noticed 7805  was dead(9v). Put a new one in...and removed yellow/green wire which i had with ground to iec. What is this wire..? I noticed some other builds with same transformer but not this wire. Nyway..fired back up also with new led's and now both neons and led's light ok(grounds hooked just not green/yellow wire from transformer)...and voltages look at about right level. So...added tubes...all good...but now there is a small buzzing, humming at power transformer...no short cause it didn't heat up...just a quiet buzzing...didn't think big deal...so, added t4. When on, same buzzing i think....but louder in speakers...relays are working (when switching relay...buzzing goes on and off with both channels.

Everything seems....ok...just don't know what to do about buzzing noise(no audio). Any ideas could help. thx. :)
Title: Re: D-LA2A Support Thread
Post by: briomusic on May 01, 2011, 04:21:37 AM
hi desol, what is the model of power transformer you use?
on the transformer you will often find a description of each wire by colorcode, what does it say about the yellow/green?
(yellow/green is usually earth which should not be completely disconnected, but can be wired in different ways relating to hum issues)
is the buzz coming from the transformer or from the audio output (speakers)?
what is your grounding scheme, can you post this either as a diagram or hi-res picture of your build?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 01, 2011, 04:57:45 AM
if it is a Rondo-Mueller transformer yellow/green is screen.
there should be nothing wrong connecting it directly to the IEC ground.
(fact is I do this all the time)

buzzing: like Brio said, show us an inside photo. the wires going to the front are important.
use shielded cables for the pots. disconnect the limit/compress switch. buzz still there?
Title: Re: D-LA2A Support Thread
Post by: desol on May 01, 2011, 09:23:17 PM
Hi Volker and Brio!

Ok. I uploaded some pictures and put a video on youtube. I figured best way is to hear it for real. So far, i know pots are reversed and shielding needs to be fixed on channel one pot. First channel meter seems functioning ok(needs new led)...but second channel meter has a problem. The buzzing/humming i haven't figured out yet...was golfing this weekend! :) I have new pots coming monday...the ones i have now have to small of bushing so they are just temporary. I tried moving some cables no real change in hum...i think maybe it's in power supply. Voltages at two 3watt resistors are at 220 and 320 volts roughly...same on both sides. I don't know if it's filter cap or not. Somehow output isn's working...so don't know if relays are switching properly...humphhh.

I built with love....but it has a bad temper now suddenly. I did have a little smoke near 3 watt resistor on left channel (which is why i asked about shield wire on power supply) but have it reconnect after blowing out with air...now no more smoke and neon is working ok. All tubes seem firing ok.... nyways, here are pics and video...

(http://img862.imageshack.us/img862/2900/dsc03077z.th.jpg) (http://img862.imageshack.us/i/dsc03077z.jpg/)
(http://img98.imageshack.us/img98/1684/dsc03076t.th.jpg) (http://img98.imageshack.us/i/dsc03076t.jpg/)
(http://img90.imageshack.us/img90/1362/dsc03074b.th.jpg) (http://img90.imageshack.us/i/dsc03074b.jpg/)

youtube
http://www.youtube.com/watch?v=Oa7JxDfQsKM
Title: Re: D-LA2A Support Thread
Post by: Audioman on May 02, 2011, 03:01:44 AM
Hello All,
Finally i finish the two D-LA2A !!! (one is mine and the other i builded for my friend)
I have noticed two problems :

1- in my unit is some hum on the second channel when i switch on the channel (with the in/bypass switch)
2- the first channel of my unit works fine but if i bypass the channel in the audio a boom appears (maybe the switch is not good..)
3- in the second unit a strange distortion appears if i push the input and ouuput stage

Any help is appreciate !!
Thank you all
Fabio
 
i post some pictures
Title: Re: D-LA2A Support Thread
Post by: Audioman on May 02, 2011, 03:03:06 AM
second picture
Title: Re: D-LA2A Support Thread
Post by: Audioman on May 02, 2011, 03:03:52 AM
third picture
Title: Re: D-LA2A Support Thread
Post by: Audioman on May 02, 2011, 03:04:49 AM
fourth picture
 
Title: Re: D-LA2A Support Thread
Post by: letterbeacon on May 02, 2011, 02:58:35 PM
Beautiful work!!
Title: Re: D-LA2A Support Thread
Post by: creal on May 03, 2011, 01:39:37 PM
Hi everybody,
Here is my new baby.
A new DLA2A is born and is sound very nice.
I love this comp.
I just buy some telefunken ECC83 on evil-bay to replace the electroHarmonics and Philipes tubes.
I also make a little pcb for the switches

Thanks Volker for make this dream a reality.
And thanks everybody for your advices and comments in this tread

Best
Cyril

(http://twin-x.com/groupdiy/albums/userpics/IMG_0308.JPG)
(http://twin-x.com/groupdiy/albums/userpics/IMG_0310.JPG)
(http://twin-x.com/groupdiy/albums/userpics/IMG_0326.JPG)
(http://twin-x.com/groupdiy/albums/userpics/IMG_0319.JPG)
(http://twin-x.com/groupdiy/albums/userpics/IMG_0321.JPG)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 03, 2011, 01:54:46 PM
desol: first remove the power switch from the middle of the case.
running 115V / 230V next to the potentiometer / switch wires is a very bad idea in this build.

Audioman, nice build with unique front panels :)
1- in my unit is some hum on the second channel when i switch on the channel (with the in/bypass switch)
2- the first channel of my unit works fine but if i bypass the channel in the audio a boom appears (maybe the switch is not good..)
the switch only triggers the relay. any DC at the output?
3- in the second unit a strange distortion appears if i push the input and ouuput stage
try swapping the tubes from unit 1 & 2. any changes?

Cyrill: congrats!
interesting 1178 front panel layout.
COOL  8) 8) 8)
Title: Re: D-LA2A Support Thread
Post by: creal on May 03, 2011, 02:06:57 PM
Cyrill: congrats!
interesting 1178 front panel layout.
COOL  8) 8) 8)

Thx man, the DLA2A is in UREI familly and it looks nice in the rack with my LA4 and 1176s
 ;D ;D ;D ;D ;D
PS: the sound of this best kill me...
Title: Re: D-LA2A Support Thread
Post by: Audioman on May 03, 2011, 03:06:55 PM
Beautiful work!!

Thank you man !!! i'm glad you like it !!


desol: first remove the power switch from the middle of the case.
running 115V / 230V next to the potentiometer / switch wires is a very bad idea in this build.

Audioman, nice build with unique front panels :)
1- in my unit is some hum on the second channel when i switch on the channel (with the in/bypass switch)
2- the first channel of my unit works fine but if i bypass the channel in the audio a boom appears (maybe the switch is not good..)
the switch only triggers the relay. any DC at the output?
3- in the second unit a strange distortion appears if i push the input and ouuput stage
try swapping the tubes from unit 1 & 2. any changes?

Cyrill: congrats!
interesting 1178 front panel layout.
COOL  8) 8) 8)

Hi Wolker
now i try to switch the tubes between the two unit , after that i let you know if  anything change .
i search also for any dc at the output
can you tell the right procedure to calibrate the unit ??

i let you know the response of the test
Ciao
Fabio

P,S, i'm glad you like the front panel
Title: Re: D-LA2A Support Thread
Post by: desol on May 03, 2011, 11:39:56 PM
desol: first remove the power switch from the middle of the case.
running 115V / 230V next to the potentiometer / switch wires is a very bad idea in this build.


Hi Volker,

Ok. So i removed p switch and no real change, but i will watch for that anyway. But i did find that the pots weren't grounded properly...so i changed and i think they are wired and grounded right now....and buzz is better but still there. I also found that on channel two, with just GR switch is engaged and input all the way up...output pot causes meter to swing up(+2) then down again to zero? Channel one doesn't do this...needle stays steady when you move channel two (output) pot. And then, engaging channel two meter....now moves channel one meter a little too?? I looked for a little while at the schematic trying to see what is causing this, ...still trying tho. I can't see what switches are which...to see what channel two pot is connected to, to see where to look. Looks like voltage is bleeding into channel 1 from channel 2 meter circuit somewhere. Will keep looking..


I also did some voltage checks at a few capacitors, i'm pretty sure they're normal:

c105, 205 - 92v and 89v
c102,203,202,203 - 89v,69v and 208v    89v,67v and 202v
c101, c201 - 80v and 82v
c115,c215 - 57v and 57.5 volts

Hmm. Back to work..
Title: Re: D-LA2A Support Thread
Post by: audiophreak on May 08, 2011, 03:41:36 PM
Hi All,
       Need a little help here ... would like to get the Rondo PT for this project, used the link posted in this thread, but cant figure out how to switch to English ( I'm in the U.S. and non German speaking / writing  )  , I messed around just clicking on stuff and found an email contact info , and sent an email about a week ago with no response, ( possible they don't speak / read English ).

  Would really like to use this PT , any help / suggestions would greatly be appreciated.

  Thanks,
             Chip
Title: Re: D-LA2A Support Thread
Post by: briomusic on May 08, 2011, 04:42:05 PM
[silent:arts] sells them in the WM:http://www.groupdiy.com/index.php?topic=39570.0 (http://www.groupdiy.com/index.php?topic=39570.0)
(english spoken  ;))
Title: Re: D-LA2A Support Thread
Post by: audiophreak on May 08, 2011, 05:54:15 PM
Thanks briomusic !!

                            not sure how I missed that   :-[   

                                                                              but email sent   :) :)

Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 08, 2011, 05:55:43 PM
Hi Chip,

Rondo-Mueller is based in the east part of germany, not many people there learned english (but most speak fluently russia).
Mr. Mueller doesn't like to do the same "one-off" winding job every day, I finally agreed with him to stock the transformers for my DIY projects.
(even it is no fun for me receiving +100kg parcels at my home)
Title: Re: D-LA2A Support Thread
Post by: audiophreak on May 08, 2011, 06:48:45 PM
Thanks Volker   :) :) :)
Title: Re: D-LA2A Support Thread
Post by: Audioman on May 09, 2011, 07:25:41 AM
Hi All,
For the distortion problem solved (wiring problem on ch 1)
but on both unit the hum is still present (on first unit on ch1 on second unit on ch2)
i have measure on first unit 55° degrees on the electrolytic c171 is it normal ??
Any idea ??


desol: first remove the power switch from the middle of the case.
running 115V / 230V next to the potentiometer / switch wires is a very bad idea in this build.

Audioman, nice build with unique front panels :)
1- in my unit is some hum on the second channel when i switch on the channel (with the in/bypass switch)
2- the first channel of my unit works fine but if i bypass the channel in the audio a boom appears (maybe the switch is not good..)
the switch only triggers the relay. any DC at the output?
3- in the second unit a strange distortion appears if i push the input and ouuput stage
try swapping the tubes from unit 1 & 2. any changes?

Cyrill: congrats!
interesting 1178 front panel layout.
COOL  8) 8) 8)
Title: Re: D-LA2A Support Thread
Post by: desol on May 09, 2011, 11:48:51 AM
Yes!!...it's working!  :)

Very nice sounding...different than my other compressor's. There is a tiny amount of buzz(-50) still; it's the limit/comp wire, which will be quickly changed over to shielded wire.

All of my problems were wiring and adjustment. If you have distortion it's almost guaranteed a wiring problem. The stereo tracking is a little off as well. It may be T4b's or 6AQ5's(different brands)...either way..a small issue and will fix later.

Right now i'm just so happy with the sound of this thing!! Thank you Volker, i'm really happy i got one up and running. My first tube project...and yes i felt a shock...so i was careful after that!

(http://img717.imageshack.us/img717/3103/dsc03089k.th.jpg) (http://img717.imageshack.us/i/dsc03089k.jpg/)
(http://img580.imageshack.us/img580/1598/dsc03085f.th.jpg) (http://img580.imageshack.us/i/dsc03085f.jpg/)


edit: Oh yes...and i did the modification for 12ay7's in V1...which worked out nicely.
 
Title: Re: D-LA2A Support Thread
Post by: electrisizer on May 09, 2011, 12:28:43 PM
All of my problems were wiring and adjustment. If you have distortion it's almost guaranteed a wiring problem.

what was the mistake in your wiring that causes distortion?

i still have distortion at some frequencies. its not caused by transformers as assumed pages before...

first time i hear them in circuit is at cathode on the v103/203
Title: Re: D-LA2A Support Thread
Post by: desol on May 09, 2011, 12:39:21 PM
Actually maybe that's not entirely true. :) I had distortion a couple times throughout troubleshooting...both instances were wiring.

I had the wires out of polarity once on GR/Meter circuit (which caused all kinds of weird things..meter bouncing with pots when channel bypassed) and then again on limit comp switch...which caused distortion. Plus i wired the link switch incorrectly..which caused no compression and distortion when engaged.  

I haven't checked it with a scope or anything, just my ears. :)
Title: Re: D-LA2A Support Thread
Post by: desol on May 11, 2011, 12:47:28 AM
EDIT: Resolved #3 http://www.groupdiy.com/index.php?topic=32677.msg540317#msg540317

Title: Re: D-LA2A Support Thread
Post by: Audioman on May 11, 2011, 01:34:01 AM
Hi Desol,
So you calibrate you unit turning right the response limiter trimmer and left the stereo adjust trimmer ??
Can you tell me if in your unit the electrolytics warming a bit ?? ( i notice in my unit 55° degrees on the electrolytic c171 )
Let me know
Thank you
Fabio


Hi Volker! (...or anyone)

I've finished my d-la2a and everything seems working good. It's quiet, gain and peak reduction are working well on both channels, switches and related functions are working ok...and it sounds nice.

When calibrating the freq resp and stereo adjust controls(freq response is on the backpanel), i noticed they were backwards? ie: they needed to be turned all the way to the 'left' for the signal to be full, lots of compression/needles to move, etc. So i reversed the wipers on the freq response potentiometers...and now they are like normal...turn all the way to the right for good response. But this didn't reverse the stereo response trimmers...they still need to be turned all the way to the left. If i turn them all the way to the right...the signal gets distorted and not too good. When i adjust both of them to the left, they move together (linked) and the signal sounds nice again.

How could i have reversed this?  ???

Now i have freq resp's all the way to the right....and stereo adjust's all the way to the left? ...and it's ok...

Thx,
Darrick
Title: Re: D-LA2A Support Thread
Post by: desol on May 11, 2011, 02:18:31 AM
Hi Fabio..

Yes. Limiter response pots all the way to the right...and stereo adjust trimmers all the way to the left.

I tested my electrolytic c171 and it's ok at 55C(131F). If i turn stereo adjust all the way to the right...i get distortion...no meter movement(linked).

Title: Re: D-LA2A Support Thread
Post by: Audioman on May 11, 2011, 02:46:21 AM
Hi Desol,
Waiting for some info from Volker .
I'm asking you about the Electrolytics because i have an hum on one channel of both unit and i don't know why !!!
I hope to discover the problem .....
today i try your trimmer setting and i let you know the response
thank you for the info !!!
Fabio


Hi Fabio..

Yes. Limiter response pots all the way to the right...and stereo adjust trimmers all the way to the left.

I tested my electrolytic c171 and it's ok at 55C(131F). If i turn stereo adjust all the way to the right...i get distortion...no meter movement(linked). All the way to the left...everything's ok.  ?

I know it should be to the right...but it's not for some reason.
Title: Re: D-LA2A Support Thread
Post by: desol on May 11, 2011, 03:02:52 AM
So you calibrate you unit turning right the response limiter trimmer and left the stereo adjust trimmer ??
 

Yes.
Title: Re: D-LA2A Support Thread
Post by: Audioman on May 11, 2011, 03:07:59 AM
Where you find the calibration procedure ???
I can't find it in the forum ....



So you calibrate you unit turning right the response limiter trimmer and left the stereo adjust trimmer ??
 

This is just my unit.

Normal calibration is turning both freq resp and stereo adjust to the right.
Title: Re: D-LA2A Support Thread
Post by: desol on May 11, 2011, 03:21:22 AM
I can't remember, it's in this thread...you just have to search a bit....and search google too. Bits and pieces everywhere...


Hi Desol,
Waiting for some info from Volker .
I'm asking you about the Electrolytics because i have an hum on one channel of both unit and i don't know why !!!
I hope to discover the problem .....
today i try your trimmer setting and i let you know the response
thank you for the info !!!
Fabio

How bad is the hum? Did you shield/check all wiring? Check input/output wiring? Wire positioning? Wire polarity?

(In the end) ...I carefully went through my unit gently(carefully) touching wires to see which caused hum, and then shielded those.
At first i had alot of hum...because i wired the inputs/outputs incorrecty..  :D
I ended up shielding pretty much all wiring except for meter wiring...

Now my unit is very quiet. :)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 11, 2011, 04:57:25 AM
taken from the UA Teletronix® LA-2A Manual (http://www.uaudio.com/media/assetlibrary/l/a/la-2a_manual.pdf):

Limiter Response Calibration (RV137/RV237):
The LA-2A was designed for use in broadcast applications.  The audio signal in FM
broadcasting undergoes pre-emphasis and results in a 17 dB boost at 15 KHz.  Due to this
increase in signal level, transmitters are subject to over-modulation.  The LA-2A provides a
control (R37) which controls the amount of high-frequency compression.
This potentiometer is factory set for a “flat” side-chain response (clockwise).  Increasing
the resistance of this potentiometer by turning it counter clockwise will result in
compression which is increasingly more sensitive to the higher frequencies.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 11, 2011, 05:00:24 AM
taken from the UA Teletronix® LA-2A Manual (http://www.uaudio.com/media/assetlibrary/l/a/la-2a_manual.pdf):

Stereo Balance Adjust (RV103/RV203):
...
The interconnecting wire should be less than 2 feet in length and should be shielded.
...
To calibrate the units for stereo operation:
- Connect the units together as described previously.
- Turn the Peak Reduction knob counterclockwise (no compression).
- Set R3 on each unit to a clockwise position.
- Set each meter to read Gain Reduction.
- Adjust the Peak Reduction control on the left channel until approximately 5dB of gain reduction is achieved.
- Adjust R3 on the unit that shows the greatest amount of gain reduction until the gain reduction indications are equal.
- When operating, set the Peak Reduction controls to the same setting on both channels.
Title: Re: D-LA2A Support Thread
Post by: Audioman on May 11, 2011, 05:40:11 AM
Thank you Man !!!

taken from the UA Teletronix® LA-2A Manual (http://www.uaudio.com/media/assetlibrary/l/a/la-2a_manual.pdf):

Stereo Balance Adjust (RV103/RV203):
...
The interconnecting wire should be less than 2 feet in length and should be shielded.
...
To calibrate the units for stereo operation:
- Connect the units together as described previously.
- Turn the Peak Reduction knob counterclockwise (no compression).
- Set R3 on each unit to a clockwise position.
- Set each meter to read Gain Reduction.
- Adjust the Peak Reduction control on the left channel until approximately 5dB of gain reduction is achieved.
- Adjust R3 on the unit that shows the greatest amount of gain reduction until the gain reduction indications are equal.
- When operating, set the Peak Reduction controls to the same setting on both channels.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 11, 2011, 06:19:56 AM
congratulations to all the new builds, welcome to the family :)
it is banner time ;D

... Finally i finish the two D-LA2A !!! (one is mine and the other i builded for my friend)
I have noticed two problems ...
I'm sure you will sort the last few issues out soon ;)

(http://www.51xaudio.com/images/DLA2A-Audioman.gif)

... Here is my new baby. A new DLA2A is born and is sound very nice. I love this comp ...
I'm sure this love lasts long :D

(http://www.51xaudio.com/images/DLA2A-creal.gif)

Yes!!...it's working!  :)
8) 8) 8)

... My first tube project...and yes i felt a shock...so i was careful after that!...
you wanted to learn it the hard way? good to know you are still alive, stay careful in the future!

(http://www.51xaudio.com/images/DLA2A-desol.gif)
Title: Re: D-LA2A Support Thread
Post by: creal on May 11, 2011, 06:35:20 AM
thanks you Volker for this great compressor and the nice banner.
Now it's time to finish the PM670 ;)
Cheers
Cyril
Title: Re: D-LA2A Support Thread
Post by: Audioman on May 11, 2011, 06:41:34 AM
Thank you for the Banneeeeeeeeeeeer !!!
And obviously for the great support !!!
your collegue ;D ;D ;D ;D ;D ;D ;D ;D ;D
Fabio
Title: Re: D-LA2A Support Thread
Post by: desol on May 11, 2011, 01:22:22 PM
Thanks Volker.  8) Cool banner..
Title: Re: D-LA2A Support Thread
Post by: desol on May 13, 2011, 07:06:21 PM
taken from the UA Teletronix® LA-2A Manual (http://www.uaudio.com/media/assetlibrary/l/a/la-2a_manual.pdf):

Stereo Balance Adjust (RV103/RV203):
...
The interconnecting wire should be less than 2 feet in length and should be shielded.
...
To calibrate the units for stereo operation:
- Connect the units together as described previously.
- Turn the Peak Reduction knob counterclockwise (no compression).
- Set R3 on each unit to a clockwise position.
- Set each meter to read Gain Reduction.
- Adjust the Peak Reduction control on the left channel until approximately 5dB of gain reduction is achieved.
- Adjust R3 on the unit that shows the greatest amount of gain reduction until the gain reduction indications are equal.
- When operating, set the Peak Reduction controls to the same setting on both channels.


I'm stumped. Following this, i turn the trimmers on both channels(137 and 103) all the way clockwise and i get no GR dual or stereo..  :-\
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 14, 2011, 02:55:26 AM
I'm stumped. Following this, i turn the trimmers on both channels(137 and 103) all the way clockwise and i get no GR dual or stereo..  :-\
I don't know what can cause this but your RV103 works reverse ???
Title: Re: D-LA2A Support Thread
Post by: desol on May 17, 2011, 02:56:41 AM
 :-\




Title: Re: D-LA2A Support Thread
Post by: Borja Lopez on May 17, 2011, 07:39:18 PM
Hi, this is my unit finished. We are using the compressor in our studio, one month ago, and it works fine, sounds great!  :D
Thanks Volker and thanks to all members of this forum!
Title: HI I can't get the 22uF / 450V NICHICON cap and the WIMA POLYESTER 10nF / 630V
Post by: mativas on May 19, 2011, 01:29:49 AM
Hi.



1. I am new in the league and i finishing to get the pieces for my D-la2a but i need to get the 22uF / 450V NICHICON> in the moser website  and the delivery times are very  very far  :( . So I need to know if you guys know  another  store that can have them in stock.. also I am watching these nichicon in ebay:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=200541624054&ssPageName=STRK:MEWAX:IT

 these can eventually replace the 22uF / 450V NICHICON from the boom list? Has the same specs but these looks smaller than the cap in the mouser list.

2. already exists a replacement for the  WIMA POLYESTER 10nF / 630V cap? the people of mouser will be having it in stock in more than six months!! I have seen caps with the same specs in ebay but i don't  know if really will works with the project..


3. I am close to pay the order in tubedepot and I picked up four sovtek 12ax7 because Is the same tube used in mesaboogie and i like it. Is necessary to get it in matched pairs? or not matching pairs will be perform well?


THANKS FOR YOUR HELP.. THIS IS MY FIRST! ;D


Mativas.





Title: Re: D-LA2A Support Thread
Post by: creal on May 19, 2011, 05:55:28 AM
Hi mativas

I've order the caps at banzai
http://www.banzaimusic.com/home.php

Quote
3. I am close to pay the order in tubedepot and I picked up four sovtek 12ax7 because Is the same tube used in mesaboogie and i like it. Is necessary to get it in matched pairs? or not matching pairs will be perform well?

Maching pair is better but not matching perform well, if the tube are in good condition.
Make your test
Hope that helps.

Cyril
Title: Re: D-LA2A Support Thread
Post by: mativas on May 20, 2011, 12:59:58 PM
Maching pair is better but not matching perform well, if the tube are in good condition.
Make your test
Hope that helps.


Thanks Cyril  I will try not matching!!

any one can help me with this  issues?... thanks a lot! :)

1. I am new in the league and i finishing to get the pieces for my D-la2a but i need to get the 22uF / 450V NICHICON> in the moser website  and the delivery times are very  very far  Sad . So I need to know if you guys know  another  store that can have them in stock.. also I am watching these nichicon in ebay:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=200541624054&ssPageName=STRK:MEWAX:IT

 these can eventually replace the 22uF / 450V NICHICON from the boom list? Has the same specs but these looks smaller than the cap in the mouser list.

2. already exists a replacement for the  WIMA POLYESTER 10nF / 630V cap? the people of mouser will be having it in stock in more than six months!! I have seen caps with the same specs in ebay but i don't  know if really will work with the project..


Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 20, 2011, 01:31:46 PM
there are a lot of 22uF/450V caps in stock at mouser:
don't know if this link expires (http://de.mouser.com:80/Passive-Components/Capacitors/Aluminum-Electrolytic-Capacitors/Aluminum-Electrolytic-Capacitors-Leaded/_/N-75hqw?P=1z0wrkiZ1z0vl82Z1z0z7l5)
Title: Re: D-LA2A Support Thread
Post by: desol on May 21, 2011, 02:39:11 AM
I found i had the pots wired incorrectly.  ::)  >:(

Now it's compressing much more.. :) More like i was expecting, would be normal.

The way it was wired before it was just barely compressing, which is why it was hard to tell.
I'm getting more voltage off of the t4b now as well..

I'm working through the schematic, trying to see what else i've done....
Title: Re: D-LA2A Support Thread
Post by: mativas on May 21, 2011, 07:47:57 PM
there are a lot of 22uF/450V caps in stock at mouser:
don't know if this link expires (http://de.mouser.com:80/Passive-Components/Capacitors/Aluminum-Electrolytic-Capacitors/Aluminum-Electrolytic-Capacitors-Leaded/_/N-75hqw?P=1z0wrkiZ1z0vl82Z1z0z7l5)

Thanks Volker.. I thought that  only the capacitors from the boom list will be doing the work.. In don't have experience in this kind of works...

So.  Should I Do the same for the   WIMA POLYESTER 10nF / 630V cap ?

Title: Re: D-LA2A Support Thread
Post by: desol on May 22, 2011, 03:46:06 PM
Volker, i just want to thank you again for offering this project. :) I've confirmed that everything is working as it should,
and it is compressing beautifully.

Awesome project.
Title: Re: D-LA2A Support Thread
Post by: briomusic on June 01, 2011, 04:27:36 AM
Nearly done with my DLA-2A: I have audio and lovely compression on both channels. :)

one of the NE2's has an intermittent fault and only lights up when I tap the PCB - probably best swap it for a spare one.

a bigger problem is the fact that the right channel meter is not showing any gain reduction. it works perfectly as a VU meter and can be biased to 0dB in GR mode but then the needle won't move. It's NOT the T4Bs fault (swapped with other channel) so that only leaves the R227 or a bad solder joint I guess? I did replace Rx25 with a trimmer but unfortunately it is mounted in a way that makes it very hard to adjust. Still this shouldn't lead to 'no movement at all from the 0 set' at any value should it?

Also I find the VU meter to be too sensitive, it shows 0VU at about -20dBFS. I would prefer -14dbFS or so. How do I make it less sensitive? Resistor in series or parallel to the meter?

Thanks Volker and everyone, can't wait to get the Frontpanel done and claim my banner  ;D
Title: Re: D-LA2A Support Thread
Post by: Kingston on June 01, 2011, 05:08:41 AM
NE2? if that's the neon, swap it for a 60-70V zener and enjoy metering that does not generate noise and lasts forever.
Title: Re: D-LA2A Support Thread
Post by: briomusic on June 01, 2011, 05:51:00 AM
What Wattage Zener? Is this one cool?
http://www.banzaimusic.com/62V-Zener-Diode-5W.html

cheers
Brio
Title: Re: D-LA2A Support Thread
Post by: Kingston on June 01, 2011, 07:01:33 AM
That'll work fine. A good idea to have it high wattage like 5W.
Title: Re: D-LA2A Support Thread
Post by: Randyman... on June 01, 2011, 03:42:25 PM
a bigger problem is the fact that the right channel meter is not showing any gain reduction. it works perfectly as a VU meter and can be biased to 0dB in GR mode but then the needle won't move. It's NOT the T4Bs fault (swapped with other channel) so that only leaves the R227 or a bad solder joint I guess? I did replace Rx25 with a trimmer but unfortunately it is mounted in a way that makes it very hard to adjust. Still this shouldn't lead to 'no movement at all from the 0 set' at any value should it?

So your CH2 does compress, but doesn't show any GR on the meter?  I have a similar issue and can also "zero set" the meter, but I'm not getting any actual compression on CH 2 (passes audio, slightly distorts when Peak Reduction is dimed but no GR to speak of).  I re-flowed all tube and T4B solder joints, and swapped tubes and T4's between channels.  Ch 2 still won't compress.

If I link the channels, Ch2's Peak Reduction does have an effect on Ch 1's GR, so it appears I'm getting sidechain audio through the Ch 2 detector (that I can tell).

Any further clues on what to check next?  I've been stuck here for over a month now - I'm somewhat timid around high-voltage and don't mind taking this as slow as I need to.


Also - On the Neons - Is it generally recommended to replace them with the Zeners mentioned above?  Will a zener really make these units quieter and more reliable?

Thanks for any input  8)
Title: Re: D-LA2A Support Thread
Post by: briomusic on June 01, 2011, 05:56:58 PM
Cool I'll try replacing the NEONs with Zeners tomorrow.

BTW, does anyone have a pinout for the T4B (-socket)? I would like to do some continuity testing with the valves and T4B removed, to find my GR metering problem.
Title: Re: D-LA2A Support Thread
Post by: volker on June 01, 2011, 08:01:10 PM
1   NC
2   GND
3   EL panel input
4   GND
5   VU meter LDR
6   GND
7   Signal LDR
8   GND
Title: Re: D-LA2A Support Thread
Post by: briomusic on June 02, 2011, 05:16:55 AM
thanks. is that counted clockwise from the notch?
Title: Re: D-LA2A Support Thread
Post by: Kingston on June 02, 2011, 12:37:39 PM
Also - On the Neons - Is it generally recommended to replace them with the Zeners mentioned above?  Will a zener really make these units quieter and more reliable?

Yes and yes. There was in depth discussion in another thread. You can still find it with the correct keywords. I seem to recall SSLTech (keith) wrote about it a lot.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 02, 2011, 12:45:40 PM
Also - On the Neons - Is it generally recommended to replace them with the Zeners mentioned above?  Will a zener really make these units quieter and more reliable?

Yes and yes. There was in depth discussion in another thread. You can still find it with the correct keywords. I seem to recall SSLTech (keith) wrote about it a lot.

Disagree ;D
My D-LA2A is dead quiet with Neons
Title: Re: D-LA2A Support Thread
Post by: briomusic on June 02, 2011, 01:18:40 PM
Well, for better or worse, I just swapped it to Zeners and now my unit is making zapping noises on power up  >:(
I am not sure if I have the orientation right... is it supposed to be like this (obviously with the Neons removed):
(http://i1196.photobucket.com/albums/aa405/briomusic/ZenerOrientation.gif)
Title: Re: D-LA2A Support Thread
Post by: Kingston on June 02, 2011, 01:25:05 PM
Disagree ;D
My D-LA2A is dead quiet with Neons

Noise is simply not there with the zener as a shunt regulator, while a neon can be considered a noise generator. You might get lucky and not have the neon interfere in a particular build. The most important part in the use of zener here is reliability. It will last "forever" and the regulation will not change over time. No need to readjust metering. Neons are light bulbs and inside the LA2A in a particularly hot furnace. They might have more limited life span than even the tubes!  :o

With this information at hand, why would anyone ever use a neon regulator anymore? It's not like it's responsible for the LA2A sound in any way or somehow visible in a finished build.

Well, for better or worse, I just swapped it to Zeners and now my unit is making zapping noises on power up  >:(
I am not sure if I have the orientation right... is it supposed to be like this (obviously with the Neons removed):
(http://i1196.photobucket.com/albums/aa405/briomusic/ZenerOrientation.gif)

Yes, that's the correct orientation. http://en.wikipedia.org/wiki/Linear_regulator

I've never heard these zapping noises. The zener is not even in the audio path, so it might be something else.
Title: Re: D-LA2A Support Thread
Post by: briomusic on June 02, 2011, 01:40:26 PM
The Zapping noise was coming from the PCB, no audio outputs are connected at this point, in fact not even the tubes or T4Bs. That's why I thought I might have the Zeners upside down maybe creating a "mini-short". I am gonna download the datasheet just to be sure.....

ETA: Triple checked Zener Orientation - still zapping/frying noise, gonna sleep over it and might put Neons back in tomorrow  :-\
Title: Re: D-LA2A Support Thread
Post by: briomusic on June 03, 2011, 02:56:39 PM
Ok, Neons in again and we're back in business - audio and Kompression Happening As normal. Right Meter showing gain reduction BUT the needle is movin UP from zero as compression is applied. Wtf?
Any help appreciated!
Title: Re: D-LA2A Support Thread
Post by: thebigskinny on June 04, 2011, 01:01:35 PM
Looking for a current dual la2a north American bom..... Email me!!!
Title: Re: D-LA2A Support Thread
Post by: desol on June 04, 2011, 01:52:09 PM
Looking for a current dual la2a north American bom..... Email me!!!

It's on the first page.
Title: Re: D-LA2A Support Thread
Post by: Grooveteer on June 05, 2011, 09:37:22 AM
Ok, Neons in again and we're back in business - audio and Kompression Happening As normal. Right Meter showing gain reduction BUT the needle is movin UP from zero as compression is applied. Wtf?
Any help appreciated!

Did you change anything besides the neon? I have the same issue you originally had (no GR metering) in my single LA2A. I've always thought it to be a faulty TB4. I only have one so I can't swap TB4s around. Not a big deal as I just use my ears, but it would be nice to get it right anyway.
Title: Re: D-LA2A Support Thread
Post by: briomusic on June 05, 2011, 04:50:30 PM
I solved it this afternoon  ;D

Problem was that the trimmer I am using instead of Rx25 was not connected (to ground) on one side. This lead to crazy voltages around the meter, I am glad I didn't damage it in the process.  :o

Now everything is working, and I am just working out what I am going to do about the (1M) Limiter Response Trimmer. Currently I have replaced it with a Lorlin Rotary which lets me switch between 0-960k in 120k increments. I am planning to have all the controls on (rotary) switches eventually, for the sake of recallability.

Once this is all sorted I can finally order a frontpanel - and then finally get my own DLA2A banner  :D
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on June 13, 2011, 10:52:08 AM
I'm a bit confused by the US-BOM from azone:

1. It lists 3x SPSD switches and 3x DPDT switches. I guess one of the additionals is the Link/Dual switch, but what is the other one for? ???

2. It lists DPDT switches with ON - NONE - ON while the Drip manual says they won't work and ON - ON switches should be used.

3. It lists SPSD (ON - NONE - ON) insead of SPST (OFF - ON). For what is the additional ON position or am I missing something?

I'm using that one because the other BOM doesn't even list the switches and I'm ordering parts from Mouser anyway.

Title: Re: D-LA2A Support Thread
Post by: desol on June 13, 2011, 11:36:09 AM
This kinda fooled me too, but then i realized someone may have set up the switches their own way....etc.

Easiest thing to do was to have a look at the wiring diagram and see how things are working, then figure what you need from there.
http://www.groupdiy.com/index.php?topic=32677.msg503869#msg503869

Limit/comp is a spdt switch, with comp in the closed position.
In/out is simply switching 5v to your relay's.
Gr/level is a dpdt switching between gr and vu for meter.
Link/dual is spdt with one wire only.
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on June 13, 2011, 11:52:12 AM
Thanks a lot desol.  :)
Title: Re: D-LA2A Support Thread
Post by: desol on June 13, 2011, 11:53:10 AM
No problem. :)
Title: Re: D-LA2A Support Thread
Post by: Audioman on June 22, 2011, 10:34:29 AM
Today i solved the Hummmmmmm problem
the problem was the connection between XLR ground (pin 1) to the case chassis
Now all is working good
Thank you All
Fabio


Hi All,
For the distortion problem solved (wiring problem on ch 1)
but on both unit the hum is still present (on first unit on ch1 on second unit on ch2)
i have measure on first unit 55° degrees on the electrolytic c171 is it normal ??
Any idea ??


desol: first remove the power switch from the middle of the case.
running 115V / 230V next to the potentiometer / switch wires is a very bad idea in this build.

Audioman, nice build with unique front panels :)
1- in my unit is some hum on the second channel when i switch on the channel (with the in/bypass switch)
2- the first channel of my unit works fine but if i bypass the channel in the audio a boom appears (maybe the switch is not good..)
the switch only triggers the relay. any DC at the output?
3- in the second unit a strange distortion appears if i push the input and ouuput stage
try swapping the tubes from unit 1 & 2. any changes?

Cyrill: congrats!
interesting 1178 front panel layout.
COOL  8) 8) 8)
Title: Re: D-LA2A Support Thread
Post by: sea_man on June 27, 2011, 03:27:16 AM
Hi to all !

I'm follow your great guide to make my own D-LA2A but i'm using 2 sowter 4383f for input and 2 sowter 8940a for output, my question is: the wiring for this is the same like the edcore ?

INPUT edcor XSM 600/10k
edcor pin 1 = 4383 brown
edcor pin 2 = 4383 pink
edcor pin 4 = 4383 green
edcor pin 5 = 4383 blue
edcor pin 8 = 4383 grey
edcor ground= 4383 black

OUTPUT edcor XSM10k/600
edcor pin 1 = 8940 yellow
edcor pin 4 = 8940 green
edcor pin 5 = 8940 grey
edcor pin 8 = 8940 pink
edcor ground= 8940 black

Also , someone can please put some pic of the connections of the AC input wiring and the jumper and c8 ( i'm confused whit this  ??? )  ?

Again thanks !!!!!
Title: Re: D-LA2A Support Thread
Post by: mativas on June 27, 2011, 11:13:43 PM

HI all of you!

I have a question.. I am close to finish the pcb building but i can't  find information about:

1. how to wire the rondo muller psu,I can't understand what is the function of the three black wires in volker's picture  neither the connection of the on off toggle switch ( in the pcb i can notice that it have only two pins)


2.  what is the small box  next to the power connector?


3.  how to wire the sowter transformers and the switches on-on  with the  six and three   ends? (terminals)


for the sowters can i use the same edcor's configuration ?

INPUT edcor XSM 600/10k
edcor pin 1 = 4383 brown
edcor pin 2 = 4383 pink
edcor pin 4 = 4383 green
edcor pin 5 = 4383 blue
edcor pin 8 = 4383 grey
edcor ground= 4383 black
OUTPUT edcor XSM10k/600
edcor pin 1 = 8940 yellow
edcor pin 4 = 8940 green
edcor pin 5 = 8940 grey
edcor pin 8 = 8940 pink
edcor ground= 8940 black


Thanks for your help.
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on June 28, 2011, 03:32:39 AM
The PCB from [silent:arts] has the connections for the Sowters printed on it.

I compiled the informations from this thread into a PDF which should answer your questions, too.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 28, 2011, 04:08:59 AM
1. how to wire the rondo muller psu,I can't understand what is the function of the three black wires in volker's picture  neither the connection of the on off toggle switch ( in the pcb i can notice that it have only two pins)
look at the picture in the pdf sonicwarrior posted above.
the PSU transformer only has 2 black wires, which are one of the two heater secondaries.
there is no main power on the PCB, you wire the on/off switch between the IEC connector and the PSU transformer primaries.

2.  what is the small box  next to the power connector?
it is a 120V/220V switch

3.  how to wire the sowter transformers and the switches on-on  with the  six and three   ends? (terminals)
for the sowter transformer use the color code printed on the PCB.
for the switch wiring use the sonicwarrior pdf (thanks btw)
Title: Re: D-LA2A Support Thread
Post by: sea_man on June 28, 2011, 10:27:02 PM
Thanks for your reply , the sowter and all the switch ( except the on/off) are ready !!!

The only part i can't understand now is the AC input for rondo power transformer ( PSU transformer primaries)... this have 4 cables in pairs whit black thermo-retractable (  one wire yellow and other white inside) each .. and i see in many pics two of this wires connected together and in others not..
Can you please guide me to connect this to the IEC connector and the on/off switch ?

Also , i left today to buy the cap for C8.. but this comes in different voltages.. which is the correct ??  0.1uf wima ***v??

Thanks !!
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 29, 2011, 03:04:14 AM
The only part i can't understand now is the AC input for rondo power transformer ( PSU transformer primaries)... this have 4 cables in pairs whit black thermo-retractable (  one wire yellow and other white inside) each .. and i see in many pics two of this wires connected together and in others not..
well, for 110V mains those 4 wires are parallel, for 220V seriell
Title: Re: D-LA2A Support Thread
Post by: rob_gould on June 29, 2011, 05:53:43 AM
I'm interested in adding LED meters to this project.

This subject doesn't seem to have come up since most people go for analogue meters for their builds, more in keeping with the classic look.

Is it possible to add LED meters to an LA2A circuit?

Would something like this be of any use?

http://www.groupdiy.com/index.php?topic=23977

Cheers,

Rob
Title: Re: D-LA2A Support Thread
Post by: sea_man on July 01, 2011, 03:39:58 AM
The only part i can't understand now is the AC input for rondo power transformer ( PSU transformer primaries)... this have 4 cables in pairs whit black thermo-retractable (  one wire yellow and other white inside) each .. and i see in many pics two of this wires connected together and in others not..
well, for 110V mains those 4 wires are parallel, for 220V seriell

Thanks ! it work fine.

For now i need wire all cables again whit shield.. i forgot this  ;D .. because this i have a lot of noise...

Also i will make a pics tomorrow for the forum .

Again.. thanks for your help , it is my firs tube project !
Title: Re: D-LA2A Support Thread
Post by: sea_man on July 05, 2011, 08:14:04 PM
I finish my project !  8)

Here are the pics:

http://www.flickr.com/photos/mar1o_bross/sets/72157627001849463/

Thanks for your help !
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on July 06, 2011, 05:31:19 AM
I finish my project !  8)

congrats! nice work, and you are still allive 8) 8) 8)

(http://www.51xaudio.com/images/DLA2A-sea_man.gif)
Title: Re: D-LA2A Support Thread
Post by: sea_man on July 07, 2011, 04:23:57 AM
Thanks !

The only problem i have now is a hum sound in the right channel

can you give me any advice?
Title: Re: D-LA2A Support Thread
Post by: sea_man on July 08, 2011, 09:39:17 PM
Hum sound is solved swapping the tubes and wiring better the front and the rondo ! ( your advice   ;) )

Now is working fine !

Thanks for all your help and for the signature/banner !
Title: Re: D-LA2A Support Thread
Post by: briomusic on July 22, 2011, 03:27:02 PM
finally finished my stepped-switch D-LA2A, and ready to collect my banner  ;D

frontpanel by NRG CNC, almost made my way through all of frank's anodized colors now.
I should add: little scratches happened during assembly not at NRG.
(http://i1196.photobucket.com/albums/aa405/briomusic/fazbuDLA2Afront.jpg)

pcb and power transformer by silent:arts, T4B by Drip, meters by Hairball
(http://i1196.photobucket.com/albums/aa405/briomusic/fazbuDLA2Ainside.jpg)

thanks to the posters in these threads for helping with the stepped switches:
http://www.groupdiy.com/index.php?topic=44553.msg558003#msg558003 (http://www.groupdiy.com/index.php?topic=44553.msg558003#msg558003)
http://www.groupdiy.com/index.php?topic=44800.msg561075#msg561075 (http://www.groupdiy.com/index.php?topic=44800.msg561075#msg561075)
I went for a custom spacing on the input gain: 1dB steps from -9 to +8dB, then 5dB steps from +10 to +35dB.
the uraltone type switches i got from ebay actually have 24 positions.
Additionally, I used a lorlin with 8 steps for the HF response trimmer. I will see over time if that's enough....
(http://i1196.photobucket.com/albums/aa405/briomusic/fazbuDLA2Arotary-1.jpg)

Title: Re: D-LA2A Support Thread
Post by: rob279 on July 29, 2011, 11:27:43 AM
wher can I buy a circut board from
Title: Re: D-LA2A Support Thread
Post by: desol on July 29, 2011, 12:27:43 PM
Welcome to the forum Rob. These circuit boards are available in the White Market section...
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on July 29, 2011, 05:45:55 PM
Brio, I nearly missed your D-LA2A - I'm sorry ...
Need a stepped switched version too 8)

(http://www.51xaudio.com/images/DLA2A-briomusic.gif)
Title: Re: D-LA2A Support Thread
Post by: briomusic on July 30, 2011, 06:31:12 PM
Brio, I nearly missed your D-LA2A - I'm sorry ...
Need a stepped switched version too 8)

(http://www.51xaudio.com/images/DLA2A-briomusic.gif)

Thanks for the banner  :D 
This guy on ebay does 24step switches now, and even pre-resistor-soldered as log pot replacement:
http://cgi.ebay.de/2P-24-Step-Attenuator-Volume-Control-Pot-Log-100K-Mono-/260806367240?pt=LH_DefaultDomain_0&hash=item3cb9455808 (http://cgi.ebay.de/2P-24-Step-Attenuator-Volume-Control-Pot-Log-100K-Mono-/260806367240?pt=LH_DefaultDomain_0&hash=item3cb9455808)
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on July 30, 2011, 06:34:37 PM
briomusic nice build,  8)

Are those 24p switches ready to go, any circuit mods to be aware of?  Thanks
Title: Re: D-LA2A Support Thread
Post by: briomusic on July 31, 2011, 12:53:21 AM
briomusic nice build,  8)

Are those 24p switches ready to go, any circuit mods to be aware of?  Thanks

Thanks!

You could get the 100k log pre-configured switches as a drop in replacement for the 100k log pots (gain and peak reduction). I wanted a different scale for the gain, so I made up my own with  higher resolution around unity gain and bigger steps towards the higher gain settings.
Title: Re: D-LA2A Support Thread
Post by: telefunk on August 27, 2011, 02:21:39 PM
Hello everybody!

I need a little bit help with this one....

The thing is: My D-LA2A has been working wonderfully for something like 8 months now, everyday. Then, suddenly today the other channel stopped working.

Like this, it passes audio when I turn the gain, normally. But when I turn the Peak Reduction pot CW, instead of more compression, it works like reversed gain pot: sound disappears. And when it's fully CW nothing comes out.

I tried changing all the tubes and switching the T4B's no change. All tubes and the T4b's work in the other channel.

So, any ideas where to start looking?

BTW, the broken channel compresses and works normally when the Peak Reduction pot is fully CCW and Stereo Link is switched on and the control voltage comes from the working channel.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on August 27, 2011, 04:10:51 PM
...
BTW, the broken channel compresses and works normally when the Peak Reduction pot is fully CCW and Stereo Link is switched on and the control voltage comes from the working channel.

which leads us to the potentiometer and its connections to the PCB, isn't it.
or maybe something around VX03 ...
Title: Re: D-LA2A Support Thread
Post by: benlindell on August 27, 2011, 06:15:43 PM
Just got my first one up and running. I had trouble finding info on the 25K +75K mod for gain, I put the 75K between the wiper and pin 2 on the molex. Should I have put it between pin 3 and the pot?

Also I have one channel working perfect and the other with just low thin sound, pretty sure it's the gain pot being not right so one thing at a time
Title: Re: D-LA2A Support Thread
Post by: telefunk on August 27, 2011, 06:17:35 PM
...
BTW, the broken channel compresses and works normally when the Peak Reduction pot is fully CCW and Stereo Link is switched on and the control voltage comes from the working channel.

which leads us to the potentiometer and its connections to the PCB, isn't it.
or maybe something around VX03 ...

Yes, it was the potentiometer! Thank you Volker!

And, btw, if I haven't already said this before I'll say it now: This is the finest piece of DIY I have witnessed, ever. My most loved compressor, ever. Just stunning quality. And..and...ok ok, you got the point.

So, thank you!
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on August 27, 2011, 07:06:18 PM
Just got my first one up and running. I had trouble finding info on the 25K +75K mod for gain, I put the 75K between the wiper and pin 2 on the molex. Should I have put it between pin 3 and the pot?
pin 3 is right
Title: Re: D-LA2A Support Thread
Post by: soundcollage on September 09, 2011, 12:23:18 AM
Finished! Thanks for the great board.

http://farm7.static.flickr.com/6181/6129342112_4ebc4aab5e_b.jpg
http://farm7.static.flickr.com/6074/6129341114_3ae3a8b22b_b.jpg

This was my first time using flickr, how do I make these show up as photos rather than links?
Title: Re: D-LA2A Support Thread
Post by: Hank Dussen on September 09, 2011, 03:02:39 AM
Nice build!
All original transformers and T4's? Probably not cheap!
How did you do the frontpanel?

Title: Re: D-LA2A Support Thread
Post by: soundcollage on September 09, 2011, 04:14:39 AM
Yes, pricey originals but fantastic tone. I gave my wife the layout and the words and she made them pretty in illustrator,  then we made a silkscreen and I printed it with Nazdar 59000 ink onto a Parmetal front panel.
Title: Re: D-LA2A Support Thread
Post by: baadc0de on September 09, 2011, 05:45:20 AM
Yes, pricey originals but fantastic tone. I gave my wife the layout and the words and she made them pretty in illustrator,  then we made a silkscreen and I printed it with Nazdar 59000 ink onto a Parmetal front panel.

Oh you'll have to go into more details for us printing / silkscreening impaired folks. Otherwise, gratz on the build. I made one with NOS T4 and trafos, so I know how hard it is to source at a good price. Very nice build :)

EDIT: oh, and great idea with 4 VUs.. I find myself flicking that VU/GR switch all the time..
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 09, 2011, 02:57:39 PM
 8) 8) 8)

a nicely done VU monster ;D
with switches instead of pots - the way to go.

now you want one banner for it, don't you.
such a unique built deserves one :D

(http://www.51xaudio.com/images/DLA2A-soundcollage.gif)
Title: Re: D-LA2A Support Thread
Post by: benlindell on September 09, 2011, 03:19:26 PM
So I thought I got the 75K+25K thing right but I'm still just using the gain knob to about 10 before I have too much gain. Did I get something wrong?
Title: Re: D-LA2A Support Thread
Post by: benlindell on September 09, 2011, 03:20:24 PM
I used this. The red is red for me too
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 09, 2011, 03:30:05 PM
Ben, looks right.
how would you describe too much gain?
meaning: does the D-LA2A starts oscillation, does it distort, too much gain for following equipment or AD converters?
many options ;)
Title: Re: D-LA2A Support Thread
Post by: benlindell on September 09, 2011, 03:34:38 PM
Too much gain as in when I flip from bypass to in to match the input signal to output signal I have the gain on 10, I thought the 75K resistor was there to make the range larger.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 09, 2011, 03:54:35 PM
Just did a little small test.

Neutrik Minirator +6dBu out -> D-LA2A bypassed -> RTW (0VU [= +6dBu])
With no gain reduction but the D-LA2A inserted my needed gain is 2,75 on my scale,
which is around 10 o'clock position.

for me this is fine, and your mod looks good.
with normal gain reduction applied you will need some more gain,
but I must admit I have never been past 12 o'clock yet.
this is a workable gain range, before the mod it must have been 8 o'clock to 9 o'clock (if I recall correctly, a few years past by)

you can still change to a 10k pot with a 91k resistor etc
Title: Re: D-LA2A Support Thread
Post by: benlindell on September 09, 2011, 06:55:42 PM
Whoops, I forgot to give the scale, I didn't mean 10:00 I meant 10/100 which is how I scaled my front panel, so its at about 7:30 or so
Title: Re: D-LA2A Support Thread
Post by: alexc on September 09, 2011, 08:26:12 PM
Nice to have is 4 vu meters for always on indication of output and gr.

I like to do it too  :)

The only issue is that the vu meter does add quite substantial noise to the output,
across the mid and high bands.

I checked it out on the spectrum analyser and was amazed at how much noise it adds,
particularly around 1K-5Khz or so.

My new 'vu monsters' have a spdt switch for defeating the Output Level VU meter.

Cheers
Title: Re: D-LA2A Support Thread
Post by: soundcollage on September 10, 2011, 04:04:03 AM
baadcode i have many more pictures of this project, but i did not want to clog this thread. when i get all my photos onto photo bucket i will start a thread of all the projects i have completed in my time lurking here and i'll be sure to go into the details of the silkscreening process.
silent thanks again for the great board! i've been sitting on it for a while gathering parts and it's great to finally have it finished. also, thanks for the banner- now i just need to figure out how to put it into my signature.
alex, i sure have not noticed any added noise with my unit, though i don't have a spectrum analyzer yet.
Title: Re: D-LA2A Support Thread
Post by: spase on September 17, 2011, 01:53:21 PM
hey guys anyone can send me up-to-date BOM for this d-la2a build?And how much will be the cost for full build?Thank you
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on September 17, 2011, 02:31:02 PM
hey guys anyone can send me up-to-date BOM for this d-la2a build?

Look closely at the first posting.  ;)

Costs depend highly on the parts you are using (especially case, tubes, capacitors and trafos may vary regarding costs).
Title: Re: D-LA2A Support Thread
Post by: salomonander on September 18, 2011, 07:38:01 AM
hey
im pretty much a beginner at this and just started stuffing my board yesterday. actually im doing fine. there arer only a few parts im not sure where to put. maybe someone can help? its:

Vr/1000V Io/1A Fairchild Rectifiers    and
100V/200mA  Fairchild Rectifiers

iguess they belong to the power supply (D1-D6). but which do belong to D1-D2 and which to D3-D6.

thanks a lot
Title: Re: D-LA2A Support Thread
Post by: spase on September 27, 2011, 07:47:22 PM
Anyone can post EU BOM?becouse i cant buy from mouser and other sites...
Title: Re: D-LA2A Support Thread
Post by: desol on September 27, 2011, 08:58:24 PM
You might have to make one yourself...
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 28, 2011, 03:24:12 AM
Anyone can post EU BOM?becouse i cant buy from mouser and other sites...
everything needed should be available from
www.tubetown.de
and
www.reichelt.de
or
www.conrad.de
Title: Re: D-LA2A Support Thread
Post by: benlindell on October 14, 2011, 05:56:46 PM
Back to troubleshooting this beast.

So I swapped tubes between channels and now both channels are almost no signal, very faint thin sound, wtf is going on?

I've probed and found signal on my input transformer molex but nowhere else, any ideas?
Title: Re: D-LA2A Support Thread
Post by: Cardinen on October 17, 2011, 10:44:22 AM
Hi,

i've finally finished my unit (but i'm still waiting for the VU meters since 4 months...  :o ).

after some initial debug the unit is working fine, but i've a minor problem.

One of the neon lamp (Ch. 2) don't make glow, so i've checked the voltages:
Neon 1 : 53-54 V
Neon 2 : 49-50 V

Maybe a little too lows ??

I've tried to change the dead neon with another but is the same. Sometimes it glow for a few seconds at startup.
I've checked the voltages before R128-228 and i have 7V of difference between them. (the same difference coming from the AC of PSU) so i guess is OK.

Any advices ??

Anyway i'm happy with the sound of this beast, thank's Volker for make this possible !!

regards,

Cardinen




Title: Re: D-LA2A Support Thread
Post by: bernbrue on October 17, 2011, 01:32:46 PM
Hi,
sonic warrior compiled a pdf file with things to keep in mind. Read the passage about the neon lights. Might be better to replace them with zener diodes. PDF attached.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: Cardinen on October 17, 2011, 05:43:14 PM
thank's bernbrue,

i had read that pdf.  I don't have here some zener to try, but i'll do soon.
However the voltages i have on lamps are fine ??

regards

Title: Re: D-LA2A Support Thread
Post by: bernbrue on October 18, 2011, 05:50:23 AM
Hi,
they are a bit low but should work. Don´t care too much about the differences between the channels. The neon lamps need 60V or more to glow. Zener diodes are more reliable. Replace the neons and you are on the saver side.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on October 20, 2011, 09:49:12 PM
 :)

a few simple questions I hope.

Regarding:

-1.)  R125/225   what is the 'cleanest' way to mount a 100K trimmer? 

-2.)  "Changing those 220k plate resistors to something lower is indeed a good idea." 
                   How about sockets for easily swapping of resistors (100K etc) depending on which
                   tube 12AY7/12AX7 etc..??  Good idea or waste of time?

-3.)  C8 listed as 100n, can anyone verify 0.1uF wima (V?)

-4.)  On the Azone US BOM, there were only 4x 9 pin sockets listed.  Though there are 6
                  allotted positions for 9 pin sockets.  I went ahead and ordered 6x sockets, is there
                  something I should be aware of for the 12BH7A?

-5.)  I'm planning on sockets for C104/204 but what are folks generally satisfied using?
                 I opted for the edcor wsm600:15K  wsm15K:600   Is anyone using these xformers
                 that care to share which cap used in designation C104/C204?


Just read this entire thread for the second time today. 

Thanks again for all of your inspiring builds
Title: Re: D-LA2A Support Thread
Post by: desol on October 20, 2011, 11:10:44 PM

-1.)  R125/225   what is the 'cleanest' way to mount a 100K trimmer?

I just used the default that was suggested. 33kohms?? (Can't remember right now) Otherwise, you could solder the middle leg to one side(underneath) of a trimmer....verify lead spacing...and should fit ok.


-2.)  "Changing those 220k plate resistors to something lower is indeed a good idea." 
                   How about sockets for easily swapping of resistors (100K etc) depending on which
                   tube 12AY7/12AX7 etc..??  Good idea or waste of time?

I used 12AY7's and put in 100k(or whatever) resistors permanently. I don't plan on changing it back to 12ax7.
Your call here...


-3.)  C8 listed as 100n, can anyone verify 0.1uF wima (V?)

Not sure what your asking, but yes, 100nf is .1uf. Whatever voltage you can find in that lead spacing. :)
Probably 100v-300v.


-4.)  On the Azone US BOM, there were only 4x 9 pin sockets listed.  Though there are 6
                  allotted positions for 9 pin sockets.  I went ahead and ordered 6x sockets, is there
                  something I should be aware of for the 12BH7A?

Nope. The BOM must be wrong. I must have noticed this too at some point???  ???


-5.)  I'm planning on sockets for C104/204 but what are folks generally satisfied using?
                 I opted for the edcor wsm600:15K  wsm15K:600   Is anyone using these xformers
                 that care to share which cap used in designation C104/C204?

I broke singles off of a sip strip and soldered those in. Seemed to work well enough. Single sockets were hard to source and the ones that i ended up buying(pricey) didn't work in the end cause the hole was ever so slightly oversized. For the value, I used the default suggested.

Everything seems to be working, sounding well. Oh yeah, and yes i used those transformers.
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on October 21, 2011, 01:42:57 PM
Thanks desol

..yet another project you hold my hand through  ;D

Another question if I may regarding Grid Stoppers..

Did you install 1K for GS101/102 GS201/202?

Thanks again!!
Title: Re: D-LA2A Support Thread
Post by: desol on October 21, 2011, 06:57:14 PM
yep...
Title: Re: D-LA2A Support Thread
Post by: benlindell on October 23, 2011, 10:29:28 PM
Back to troubleshooting this beast.

So I swapped tubes between channels and now both channels are almost no signal, very faint thin sound, wtf is going on?

I've probed and found signal on my input transformer molex but nowhere else, any ideas?
Anyone have some clues for what might be going on with mine?
Title: Re: D-LA2A Support Thread
Post by: bernbrue on October 30, 2011, 02:46:02 PM
Only a guess, it might help:
check
- transformer wiring and molex connectors
- XLRs wiring
- grounding
- bypass relays (switch wiring)
- heater wiring (has to be wired on solderside)
- correct voltages
- bad tubes
- .....
I´m shure there is an easy to find mistake. Don´t give up, the compressor is worth every hour you spend in building and troubleshooting.
regards
Bernd


Title: Re: D-LA2A Support Thread
Post by: benlindell on October 30, 2011, 09:04:04 PM
I double checked the transformer and xlr wiring, they appear to be good, my grounding appears fine, the relays are clicking and working (signal to no signal).

The Heaters.... I measure 6.5V between pin 4 and pin 9 on all but the 6aq5a (pin 3 and 4). But whats weird is that on the left channel I get 3.3V between pin 4 and every pin but 5, that shouldn't happen right?
Title: Re: D-LA2A Support Thread
Post by: bernbrue on October 31, 2011, 06:43:37 AM
For all tubes (except 6AQ5) heater is wired to pins 4&5. For the 6AQ5 heater is connected to pins 3&4 (pcb turned around and counted clockwise)
check left channel for bad tube, soldering of the tube sockets, heater wiring, power transformer specs & wiring, values of R1&R2. So you´ve already narrowed the problem, you should be quite close to find the mistake. Go on!
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 01, 2011, 12:40:49 AM
Yea I'm getting 6.7V on pins 4 and 5 (referenced to pin 9) but I'm getting 3.3V from the rest of the pins (still referenced to pin 9), why would this be?
Title: Re: D-LA2A Support Thread
Post by: bernbrue on November 01, 2011, 03:47:11 AM
Pin 9 is useless for measuring. You´ll get half the heater voltage. If you´ve got 6,3V between 4&5 everything is allright with the heater. What are the other voltages? There is a schematic with correct measured voltages out there. Take it for reference and compare your voltages with them. Check the voltages at R129 and R229 (attention !!!!!!!!! , very high voltages). Measure with reference to ground.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 01, 2011, 02:43:55 PM
ok so if I shouldn't reference pin 9, should I be referencing the star ground? if so then I'm getting even weirder voltage readings. I'm getting +350VDC on R129 and R229 though
Title: Re: D-LA2A Support Thread
Post by: bernbrue on November 01, 2011, 03:29:39 PM
Yes, always measure the voltages with reference to star ground. Your voltages are fine. There should be about 350V before (on the right side of) R129 and R229. After the resistors (other leg of the resistors) there should be something like 275V. Have a look at the schematics below and compare your voltages with those shown in the schematic. Keep in mind that heater voltage is AC whereas H.T. voltage is DC.

http://www.twin-x.com/groupdiy/albums/userpics/LA2A-deconstructed.jpg

http://www.waltzingbear.com/Schematics/Urei/Urei_LA-2A.JPG

Hope this helps.
regards
Bernd


Title: Re: D-LA2A Support Thread
Post by: benlindell on November 09, 2011, 12:30:59 PM
Yes, always measure the voltages with reference to star ground. Your voltages are fine. There should be about 350V before (on the right side of) R129 and R229. After the resistors (other leg of the resistors) there should be something like 275V. Have a look at the schematics below and compare your voltages with those shown in the schematic. Keep in mind that heater voltage is AC whereas H.T. voltage is DC.

http://www.twin-x.com/groupdiy/albums/userpics/LA2A-deconstructed.jpg

http://www.waltzingbear.com/Schematics/Urei/Urei_LA-2A.JPG

Hope this helps.
regards
Bernd

Thanks for sharing those. I just had a chance to run through one channel and all the voltages are close but generally under by a little bit (250V instead of 275V)

Both with and without the t4b installed I'm getting super quiet and thin sound that goes up and down with the gain pot.

I just went through resistor by resistor and verified they are the correct values, and also the caps. I continuity checked all the molexes as well.

When I measure the heaters referenced to star ground on the left channel at pin 4&5 I get 3.3v and pin 9 I get 3.2V, all the other pins are 0V now. but on the right channel at pin 4&5 I get 0.2V and pin 9 i have 6.3V. What would be causing this?

I've swapped input and output transformers.

The only thing I haven't tried yet is new tubes I've been mixing up the 8 original ones I put in, before using another set I wanted to make sure it's not something I'm doing that killed these ones.
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 09, 2011, 12:38:46 PM
I should also add that this one did definitely work a few months ago when I wired it up on the bench, then I left it for a couple months and then finally put it in the case, makes this all even weirder
Title: Re: D-LA2A Support Thread
Post by: bernbrue on November 09, 2011, 01:10:04 PM
Hi Ben,
there must be a misunderstanding. I attached a picture for checking the heater voltages.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 09, 2011, 06:46:25 PM
So I should be reading 6.3 between pin 4&5? I'm getting 6.3 on the terminals in the pairs like you have drawn.
Title: Re: D-LA2A Support Thread
Post by: bernbrue on November 10, 2011, 01:59:53 AM
Yes, except for the 6AQ5, which has its heater on pin 3&4. Check the heater wiring twice and compare it to the picture. Then check the pot wiring.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 10, 2011, 12:22:38 PM
Here's what I'm getting, referenced to star ground. Thanks for your help and patience with this, I feel there must be something silly that's going on, especially since this worked before I put it in the case.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 10, 2011, 01:56:03 PM
Ben,

I don't know anything about your "black marking" scheme ...
but there is some inconsistence there.

I'm sure you disconnected it from your PSU transformer while putting it in the case ;)
Title: Re: D-LA2A Support Thread
Post by: bernbrue on November 10, 2011, 02:23:45 PM
Ben,
Volker is right, double check the power transformer wiring, especially the  flying blue lead. I saw a bad connection at one of the XLRs in the picture, too.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 10, 2011, 02:59:12 PM
Ben,

I don't know anything about your "black marking" scheme ...
but there is some inconsistence there.

I'm sure you disconnected it from your PSU transformer while putting it in the case ;)

Disregard the black marks, I made them so I knew how I hooked it up when I initially put it in the case.

I did disconnect it after it working while putting in the case :(. I'm really confused as to how I could get 3.3V though.

I just unplugged the wires from the terminals and measured 6.7V between blue and green for both sets. Then when I put them back in the terminals I get the same results as before when referenced to star ground (3.4, 3.4, 6.4, .3), but still 6.7V when measured between the pair in the terminals (I hope that makes sense).

Ben,
Volker is right, double check the power transformer wiring, especially the  flying blue lead. I saw a bad connection at one of the XLRs in the picture, too.
regards
Bernd

The flying blue wire is the pilot light which I'm leaving disconnected for the time being. What issue do you see with the XLR?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 10, 2011, 03:38:58 PM
Ben, referenced to star ground arround 3,3V each heater is correct.
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 10, 2011, 03:55:47 PM
So then is it wierd that the other one reads 6.3 and .4?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 10, 2011, 04:57:19 PM
So then is it wierd that the other one reads 6.3 and .4?
yes

and please measure the high voltage.
while I don't know your PSU transformer it looks uncommon, like out of phase.

PS: watch your grounds. one channel isn't grounded correctly
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 10, 2011, 06:21:22 PM
So then is it wierd that the other one reads 6.3 and .4?
yes

and please measure the high voltage.
while I don't know your PSU transformer it looks uncommon, like out of phase.

PS: watch your grounds. one channel isn't grounded correctly

I'm using this transformer, should be fine right? http://www.antekinc.com/pdf/AS-1T250.pdf

I'm getting 350VDC on the right side of R129 and R229. I went through http://www.twin-x.com/groupdiy/albums/userpics/LA2A-deconstructed.jpg and all my high voltages were really close (with tubes installed on one channel) just a few volts low across the board.

both channels are tied to star ground, I just didn't use the quick connect that's recommended, I soldered a wire in there, just to be safe I just double checked the continuity on that too.
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 10, 2011, 06:44:51 PM
In the interest of thoroughness I swapped the pairs of blue and green a bunch and no matter what combo, I can only ever get 3.4, 3.4, 5.9, .4)

Title: Re: D-LA2A Support Thread
Post by: Cardinen on November 11, 2011, 07:05:22 AM
Finally finished my unit   ;)

(http://img217.imageshack.us/img217/3939/la2p.th.jpg) (http://imageshack.us/photo/my-images/217/la2p.jpg/)

(http://img543.imageshack.us/img543/4839/la22.th.jpg) (http://imageshack.us/photo/my-images/543/la22.jpg/)


I've replaced R25 with a trimmer, and now the VU tracking is quite good.
The right meter moves a little in Gr. mode but is not a problem at the end; tried to change the lamp with a zener did not solved the problem.
Anyway i'm really happy with this build.




Title: Re: D-LA2A Support Thread
Post by: bernbrue on November 11, 2011, 10:01:30 AM
In the interest of thoroughness I swapped the pairs of blue and green a bunch and no matter what combo, I can only ever get 3.4, 3.4, 5.9, .4)

Ben,
measure AC coming from the power transformer. Therefore disconnect green and blue wires form pcb and measure the AC voltage between green/blue. Check the heater wiring underneath the pcb (bad solder connection, broken wires, scratched isolation, wrong pins, etc.). When everything is correct, reconnect the blue/green wires for one channel only, measure voltages once again without the tubes plugged in. If voltages aren´t correct there must be a mistake with R1&2 or R3&4 (resistor values, badly soldered, etc.). If voltages are correct, measure with one tube plugged in and so on. It shouldn´t be too difficult to find the mistake.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 11, 2011, 10:26:01 AM
Ok will do. I do get 6.7V between both pairs of the blue and green wire when not connected to the board. Just a note, when I measure either one referenced to star ground I get 70V, is that not a good thing?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 11, 2011, 10:41:13 AM
Ben, while there is still something wrong with your heaters (where the colors doesn't matter, it is AC),
change your high voltage PSU connection zo white/yellow white/yellow.

look at the schematic and your transformer PDF!
Title: Re: D-LA2A Support Thread
Post by: bernbrue on November 11, 2011, 10:42:01 AM
Just a note, when I measure either one referenced to star ground I get 70V, is that not a good thing?

Just ignore the 70V for the moment and measure between the leads/pins. Now connect the transformer leads to the board and measure without tubes plugged in.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: bernbrue on November 11, 2011, 10:45:47 AM
Hi Volker,
I had a look at the tx pdf. You´re right.  Besides that there is more going on. Greetings to Berlin.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 11, 2011, 10:51:54 AM
Ok so I get the right value between the leads, then when connected to the board without tubes I get the same problem. I think it may be time to take it all out of the case again so I can get to the bottom (pun intended) of this.

For the high voltage, the board is labeled 250 GND GND 250 (going top to bottom). White is 250 and Yellow is 0 on the sheet so thats why I did White, yellow, yellow, white. Why does it need to be white yellow white yellow?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 11, 2011, 11:01:24 AM
For the high voltage, the board is labeled 250 GND GND 250 (going top to bottom). White is 250 and Yellow is 0 on the sheet so thats why I did White, yellow, yellow, white. Why does it need to be white yellow white yellow?
look at the original schematic, which uses a 500V center taped transformer.
the labels on the PCB are fine, but for sure don't match the PSU labels.
for your specific transformer:
the first 250V label is white from the first secondary.
the second 250V label is yellow from the second secondary.
first secondary yellow + second secondary white = center tap.
wired like you have it at the moment it is out of phase.
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 11, 2011, 12:12:54 PM
OK cool, so I switched them, I'm still getting the same readings everywhere though. Just curious, what does having the AC power be out of phase do to the unit?
Title: Re: D-LA2A Support Thread
Post by: bernbrue on November 11, 2011, 12:23:20 PM
I think it may be time to take it all out of the case again so I can get to the bottom (pun intended) of this.

Ben,
it would be nice to see a picture of your heater wiring.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 11, 2011, 04:38:24 PM
... Just curious, what does having the AC power be out of phase do to the unit?
correct is 250V each halfwave,
out of phase it is 2x250V each 2nd halfwave
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on November 11, 2011, 05:27:11 PM
(http://img217.imageshack.us/img217/3939/la2p.th.jpg) (http://imageshack.us/photo/my-images/217/la2p.jpg/)

(http://img543.imageshack.us/img543/4839/la22.th.jpg) (http://imageshack.us/photo/my-images/543/la22.jpg/)

Finally someone with a case from the evil man. Where did you get the lamp/LED holder from?
Any problems with the power switch in the middle?
Title: Re: D-LA2A Support Thread
Post by: Cardinen on November 12, 2011, 10:26:01 AM

Finally someone with a case from the evil man. Where did you get the lamp/LED holder from?
Any problems with the power switch in the middle?

Ahaha why evil man ? (i got this since a looong time)
The VU lamp are simple a blue led above the meter.

no problem with the power switch in the middle, both channels are very silent (Ch2 have slighty more hum than 1 but is not relevant... both are below -90 !!)
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on November 12, 2011, 11:50:55 AM
Ahaha why evil man?

He pissed off a lot of people here. E.g. I have a dual mic pre case from him were the front panel turned violet because of UV sensitiveness.

The VU lamp are simple a blue led above the meter.

I didn't mean the VU meters but the lamp in the middle. I don't know where to get a lamp/LED holder that fits this f****ing big hole.
Title: Re: D-LA2A Support Thread
Post by: Cardinen on November 13, 2011, 08:49:31 AM

I didn't mean the VU meters but the lamp in the middle. I don't know where to get a lamp/LED holder that fits this f****ing big hole.

Sorry I misunderstood, mine is this : http://www.banzaimusic.com/Jewel-Full-Assembly-Deep-Blue.html

p.s: Hope my case don't turn violet this night...  :)
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on November 13, 2011, 09:56:51 AM
Oh, I got the translation wrong. It's purple, not violet and it's a very dark purple. I also got a purple area at my Dual 1176 case.

Thanks for the Banzai. Comes in handy as I need to order from them anyway.
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 13, 2011, 11:51:16 PM
Here's some pics of the bottom of my board
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 13, 2011, 11:51:41 PM
Closer look at the right channel
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 13, 2011, 11:52:16 PM
And the Left
Title: Re: D-LA2A Support Thread
Post by: bernbrue on November 14, 2011, 02:05:25 PM
Well, the heater wiring look ok for me, but what is that wire on top of the picture doing there? I would also check a few solder points for bad contact  or even shorts. I marked a few spots in the picture.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 14, 2011, 03:41:05 PM
Well, the heater wiring look ok for me, but what is that wire on top of the picture doing there? I would also check a few solder points for bad contact  or even shorts. I marked a few spots in the picture.
regards
Bernd
Good to know I got the heaters right. The wire at the top is the relay ground. I'm planning on going the whole thing joint by joint and double checking everything.
Title: Re: D-LA2A Support Thread
Post by: bernbrue on November 14, 2011, 04:21:28 PM
Ben
remove the wire, there is no need to ground the relay. It does´t make sense. Volker provided everything for proper grounding. This wire could be the reason for your problems.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 14, 2011, 04:50:41 PM
Oh, I thought the 0V of the relays weren't tied together hence the molex for the relay having 0V and 5V, I didn't use a molex connector for the relay power so I figured I had to hardwire it.
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 14, 2011, 09:50:23 PM
Ok so..

Out of the case, and I reflowed a bunch of joints and I now have the left channel working (this is the one that has worked before then stopped working)

I then took everything plugged in to the left and put it on the right (XLRs, Transformers, Tubes, T4B, Pots, switches) and I get a big fat nothing :( I checked the heaters and I'm now getting the same on both channels (and the tubes are getting warm on the right as well) and I went through the high voltages and once again they're all pretty close, just a little under in most cases.

I just checked my relays to make sure they are working correctly on both channels.

I'm getting stumped.... Where should I be looking? It's weird to be getting no sound right?

Luckily I've eliminated a lot of variables
 - Tubes
 - T4B
 - Pots
 - Switches
 - Transformers
 - XLR connectors
 - Heaters
 - High-Voltage

Also on the working channel I'm getting way too much gain, did I still do the 25k pot + 75k thing wrong? I'm at unity at around 8:00, it's way too sensitive, even more so than real units I've worked with. I attached a pic of my gain pot hopefully I just got something backwards there.
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 14, 2011, 10:25:23 PM
I just did a detailed check of all the resistors and caps from one channel to the other. I also checked the tube sockets and molexs for continuity.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 15, 2011, 03:42:44 PM
Ben, does the right channel passes audio in bypass?
(just give the unit no power and check)
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 15, 2011, 04:25:50 PM
Ben, does the right channel passes audio in bypass?
(just give the unit no power and check)
Yes it does
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 15, 2011, 04:56:24 PM
Ben, if you get nothing it could be something with the relays (one switching, one doesn't).

Do you have a scope to trace where the signal disappears?
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 15, 2011, 05:15:12 PM
Ben, if you get nothing it could be something with the relays (one switching, one doesn't).

Do you have a scope to trace where the signal disappears?
I tested the relays for continuity both In and Out and they test fine, this was my first guess as well.

I don't have a scope but an audio probe. I'm gonna follow the schematic and see how far the signal gets. I'm excited to be done with these, they sound great when working.

Any hints on the Gain problem on the working channel?
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 16, 2011, 08:04:29 PM
So I'm getting signal in most places that are supposed to have signal, it's just all very low, this is all with tubes and t4B that work perfectly in the other channel, even the output transformer is getting signal as well as in and out of the relay, albeit all low level.

I think the tell of the problem is that the Gain reduction meter isn't moving from 0 at all and I hear/measure no difference when moving the threshold pot, so I'm guessing my problem is in the sidechain right? The Gain pot does have a little effect, it goes from no signal to weak signal with noise.

Where in the side chain should I be able to measure signal? I must be dealing with a defective part, I've now triple checked the resistors and caps, looked for shorts, tested continuity, used all known good removable parts...
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 16, 2011, 09:57:11 PM
I went through the whole schematic testing for continuity and the darn thing is all good. Anyone have an idea for where to keep looking? I'm running out of things to test.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on November 17, 2011, 12:52:11 AM
Ben, first make sure the audio patch is working properly.
take the T4Bs in both channels out.
do both react the same now?
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 17, 2011, 05:03:13 PM
Ben, first make sure the audio patch is working properly.
take the T4Bs in both channels out.
do both react the same now?
They both get no sound now (with and without t4bs) :( I'm starting to feel like throwing this thing out the window, it works once then stops working again! I'm trying different transformers, different tubes, nothing works.

Edit: It's gotta be the molex on the input transformer, even though all 3 of my sowters I've tried, the 3rd one was touchy, it'd work sometime and then if i moved the wires it'd stop. I'm using the pushdown type molexs not the solder type, so now I'm gonna solder it instead and report back. Also when I injected signal into the gain pot it worked fine, lots of gain.
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 17, 2011, 06:11:18 PM
AND YES it seems to have been all the molexs for the input transformers weren't making a good connection, I tested with one being soldered instead and it works, both channels! Now if I can figure out how to control the gain on this bad boy. when I'm at unity gain my gain pot measures 96kOhms (removed from the circuit). Should I try different tubes instead of 12ax7s or maybe go get a 90k res with 10k pot? Maybe it's cause I'm using a linear pot, that's probably what's doing it right?
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on November 17, 2011, 06:25:44 PM
Hi Ben, I've been quietly following along the issues you've been having and am thrilled to hear you've got her worked out!   :D

For anyone that has stuck the 'limiter response 1M' to the front panel, are you using it and in what regard?  I'm not quite sure if I want to populate it on the pcb or stick it on the panel......    ::)



Title: Re: D-LA2A Support Thread
Post by: benlindell on November 17, 2011, 06:52:58 PM
Hi Ben, I've been quietly following along the issues you've been having and am thrilled to hear you've got her worked out!   :D

For anyone that has stuck the 'limiter response 1M' to the front panel, are you using it and in what regard?  I'm not quite sure if I want to populate it on the pcb or stick it on the panel......    ::)

Thanks man!

I always like what it does, to me it just makes it less sensitive to the "body" of the sound which I like to have control over when setting it up, it's almost another threshold control.
Title: Re: D-LA2A Support Thread
Post by: desol on November 17, 2011, 07:31:20 PM
I'm starting to feel like throwing this thing out the window, it works once then stops working again!

It a basic rule of DIY, that when you reach this point, if give up, your not cut out for DIY...but if you keep going...you WILL find the answer soon. Seems to be a test of some sort. :)

Nice to hear you got it worked out...thus far. Those molex's can be tricky. Both properly crimping and soldering and pushing them in the hole. I didn't get my proper stride till about the thirtieth one. Pretty much all of my problems with this build were wiring.
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 18, 2011, 11:59:31 AM
Hi Ben, I've been quietly following along the issues you've been having and am thrilled to hear you've got her worked out!   :D

For anyone that has stuck the 'limiter response 1M' to the front panel, are you using it and in what regard?  I'm not quite sure if I want to populate it on the pcb or stick it on the panel......    ::)

Thanks man!

I always like what it does, to me it just makes it less sensitive to the "body" of the sound which I like to have control over when setting it up, it's almost another threshold control.

Here's sweeps of my unit to show the effect of the response control.

The blue line is with the response set to high and the green line is response set to low, the other two are intermediate steps to show how the response changes.

This shows exactly what I hear, the unit doesn't compress until it detects signal at higher frequencies, useful right?.

One observation, on my unit I used linear pots for the response adjustment, in the future I'd probably want them to be log as there was no change from high down to about 30%, 50% was the exact same as 100%
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on November 18, 2011, 12:13:04 PM
Oh awesome!  Thanks for that graphic Ben, I'll be sure to put this on the front panel.

I did see a member used a Lorlin rotary of 120K increments, I think I may go that route. 

Is there a better or worse trimmer for R25?  Am I ok sticking any old 100K pot I have laying around in there?

Edit:  Looking back, it was Briomusic who used an 8 step Lorlin, perhaps he can help with a part number and any feedback if he intends on changing or is happy with the performance. 
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on November 18, 2011, 07:10:43 PM
Hey Briomusic, can you also share with us the stepped attenuator calculations you used for your input gain switches?  I think I'm gonna leave pots for peak reduction, but I want switches on the gain.

Thanks, it's much appreciated!!   ;D
Title: Re: D-LA2A Support Thread
Post by: benlindell on November 19, 2011, 01:12:54 PM
What is a safe case temp for these? I'm definitely going to leave a space above this guy cause it's running about 137°F/57°C
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on November 19, 2011, 01:15:03 PM
What is a safe case temp for these? I'm definitely going to leave a space above this guy cause it's running about 137°F/57°C

 ;D might get double use as a foot heater over the winter, perhaps warm the coffee also.. kidding of course.  That is one hot mama
Title: Re: D-LA2A Support Thread
Post by: audiophreak on December 02, 2011, 10:42:43 AM
Hi All,
      need a little front panel labeling help .... I'm doing the graphics for a front panel for my D-LA2A and I'm using a 6 pos. switch for the SC HP Response . Currently have the positions labels as (  0R , 200K , 400k , 600K , 800K , 1M )   as those are the resistor values used , but not sure I like that description/labeling . 

  any thoughts as to another way to label these position  ? 

 
Title: Re: D-LA2A Support Thread
Post by: benlindell on December 02, 2011, 10:45:36 AM
Hi All,
      need a little front panel labeling help .... I'm doing the graphics for a front panel for my D-LA2A and I'm using a 6 pos. switch for the SC HP Response . Currently have the positions labels as (  0R , 200K , 400k , 600K , 800K , 1M )   as those are the resistor values used , but not sure I like that description/labeling . 

  any thoughts as to another way to label these position  ?
I would probably suggest just doing a simple 0-10 scale maybe as it isn't a very linear nor definable control. Also I'm going to switch my linear pot to a log (audio) taper pot because from halfway to fully clockwise it really didn't change much at all.
Title: Re: D-LA2A Support Thread
Post by: audiophreak on December 03, 2011, 08:05:30 AM
Thanks Ben,
                    I wan t to stick with switch positions for recall ability but panel real estate is tight, so 6 position is it. Just obsessing over how to label the positions " A,B,C" , " 1,2,3 " ,  in Hz ?  " 30, 60, 90, 120, 180, 220 "   , "  Flat , Mid, Open  "   ????   
 
   I was also thinking of using a Pot to select the increments then measure the resistance of the pot, then insert the corresponding resistor in the switch position.

  ..... or am I WAYYYyyyy over thinking this  ....  ;D
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on December 03, 2011, 11:53:31 AM

 
   I was also thinking of using a Pot to select the increments then measure the resistance of the pot, then insert the corresponding resistor in the switch position.

  ..... or am I WAYYYyyyy over thinking this  ....  ;D

I would appreciate your efforts in this please post your results. 

For my own clarification, 1M gives the most 'flat' response, whereas 0 would be less sensitive to the low end?  Or is it vice versa?
Title: Re: D-LA2A Support Thread
Post by: audiophreak on December 03, 2011, 03:45:46 PM


I would appreciate your efforts in this please post your results. 

For my own clarification, 1M gives the most 'flat' response, whereas 0 would be less sensitive to the low end?  Or is it vice versa?

  ... Not sure on that myself  :-[   was hoping someone with more knowledge of the circuit would chime in. 
  I will definitely post whatever I find out , I have the PCB, PT, heater wiring, all mounted in the case, front panel is at Prodigy Engineering for Laser engraving- just agonizing over the naming convention of this control , then spend the $ on the Sowters and T4Bs

EDIT : spelling
Title: Re: D-LA2A Support Thread
Post by: tmuikku on December 04, 2011, 03:14:29 AM


I would appreciate your efforts in this please post your results. 

For my own clarification, 1M gives the most 'flat' response, whereas 0 would be less sensitive to the low end?  Or is it vice versa?

  ... Not sure on that myself  :-[   was hoping someone with more knowledge of the circuit would chime in. 
  I will definitely post whatever I find out , I have the PCB, PT, heater wiring, all mounted in the case, front panel is at Prodigy Engineering for Laser engraving- just agonizing over the naming convention of this control , then spend the $ on the Sowters and T4Bs

EDIT : spelling

Hi! I haven't looked the schematics but it is most propably just an RC filter with variable R so it is time for learning for you fellows ;) Do a Google search with "rc high pass filter". If you are lazy and don't want to do the math (just look the equations and you'll know how R affects the filter) try some of those online calculators and see how changing the R affects.
Title: Re: D-LA2A Support Thread
Post by: audiophreak on December 04, 2011, 07:44:24 PM
Thanks tmuikku ,
                         I did some searching and thinking , still a little confused , but this  what I've got so far :

   Kingston posted this calculator link  - http://www.muzique.com/schem/filter.htm
 -  to help me with my NewYorkDave One Bottles.

   Looking at the D-LA2A schematic ,  C112  ( 1n ) is the Cap associated with VR137  , using these values in this calculator -
     1M = 159.2Hz
  800k = 199Hz
  600k = 265.4Hz
  400k = 398.1Hz
  200k = 796.2Hz
  100k = 1,592.4Hz
  50k = 3,184.7Hz
  20k = 7,961.8Hz
  15k = 10,615.7Hz
  10k = 15,092.6

    also from the first page on Limiter Response Calibration  - " This potentiometer is factory set for a “flat” side-chain response (clockwise).  Increasing
the resistance of this potentiometer by turning it counter clockwise will result in
compression which is increasingly more sensitive to the higher frequencies. "   

  ... does this mean its LESS SENSITIVE to lower frequencies  ?   as the Super Side Chain for the GSSL ?   

  I think whats confusing me is that increasing the resistance Lowers the corner frequency - according to what I've found above - and I could be totaly wrong  ;D
Title: Re: D-LA2A Support Thread
Post by: Kingston on December 04, 2011, 08:36:45 PM
That's because it's not a simple RC filter. It's close, but not a plain RC. See the schematic below for a great drawing of LA2A signal chain. Much easier to follow the signal flow there compared to the usual fifties drawings around.

Notice: the 1meg trimmer is in parallel with the 1nF cap. The R of this RC filter is elsewhere.

1. When the sidechain filter is at max resistance the signal is almost completely going through the 1nF cap: now we have a high pass filter, and no bass is going to the sidechain. Calculate it roughly as a 1nF/47k RC filter. But it's actually a bit more complex than that.

2. Lowest resistance is effectively a bypass. No 1nF cap in the signal chain, no high pass, and all bass is now going to signal chain.

I just went with 0R, 500k and 1meg selectable switch. It works well, the steps are not too coarse and you can easily hear what this does to compression. This feature is not subtle, but I would personally have no use for finer range (like 250k and 750k added). A Linear 1meg pot would also work very well.
Title: Re: D-LA2A Support Thread
Post by: audiophreak on December 04, 2011, 09:21:52 PM
Thanks so Much Kingston  :)
 
    That makes more sense now  ... I was looking for where the ground connection was following the other D-LA2A schematic as with a plain RC . 

  Thanks again for taking the time ,   I gots me some reading to do   ;D
Title: Re: D-LA2A Support Thread
Post by: benlindell on December 05, 2011, 01:48:53 AM
The only thing I noticed when measuring my sidechain is that the 1M pot probably shouldn't be linear, at 50% it was effectively identical to full, all the tweaking range was between 0-50% I just ordered a log pot to try out and see if I can get a better range out of it.
Title: Re: D-LA2A Support Thread
Post by: Kingston on December 05, 2011, 05:04:47 PM
My experience is quite different. Feeding it a very bassy drum loop and setting compression so that I get 10dB gain reduction. Then switch to 500k and gain reduction goes to about 7dB. Finally set it to 1meg and it goes to 5dB. That to me is an even spread.
Title: Re: D-LA2A Support Thread
Post by: bkbirge on December 18, 2011, 11:12:47 AM
re: gain mod question & help! I am having trouble getting the gain mod to work the way I expect so I guess I'm doing it wrong, can anyone help? I've tried 100K log, 100K linear (just for the heck of it) and 25k log pots in the gain along with 47k or 100k resistors, either on the wiper to cable or on one of the legs to cable. Almost no difference that I can tell before gain is way too much. It is usable and always has been but I can't get gain past about 8 o'clock on the dial before it's just too much. I've also done the 12ay7 mod and changed R9/13 to 100k's. Clearly I'm missing something obvious, anyone care to clue me in?
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on December 29, 2011, 03:39:30 PM
Alright so I fired up my unit for the first time last night with no T4Bs, no sparks, no flames.

First off, cheap pots both feel, and sound awful  :(  my gain sounds scratchy and grainy when adjusted.  Need to find a nice pot to swap in.

Both channels noise-floor sit ~-74dB with gain at 12O'Clock, with no signal or load at the input, the noise floor has an ever slight hum, I haven't checked on an analyzer but sounds of 60Hz/harmonics and increases with gain. 

Channel 2, the one nearest the PSU/Toroid side, is a touch noisier.  This is with nothing in the Octal socket on either channel. 

I'm only listening to D-LA2A output-->FF UFX frontpanelpre(0dB gain applied)---> ADC  even with the slight hummy noise-floor, I'm surprised how quiet it is.  At max gain the noise-floor is some -65dB with no load at the input.   I'm not sure how to or if I should attempt to bring noise down, or if I just live with this small bit of hum.  Perhaps when shown a load the signal:noise will be so much that it's non-issue?

At first I had my VU/GR switch wired backwards, which then caused me to turn the zero trimmer too far in attempt to zero the meter, which then knocked out the neon  :o .   Once I realized this, the neon came back and the meter now rests at 0 in gain reduction mode.

Waiting on T4 cells so figured I'd come on here and blab some.
Title: Re: D-LA2A Support Thread
Post by: etiefenthaler on December 30, 2011, 06:56:46 AM
Hi,

Thanks to Volker and  this forum for making this build possible.

My unit is working great. no hum, no smoke, still alive  etc..

Pictures below:

(http://www.flutemusic.ch/IMG_2212.JPG)

(http://www.flutemusic.ch/IMG_2211.JPG)

(http://www.flutemusic.ch/IMG_2195.JPG)

(http://www.flutemusic.ch/IMG_2197.JPG)

(http://www.flutemusic.ch/IMG_2200.JPG)

(http://www.flutemusic.ch/IMG_2202.JPG)

(http://www.flutemusic.ch/IMG_2203.JPG)


One issue I have: While there is no hum when using the alpha pots.
I get hum whith the stepped switches. (picture above)
Could someone please give me an advice how to wire this switch?


Thanks a lot again to Volker and this Forum.

Erich T.


p.s. amplifier without "l"  8)



Title: Re: D-LA2A Support Thread
Post by: spase on December 30, 2011, 08:37:32 AM
where did you get that t4b's?
Title: Re: D-LA2A Support Thread
Post by: etiefenthaler on December 30, 2011, 09:26:29 AM
Hi Spase


these are the Drip t4Bs

http://www.dripelectronics.com/index.php?option=com_content&view=article&id=9&Itemid=30


Title: Re: D-LA2A Support Thread
Post by: etiefenthaler on December 30, 2011, 12:06:31 PM
Hi,

since I got some pm questions I try to reply here:

Lamps get V from relay 5V. Voltage for meter leds is reduced through resistor to 4V.
regulators heatsink temp is 39° C.

Original Track recorded by college students (not at my studio)
http://www.flutemusic.ch/mp3/vocal%20raw.wav (http://www.flutemusic.ch/mp3/vocal%20raw.wav)

here through dla2a
http://www.flutemusic.ch/mp3/vocal%20dla2a.wav (http://www.flutemusic.ch/mp3/vocal%20dla2a.wav)


Noise:
Setting: no input, both PR and Gain at 12 o clock then gradually raised gain noise at 3 o clock pm
then raised PR to full and raised gain to fully open.

http://www.flutemusic.ch/mp3/dla2a%20noise.wav

Erich
Title: Re: D-LA2A Support Thread
Post by: etiefenthaler on December 31, 2011, 12:05:49 PM
Hi

I dont  want to be impatient, but i'd like to try the stepped gain pots in my la2a.

Between 1 and 2 stepped values can be meausured. form 0 to 100 kohms.
Between 1 and 3 always 100 kohms.

no connection between brassbackplate and case ground.

thanks

Erich
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on December 31, 2011, 02:01:08 PM
 :o 

OK so my hum problem was user error.  When shown a proper load to the input this thing sounds beautiful!

I was monitoring the output with NO load to the input but when I shorted the input the hum completely went away. 

With proper chain in front of LA2 it sounds very nice, and doesn't take much LA2 gain to match bypass/in.

Just waiting on optos to find out if I screwed something up in the side-chain amp.

I've got Blackburn Mullard 7025 and EH 12BH7A in the line amp, with Tele ECC83 and NOS RCA 6AQ5A in the side-chain amp. 

I can't thank enough everyone in this thread Volker especially for the project, as well as those who posted at Frank's place.  Don't think I'd have made it without reading over and over analyzing the posts in this thread and at Frank's.

I've learned so much from this project, more so than with any other.

Thanks again to all of you posters and again Volker!  Now to get this PM670 rocking   8)

Happy New Year everyone!!     ;D

(http://img513.imageshack.us/img513/7879/dla2ac.jpg) (http://imageshack.us/photo/my-images/513/dla2ac.jpg/)
(http://img651.imageshack.us/img651/3876/dla2ab.jpg) (http://imageshack.us/photo/my-images/651/dla2ab.jpg/)
(http://img28.imageshack.us/img28/5748/creepyface.jpg) (http://imageshack.us/photo/my-images/28/creepyface.jpg/)

Title: Re: D-LA2A Support Thread
Post by: audiophreak on December 31, 2011, 02:20:16 PM
Nice work Ben   :)

   Just got my front panel back from machine shop , still need IP / OP transformers and T4Bs - gotta save a little more $    ;D

  Happy New Year !! 
Title: Re: D-LA2A Support Thread
Post by: Cardinen on January 01, 2012, 11:17:07 AM
Hi

I dont  want to be impatient, but i'd like to try the stepped gain pots in my la2a.

Between 1 and 2 stepped values can be meausured. form 0 to 100 kohms.
Between 1 and 3 always 100 kohms.

I've used the same stepped attenuators as yours. Mine is 25K + 75K resistor (too much gain with 100K).
This is the wiring diagram.
(http://img197.imageshack.us/img197/6903/volumecon.jpg) (http://imageshack.us/photo/my-images/197/volumecon.jpg/)

Title: Re: D-LA2A Support Thread
Post by: etiefenthaler on January 01, 2012, 01:14:03 PM
Wow 


thanks a lot @ Cardinen :)

Title: Re: D-LA2A Support Thread
Post by: django on January 03, 2012, 09:28:20 AM
Just started up wiring up my LA2A and i'm having some problems wiring up the in / bypass, link / dual and g.r / output switches and i can't find much info on how to wire them up and which way the wires go. Can anyone give me a bit of help with this please?
Title: Re: D-LA2A Support Thread
Post by: julien31 on January 04, 2012, 05:12:56 AM
Django, look at post 1, and download "compiled informations from this thread in a single PDF", you'll find what you want (and more!)
Title: Re: D-LA2A Support Thread
Post by: julien31 on January 04, 2012, 05:21:21 AM
I just finished my 2-LA2A and I found that 1 of the output transformer doesn't work (Edcor XSM 10K/600). As it's very long to have 1 more from the US I try to find another supplier. I saw audiomaintenance sells carnhill VTB 2290 (9600:600 gapped) and VTB 2291 (9600:600 ungapped) for a very decent price. Do you think they'll work?
Thanks

Julien
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 04, 2012, 06:39:06 AM
Julien, the Carnhills will worked, gapped is not required.

And no, I did not forget the recent finished units, I have just been lazy ;D

(http://www.51xaudio.com/images/DLA2A-Cardinen.gif)

(http://www.51xaudio.com/images/DLA2A-etiefenthaler.gif)

(http://www.51xaudio.com/images/DLA2A-MicDaddy.gif)
Title: Re: D-LA2A Support Thread
Post by: django on January 04, 2012, 08:15:35 AM
Django, look at post 1, and download "compiled informations from this thread in a single PDF", you'll find what you want (and more!)

thanks dude, not sure how i missed that one!
Title: Re: D-LA2A Support Thread
Post by: etiefenthaler on January 04, 2012, 03:34:13 PM
Hi Volker,

:)  [dank dir vielmals für den Banner - hab ihn gleich eingepflegt] :)

thanks @ soundcollage and Cardinen
I successfully installed the stepped switches.

Erich T.
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on January 04, 2012, 05:03:15 PM
 ;) Volker,

Thanks for the Banner  ;D

T4Bs have arrived  (DripV2-matched)

Took a few cups of coffee to wrap my head around calibration, now it seems so simple and everything is as it should be.   8)

Mods to be done will be to move the limiter response trimmer to the front panel like Kingston 0-500K-1M.  Other than that I think I'll leave it be cause this box sounds wonderful!  I've been using it as a line amp to add some '3D' to various material, love me some tubes.
Title: Re: D-LA2A Support Thread
Post by: Cardinen on January 05, 2012, 06:33:05 AM
And no, I did not forget the recent finished units, I have just been lazy ;D

Wow !!! Thanks a lot Volker ! love the banner.
Title: Re: D-LA2A Support Thread
Post by: mrclunk on January 05, 2012, 01:19:19 PM
I just finished my 2-LA2A and I found that 1 of the output transformer doesn't work (Edcor XSM 10K/600).

Julien, have a close look at the wires going to the tabs of your edcor. You may of inadvertently broken a wire when moving the tabs.
I've done this a few times myself and fixed it buy carefully stripping back the insulation and re-soldering.
(you've probably checked this already but i thought i'd post just in-case)
Title: Re: D-LA2A Support Thread
Post by: julien31 on January 05, 2012, 05:26:34 PM
Thanks for the advice, i'll check that tomorrow
Title: Re: D-LA2A Support Thread
Post by: django on January 06, 2012, 10:50:57 AM
Another quick question, on the pcb for the inputs and outputs is the negative symbol for the ground or the negative half of the input?
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on January 06, 2012, 12:35:11 PM
Another quick question, on the pcb for the inputs and outputs is the negative symbol for the ground or the negative half of the input?

I wired mine as negative=audio cold, ground (shield) was in the middle of the 3 pin molex...  (hope I did it right  ;)  )

Can I reiterate how freaking awesome this thing sounds?!   8)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 06, 2012, 12:39:09 PM
you did it right
Title: Re: D-LA2A Support Thread
Post by: ethervalve on January 12, 2012, 12:42:59 PM
Hey Volker what a superbly designed project--mine worked right straight away (not counting an idiotic power transformer hookup error on my part).

Just one question--I only ordered 150pf mica caps for the C104/C204 (C4) spot and I have a fairly severe high-end roll-off. I did some alligator clip experimenting and found that adding a couple ceramic caps I had lying around in parallel (bringing the value nearer to 380pf) would restore the highs and flatten the frequency response.

Do you all reckon it's acceptable to use ceramic caps in this part of the circuit? Or should I suck it up and mail order some more silver mica caps?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 12, 2012, 02:44:53 PM
freestyle is the way to go 8)
the parts I used are neither "original" nor "the only way to go"
Title: Re: D-LA2A Support Thread
Post by: G-Sun on January 12, 2012, 04:08:18 PM
Has anyone built the D-LA2A with 3 T4B’s - slow | medium | fast ? Or two?
Title: Re: D-LA2A Support Thread
Post by: baadc0de on January 13, 2012, 07:49:02 AM
Has anyone built the D-LA2A with 3 T4B’s - slow | medium | fast ? Or two?

I will be testing this feature in the near future. As soon as i receive drip's fast optos in fact.. ordered them more than 3 weeks ago so they should be here soon.
Title: Re: D-LA2A Support Thread
Post by: sirko on January 18, 2012, 10:20:26 AM
Hello,

my D-LA2A board ist nearly finished. Since this unit is (after Bo Hanséns DI Box) my second diy project, forgive me my stupid question:
I'm afraid toasting it when connecting it to power supply without testing for shorts before. Could you give me some advise for certain points I should start checking?

Sirko
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 23, 2012, 12:30:48 PM
congrats  8)

(http://www.51xaudio.com/images/DLA2A-YASS.KHAY.gif)
Title: Re: D-LA2A Support Thread
Post by: timmygrimm on January 24, 2012, 01:29:23 PM

Is there a US source for the ground lug connectors? I searched the thread to no avail...
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 24, 2012, 01:48:21 PM
Is there a US source for the ground lug connectors? I searched the thread to no avail...
you can just solder the ground wire directly ;)
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on January 24, 2012, 01:55:06 PM
you can just solder the ground wire directly ;)

Which is exactly what I did, only soldered to the underside of the pcb to keep it pretty.

EDIT:   ::) of course when I get off my butt and use the google, I find this:  http://parts.digikey.com/1/parts/386373-term-qf-male-ra-110-tab-052-d-4906.html (http://parts.digikey.com/1/parts/386373-term-qf-male-ra-110-tab-052-d-4906.html)

Not too sure of exact dimensions/lead spacing so double check to find one that fits.
I simply searched for a 'right angle male disconnect'
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 24, 2012, 02:53:42 PM
you can just solder the ground wire directly ;)

Which is exactly what I did, only soldered to the underside of the pcb to keep it pretty.
while it is all through plated and shouldn't matter: ground is on top
Title: Re: D-LA2A Support Thread
Post by: timmygrimm on January 24, 2012, 05:14:39 PM

Thanks for this link. The challenge for me with parts like this is knowing what to search for.

According to the datasheet

http://mail.keyelco.com/ENG._DEPT/PDF%20CAT%20NO%20Drawings/4906.pdf

It looks like the terminal spacing is 5.08mm. Will these fit?

you can just solder the ground wire directly ;)

Which is exactly what I did, only soldered to the underside of the pcb to keep it pretty.

EDIT:   ::) of course when I get off my butt and use the google, I find this:  http://parts.digikey.com/1/parts/386373-term-qf-male-ra-110-tab-052-d-4906.html (http://parts.digikey.com/1/parts/386373-term-qf-male-ra-110-tab-052-d-4906.html)

Not too sure of exact dimensions/lead spacing so double check to find one that fits.
I simply searched for a 'right angle male disconnect'
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 25, 2012, 04:37:30 AM
It looks like the terminal spacing is 5.08mm. Will these fit?
yes, sounds good
Title: Re: D-LA2A Support Thread
Post by: django on January 25, 2012, 10:34:55 AM
Right i'm having some problems with my LA2A. I'm getting pretty much no gain reducation on either channel and I have to drive the input really hard to get any gain reducation aswell. I've checked all the component values and swapped the valves around etc. Can anyone point me in the right direction for troubleshooting here?

Title: Re: D-LA2A Support Thread
Post by: Hank Dussen on January 25, 2012, 10:48:56 AM
...reversed input transformer?
Title: Re: D-LA2A Support Thread
Post by: django on January 25, 2012, 05:37:41 PM
Input transformer is working fine and providing a voltage increase, just atm i'm having to put a really hot signal into the input to get any gain reduction and the output from the la2a is far to hot aswell
Title: Re: D-LA2A Support Thread
Post by: baadc0de on January 27, 2012, 04:37:15 PM
I'll be remaking my DLA2A with a new PCB (the old one has had some traces damaged with soldering/desoldering etc) and I thought to maybe install some high(er) quality filter capacitors for the PSU. Not that I thought the current cheap multicomp ones are bad as such, just wanted to see if investing a bit there pays off measurably / audibly.

I went with Russian military PIO and Styroflex for signal caps.

Banzai sells illinois capacitor 22uF/500V as "good for ripple performance" so I thought that's a good thing - I didn't check any specs since I couldn't relate them to performance anyway but I thought to ask your opinion on these or some other brand / style of capacitor that would be good in this position. The price these are going for is about right on how much I thought to spend on filter caps. I don't mind that they're axial, I would shield one leg and twist it around to the pad, I have done this dozens of times.

For reference:
http://www.banzaimusic.com/Illinois-22uF-500V.html

EDIT: also, do ceramic and/or gold plated tube sockets help any? Is it just for safety or is there actually some performance benefit?
Title: Re: D-LA2A Support Thread
Post by: mrclunk on January 29, 2012, 12:03:01 PM
Finally finished mine, only took me a couple of years!

Having some metering issues at the moment. They're fine up to about -10dB and the they seem to almost reverse, showing less compression?
Possibly a calibration problem, going to have another go later. Need to tidy up the wiring a bit anyway.

Sowter 10k:10K on the input, edcor 15K:600 outs. 12ay7's for V1 and 6414 for the outputs.

(http://www.groupdiy.com/gallery/0/4394-290112113515-711834.jpeg)
(http://www.groupdiy.com/gallery/0/4394-290112113428-681946.jpeg)
(http://www.groupdiy.com/gallery/0/4394-290112113515-701383.jpeg)
(http://www.groupdiy.com/gallery/0/4394-290112113428-651750.jpeg)
Title: Re: D-LA2A Support Thread
Post by: audiophreak on January 29, 2012, 03:46:13 PM
Finally finished mine, only took me a couple of years!

  Thats some Beautiful work !!!   unique configuration !!!  Congratulations !!!   8)
Title: Re: D-LA2A Support Thread
Post by: bernbrue on January 29, 2012, 03:52:46 PM
Holy Moly, that´s a pecular bird. Very uncommon but extremely nice. Congratulations.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: alexc on January 29, 2012, 04:20:45 PM
Yeah, nice!

Love those meters

And those additional features are a great idea. Looks like you implemented them nice and neatly too.

Great job.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 30, 2012, 03:45:19 AM
IMPRESSIVE 8) 8) 8)

(http://www.51xaudio.com/images/DLA2A-mrclunk.gif)
Title: Re: D-LA2A Support Thread
Post by: electrisizer on January 30, 2012, 09:06:54 AM
@mrclunk

very nice build!

i want to ask if you can soundwise recommend the SC + drive mod. i think its the kensington suggestion taht youve done?
ive deconstructed my unit at the moment and think about adding the mods :)
Title: Re: D-LA2A Support Thread
Post by: sirko on January 30, 2012, 09:59:09 AM
Hi,

since the former link to conrad for NE2 is not working, is this the right neon?

http://www.conrad.de/ce/de/product/725200/GLIMMLAMPEN-5-STUeCK-BEUTEL (http://www.conrad.de/ce/de/product/725200/GLIMMLAMPEN-5-STUeCK-BEUTEL)

Because its for 230V and the one listed in US BOM is 110V?

http://de.mouser.com/ProductDetail/36NE002/?qs=kqYKojPRcqBQLqGRUMHGSg%3d%3d (http://de.mouser.com/ProductDetail/36NE002/?qs=kqYKojPRcqBQLqGRUMHGSg%3d%3d)


Regards
Sirko
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 30, 2012, 10:13:34 AM
Sirko, that Neon is fine (but most people prefer a zener diode these days)
Title: Re: D-LA2A Support Thread
Post by: sirko on January 30, 2012, 10:29:39 AM
Thank you, Volker.

Next question: Does anybody have an fpd file for an 3U front panel? All knobs and switches are parts from mouser US bom.


Regards
Sirko
Title: Re: D-LA2A Support Thread
Post by: timmygrimm on February 01, 2012, 08:53:09 PM
Done and works!

(http://farm8.staticflickr.com/7159/6804407985_f3af9baba7.jpg)

(http://farm8.staticflickr.com/7014/6804408301_45969f31ff.jpg)

This forum is amazing. Thanks to everyone here for the knowledge and supplies to make this happen.

One channel was not working at first, but turned out to be a molex issue. Gain is out of hand, and I have the oscillation problem at high settings, but will sort that all out.

So Stoked!

Now I just need some knobs :)
Title: Re: D-LA2A Support Thread
Post by: audiophreak on February 01, 2012, 09:35:11 PM
Congratulations timmygrimm !!!   :)

                                                     ( I still need in/out transformers and Opto's )
Title: Re: D-LA2A Support Thread
Post by: mrclunk on February 03, 2012, 06:51:59 AM
Thanks guys!
It is a 'peculiar bird' indeed!
I based the look on some old Vortexion gear we have here. The panels are Trafolyte, cut and engraved on my new CNC! I'm going a bit cnc nuts at the mo...

electrisizer,
The 'mods' are as Kingston mentioned earlier in the thread.  The SC Filter is just RVx37 on a rotary switch, i recommend this for stereo operation. My values are biased toward the low frequency range.

The 'drive' control is my my kinda experimental control. At the moment its a 470K pot in series with the 68K / Rx11 feedback resistor. Increasing the resistance reduces neg-feedback, more gain, more distortion. But its too subtile for me. I'm thinking of building a multi deck switch that simultaneously increases gain and pads the output.
Unless anyone else has a better idea for adding mojo?


Issues:-
I have to hit it pretty hard to get lots of compression, i believe this is due to my input transformer not having the 1:4 step up of the original. I can use the center tap on my input to give me 1:2 which maybe enough though i'll lose some input headroom. maybe i'll add an input sensitivity switch...

nice build Timmy
Title: Re: D-LA2A Support Thread
Post by: AudioGimmer on February 03, 2012, 07:00:42 AM
Nice work Mr Clunk!


The Gimmer
Title: Re: D-LA2A Support Thread
Post by: audiophreak on February 12, 2012, 09:13:00 AM
ok .... going for the Drip T4B's  - any feedback / recommendations / sugestions on the " Fast  / Slow - and now  Medium "    ???

 Thanks  :)
Title: Re: D-LA2A Support Thread
Post by: sirko on February 22, 2012, 08:40:56 AM
@audiophreak: It depends on what you want. The original LA2A has a slow T4B.
Title: Re: D-LA2A Support Thread
Post by: audiophreak on February 22, 2012, 11:11:49 AM
Thanks sirko ,
                      I figured it was something like that   ;D
Title: Re: D-LA2A Support Thread
Post by: desol on February 22, 2012, 11:15:38 AM
I've been wondering how Drip's new T4 compares with the old.  The old one seems to have a steeper compression curve which isn't really that desirable, from what i understand.
Title: Re: D-LA2A Support Thread
Post by: baadc0de on February 22, 2012, 12:32:54 PM
I've been wondering how Drip's new T4 compares with the old.  The old one seems to have a steeper compression curve which isn't really that desirable, from what i understand.

I've just tested the fast one yesterday and we're all pleased as punch here! tested against a NOS UREI 1970 for reference. It sure is faster, but just as optoish and "nice".
Title: Re: D-LA2A Support Thread
Post by: audiophreak on February 25, 2012, 12:24:05 AM
great info , Thanks  :)
Title: Re: D-LA2A Support Thread
Post by: desol on February 27, 2012, 05:52:44 PM
I finally settled on a piece of analyzing software and decided to purchase TrueRTA, in order to learn to measure my gear. I hope you guys don't mind me posting a few shots so i can maybe get some help with basic interpretation. Here are 4 quick sweeps with my Dla2a, with the gain reduction progressively increasing from zero to around 65% reduction and one square wave input at 1k. I noticed that it really doesn't start to do anything until the peak reduction knob is at around 35%. Seems to have a bit of HF peak up around 18k. I used edcors on the output, no zobel installed. The unit looks to measure fairly well in terms of freq response i think, and i don't mind the peak at ~ 18k...adds a slight shimmery quality despite the compression(hf reduction). The square wave looks a little off and i'm not quite sure how to interpret the overshoot/ringing on both the leading and falling edge?. Anybody have any advice they can offer me? Thanks.

(http://img707.imageshack.us/img707/1883/la2anoreduction.th.jpg) (http://imageshack.us/photo/my-images/707/la2anoreduction.jpg/)(http://img841.imageshack.us/img841/8220/la2apeakreduction35.th.jpg) (http://imageshack.us/photo/my-images/841/la2apeakreduction35.jpg/)(http://img41.imageshack.us/img41/2762/la2apeakreduction50.th.jpg) (http://imageshack.us/photo/my-images/41/la2apeakreduction50.jpg/)(http://img826.imageshack.us/img826/7371/la2apeakreduction65.th.jpg) (http://imageshack.us/photo/my-images/826/la2apeakreduction65.jpg/)(http://img210.imageshack.us/img210/8349/la2asquarewave1khz.th.jpg) (http://imageshack.us/photo/my-images/210/la2asquarewave1khz.jpg/)
Title: Re: D-LA2A Support Thread
Post by: alexc on February 27, 2012, 08:02:06 PM
Good questions - not sure myself   ???

The LA2A should begin limiting fairly quickly and remain in limiting part of envelope for the whole duration of True RTA sweep

(around 1s or so from low to high with level as set by True RTA's signal generator section)

So the display at the high frequency part is being influenced by the limiting that started earlier at the low frequency part of sweep.

Be interesting to make frequency sweeps band limited and then aggregate the results so as to see more clearly the spectral response of the opto.

I mostly try to 'see' the response of a limiter using a DAW where I prepare a test signal track comprising of pulses of varying amplitudes and varying durations and different constant frequencies.  Then try to infer something about the frequency response under limiting

Or not  :o :o

It's a complex subject and I've never really gotten much satisfaction from frequency sweeps with limiting action enabled. Limiter's response depends very much on the shape of the signal.

Be great to have some light shed on this subject.
Title: Re: D-LA2A Support Thread
Post by: desol on February 27, 2012, 11:19:02 PM
Good questions - not sure myself   ???

The LA2A should begin limiting fairly quickly and remain in limiting part of envelope for the whole duration of True RTA sweep

It's a complex subject and I've never really gotten much satisfaction from frequency sweeps with limiting action enabled. Limiter's response depends very much on the shape of the signal.


Hey Alex. Thanks for your response...as you can see i took your advice and picked up trueRTA. Level 3. Glad you recommended it. :) What i meant to say was, i increased the amount of reduction from 0 to about 65% by turning the peak reduction knob for each graph. So yes...the compressor did engage properly and hold during each sweep. I'm kind of concerned about the square wave tho. Freq response looks ok...i think...but square wav looks sorta mangled.  :o

Maybe it's not so bad? Maybe it's distortion and hi freq lift? I need to learn what the square wav's are telling me.

Oh btw, square wav is without any reduction...just straight through w/amplifier engaged.
Title: Re: D-LA2A Support Thread
Post by: desol on February 28, 2012, 12:23:16 AM
Ok. Let me take a stab at this.

(http://img210.imageshack.us/img210/8349/la2asquarewave1khz.th.jpg) (http://imageshack.us/photo/my-images/210/la2asquarewave1khz.jpg/)

The slanted rising and falling edges indicate that the amplifier is a little slow in terms of slew rate; the speed at which it can reproduce the square wave. I'm not sure if anything can be done about this, as it may be a part of the inherant design. The overshoot/ringing on the corners is the over-emphasis of the high frequency response, which is also noticeable in the freq response graph above, at ~18khz. This means that the output of the amplifier needs to be dampened slightly by adding a zobel network(what this can also tell in terms of the input transformer, i'm not sure). The inclination of the ceiling and floor of the square wave towards the centre, indicates that the amplifier isn't reproducing low freq? as good as it could(i read this)...but it isn't too bad. Again, i'm not sure if this is the fault of the output/input transformer or both. Anybody care to add, correct? I find this super interesting..
Title: Re: D-LA2A Support Thread
Post by: alexc on February 28, 2012, 12:35:33 AM
The square waves don't look too bad to me.
Yes there is some ringing and some not perfectly horizontal tops and bottoms.

Many audio units show this sort of thing and can be minimised with some attention to the zobels and such.

Basically I agree with your explaination except I don't think that correlates to what the frequency sweeps show. I could be wrong tho'.

I would also compare these with a CRO to ensure what you are seeing is not an artifact of the analyser.
Square waves are a bit of an approximation with sound card interfaces, particularly at non HD sample rates.

PS - Glad you're liking the analyser. Set it to max speed and max resolution and use it to optimise noise performance by positioning of traffos and wires.

Then try to find some theory to explain the observations!

Real 'butterfly effect' stuff.

Cheers
Title: Re: D-LA2A Support Thread
Post by: bernbrue on February 28, 2012, 12:11:34 PM
Hi,
I tested my Rude Tube with a square wave and had almost the same results as shown in your picture. Lots of reading about zobel network and transformer ringing didn´t give me a solution. Finally I took the unit out of the loop and connected input with output xlrs, just to check that it really is the tube amp that causes this strange waveform. In fact, it was my soundcard that was not able to reproduce an accurate square wave. You might want to check this.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: desol on February 28, 2012, 12:40:07 PM
Thanks Alex and Bernbrue for pointing this out. I'm using an mbox3 to and from the DLA2A.

 - Indeed, it is the mbox, apart from one small difference. It would be nice to build a square wave/sine wave signal gen, with switchable 150/600ohm output impedances, and xlr connectors.
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on February 28, 2012, 03:16:31 PM
I have a maybe stupid question:

I've nearly finished my PCB but did solder the 7805 standing up. How much cooling does it really need? Will a normal heat sink be sufficient?

So far I've only seen pictures where it's connected with the case. I mean it's only used in the relais, isn't it?
Title: Re: D-LA2A Support Thread
Post by: mrclunk on February 28, 2012, 03:54:21 PM
sonic,
It does get surprisingly hot, originally i had a little clip on heatsink but changed it for a larger one to be safe.
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on February 28, 2012, 04:09:42 PM
Thanks! Do you have a pic of your current heatsink?

I planned to use one of those, but it will be tough to connect the nearby connectors then:
(http://www.reichelt.de/bilder/web/artikel/C800/VFI356.jpg)

Otherwise I would have to desolder the 7805 and solder another 7805 instead because the legs are too short now.
Title: Re: D-LA2A Support Thread
Post by: mrclunk on February 28, 2012, 04:27:21 PM
I think thats exactly what i used.
Mine's about an inch wide.

I layed the regulator horizontal and supported the heatsink weight with a piece of plastic coming off the pcb mount next to it.
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on February 28, 2012, 05:15:22 PM
Crappy photo, but here's mine.  The heat-sink I pulled from an old TV PSU, and the IC runs very cool.  It's a lot beefier than the typical clip-on bolt-on that I see on a lot of regulators.

PS, old busted/failed household or other electronics are an awesome source for parts like these if you don't mind keeping a bone-yard around.  It's sure saved me shipping from mouser etc several times.

I bent the IC horizontal for the wiring, and then bent it back vertical once it was complete, just don't tweak it so much you bust a leg.
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on February 28, 2012, 05:47:01 PM
Thank you both, that was very helpful!  :)
Title: Re: D-LA2A Support Thread
Post by: salomonander on March 04, 2012, 01:37:23 PM
hey
im finally almost done with this. i have three questions remaining:

- for d101, d102 etc it says to get a 1N4141 but using the part number i get an 1N4148. is this the same part or interchangable?

- do these go right next to the relais? i dont have their positions marked on my board..

- can anyone explain to a dummy like me how to wire the board properly with utc a10s and a24s?

thanks a lot, i appreciate any help.

jakob
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 05, 2012, 02:21:05 AM
for d101, d102 etc it says to get a 1N4141 but using the part number i get an 1N4148. is this the same part or interchangable?
1N4148 is the correct part (where does it say 1N4141? if it is in any of my posts I will edit the typo ...)

do these go right next to the relais? i dont have their positions marked on my board..
yes
Title: Re: D-LA2A Support Thread
Post by: daveode on March 10, 2012, 03:44:46 PM
Can anyone help me? I'm not understanding the way this thing is suppose to operate?

1. I've never owned or heard a LA2A operate so I'm not sure of it's character or if this is the way its suppose to sound. But It seems to be a Distortion compressor more than anything. As I turn up the reduction knob, It really doesn't do much until it's well past half way up, and by then it's distortion. Is it that  that I'm not hitting it with signal hard enough? but when I do hit it hard to get some gain reduction and say a vocalist is singing but then gets loud, it distorts bad! Is this normal? I'm not sure what may be wrong or if there is anything wrong with the way it compresses. It's not much at all but when it does it's distortion.

2. I can't seem to calibrate the meters right? I'm using a 02R96 to run it's osc through the la2a and back to the 02R96. With the limiter knob all the way down and I try to match the bypassed signal with the gain, I can't without the meter being pegged well beyond +4 and then I can hear the osc. distorting?!? There seems to be a 4-6db difference when it's in bypass and when it's on? Like when it's in bypass, the signal is fine, but when I flick the switch from bypass, it's 4-6db lower in volume, but the meters read +4?? Also, when the meters are in limiter view, they go positive before going to reduction? And the needles move REALLY slow? but when the meters are reading output, the needles move fast.

I'm using Hairball 8020 meters with a 3.9k resistor running in line on the + terminal. I am also using a 100K pot for RX25. I hooked it up with pin 1 of the pot to the one through hole for RX25 and pins 2 and 3 through the other hole for RX25. Is this correct? Oh! and I'm using the recommended Sowter input TX and Edcore OT.

Please!! any help will be appreciated!!
Title: Re: D-LA2A Support Thread
Post by: daveode on March 14, 2012, 12:33:56 PM
Anyone?

Can someone at least tell me if it's normal for the gain reduction part of the meter to move real slow on this thing? All the other la2a's I seen on you tube move way faster.
Title: Re: D-LA2A Support Thread
Post by: bernbrue on March 14, 2012, 02:38:16 PM
Anyone?

Can someone at least tell me if it's normal for the gain reduction part of the meter to move real slow on this thing? All the other la2a's I seen on you tube move way faster.

http://www.groupdiy.com/index.php?topic=22288.0;topicseen

this thread answers at least your distortion problem. Search further threads about modern soundcard levels and analog gear level. Meter movement in gain reduction mode depends of course on the audio material you send through the compressor. Try to regard the meter movement as a kind of envelope follower and you´ll see that the LA2a does wonders to vocals and bass guitars
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: daveode on March 14, 2012, 06:20:46 PM
Thanks for the reply! But I do understand the difference between digital meters and analog. and I got the opposite problem for the distortion, he explains he has to "hit it light" or he gets distortion. On mine I have to crank the output hard to match the incoming signal or hit it hard with signal to get the reduction to work. and when I mean hard, I mean like turning my access 312 half way up or more with a condenser mic to get it to compress!! And when I mean the meter moves slow I mean a singer holding a loud note out the meter goes to +1Vu before it swings to  negitive Vu which takes a full second or more?? I don't think its working right at all (meter, reduction or gain).

I take it I got a problem somewhere on the input which is probably why everything else isn't working? I used my Phonic PAA2 to send a 1K signal through the la2a and back into the PAA2. The PAA2 is outputing a 1k tone at -10dbu. When the la2a is in bypass, the PAA2 reads (you guessed it) -10dbu. With the la2a on (bypass off) and the gain reduction knob is all the way down, I have to crank the gain Half way up to match the -10dbu?? I just wanted to know if this is normal for the gain? I have the 25K pot/75k resistor installed. And the meter on the la2a is reading -18VU??

As for the reduction, with the Phonic reading the -10dbu, turning the reduction knob up half way only yields .1dbu of reduction?? turning 3/4 way up gets only 1.7dbu reduction? and all the way up gets 6dbu reduction? This is on both channels. :-\
Title: Re: D-LA2A Support Thread
Post by: bernbrue on March 15, 2012, 07:24:48 AM
Ok,
a few recommendation for checking the LA2a:

- Input/output transformer wiring: maybe you turned around the sowter input tx (has it the 1:4 ratio?), molex connectors connected wrong or may have bad contacts.
- check the relays, if these are suitable for this project (infos are here as well, check first thread)
- check the voltages and grounding for each channel. (heater, B+ and relay psu), measure also directly at the tube sockets
- verify that the heater wiring is correct
- double check meter wiring (polarity and trimpot)
- T4b (Drip?): sometimes the EL panel gets loose or is not in correct position caused by shipping, transport etc., open it up and check
- tubes: try another set if available or swap tubes from one channel to another
- verify that limiter response and stereo link potentiometer are trimmed correctly (there is a pdf with very good instructions)
- check for faulty contacts, cold solder points, etc.

I´m quite shure that there is some basic wiring problem that causes your "low gain" and "distortion problem". I would check the T4B first, since your "meter strangeness" is directly related to it. A few picture would help a lot.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: daveode on March 17, 2012, 02:28:08 PM
Cool! Thanks Bernd!! I'll check these things in a bit. My priorities changed (FF800 broke so I'm transfering projects from Logic to Radar). I'll report back soon.

Thanks, Dave
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on March 18, 2012, 03:56:00 PM
I finished the PCB today. Would be nice if someone could look over the pics to see if I made any obvious errors:

(http://www.sdiy.de/Dual-LA2A-Finished-PCB.jpg)

I used 0.5 mm² dual cable for the heater wiring (doesn't look good, I know):

(http://www.sdiy.de/Dual-LA2A-Heater-Wiring.jpg)
Title: Re: D-LA2A Support Thread
Post by: bernbrue on March 18, 2012, 04:50:57 PM
Hi,
since we have AC for the heater it might be better to twist the heater wiring in order to avoid hum. Other wise it looks fine. What I always do before firing up a new built is to measure for shorts. Just take your multimeter and check, whether there is any resistance between -/+ of each, heater, B+ and relay psu. Do the same for the audio path.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on March 19, 2012, 08:19:25 AM
OK, thanks. If I'll experience hum I'll redo the heater wiring. Didn't thought about that.  :-[

Checked for shorts and it looked OK.
Title: Re: D-LA2A Support Thread
Post by: desol on March 23, 2012, 11:28:24 AM
Just wanted to give a few observations as per my DLA2A, now that i've had it for a while. I did both the gain pot modification and the 12AY7 input gain substitution. I never used an LA2A before so it was a bit of a learning curve. (actually, every compressor seems a new learning curve, in use) This unit needs a good deal of input gain to drive the gain reduction circuit. My 1290 pre is probably on 45-55 db of gain to get the needle moving well. I'm assuming this is because of the 12ay7 substitute. Gain knob seems to make no difference over how much gain is applied to peak reduction...only external preamp gain(output). I didn't realize this before. I assumed gain was connected to peak reduction...it isn't. Anyway, the single biggest improvement in sound(and usability), was moving to a better optical attenuator. 
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on March 23, 2012, 11:51:09 AM
desol, what Opto did you go to, from what looks like V1 Drips?
Title: Re: D-LA2A Support Thread
Post by: desol on March 23, 2012, 12:26:55 PM
No comment...although i will say...a normal one.

I'm officially against inflating prices any higher than they already are.
Title: Re: D-LA2A Support Thread
Post by: daveode on March 26, 2012, 06:29:36 PM
Just wanted to give a few observations as per my DLA2A, now that i've had it for a while. I did both the gain pot modification and the 12AY7 input gain substitution. I never used an LA2A before so it was a bit of a learning curve. (actually, every compressor seems a new learning curve, in use) This unit needs a good deal of input gain to drive the gain reduction circuit. My 1290 pre is probably on 45-55 db of gain to get the needle moving well. I'm assuming this is because of the 12ay7 substitute. Gain knob seems to make no difference over how much gain is applied to peak reduction...only external preamp gain(output). I didn't realize this before. I assumed gain was connected to peak reduction...it isn't. Anyway, the single biggest improvement in sound(and usability), was moving to a better optical attenuator.

This is exactly what mine is like. Except mine has the 12AX7's in it. If I use a preamp and crank it, I can get it to reduce, but if it's a line level signal from my DAW, it's not enough to get the thing to go to reduction.

I will try the things tonight I was asked a few post up to see if I have a problem somewhere. I'll report back soon.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 27, 2012, 01:09:49 AM
I will report how mine behaves:
Gain: I have unity gain @ 12 o'clock
Peak reduction: with normal line Level (+6 dBu) my "standard" peak reduction setting is around 12 0'clock, giving me 2 to 6 dB gain reduction (signal dependent, of course).

I guess your "line level signal from my DAW" is -10dBV ?
Title: Re: D-LA2A Support Thread
Post by: electrisizer on March 27, 2012, 06:52:20 AM
i have 1:1 input trannys and Rx05 set to 10k -> tons of gain reduction with soundcard line level signals. its called the "jensen mod" a more modern behavior of the compressor...

the only issue i have: one of my drip T4 catches oscillation. its a grounding problem in the cell. got to order a new one.

when i make a THD picture with 1k sinus of the working channel i see some light harmonics in GR mode. is that ok?
(however the sound is very nice on vocals and analog synthis)
Title: Re: D-LA2A Support Thread
Post by: audiophreak on March 27, 2012, 08:32:35 PM
Hello ,
          I received my Sowter order and went to wire them in , printed the spec sheets from  the 1010 and 1009 , then for the 4383 and 8940 listed on the PCB - so I just want to make sure I have the connections right ,
so from edge of PCB down

 for input :  On Trans   /   On PCB
                      RED       =   BROWN
                    WHITE     =   PINK
                     BLUE       =  GREEN
              ( NO BLACK )  =  BLACK
                     GREY       =  GREY
                    GREEN     =   BLUE

 for Output :   On Trans  /  On PCB
                         RED      =  YELLOW
                     YELLOW    =  GREEN
                      BLACK      =  BLACK
                      WHITE     =   PINK
                       GREY       =  GREY


  ... is this right ??    I did a search , but didn't  find anything - also - I got the 1009's with the threaded mount , and it has no BLACK lead ... so should I mount these to the case to ground/ shield the housing ?

  Thanks in advance   :)
             
Title: Re: D-LA2A Support Thread
Post by: andia on March 28, 2012, 05:00:47 AM
can I ask you how long it took till you got your xformers from sowter?
Title: Re: D-LA2A Support Thread
Post by: audiophreak on March 28, 2012, 05:18:49 AM
I emailed Sowter first - very quick reply, said about two weeks to the U.S.,   ... I placed the order March 7 ,  New York USPS  received on March 12 , but I didn't receive them in CT till March 22,  ( probably Customs ? )   ... so , 16 days but most of the time was customs . 

   .. only 6 days from order to New York   :)
Title: Re: D-LA2A Support Thread
Post by: andia on March 28, 2012, 06:23:02 AM
thanks, sounds nice! so, i might get them even faster because I'm in europe :-)
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on March 28, 2012, 02:19:37 PM
I got my xformers 8 days after I placed the order (in the evening I have to say). They have been shipped 3 days after the order. UK to Germany.
Title: Re: D-LA2A Support Thread
Post by: Lowfreq on April 07, 2012, 03:14:13 AM
The VU meter on the right side of my D-LA2A has suddenly decided to stop showing me Gain Reduction.  >:(
I can hear the compressor working, so i know it is compressing, but the needle just sits at 0. The zero adjust pot still works, the NE2 still lights up, and I've tested all the connections  according to the schematic with a multimeter. All good here, so I'm a bit stumped as to where I should be looking with this issue.

It's been working fine for over a year, and only decided to stop in the last week. The problem is on the pcb somewhere, because when I swap the VU meters over, the same thing happens. It dosen't follow the meter. Connections are good too, and when I switch to VU instead of GR its all fine and dandy.

Any ideas for my next move? I can live with it for now, coz at least the compressor still works.
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on April 07, 2012, 11:32:01 AM
Lowfreq, try swapping T4bs see if the problem follows the optos?
Title: Re: D-LA2A Support Thread
Post by: Lowfreq on April 07, 2012, 08:59:44 PM
Yeah, I tried that too. Still the right channel wasn't showing the gain reduction with either T4B, but they both worked perfectly on the left channel.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 08, 2012, 04:15:40 AM
If swapping the T4B doesn't solve the meter problem,
check R226, R227 and R225.
There aren't much more components in the meter circuit ...

Comparing voltages in that arear with the working channel might be a good idea as well.
Title: Re: D-LA2A Support Thread
Post by: andia on April 09, 2012, 08:35:17 AM
Does somebody know the measurements of the mounting-points of the pcb? I'm gonna drill my case soon, but don't have the pcb here... :-\

Thank you very much!!!!  :)

andi
Title: Re: D-LA2A Support Thread
Post by: audiophreak on April 11, 2012, 09:18:31 AM
Hi,
     I got bit by the " didnt read the full details " about the bypass relays I purchased  , I thought I had the right orientation , but didnt read the fine print on the relay - the legend printed on the relay was " Bottom View "  ( like most Lundahl Transformers )  ... so the polarization is backwards   :( 

      Question :  If I reverse the diode .. can I just feed the 5v to the 0v pin , and ground the 5v pin on the Relay Power  molex connectors on the Left and Right Channels ?


EDIT :
Title: Re: D-LA2A Support Thread
Post by: audiophreak on April 11, 2012, 10:10:05 PM
well ... the answer is Yes ... I reversed the 4148 diode, then switched pin orientation on the two pin molex connectors feeding the relays on the Left and Right channels - so 0v is now 5v and vise/versa on the channel connectors, ( the 5v molex on the PSU side is in its normal orientation ) 

   Question, so now when comp is in / on   - the relay is " energized "   and Bypassed / out in the " Rest or Non-energized state " - is this how it is with the correct Relay ?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 12, 2012, 01:03:15 AM
yes - no power to the relays = bypass.
this way the comp passes signal even if the fuse blows  ;)
Title: Re: D-LA2A Support Thread
Post by: audiophreak on April 12, 2012, 06:26:54 AM
yes - no power to the relays = bypass.
this way the comp passes signal even if the fuse blows  ;)


 Thank You  :)
Title: Re: D-LA2A Support Thread
Post by: audiophreak on April 13, 2012, 02:34:20 PM
Hello ,
         O.K.  ... so I wanted to have DC heaters ... I used the heater schematic from the G7 microphone with a 3A bridge rectifier and a lt1085 LVD voltage reg rated at 3A   -  I wired the heaters as specified, but with the trimmer adjusted to all the way out , loaded with all four tubes I could only manage to get 5.5vdc ( I'm using the Rondo PT )  - so I cut the trace between pins 4 and 5 and wired the heaters on one channel just to pins 4&5 ( without CT  pin 9 ) and I'm able to get 6.2vdc .  Alternately I removed the " regulated " part of the heater circuit on the other channel , just went directly from the POS. side of the bridge rectifier through the smoothing caps to the PCB to the channel thats heaters are wired as specified and am able to get 6.6vdc.

   ... so I guess my questions are:

   1)  Can I leave the traces cut and just feed pins 4&5 and leave it at that ?

   2)  Should I leave the heaters wired as specified and put a small dropping resistor after the smoothing caps with no regulator ?

   3)    or should i just man-up and wire them as AC heaters

  Thanks in Advance  :-[
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on April 24, 2012, 06:43:25 PM
This may be very obvious but if you use the molex with crimps, don't buy the crimps on a reel.  I overlooked this and spent quite some time cutting and working them over with a dremel. 
Title: Re: D-LA2A Support Thread
Post by: ethervalve on April 25, 2012, 10:54:00 AM
This may be very obvious but if you use the molex with crimps, don't buy the crimps on a reel.  I overlooked this and spent quite some time cutting and working them over with a dremel.
+100100
Title: Re: D-LA2A Support Thread
Post by: andia on May 12, 2012, 06:53:34 AM
Hi all!

I've nearly finished my D-La2a but I'm running into some small problems...

1. where do i get the power for the lamps best (vu's and power indicator lamp). so far I've tried the 5v for the relais and the 6,3v for the tube-heaters. on both the lights were not steady and flickering or dimmed when switches are turned.

2. right now I have disabled the stereoswitch because when connected only the left channel worked. this is most likely just a mistake in connecting them. How are they connected together properly?

3. are there any calibrationsteps beside the ones in the compiled doc file from the first post.

many thanks for your help,

andi
Title: Re: D-LA2A Support Thread
Post by: desol on May 12, 2012, 10:56:10 AM
Use the on-board 5v supply up in the right corner of the board. R103 all the way to the left...R137 all the way to right...then do the stereo adjust procedure.
Make sure to double check that all your wiring polarity is right and shielded cables are used on almost everything.
Title: Re: D-LA2A Support Thread
Post by: abechap024 on July 26, 2012, 08:53:49 PM
So I'm putting together an La2a and have regular potentiometers in there now, But I have some stepped switches that are in this configuration->

http://www.hificollective.co.uk/images/shinkoh_fig7l.gif

Wired in the shunt attenuator configuration. Only problem is I know this changes the input impedance, depending on the switch position, has anyone tried this? Will it show the circuit the wrong impedance and do funky things or will it be fine?
Thanks!
Abe
Title: Re: D-LA2A Support Thread
Post by: creature.of.habit on August 08, 2012, 12:04:08 PM
Greetings everyone, i was just wondering if anyone can tell me how small can this one get in terms of not building it into a standard size chassis. I was hoping i could swing for something "tabletop", and as compact as possible. Can't really get it to see if it can be done unless i'm sure about it. Would really appreciate any thoughts on this.
Title: Re: D-LA2A Support Thread
Post by: desol on August 08, 2012, 05:37:41 PM
You need quite a bit of space as the unit runs hot....or fairly warm and needs room for shielding/wiring. A 3u case like the one pictured in mine and other builds(page 1)  is what i would probably recommend. You could put it in a non-rack box, say, with a handle on top...but it wouldn't be much smaller in terms of length, width or depth. Have a look at some internal pictures...you'll see there's not much room else wise.
Title: Re: D-LA2A Support Thread
Post by: creature.of.habit on August 09, 2012, 05:33:14 AM
thanks desol, that certainly helps.

You need quite a bit of space as the unit runs hot....or fairly warm and needs room for shielding/wiring. A 3u case like the one pictured in mine and other builds(page 1)  is what i would probably recommend. You could put it in a non-rack box, say, with a handle on top...but it wouldn't be much smaller in terms of length, width or depth. Have a look at some internal pictures...you'll see there's not much room else wise.
Title: Re: D-LA2A Support Thread
Post by: martthie_08 on August 13, 2012, 11:34:02 AM
wow, it's been some time since my last diy project, but I finally got down on the D-LA2A that has been sitting around the studio for the last year.
Anyways, I wired it up last week, fired it up today and it worked right off the bat. What a beautiful compressor, why didn't I finish it earlier, couldn't anyone have told me so?

I will post some pics and detailed info later, still got some homework to do: calibration and lighting up the hairball VU.
What's good place to steal around 12V DC for the VU lights, at the junction of rectifiers and 3300uF (before the 7805) for the 5V relays?

EDIT: oh, and another question comes to mind: are the resistors R105 / R205 @68k specifically for loading Sowter 4383 secondaries and will I need to replace this one with a different R(C) when using other input transformers?

EDIT: kind of answering my own question here: there is an application note from Jensen where they suggest to replace the 68k resistors with 11k for their JT-11P-1.
I guess that means ditch their included 13k / 620pF loading resistor / capacitor?

last question for today: what the hell happened to nrgrecording.de ?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on August 13, 2012, 01:41:48 PM
last question for today: what the hell happened to nrgrecording.de ?
use www.nrgrecording.de
without www. it doesn't work for me either ...
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on August 13, 2012, 01:43:01 PM
and congrats on the D-LA2A.
we want to see some pics, you know this ;-)
Title: Re: D-LA2A Support Thread
Post by: martthie_08 on August 13, 2012, 06:16:25 PM
Quote
and congrats on the D-LA2A.

thank you, it has been joy and pain to build :-)


Quote
we want to see some pics, you know this ;-)

yeah, I know, but it's late and I really want to take some pictures with a nice camera, but hell, here's the iphone version as a preview:

(http://www.martenthielges.com/diy/image/la2a_1.jpg)
(http://www.martenthielges.com/diy/image/la2a_2.jpg)


here some technical info on the build:
Mueller Rondo power transformer
Jensen JT-11P-1 input transformers
UTC A24 output transformers
DRIP t4b (slow)
new 12AX7 tubes from Tung Sol
new 12 BHA-STR from TAD
old 6AQ5A from Tung Sol
Zener diode instead of neon lamp
Hairball VU meters & knobs
custom designed UREI ripoff frontplate
Robeshop industrial 19" case
mostly shielded cable wiring except for input / output / VU gain reduction

Noise floor is ok both channels sitting at around -78dB RMS, which is due to a little 50Hz hum.
the gain range is nice using the 1:1 with the standard 100k pot, around 12 o'clock on the gain pot is unity gain running in and out of the DAW. It starts to get a little sensitive with increasing gain. Anyways much less touchy than say an ADL 1500 which I've had before.

It is pretty tight in the housing and this beast gets pretty hot over time, I will have to drill a couple extra holes in the top and sides of the case.

The VU lamps are connected after the rectifier before the regulator of the 5V relay section. This is not ideal, as when the relays are switched in, the light on the VU goes down a notch. Those 5V relays really pull a lot of current, I'll have to check whether the power transformer is fine with that, it's getting a little warm around that toroid.

I changed the 68k to 11k on the input as per Jensens note, but did not really notice much of a difference.

Did I mention it sounds fabulous?
cheers, Marten
Title: Re: D-LA2A Support Thread
Post by: drumminkiger on August 26, 2012, 07:14:18 PM
This may be a horse that has been beaten to death and I am just missing it, but, say for instance I am a cheap bastard and just need one channel for now, but want to build a 2nd in the future. Are there parts that I can omit from the BOM to keep the cost down in the mean time (such as the most expensive ones like a TB4) so I can build just one channel now, have a functional unit, and then add the second channel components later? Or is it pretty much an all or nothing deal?  I figure i'll get all the simple resistors and caps in one sitting, but if i can get some of the bigger ticket items one channel at a time, that would be nice. If not, I still totally want to build this project, but it'll just take longer :P
Title: Re: D-LA2A Support Thread
Post by: abechap024 on August 27, 2012, 03:13:20 PM
This may be a horse that has been beaten to death and I am just missing it, but, say for instance I am a cheap bastard and just need one channel for now, but want to build a 2nd in the future. Are there parts that I can omit from the BOM to keep the cost down in the mean time (such as the most expensive ones like a TB4) so I can build just one channel now, have a functional unit, and then add the second channel components later? Or is it pretty much an all or nothing deal?  I figure i'll get all the simple resistors and caps in one sitting, but if i can get some of the bigger ticket items one channel at a time, that would be nice. If not, I still totally want to build this project, but it'll just take longer :P

Sure you could build one channel at a time. I would stuff all the resistors for both channels now, as the expense is probably going ot be mitigated by shipping. But up to you....why don't you just get a turret board and do it point to point (i know i know it will take more brain energy, but will be cheaper)
Title: Re: D-LA2A Support Thread
Post by: johnnyscotch on September 13, 2012, 10:12:13 PM
Hey guys, I'm sourcing all the parts now to build a DLA2A

Where did you find Drips T4Bs?? They aren't on the site anymore??

What other options would I have that won't double the price of the project??

THanks!!

Eric
Title: Re: D-LA2A Support Thread
Post by: Kamel on September 14, 2012, 04:22:58 AM
http://www.kenetek.com/T4AT4BUnits/KenetekT4BModules/tabid/300/Default.aspx

the T4b does'nt double the price, transformer can
Title: Re: D-LA2A Support Thread
Post by: desol on September 15, 2012, 03:48:51 PM
I don't believe the Kenetek are available either.
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on September 15, 2012, 08:59:38 PM
Looks like Keneteks are back for sale... which is odd cause now it looks like there are no more Drip V2s...   
Title: Re: D-LA2A Support Thread
Post by: johnnyscotch on September 15, 2012, 09:31:04 PM
So, Keneteks are about the only option?

Has anyone heard from Drip? Will his be re-stocked?

Is he on this board?
Title: Re: D-LA2A Support Thread
Post by: audiophreak on September 15, 2012, 09:40:07 PM
Hi,
   I sent an email to Gregory ( DripElectronics )  about a month ago , he replied that it would be a couple weeks , I still dont see them listed on his web page , I sent another email yesterday and have not gotten a reply yet , I also need some for this project , but not really in hurry , hopefully  soon.  I will post back if I hear anything.
Title: Re: D-LA2A Support Thread
Post by: johnnyscotch on September 16, 2012, 02:08:20 AM
Hi,
   I sent an email to Gregory ( DripElectronics )  about a month ago , he replied that it would be a couple weeks , I still dont see them listed on his web page , I sent another email yesterday and have not gotten a reply yet , I also need some for this project , but not really in hurry , hopefully  soon.  I will post back if I hear anything.

Cool, please do!

cheers
Title: Relays
Post by: johnnyscotch on September 17, 2012, 02:03:21 AM
I was reading through the thread and I noticed some info about the 5v relays.

These are the ones in the current BOM: http://www.mouser.com/ProductDetail/Omron/G5V-2-DC5/?qs=%2fha2pyFaduiP%2fpKRK%2fe1cWl7h9DP4yrNWPXtM1DhKn7n0Pslql4ewQ%3d%3d

I ordered them, are they going to work??

cheers!
Title: Re: D-LA2A Support Thread
Post by: abechap024 on September 18, 2012, 09:27:34 PM
Hi,
   I sent an email to Gregory ( DripElectronics )  about a month ago , he replied that it would be a couple weeks , I still dont see them listed on his web page , I sent another email yesterday and have not gotten a reply yet , I also need some for this project , but not really in hurry , hopefully  soon.  I will post back if I hear anything.

why not build your own? i know there is a lot of hockus pocus voodoo surrounding it, but because its feedback type compressor, its really not that hard...i only say this cause i built 2 and they sound surprisingly nice. I woundt sell them, but i sure would run some audio through them, thank you very much! bought the EL panels on fleabay for 7 bucks and the nsl photo-resistors that were recommended.
Title: Re: D-LA2A Support Thread
Post by: audiophreak on September 19, 2012, 03:36:20 PM
Hi,
   I sent an email to Gregory ( DripElectronics )  about a month ago , he replied that it would be a couple weeks , I still dont see them listed on his web page , I sent another email yesterday and have not gotten a reply yet , I also need some for this project , but not really in hurry , hopefully  soon.  I will post back if I hear anything.

why not build your own? i know there is a lot of hockus pocus voodoo surrounding it, but because its feedback type compressor, its really not that hard...i only say this cause i built 2 and they sound surprisingly nice. I woundt sell them, but i sure would run some audio through them, thank you very much! bought the EL panels on fleabay for 7 bucks and the nsl photo-resistors that were recommended.

  Normally I would say " Challenge Accepted " but I just dont have the time right now to experiment  :(   .. but I'm busy work wise , so not complaining.  This is my first foray in to optical compressors , and after gettin my butt kicked from the mnats dual 1176 rev j. I just  finished ... I'm taking my time with this one, but after I get this one running normally, I my just try my hand at that and compare. If I do, I may have some questions for you.   ;D
Title: Re: D-LA2A Support Thread
Post by: johnnyscotch on September 19, 2012, 07:47:16 PM
why not build your own? i know there is a lot of hockus pocus voodoo surrounding it, but because its feedback type compressor, its really not that hard...i only say this cause i built 2 and they sound surprisingly nice. I woundt sell them, but i sure would run some audio through them, thank you very much! bought the EL panels on fleabay for 7 bucks and the nsl photo-resistors that were recommended.

I'd take a crack at it, where could I find more info or a schematic or something? What about the housing/socket pins for it?
Title: Re: D-LA2A Support Thread
Post by: audiophreak on September 24, 2012, 07:20:17 PM
HI All,
         Well ... I flipped the switch .. and Nothing blew up !!!   YYYyaaaaa   ;D
I took voltage readings , they are :

V101 - pin 1 = 113.9vdc      v102 - pin 1 =  93.3vdc     v103 - pin 1 =  87.5vdc     v104 - pin 1 =0.004
           pin 2 =     0.0vdc                 pin 2 =    0.003vdc            pin 2 =   -0.001vdc            pin 2 = 6.08
           pin 3 =     0.927vdc             pin 3 =    3.78vdc              pin 3 =     0.739vdc           pin 5 =127.4
           pin 6 = 111.4vdc                 pin 6 = 204.6vdc               pin 6 =    87.5vdc              pin 6 =102.0
           pin 7 =     0.001vdc             pin 7 =   71.5vdc               pin 7 =     -0.001               pin 7 =0.004
           pin 8 =     1.04vdc               pin 8 =   98.1vdc               pin 8 =      0.74vdc


V201 - pin 1 = 114.3vdc      v202 - pin 1 =  90.9vdc     v203 - pin 1 =  94.6vdc     v204 - pin 1 =0.003
           pin 2 =     0.001vdc             pin 2 =    0.001vdc            pin 2 =   -0.001vdc            pin 2 = 6.18
           pin 3 =     0.923vdc             pin 3 =    3.73vdc              pin 3 =     0.704vdc           pin 5 =124.8
           pin 6 = 118.8vdc                 pin 6 = 204.7vdc               pin 6 =    94.6vdc              pin 6 =105.0
           pin 7 =   - 0.001vdc             pin 7 =   69.1vdc               pin 7 =     -0.001               pin 7 =0.003
           pin 8 =     0.967vdc              pin 8 =  95.15vdc              pin 8 =      0.704vdc

R133  = L= 249.9 / 87.5vdc      R=248 / 94.7vdc
R131  = L= 0.74vdc                  R= 0.71vdc
R134  = L= 250.7 / 126vdc       R= 250.3 / 123.6vdc
R136  = L= 6.1vdc                     R= 6.22vdc
R109  = L= 197.6 / 114.3vdc     R= 198.9 / 114.5vdc
R138  = L= 102.2vdc                  R= 105.4vdc
R118  = L 98.6vdc                      R= 95.9vdc
R117  = L 251 / 205.1vdc           R= 250.5 / 205.2vdc
R113  = L 197.5 / 118.7vdc        R= 198.6 / 118.9vdc

  and    63.8vdc on both diodes in place of Neon lamps

EDIT :  ... and heaters are all 6.6vAC

  I'm pretty sure its all within +/-  limits , and it passes clean audio - tons of gain , I did the 75k resistor and 25k pot - waiting to purchase the T4B's  -  noticed that the 6AQ5a's get REAL HOT  - and the Lytic caps next to them are getting hot from the tubes, not sure if this is something I should be concerned about, just thought I'd mention it.

   ... just looking for more experienced eyes to look over these readings, also wondering what type of load / resistor to put across inputs to check noise floor , or if that can be done without the T4B's in place , also I'm using the Rondo PT , and notice it has a little physical  " Buzz " noise  that I've heard on other types of PT , but not Toroidal type.

   Thanks as always ,
                                          Chip

Title: Re: D-LA2A Support Thread
Post by: abechap024 on September 25, 2012, 11:43:08 AM
why not build your own? i know there is a lot of hockus pocus voodoo surrounding it, but because its feedback type compressor, its really not that hard...i only say this cause i built 2 and they sound surprisingly nice. I woundt sell them, but i sure would run some audio through them, thank you very much! bought the EL panels on fleabay for 7 bucks and the nsl photo-resistors that were recommended.

I'd take a crack at it, where could I find more info or a schematic or something? What about the housing/socket pins for it?

Look for octal 8 pin relay housings. Easy to find, lots of varieties. I bought some that were clear and gave them a couple coats of black spray paint in and out. I bet with just a little more effort an inexpensive testing rig could be made to test the various photo-resistors. Seems like the modern ones are a lot closer in spec to each other, just there is that one or 2 oddballs that could throw things off.

But for the 40 or so dollars I have invested for 2 I feel its worth it. Especially since the gear I make for myself I prefer it to have personality that I have to get to know; sometimes I find some real winners that just sound really cool (like using fets in 1176s that don't have the "optimal" curve)
Title: Re: D-LA2A Support Thread
Post by: johnnyscotch on September 27, 2012, 12:11:10 AM
Cool thanks. That's probably over my head I guess. Besides finding a housing for it and some photo-resistors, I wouldn't know where to start.
I don't know WHICH photoresistors to get!! LOL


why not build your own? i know there is a lot of hockus pocus voodoo surrounding it, but because its feedback type compressor, its really not that hard...i only say this cause i built 2 and they sound surprisingly nice. I woundt sell them, but i sure would run some audio through them, thank you very much! bought the EL panels on fleabay for 7 bucks and the nsl photo-resistors that were recommended.

I'd take a crack at it, where could I find more info or a schematic or something? What about the housing/socket pins for it?

Look for octal 8 pin relay housings. Easy to find, lots of varieties. I bought some that were clear and gave them a couple coats of black spray paint in and out. I bet with just a little more effort an inexpensive testing rig could be made to test the various photo-resistors. Seems like the modern ones are a lot closer in spec to each other, just there is that one or 2 oddballs that could throw things off.

But for the 40 or so dollars I have invested for 2 I feel its worth it. Especially since the gear I make for myself I prefer it to have personality that I have to get to know; sometimes I find some real winners that just sound really cool (like using fets in 1176s that don't have the "optimal" curve)
Title: T4B update
Post by: johnnyscotch on September 30, 2012, 11:08:32 PM
I made some head-way on the T4B front.

Frank has everything you need to make them, right here:
https://sites.google.com/site/diypartsstore/catalog/new-t4b-opto-el-panels (https://sites.google.com/site/diypartsstore/catalog/new-t4b-opto-el-panels)

I ordered the parts and I'm going to have a go at rolling my own. It actually looks surprisingly easy, as AbeChap mentioned. There's a little slideshow on the site, it's only a few steps. I'm actually surprised these are so hard to come by, based on the cost and availability of the components.

I'll post here if successful.

Title: Re: D-LA2A Support Thread
Post by: ethervalve on October 01, 2012, 01:16:00 PM
Hi all,
I just realized that my D-La2a is suffering from a bit of cross-talk at high frequencies.
Has anyone else encountered this? Any ideas for troubleshooting? I wonder if running shielded cabled from the board to the Edcor transformers would help? (tried--didn't help) Maybe, lowering the value of C4 (current 330pf)? Lowering the overall gain with that 12ay7 mod?

I do also have the oscillation issue (really a non-issue because it only occurs at freakishly high gain levels).
Thanks in advance for any insights.
Title: Re: D-LA2A Support Thread
Post by: django on October 02, 2012, 05:08:11 PM
having problems with my la2a, it seems to need a pretty epic input signal before it does any compression and the output signal is huge aswell, have to have it below 1 to avoid clipping inputs.

What should r125 be roughly? Would the type of neon have a big effect on it working? (fairly sure i ordered the right type but it was a while ago now so can't remember) Also i have a 33uf for c174, wondered if this would be slowing the compression down at all aswell?

thanks michael
Title: Re: D-LA2A Support Thread
Post by: ethervalve on October 02, 2012, 05:14:51 PM
it seems to need a pretty epic input signal before it does any compression
Hi Michael, as bernbrue said earlier in this thread "- verify that limiter response and stereo link potentiometer are trimmed correctly"
It's quite easy to hook these pots up backwards; having them turned all the way in the wrong direction would have a huge effect on the threshold of compression.
Title: Re: D-LA2A Support Thread
Post by: django on October 02, 2012, 05:30:45 PM
I can remember adjusting these a while ago (had this project on the shelf for a while) with little success. are there any other things i could be checking? Also whats the ideal input voltage?
Title: Re: D-LA2A Support Thread
Post by: ethervalve on October 02, 2012, 05:32:54 PM
That's the extent of my advice. Wish I could help you. But I'm still troubleshooting my own issues (crosstalk). Good luck! I'm sure the experts will chime in soon enough.
Title: Re: D-LA2A Support Thread
Post by: django on October 02, 2012, 05:47:23 PM
have you posted a picture of your layout? I can help with lead dress!
Title: Re: D-LA2A Support Thread
Post by: django on October 04, 2012, 05:25:07 PM
Got it working, I now have a similar problem to you ethervalve.

If i turn up the gain or compression to high i get oscillation. Turning on the stereo link seems to cure it a bit but it also lowers the amount of compression i can get. Going to spend a bit of time hunting it down tommorow but some ideas of where to start would be great.

ta,
michael
Title: Re: D-LA2A Support Thread
Post by: ethervalve on October 04, 2012, 05:29:53 PM
Hi Michael,
sorry i missed your previous message. thanks! i will take a photo. I'm woefully ignorant of the vagaries of lead dress (shorter wire vs wire routing etc).
I'm expecting a pair of 12ay7 and lower value c4 caps tomorrow. I'll report back how that works out.
Title: Re: D-LA2A Support Thread
Post by: ethervalve on October 09, 2012, 12:23:29 PM
Hi Michael,
I finally found time this weekend to work on my D-LA2A again.
The good news is that is that I was able to fix all the issues it was having.
Slight bad news: I was stupidly troubleshooting from the hip and I'm not certain exactly what it was that fixed things....
I basically did the following at the same time:
1) I installed sockets for C4 (C104 and C204 on the boards) http://i630.photobucket.com/albums/uu30/cejl/dla2aC4sockets.png
2) I performed the 12ay7 Mod (using 100k resistors for R9 and R13)
3) I replaced the neon lamps with zener diodes
4) I shortened the many of the wire runs (I did this before I saw your offer to check out the lead dress--here's what my wiring looks like in any event: http://i630.photobucket.com/albums/uu30/cejl/dla2ainnards.jpg )
Here's what it looks like (my letraset technique could use some work): http://i630.photobucket.com/albums/uu30/cejl/dla2aLidoff.jpg
Now everything works fine: I get no oscillation, hiss or noticeable crosstalk.
One curious thing tho: To get the frequency response equal between sides, I had to use a significantly smaller cap in ch1 (100pf) vs ch2 (250pf). Does anyone know if this is normal? (I'm using Edcors for inputs and outputs).
Title: Re: D-LA2A Support Thread
Post by: audiophreak on October 09, 2012, 04:13:40 PM

 Hi All ,
        I spoke with Gregory  ( Drip Electronics )  today and he said about two weeks for the T4Bs  :)
Title: Re: D-LA2A Support Thread
Post by: johnnyscotch on October 10, 2012, 02:03:35 AM
Can anyone help with wiring up the Edcors for this guy, as it relates to the "Sowter" indications on the pcb?

Has anyone done a diagram?
I was trying to go off the tech docs on the Sowter site, but I'm still afraid I might confuse the pri and sec......

Thanks!
Title: Re: D-LA2A Support Thread
Post by: abechap024 on October 10, 2012, 11:47:06 AM
Can anyone help with wiring up the Edcors for this guy, as it relates to the "Sowter" indications on the pcb?

Has anyone done a diagram?
I was trying to go off the tech docs on the Sowter site, but I'm still afraid I might confuse the pri and sec......

Thanks!

I'm getting ready to wire the edcor transformers in mine in the next couple days, I'll take note. But what I've had to do on previous builds of this unit is look at the original sowter info....

input tx 4383:
http://www.sowter.co.uk/conpics.htg/4383.gif

and output 8940:

http://www.sowter.co.uk/conpics.htg/8940.gif

I used both of these transformers in a build for a friend and they sounded gorgeous! The wait and money involved to get them though, I wasn't expecting anything less. It will be interesting to hear the edcors by comparison, I think they will work just fine.
Title: Re: D-LA2A Support Thread
Post by: johnnyscotch on October 10, 2012, 02:14:24 PM
Can anyone help with wiring up the Edcors for this guy, as it relates to the "Sowter" indications on the pcb?

Has anyone done a diagram?
I was trying to go off the tech docs on the Sowter site, but I'm still afraid I might confuse the pri and sec......

Thanks!

I'm getting ready to wire the edcor transformers in mine in the next couple days, I'll take note. But what I've had to do on previous builds of this unit is look at the original sowter info....

input tx 4383:
http://www.sowter.co.uk/conpics.htg/4383.gif

and output 8940:

http://www.sowter.co.uk/conpics.htg/8940.gif

I used both of these transformers in a build for a friend and they sounded gorgeous! The wait and money involved to get them though, I wasn't expecting anything less. It will be interesting to hear the edcors by comparison, I think they will work just fine.

Thanks, I was looking at those on the sowter site. I just don't want to botch it up.
Is black on the Sowter the other center tap? Or more specifically, if it's just a ground, can I use the other ct on the edcor for that lead?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on October 10, 2012, 03:39:37 PM
We don't use any center taps!
Title: Re: D-LA2A Support Thread
Post by: MicDaddy on October 10, 2012, 06:32:16 PM
I've got the lid off of mine (I like to watch the street lights in tube city at night) I'll take a peek and relay what I find.

WSM600/15K
1--Brown
4--Green
5--Blue
8--Grey

WSM15K/600
1--Yellow
4--Green
5--Grey
8--Pink

Thanks again to the contributor that helped me with this when I was lost.
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on October 11, 2012, 01:36:12 AM
I got mine up and running finally.  I still need to work my stepped switches up but its working great with the standard build.  Now its time to do some tweaking. 

Are you guys finding the 12Ay7 mod doesn't really give you enough gain for proper reduction or is it a different issue you are having.  I am thinking about trying it but not if it doesn't really work? 

Also, are any of you guys putting 600r on the outputs or are you running them with out a load?  I will test that for sure.

Title: Re: D-LA2A Support Thread
Post by: dandeurloo on October 11, 2012, 09:47:26 PM
A few more questions in regrades to my testing. 

1. Has anyone padded down the outputs of the D-LA2A?  If so how much pad did you add?  I have tested 20db and 5 db pads.  5db seems to be best.  You are then able to turn up the gain a little more and slightly more color form the outputs.  20db was way to much.

2. I am also testing loading the outputs.  So far the cinemags have sounded pretty good with a 1.8k.  Wondering if anyone else has done this as well?


Overall, I am wondering if just padding and loading the outputs would be a solution to the super high gain of the units.  Maybe a alternative to the 12AYY mod.

Title: Re: D-LA2A Support Thread
Post by: desol on October 12, 2012, 03:34:23 AM
I did the 12ay7 mod. Works good and there is still plenty of gain. I changed a couple resistors too that cj had mentioned. Plate bias resistors i believe....from 220k to 100k if i remember correctly. Twas a long time ago.  :)

Info is here and there somewhere. Otherwise, works great and sounds fine, still plenty of gain. Didn't fool with any zobels on the outputs....and i used the edcors. 15k... did test with some software and a 1k sine....looked pretty flat from bottom to top.
Title: Re: D-LA2A Support Thread
Post by: Hank Dussen on October 12, 2012, 03:54:59 AM
1. Has anyone padded down the outputs of the D-LA2A?  If so how much pad did you add?  I have tested 20db and 5 db pads.  5db seems to be best.  You are then able to turn up the gain a little more and slightly more color form the outputs.  20db was way to much.

I added a switchable 10db pad right after the output transformer. That way you can really push the output gain for some nice distortion without going over +4dB output.
I also added a switch that bypasses R6 (68k) at the input. This gives me some extra gain so I can also use it as a preamp.

With the combination of these added switches you can get some really fat distortion sounds...
Title: Re: D-LA2A Support Thread
Post by: Kingston on October 12, 2012, 07:00:02 AM
I added a switchable 10db pad right after the output transformer. That way you can really push the output gain for some nice distortion without going over +4dB output.
I also added a switch that bypasses R6 (68k) at the input. This gives me some extra gain so I can also use it as a preamp.

With the combination of these added switches you can get some really fat distortion sounds...

I've a similar case but would add that the distortion tends to be on the harsh side. The stock amplifier of LA2A is very linear and it's like a guitar lead channel when it clips. Useful as effect. Beatles revolution style guitar sounds are quite possible with it. The output transformers that we use for LA2A commonly are not clipping in this at all. All the distortion comes from the NFB tube amp. Output transformer clipping threshold is much higher/louder.
Title: Re: D-LA2A Support Thread
Post by: Hank Dussen on October 12, 2012, 07:39:55 AM
I did change the 12AX7 to an 12AY7 which should make the distortion nicer.
Still it's not a subtle harmonic distortion but I really like the combination of compression and distortion on for example a drum loop.

BTW, I also tried to replace the feedback resistor R11 with an 470K pot, but this didn't change a lot to the sound...
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on October 12, 2012, 12:41:51 PM
I've been testing R11 as well and it doesn't seem to be much more then another volume control (I think Kingston mentioned this as well).  I was thinking I would see more harmonics but seems to be just gain.  Maybe if I try the tube switch.  I was also thinking it still had so much gain that the padded outputs plus the tube switch would allow for the tubes to actually start to put out some harmonics.

I have found the R37 on a switch and the output termination to have more of a sonic change on the comp.  I also have had interesting findings with different values of the Gain pot.  The 25k pot and 75k resistor only seems marginally better then the 50K pot and 50k resistor.  Maybe its because the pots I am test with don't have the best resolution.  I am hoping stepped switches will act a little better. 
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on October 12, 2012, 12:44:44 PM

I added a switchable 10db pad right after the output transformer. That way you can really push the output gain for some nice distortion without going over +4dB output.


What kind of Pad did you add?  I'm wondering which kind of pad will not effect the impedance and balancing.

Kingston and Hank, do you find 10db pad to be to much?  Would it be more useful if it was maybe 8db or something like that?  Just wondering what you have found over time in regards to this.
Title: Re: D-LA2A Support Thread
Post by: johnnyscotch on October 12, 2012, 01:22:11 PM
If you don't want a switched pad, would it just be a matter putting the applicable resistor(s) at the output XLR?

Have you discovered what combination of resistors gives which dB reduction? I suppose it's just ohms law, I'm absolute sh*te at figuring it out though
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on October 12, 2012, 01:32:53 PM
I am talking about 2 different things that all happen at the outputs. 

1. output loading / termination  - I think this what you are talking about.  I have been doing that and like a 1.8k across pins 2&3. 

2. padding down the output - this is so you can drive the comp harder and get more color out of it and also hopefully get more resolution out of the makeup gain pot. 

I'm trying to figure out what kind of pad would not effect the loading when switched in and out. 
Title: Re: D-LA2A Support Thread
Post by: Hank Dussen on October 12, 2012, 01:57:26 PM
Since the output of the transformer is 600 ohm, I used a 600 ohm T attenuator.
You can use this pdf to find the correct resistors: http://www.groupdiy.com/index.php?topic=45632.msg571875#msg571875 (http://www.groupdiy.com/index.php?topic=45632.msg571875#msg571875)
So for a 10dB pad you'd need 2 x 620R, a 287R and a 1K33 resistor
I did 'reverse' my attenuator compared to the attenuator drawing in the link. The 'load-side' should be the transformer, and hot and cold on the XLR side. I'm not sure if this matters but it seems logic and worked for me...

I found 10dB of attenuation to fit perfect. No matter how hard I push the gain I never seem to get more then +4dB at the output.
But I guess this largely depends on the tube that's distorting.

Of course you can also use 600 ohm attenuator potentiometer. http://hairballaudio.com/shop/product_info.php?cPath=27&products_id=65 (http://hairballaudio.com/shop/product_info.php?cPath=27&products_id=65)
Or a rotary switch with different attenuator settings...
Title: Re: D-LA2A Support Thread
Post by: Kingston on October 12, 2012, 03:04:13 PM
I've a 600-ohm stepped attenuator for debugging. I found out a 12-15dB output pad gave me the strong effect-like distortion I was looking for. Others like different so don't take that value as a recommendation. Then I just made a 14dB 600-ohm H-pad using some calculator I found on the net. I switch it in and out with a DPDT relay.

Switching in and out that series 68k input resistor increses the gain/distortion pallette even further.

I wouldn't spend any brain cells or time with output loading selectors with 600-ohm output transformers. I've found they have little to no effect in any project I've ever done. Maybe some transformers are more picky, or maybe I've been lucky. No weird high frequency shifts in any of my projects from any output loading scenarios. But then I've mostly 600 ohm I/O everywhere.
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on October 12, 2012, 03:13:06 PM
Great info guys!  Thanks for all the feedback.

I wouldn't spend any brain cells or time with output loading selectors with 600-ohm output transformers. I've found they have little to no effect in any project I've ever done. Maybe some transformers are more picky, or maybe I've been lucky. No weird high frequency shifts in any of my projects from any output loading scenarios. But then I've mostly 600 ohm I/O everywhere.



Kingston this is interesting.  I have found the loading makes really cool sonic flavors. I am using cinemag CM-9589L's and I am testing just going back into the DAW.  So that may have something to do with it. 

I also just swapped in a 6072/12AY7 and seems to have a little less gain.  May need to try the r109 & r113 mods and then wire in the pot again for feedback and hear whats happening. 

Title: Re: D-LA2A Support Thread
Post by: Kingston on October 12, 2012, 04:49:07 PM
Kingston this is interesting.  I have found the loading makes really cool sonic flavors. I am using cinemag CM-9589L's and I am testing just going back into the DAW.  So that may have something to do with it. 

CM-9589L is great. I've used in a few places too. The minor sonic differences I've found are:

1) about 1dB gain drop with 600ohm loading recommended by the datasheet with very flat response to +30khz.
2) 1-2dB high frequency roll off from maybe +10khz onwards with very light load (AD input for example)

experiences with edcor and sowter have been similar with negligible (in my opinion) differences and at some point I stopped caring. Mic input transformers are another thing, there I've used whatever they recommend in datasheets (if available).

From what I gather from experienced vintage transformer twiddlers here on the forum, some of them (input and output) can be very tweaky with different loads so I don't doubt if people are hearing significant changes with loading.
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on October 12, 2012, 05:27:19 PM
Switching in and out that series 68k input resistor increses the gain/distortion pallette even further.

Do you mean R11?  I am playing with that now.  I can't decide if I want to put that on a pot or a switch with a fixed point.  Are you just switching it out completely?
Title: Re: D-LA2A Support Thread
Post by: Kingston on October 12, 2012, 07:34:43 PM
Switching in and out that series 68k input resistor increses the gain/distortion pallette even further.

Do you mean R11?  I am playing with that now.  I can't decide if I want to put that on a pot or a switch with a fixed point.  Are you just switching it out completely?

I mean R6/R106 depending on what schematic you are reading. It's an internal input pad. Bypass that, and you'll have the LA2A working as a "mic preamp" of sorts. More gain available. I wouldn't bother playing too much with the line amp stage at all (that R11 feedback resistor for example). It is what it is and it needs drastic changes to get anywhere closer to nicer sounding and softer clipping. The 12AY7 swap with the minor resistor changes often suggested is nearly pointless. It's still going to clip hard and nasty. No euphonic tube sound in LA2A's (less than 0.1%THD unless it's broken), just utilitarian clean line level gain. The points of interest (soundwise) are the transformers and the optical stage response.
Title: Re: D-LA2A Support Thread
Post by: desol on October 12, 2012, 08:58:06 PM
Switching in and out that series 68k input resistor increses the gain/distortion pallette even further.

Do you mean R11?  I am playing with that now.  I can't decide if I want to put that on a pot or a switch with a fixed point.  Are you just switching it out completely?

It is what it is and it needs drastic changes to get anywhere closer to nicer sounding and softer clipping. The 12AY7 swap with the minor resistor changes often suggested is nearly pointless.

I don't think CJ originally suggested the swap to make it sound better....even though he did say that. Pretty sure it was just about allowing more movement on the input....which it does.
Title: Re: D-LA2A Support Thread
Post by: ethervalve on October 12, 2012, 09:49:54 PM
hi all, I asked this earlier but it got buried really quickly:
Just wondering if anyone else had to use a different value for C4 on the left and right channel to get the frequency response equal?
A 100pf got me flat response on channel one, but i needed to use 250pf on second channel. Just wondering if this is normal... (Edcors on in/outputs)
Title: Re: D-LA2A Support Thread
Post by: Kingston on October 13, 2012, 12:23:49 AM
Pretty sure it was just about allowing more movement on the input....which it does.

The what now? Swapping the tube or changing its operating point has absolutely no effect on the compression. It has a minor effect on the first stages of the line amp. The amp is there only for the make up gain, and has no interaction with the compressor circuit whatsoever.

LA2A signal chain:

input transformer -> light/optical element based gain reduction -> very linear medium gain line amp for make up gain -> output transformer

Just wondering if anyone else had to use a different value for C4 on the left and right channel to get the frequency response equal?
A 100pf got me flat response on channel one, but i needed to use 250pf on second channel. Just wondering if this is normal... (Edcors on in/outputs)

This is normal. Some people use trimmer capacitors to perfectly match the channels, but it's not that critical really.
Title: Re: D-LA2A Support Thread
Post by: desol on October 13, 2012, 10:00:56 AM
Yes, you're absolutely right. In fact, i remember that it struck me as being odd the first time i used it? Compared with other units...

The tube swap doesn't do that much. It does allow a little more movement on the pot for adjusting makeup gain(which is otherwise at ~ 2) and maybe it sounds a smidge different. Although, i wouldn't know...cause i didn't bother comparing tubes. I think i also put the 25k pot in there with the 75k resistor. So that allows even a bit more...

Plus...12ay7 remains cheaper than 12ax7....which is a little bonus.  :)
Title: Re: D-LA2A Support Thread
Post by: Hank Dussen on October 13, 2012, 10:04:57 AM

I added a switchable 10db pad right after the output transformer. That way you can really push the output gain for some nice distortion without going over +4dB output.


FWIW, I checked, and it seems to be closer to a 12dB pad...
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on October 13, 2012, 12:01:51 PM
Hank thanks! 


Yes, you're absolutely right. In fact, i remember that it struck me as being odd the first time i used it? Compared with other units...

The tube swap doesn't do that much. It does allow a little more movement on the pot for adjusting makeup gain(which is otherwise at ~ 2) and maybe it sounds a smidge different. Although, i wouldn't know...cause i didn't bother comparing tubes. I think i also put the 25k pot in there with the 75k resistor. So that allows even a bit more...

Plus...12ay7 remains cheaper than 12ax7....which is a little bonus.  :)

I've compared both the 12AY7 and the 12AX7 and for me I think I am going to use the 12AY7.  It does allow a little more control on the gain pot and I like the sound.  It is a little warmer, less crunchy.  Not great description but I hope that helps.  I am leaving R11 and the plate R's alone.  Those mods didn't do anything for me.  Plus then I can just switch in 12AX7's if I want to.

I also did more work on the 25k pot.  I found that by strapping a 27k resistor across pins 1 & 3 I got more resolution across the whole pot.  The center stays the same pretty much but the edges are much better.  It lowered the value of the pot to about 12k so you have to make up for that on the other resistors.  I also put a 220r on the ground side of the pot.  So it doesn't turn all the way off.  No need for that we have BYPASS! 
Title: Re: D-LA2A Support Thread
Post by: Kingston on October 13, 2012, 01:30:58 PM
For anyone trying to justify the tube swap with better gain pot control: please don't, there are better ways. Leave the line amp the ancients designed alone and don't ruin it's specs or the utilitarian "signature sound". It's not exactly the greatest tube line amp design in the history of mankind, but you wanted LA2A, right?

Let's concentrate on the gain pot itself. The main issue here is that the line amp has way too much gain for modern usage, like +20dB too much. You can knock this down with other tube choice with the cost of more THD due to unoptimal tube operating points and other issues, but really all you need to change/control is the gain pot.

The 100k value for the pot is uncritical by the way. anything between, say 50-250k works fine. This way you are also free to scale those resistors with much more tolerance.

My solution? 24-step rotary switch with 1-3dB steps from about -50dB to 0dB (relative to input). I think I even posted the exact values somewhere on the forum years back, maybe even on this thread.
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on October 13, 2012, 01:39:26 PM
Kingston, isn't that kind of what I did to my gain pot?  I'm not 100% but it did sound better and was much more full range then a standard 100k pot. 

The other thing I am confused by.  Doesn't the overall value of the pot have to remain 100K.


Thanks for your help.  I am glad guys like yourself and others are willing to help!

NOTE:  I am interested in building a stepped switch like the one on this.
http://www.requisiteaudio.com/products/studio_electronics/l2m_limiter/index.html
I have a number of friends who have one and LOVE it.
Title: Re: D-LA2A Support Thread
Post by: Kingston on October 13, 2012, 03:56:36 PM
Doesn't the overall value of the pot have to remain 100K.

Not at all. This part of the circuit is "reasonably high impedance". It means the stage before the pot can only drive weak high impedance loads. It's not written into stars it must be 100k. Maybe the original designer picked that because there were gazillion 100k log pots around and thought it was a safe choice. But we can just as well pick 50k or 250k. Gain and frequency response will stay unaffected. Very basic electronics. And as you may at some point find out stepping out the painting by the numbers dighole, audio electronics is not ultra exact discipline. Instead we recognize the limits of certain points of the design and shoot in that general direction. The values are uncritical. Tubes are especially forgiving.

I would go out on a limb and say you can safely deviate 30% in any direction of all the parts of an LA2A unit and it would still function quite perfectly. Long a go, you couldn't even ask for better tolerance for many of the parts in the first place.
Title: Re: D-LA2A Support Thread
Post by: johnnyscotch on October 13, 2012, 05:04:53 PM
Can you gents help a brotha out with wiring the power trafo for this puppy?
I just need 110, I'm not putting a switch in for dual voltage. Two pairs of yellow and white wires? I can only find help in the threads for 220 or both, not just 110.

I assume the green/yellow wire goes to star ground and the IEC ground goes to star as well?

Also, my IEC has the built in fuse, does this complicate wiring the power switch in?
Title: Re: D-LA2A Support Thread
Post by: desol on October 13, 2012, 09:19:59 PM
For anyone trying to justify the tube swap with better gain pot control: please don't, there are better ways. Leave the line amp the ancients designed alone and don't ruin it's specs or the utilitarian "signature sound".


I wasn't the original one to suggest it?? It was him... >>

Sheesh.  ;D


Edit: Besides, wasn't it originally designed for a different application? One that the ancients designed it for?
Title: Re: D-LA2A Support Thread
Post by: johnnyscotch on October 13, 2012, 11:54:07 PM
Also, any hints about wiring the Meter LEDs?

I have the Hairball meter. Just wondering where to pull the LED power from?  ???

thanks
Title: Re: D-LA2A Support Thread
Post by: kilmister on October 14, 2012, 01:34:51 AM
Hi all!

Finally, after one year lazyness to do a front panel, I swapped temporary front panel to the decent one and finished my unit.
Nothing too fancy here except it's build in 2U case and that was a tricky part.
Urei T4's, caps russian PIOs and Wima 10u films (leftovers from PM670 project)
Stepped attenuators, Freq Response trimmer on the front panel.
Some extra filtering for HT and rectified filament voltages. Trafos from Edcor.

Once again, thank you sir [silent:arts]!

And here's the pictures (click for hi-rez)

(http://www.5by5.fi/diy/dla2a/tn_dla2a_front_1.jpg) (http://www.5by5.fi/diy/dla2a/dla2a_front_1.jpg)

(http://www.5by5.fi/diy/dla2a/tn_dla2a_front_2.jpg) (http://www.5by5.fi/diy/dla2a/dla2a_front_2.jpg)

(http://www.5by5.fi/diy/dla2a/tn_dla2a_innards_1.jpg) (http://www.5by5.fi/diy/dla2a/dla2a_innards_1.jpg)

(http://www.5by5.fi/diy/dla2a/tn_dla2a_innards_2.jpg) (http://www.5by5.fi/diy/dla2a/dla2a_innards_2.jpg)

(http://www.5by5.fi/diy/dla2a/tn_dla2a_innards_3.jpg) (http://www.5by5.fi/diy/dla2a/dla2a_innards_3.jpg)

(http://www.5by5.fi/diy/dla2a/tn_dla2a_front_3.jpg) (http://www.5by5.fi/diy/dla2a/dla2a_front_3.jpg)

(http://www.5by5.fi/diy/dla2a/tn_dla2a_top_1.jpg) (http://www.5by5.fi/diy/dla2a/dla2a_top_1.jpg)
Title: Re: D-LA2A Support Thread
Post by: Hank Dussen on October 14, 2012, 05:02:32 AM
Very nice!
Is that a silkscreened frontpanel? How did you do that?
It's nice to see a more 'non-chalant' font on a front panel!
Title: Re: D-LA2A Support Thread
Post by: Uhl on October 14, 2012, 11:16:03 AM
Nice build! The cutouts for the T4's look funny.

Where did you get the perforated board on which everything is mounted?
Title: Re: D-LA2A Support Thread
Post by: kilmister on October 15, 2012, 10:11:59 AM
Is that a silkscreened frontpanel? How did you do that?
It's nice to see a more 'non-chalant' font on a front panel!

Front panel is made by UV color (flatbed)printer. Very easy, very cheap. It need clear coating on it thought. I've made all my finished units (2x1176, PM670) with this kinda style. After I'll finish the PRR176 project we have quite nice looking row of units in our rack 8)

Nice build! The cutouts for the T4's look funny.

Where did you get the perforated board on which everything is mounted?
Theres also those rubber rings for 12BH7's... But yeah, cutout was only option left to fit everything in 2U because I used perforated plate which eats 5 to 7mm of the headroom.
I use Modushop (http://www.modushop.biz) cases. They are offering these perforated plates which are very handy in DIY.

Cheers,
Paavo
Title: Re: D-LA2A Support Thread
Post by: johnnyscotch on October 20, 2012, 03:12:25 PM
Hey guys, need some help here, desperately

So, I fired up the DLA2A, and I get power to all the tubes, neons, indicator lamp, etc.....and nothing blew up or smelled bad. Check.

It passes audio, I ran a 1k tone through it, and bypass works. It goes straight through unaffected in bypass, and when I switch it in I have gain control. LOTS of gain. Too much actually. I went with the 75k/25kPot thing and it still hits unity around 1.5 (8 o'clock), which is pretty useless. I guess I'll try 90k/10kpot, but later.

My big issue right now is the left channel gain seems to be greatly affected by the GR/Output VU switch. The wiring is the same on both channels and the Right channel seems to be working OK. The left channel works, but as soon as I switch the VU to "GR", the level shoots through the roof! Does anyone know why there should be a correlation between the gain and GR/VU switch?

Is there anything I can do troubleshooting-wise to check everything is OK before the wiring? I assume since I'm getting signal at all that my trafo and input wiring is fine. I guess I also assume since I'm getting power everywhere that my Power trafo and heater wiring is fine. I'm thinking about ripping out all the switch wiring and starting from scratch.

Also, I felt like my trimpots for 125/225 weren't making a good connection due to the way I mounted them, so I basically just took a pair of 100k pots and wired them to the board till I can get some more trim pots. I'm not even sure what these two are doing in the signal chain, they don't seem to affect anything in my preliminary gain tests.

I was really pretty bummed when I fired it up and already ran into issues. I really felt like I was patient and attentive with this build and I guess it didn't seem to matter......... :(

thanks
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on October 20, 2012, 10:58:36 PM
I think you will find 15K pot the best.  You can get close to that by putting a 27K resistor across the pot.  Seems to be working good for me.  I did that on one channel.  Now I need to build my stepped switches.

I'm looking at the schematic trying to see if I can find a spot to look.  But in the meantime, keep one hand in your back pocket while trouble shooting!  No need to die trying to test it.  The good news is one channel is working so it will be a small fix more then likely.

Also, double check your wiring.  It is most likely in there some how.  I'll let ya know if I see something.  Someone smarter will probably come up with a trouble shooting suggestion for you.

Maybe check your resistor values around R128, R126, R127 and R125.  I believe those and the trimmer R104 are all in the meter circuit.  It would be good to rule those out.
Title: Re: D-LA2A Support Thread
Post by: johnnyscotch on November 04, 2012, 09:45:45 PM
I give up, can't spend any more time on this thing

http://www.groupdiy.com/index.php?topic=50367.0

Maybe someone will have better luck than me
Title: Re: D-LA2A Support Thread
Post by: desol on November 05, 2012, 04:20:56 PM
Sounds like you're frustrated. Maybe you should put it away for a bit...and forget about it.

Come back to it later, and get it going. It's worth it.  :)
Title: Re: D-LA2A Support Thread
Post by: abechap024 on November 06, 2012, 01:03:48 AM
I give up, can't spend any more time on this thing

http://www.groupdiy.com/index.php?topic=50367.0

Maybe someone will have better luck than me

Man you did 99% of alll the hard work! Now forever you are going to have a bad taste in your mind about DIY. Its ALWAYS something simple....just a huge pain finding out what. Try switching around the tubes, connectors, anything you can. Its a sweet deal, but i bet you could get it going. Shoot me an email if you want, I just built a couple and am in the middle of one so maybe I can help trouble shoot.
Title: Re: D-LA2A Support Thread
Post by: chris77 on November 09, 2012, 10:27:57 AM
Hi folks,

I've Just about completed my D-LA2A ,i have have to tidy the wiring up a little ,also have a hummmmmm  :o on the left channel which i'm trying to diagnose  i've swapped the valves one at a time also tried swapping the transformers ,heating wiring is ok (i think)and the channel is properly grounded,using a scope i have found some ripple on c105 which isn't there on c205 but i'm not sure if the cap is faulty? the hum stops when bypassed,the unit sounds great besides the hum and is compressing properly,i'll be doing the 25k pot+75k resistor mod for the gain also.

(http://i1358.photobucket.com/albums/q769/Similarvoid/la2a.jpg)

(http://i1358.photobucket.com/albums/q769/Similarvoid/la2a2.jpg)

cheers !

Title: Re: D-LA2A Support Thread
Post by: desol on November 09, 2012, 11:08:42 AM
Try moving the wiring around a bit with a chopstick and see if the hum changes. Also, make sure the polarities are correct on the wiring. I had to remove and install sheilded wire in a few places. Wiring is pretty important in this build...can make all kinds of little noises and hum.

Title: Re: D-LA2A Support Thread
Post by: dandeurloo on November 09, 2012, 12:28:46 PM
Also, make sure you remove the paint on the back side of the front panel by the pots and on one of the side.  This helps a bunch with rumble.  Also I would make your twisted pairs much tighter.  That helps with the noise.  I bet a little clean up and you will have the noise worked out!
Title: Re: D-LA2A Support Thread
Post by: jonathanmorbin on November 23, 2012, 07:34:11 AM
Hi,

Does anyone know where i can get the PCB's for the D-La2a or the single La2a? I really want to build one of these.
Title: Re: D-LA2A Support Thread
Post by: websoul on November 23, 2012, 07:55:15 AM
If you look under the White Market, you'll see them offered in there
http://www.groupdiy.com/index.php?topic=39570.0 for example.
Title: Re: D-LA2A Support Thread
Post by: jplebre on December 27, 2012, 02:27:38 PM
Hey guys

doing some research and hoping to join the clan of successful D-LA2A builders.
Most of the builds I've seen don't have the meter adjust pot mounted, only PCB mounted trimpots.

Am I right to assume that the meters, because they use the Opto-cell as tracking won't need the same adjustments as often as the other fet "driven" models would? (eg. á-la 1176 where any change in temperature drifts the needle completely?)

I'm asking because I will be contacting some people to get the enclosure done so can't really experiment with this until its too late.

Wadda you think, boys?

Cheers
Title: Re: D-LA2A Support Thread
Post by: desol on December 29, 2012, 02:09:22 PM
I find with mine that the meter does drift with temperature change. Pretty sure the 6bq5 drives the meter as well...
Title: Re: D-LA2A Support Thread
Post by: jplebre on December 29, 2012, 05:37:04 PM
Desol, so you find yourself popping the hood all the time for the 1M?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on December 29, 2012, 08:02:47 PM
The (GR) Meter (zero point) drifts with temperature.
Calibrate it after one or two hours and you are gone.
(I don't see any changes later on, once it has "temperature" it doesn't drift anymore)

This is no high end measuring system anyway, fun to see the needle move, but it doesn't matter if it is exact.
Can't see any reason to re-calibrate every few hours.
Title: Re: D-LA2A Support Thread
Post by: ethervalve on December 29, 2012, 08:24:51 PM
Just to add to what [silent:arts] said: I built my D-LA2A with panel-mounted zero-set pots but I've never had to adjust them after the initial calibration. For comparison's sake, my 1176 rev a and d clones have far more GR zero drift.
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on December 29, 2012, 08:32:26 PM
I took a quick pic of mine that I finished a few months back.  I built it to be more of a buss comp but I have found it works just as well as my other LA 2A for tracking.  I really like this compressor.  Great sound and great build.

I did stepped gain switches, and a few other nice little mods.  The center switches are a stereo attenuator (0, -2, -4) and the other two toggles are 3 positions with different output load resistors.  Thanks everyone for your help!

(http://dandeurloo.com//diy/Dual-LA-2A.jpg)
Title: Re: D-LA2A Support Thread
Post by: desol on December 29, 2012, 10:10:33 PM
Desol, so you find yourself popping the hood all the time for the 1M?

It depends on where the unit is located. Like the other guys said, if you put it in a rack and you calibrate it after a while, that's where it'll end up every time....unless you move it and change the relative temp (ie: inside/outside of rack) ...then it'll be somewhere else. I don't worry about it too much.
Title: Re: D-LA2A Support Thread
Post by: stanz on January 01, 2013, 05:59:43 PM
OK, almost finished my D-LA2A. Had to wait a bit for the optos, but got them recently and time to finish this project off. Still have a small problem with the right meter. It worked fine for a while, but I suspect that while adjusting R25, went to far and fried it. Confirmed this by bridging the signal to the left meter and all works as it should. The zero position adjust is not linear, but a parabola, where the lowest meter adjustment is in the middle, and going either direction from there will increase the needle's position.



Quite a few mods thrown into this project. I had scoured through the posts and decided these where what I wanted.

12AY7 tubes for the first stage of the amp with corresponding 100K plate resistors for less gain. The picture of the front panel is showing the unit at unity gain receiving a 1.23v input signal. There is a slight 1db difference between input and output in bypass. Whatever.

Added Kingston's mod of shorting the 68K resistor after the input transformer in addition to the 2K7 comp/limit resistor to give it about 6-8db more gain when using it strictly as a tube amp. Was worried about sending the signal up to the front panel and back right after it comes off the input transformer, but it works great. This is the added "Preamp" selection along on the Comp/Limit switch.

Drive control reduces negative feedback. Replaced R11 with a 50K resistor in series with a 500KA pot. Also works well as a fine gain control between the gain steps when testing and adjusting the meters.

SC HPF on front panel.

T4B Optos are from Kenetek

Stepped Gain and Peak pots.


Have to say it all went together fairly easy. Had connected one output transformer backwards making it a step up instead of step down transformer. oops.  And one of the resistors in the gain pot were shorting causing full gain at only the second position. Yikes. Pretty easy fixes all in all. All voltages seemed a bit lower than expected, but pretty consistent.

Finally fired it up and throw an instrumental mix as well as a drum mix at it. Very nice indeed. Not too heavy and very smooth. Didn't measure the noise, but I had to crank about 3/4 of the gain before I was hearing anything.


Thanks for the boards Volker, and all the effort.

Front panel was done at Prodigy Laser. Great service. Chae noticed a small missing text as I had to redo the file into a Correll format and missed it on the redo. Very fast turn around too. Way cool.

It sure is great how everyone puts a little something into a project like this. May thanks to ALL the contributions.
Title: Re: D-LA2A Support Thread
Post by: deuce42 on January 03, 2013, 02:09:36 AM
Great build - you must be very proud:)
Title: Re: D-LA2A Support Thread
Post by: jonathanmorbin on January 11, 2013, 05:31:35 AM
Hi,

Ive just finished building my unit. All seems to be working fine. The only problem im having is the power for the LED VU Meters and the Bulb. I am currently taking the power from the 5V section on the power supply on the far top right of the board but i am finding that the VU's Flicker and drop in and out. Is there a better place to take the 5V tap from? I put some resistors on the VU Meters LED's and it's better but still not constantly on. I am using the Hairball Audio VU Meter and normal fender Bulb.

Jon
Title: Re: D-LA2A Support Thread
Post by: jplebre on January 11, 2013, 05:59:44 PM
question on heather and AWG.
The 12AX7 pull 300mA, the 12BH7 600mA and the 6AQ45 pulls 450mA if I'm not mistaken?

Since the 2 channels are separate, would 24AWG wire be ok? :P

Title: Re: D-LA2A Support Thread
Post by: jplebre on January 16, 2013, 07:09:15 PM
And, back with another question. After enquiring on the T4B, I've noticed the original schem has a 2.2M resistor (R8) across pin 3 and pin 1/4 of the opto.
This resistor is not on the board and from the looks of it (old T4B pictures) is quite massive - probably 2w or more.

Should I install this resistor inside the T4B ? if so, in which cases?

I'm building a T4B replica with EL panel, not vactrols.

Thanks :)
Title: Re: D-LA2A Support Thread
Post by: jplebre on January 26, 2013, 06:08:46 AM
Bump on the wire gauge for heaters.
According to farnell, my cable is rated 600v/10A

Should be fine for the heaters, no?
http://uk.farnell.com/alpha-wire/3071-bk001/wire-ul1015-22awg-black-305m/dp/1199054
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 26, 2013, 06:11:45 AM
Should be fine
Title: Re: D-LA2A Support Thread
Post by: jonathanmorbin on January 27, 2013, 01:50:13 PM
Has anyone got any thoughts on my VU Meters? I am still having the same problem.....
Title: Re: D-LA2A Support Thread
Post by: desol on January 27, 2013, 02:00:28 PM
Sounds like you may have an intermittent connection somewhere on the 5v supply.
What voltage are the led's rated at, that you used>?

Just keeping asking yourself questions and searching and measuring, etc...it's something minor and i'm sure you'll find it.
Just be very careful with this circuit. I've felt the power behind it.
Title: Re: D-LA2A Support Thread
Post by: jonathanmorbin on February 04, 2013, 05:00:35 AM
The VU Meters are rated at 3.6v-5.2v 20mA (Hairball Audio Meter). I also get the relays ticking over of there own free will when i have the VU meters LED connected and i have been working the compressors for a while.

have other people taken the 5v for their VU Meter LED's from the 5v supply on the board that is meant for the relays?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on February 04, 2013, 05:35:02 AM
have other people taken the 5v for their VU Meter LED's from the 5v supply on the board that is meant for the relays?
yes, I do - with no problems (and I have light bulbs in the meters, your 20mA LEDs shouldn't be any problem)
do you have a proper heatsink on the 5V regulator?
Title: Re: D-LA2A Support Thread
Post by: g9builder on February 04, 2013, 05:36:59 AM
Hi Just finishing my build and I am in the troubleshooting stage!!!

I have a couple of questions/queries the answers to which will hopefully help me to solve the issues I am having.

1. The BYPASS/IN switch - When in the BYPASS mode how should the unit behave.?  I understand the unit should pass audio but does this just bypass the compression stage? Should the VU meter still show the input level and the gain pot still effect input level in the BYPASS mode?

Currently when in BYPASS the unit passes sound and the Gian POT works for input level. The VU meter shows input level BUT the Gain Reduction does nothing.

When I switch to IN I get silence.Nothing works and nothing is shown on the VU meter.

I know people have reported problems with relays being incorrect and I know the fix for this BUT does this sound like this is the problem or does this sound like something else ( possibly wiring ).

I purchased the board fully populated and therefore am unsure exactly what relays were fitted and I don't want to go about desoldering them if the problem lies elsewhere.

Any help geatly appreciated.

Ian 

Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on February 04, 2013, 05:42:41 AM
Ian, is the unit passing sound when not powered up?

While SSLtech does not believe in bypass, the D-LA2A has a "true bypass".
with no power (or not switched to "In") the relays are passing the input XLR to the output XLR,
no signal to the circuit, nothing shown in the meter (neither output/VU nor gain reduction)
Title: Re: D-LA2A Support Thread
Post by: g9builder on February 04, 2013, 07:48:24 AM
Hi,

Thanks for the fast response - no audio passes through the unit when power is turned off. Does this therefore mean the relay is of the incorrect orientation?

Regards

Ian
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on February 04, 2013, 07:54:43 AM
Yes, there is something wrong.
Could you post a foto of the relays?
Title: Re: D-LA2A Support Thread
Post by: g9builder on February 04, 2013, 08:10:08 AM
Yes I will take one later and post it. many thanks - I was pretty sure this was the cause of my problems.  I read earlier in the thread that they simply reversed the power traces to the relay switches and removed the diode and this corrected the problem. Maybe I should try this.

Attached is a pic of the whole board showing the relays (if this helps) i will take a close up later and post also. From memory they are GS5,s


Ian
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on February 04, 2013, 08:24:40 AM
... I read earlier in the thread that they simply reversed the power traces to the relay switches and removed the diode and this corrected the problem. Maybe I should try this.

Attached is a pic of the whole board showing the relays (if this helps) i will take a close up later and post also. From memory they are GS5,s
G5V2 would be right. If it is G6 (polarized) removing the diode and reversing the power traces will work - however: without any power the footprint is the same = unit must pass audio!
Title: Re: D-LA2A Support Thread
Post by: bernbrue on February 04, 2013, 08:45:44 AM
wrong XLR wiring?
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: g9builder on February 04, 2013, 09:05:29 AM
Hi Bernd,

I will check but I don't think so. When the unit is turned on audio passes through fine and the gain and vu meter work correctly (although only when the switch is set to Bypass?)  Surely this wouldn't happen would it if the xlr's where wrong - or am I missing something?

Ian
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on February 04, 2013, 09:09:23 AM
Let us know the exact relay type
Title: Re: D-LA2A Support Thread
Post by: g9builder on February 04, 2013, 02:18:11 PM
Here is the close up of the relay.

It is an Omron G5V-2

Many thanks for the assistance
Title: Re: D-LA2A Support Thread
Post by: jonathanmorbin on February 04, 2013, 03:03:50 PM
have other people taken the 5v for their VU Meter LED's from the 5v supply on the board that is meant for the relays?
yes, I do - with no problems (and I have light bulbs in the meters, your 20mA LEDs shouldn't be any problem)
do you have a proper heatsink on the 5V regulator?

I have this attached to my 5v Regulator however i have not screwed it to the chassis.

http://uk.rs-online.com/web/p/heatsinks/1898094/?searchTerm=189-8094&relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D6265724D504E266C753D656E266D6D3D6D61746368616C6C26706D3D5E5C647B337D5B5C732D2F255C2E2C5D5C647B332C347D2426706F3D313426736E3D592673743D52535F53544F434B5F4E554D424552267573743D3138392D383039342677633D4E4F4E4526

 Should i maybe do this? Could this be a cause of the flickering LED's also?


g9Builder where abouts in the midlands are you? I am in birmingham myself and i recently built one of these units. Would be happy to help out if you live close.
Title: Re: D-LA2A Support Thread
Post by: bernbrue on February 04, 2013, 03:45:26 PM
Here is the close up of the relay.

It is an Omron G5V-2

Many thanks for the assistance

The relay seems to be correct.
Check:

- D3-D6 orientation
- grounding of the 5V psu via jumper next to C8
- wiring from 5V psu molex connector to both relais molex connectors
- orientation of the diodes above the relais

I suppose the 5V grounding could cause the issue.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: g9builder on February 15, 2013, 04:43:49 AM
Found my problem! I swapped the input xlr cable and all now works! There was a problem with the bl**dy cable nothing wrong with the DLA2A!!!

Channel 1 works great - no compression on channel 2 though so need to trouble shoot this now!? Gain knob works and passes audio fine just no gain reduction. Disconnected the stereo link but this did not solve the problem.

Anyway glad i am nearly there - thing is quiet as and channel 1 sound great! Thanks for all the help.
Ian
Title: Re: D-LA2A Support Thread
Post by: jplebre on February 15, 2013, 05:52:32 AM
did you swap the T4B?
Title: Re: D-LA2A Support Thread
Post by: g9builder on February 15, 2013, 06:17:55 AM
No not yet shall try this tonight and also tubes. Ran out of time last night!!
Title: Re: D-LA2A Support Thread
Post by: desol on February 15, 2013, 04:12:18 PM
I think it's safe to say 80% of the problems people have with this build are wiring related.  :o
Title: Re: D-LA2A Support Thread
Post by: Cashp on February 15, 2013, 07:10:33 PM
Could someone tell me exactly where the six mini toggle switches 3-SPDT & 3-DPDT (BOM lines 64 & 65) go and what they are supposed to do?

THanks a bunch!
-= Cash
Title: Re: D-LA2A Support Thread
Post by: Cashp on February 15, 2013, 07:52:24 PM
One more stupid question... I can only find seven switches on the BOM... the six between the two large Gain pots, and the On/Off switch.  I can't seem to see where the Dual/LINK switch is specified.  Can someone tell me exactly what the specifications are for it... and perhaps a source.

Thanks in advance for your help!
-= Cash
Title: Re: D-LA2A Support Thread
Post by: jplebre on February 16, 2013, 09:19:44 AM
Cash the link is a SPST. Only one wire goes to the switch from each channel.

I highly recommend you donwload the pdf on the first page compiled by a forumite as it has a great diagram on wiring possibilities
Title: Re: D-LA2A Support Thread
Post by: Citrus Hill on February 17, 2013, 09:44:01 PM
soooooo...  i have finally saved up enough money for iron for my D-LA2A.  I've decided to go with Sowter, but i need some advice on the different models.  All of these are listed on their site as usable in an LA2A.

1009 = input transformer -  1:9.1,   600/50k,   "f" Mumetal - Mumetal can  UTC A10 replacement - can type
4383 = input transformer - 1:4  600/10k - Can type

8940 = Output transformer - 5K/600 Line output Ratio 3:1  5k/600 ohms
1290 = Output transformer - 15K/600 Line output Ratio 5:1  15k/600 ohms UTC A24 replacement - can type
1010 =Output Transformer - Teletronix LA-2A 1968 15K/600 Line output Ratio 5:1. 15k/600 ohms UTC A24 replacement - open type

I have a BOM that says to use 4383 and 8940, but i'm thinking that the orig replacements would be more accurate to the original's sound.  I see the differences in impedances and ratios, and i've read the thread a few times, but I'm learning about all this stuff as i go, and i don't have a ton of money to experiment with.  Just looking for a little advice.
Thanks for your help, and hopefully i'll understand more after i get through a few of these projects.
Title: Re: D-LA2A Support Thread
Post by: desol on February 18, 2013, 09:42:27 AM
If it were me, i'd probably go with the Sowter 1009 inputs and the Edcor XSM outputs to save on $!

http://www.edcorusa.com/p/164/xsm15k-600

I used Edcors in and out on my build and they sound good...but the Sowter inputs would be better with the mu metal cans, etc. When i looked at the output on my build with an analyzer...i could see a tiny bit of noise down in the 50/60hz region...although you can't hear it (in certain cases, i think you can, just barely...if you crank the makeup and the unit is in a rack with toroids above/below)...and i attributed it to the fact that the edcor inputs aren't shielded.

I haven't used the unit in a little while, so i have a hard time remembering...but i am still considering swapping to better inputs.
Title: Re: D-LA2A Support Thread
Post by: jplebre on February 18, 2013, 10:48:54 AM
Desol, I got the WSM (or is it xsm? the one with smaller wattage rating) as my pair of I/O trafos.
If you do change to sowters, can you please do a couple of samples before and after (different material, driven harder?)

Very interested in hearing the difference :) I fill I'm barely beginning to scratch the surface when it comes to trafos.
Title: Re: D-LA2A Support Thread
Post by: desol on February 19, 2013, 12:04:29 AM
Sure...if/when i do it...i'll certainly try to remember. I just like inputs that are shielded well, to reduce any noise being fed into the front end of the unit.

Title: Re: D-LA2A Support Thread
Post by: g9builder on February 22, 2013, 10:06:17 AM
I think it's safe to say 80% of the problems people have with this build are wiring related.  :o

I think you might be right there Desol. :-) Both channels are now compressing nicely on my unit after finding a wiring fault. Just carn't get channel 2's VU to work properly. Checked the wiring on this though and all ok  ???
Title: Re: D-LA2A Support Thread
Post by: rooster21 on March 02, 2013, 06:15:18 PM
Interested in this project, but i'm wondering if the only source for T4B cells are from studioelectronics, since Drip doens't seem to be producing them anymore..

Anyone build this recently, and source T4B's from anywhere else?

Thanks
GdS
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on March 02, 2013, 06:30:04 PM
Drip still sells them.  Just email him. I think he may have a hundred in stock.  That's what I was told a few days ago.
Title: Re: D-LA2A Support Thread
Post by: desol on March 03, 2013, 12:12:18 AM
Kenetek as well...although i don't know his current situation.
Title: Re: D-LA2A Support Thread
Post by: jplebre on March 03, 2013, 06:29:43 AM
I'll try and power on the T4B I made with the EL panels from Frank at eletrochronic this weekend on next weeken and will let you know
you can build the 2 T4b for a third of a price of one T4B if it works correctly :P
Title: Re: D-LA2A Support Thread
Post by: delaymix on March 09, 2013, 01:08:15 PM
Hi, I'm building this compressor, but I'm having some problems.

In the left channel I have some oscillation when the input level is at maximum.
I changed the tubes by other different and I have also changed the tubes from one channel to another and the problem remains the same.
The right channel works perfectly, no noise, no vibrations, everything works fine (this channel is the one that is physically closer to the power transformer). I think the first tube circuit is overly sensitive to gain, so I'm trying to solve this, but do not know how to deal with this problem. All voltages are correct, all the pieces are well. Any idea how can solve this problem?

Another thing that worries me a lot is that the input level control responds too quickly, meaning that just give a little input gain almost to the very high signal level. If anyone has any suggestions are welcome. Thanks.
Title: Re: D-LA2A Support Thread
Post by: desol on March 09, 2013, 01:15:19 PM
There's a few different solutions for the high makeup gain throughout the thread. As far as the oscillations, how are the transformers placed in the enclosure?
Title: Re: D-LA2A Support Thread
Post by: Biasrocks on March 09, 2013, 01:36:16 PM
In the left channel I have some oscillation when the input level is at maximum.

The right channel works perfectly, no noise, no vibrations, everything works fine (this channel is the one that is physically closer to the power transformer). I think the first tube circuit is overly sensitive to gain, so I'm trying to solve this, but do not know how to deal with this problem. All voltages are correct, all the pieces are well. Any idea how can solve this problem?

Another thing that worries me a lot is that the input level control responds too quickly, meaning that just give a little input gain almost to the very high signal level. If anyone has any suggestions are welcome. Thanks.

Easy, don't turn it up more than you need to.

You can pad the input.

When I have the input padded on my stock LA2A the gain rarely goes beyond the half way point for line level sources, without the pad you don't get past 1/4 up.

Regards,
Mark
Title: Re: D-LA2A Support Thread
Post by: delaymix on March 09, 2013, 02:03:09 PM
I have read the thread about seventeen times ... but I have not found anything like that, so I will have to read again ...

As am using Sowter transformers 4383 for input and 8940 for the output. I think they are reasonably well placed in the back of the box, but I tried to get them out of the case and the oscillation problem persists with the input level to the maximum in the left channel.

Quote from: Biasrocks

Easy, don't turn it up more than you need to.

You can pad the input.

When I have the input padded on my stock LA2A the gain rarely goes beyond the half way point for line level sources, without the pad you don't get past 1/4 up.

I appreciate the answer, but wanted to be more empirical. The right channel is working properly. There no oscillation. I understand that I will not introduce a signal with a high input level as ever, but I like to get the best technical conditions for the two channels, without noise or oscillation, even with the input level to full.

In another vein, I've never worked with a LA-2A original so I do not know always whether to use an attenuator at the input to process line signals. Do you want to say that this is one of the solutions to obtain a more reasonable way in the input level pot? Thanks again for your help.
Title: Re: D-LA2A Support Thread
Post by: desol on March 09, 2013, 10:25:07 PM
Look for the 'gain mod' in the thread with the search. There's 2 or 3 different approaches.
Maybe Kingston will chime in with some advice.

I used the 25k/75k change and the 12ay7 on 1st stage...(with adjusted plate resistors).
I seem to get quite a bit more swing on the makeup.
Title: Re: D-LA2A Support Thread
Post by: jplebre on March 18, 2013, 07:05:22 PM
stupid question of the day - I'm having trouble controlling the meter on O/p
And I just went back to the schemo and can't find R24 (3.3k) on the PCB.

Do I need to add this out of the board?

If so, do I add it so both O/p and GR signals go through it on the negative side, or only O/p?

Thanks
Title: Re: D-LA2A Support Thread
Post by: delaymix on March 19, 2013, 05:58:27 PM
R24 can be seen in the original scheme whose value is indicated as 3K9. Obviously this mounted outside pcb, the circuit in series with the meter.
Title: Re: D-LA2A Support Thread
Post by: jplebre on March 19, 2013, 06:10:42 PM
Yeah I was about to post that I found a 2010 post saying External resistor for Rx24:)
That will explain why I had mismatching in gain reading

Any reports from ppl that swapped from edcor 600:16k (i/p) to the sowters 1009 "La2a replacement) or sowter 4383?
Did it colour the sound in any way or saturate or help with the gain? (eg. bring +4dBu from "10" to something more manageable like 20? :D

I don't want to do the mod just yet as I want to use it as a preamp. I've heard some cool stuff done this way.

EDIT: stupid sentence structure that didn't make sense to myself.
Title: Re: D-LA2A Support Thread
Post by: chris77 on March 21, 2013, 07:13:58 AM
Hey folks,

Quick question regarding stereo link ,up untill now i have been using the D-La2a for mono ,when linked do i use one or both peak reduction pots ?


cheers
Title: Re: D-LA2A Support Thread
Post by: jplebre on March 21, 2013, 07:34:26 AM
both. You need to match them

But the calibration procedure is done with only one peak reduction knob - left channel.
Title: Re: D-LA2A Support Thread
Post by: audiophreak on March 26, 2013, 04:57:33 PM
ok ... I know this is soooo simple and i may be wayy over thinking this .. but ,

" Somewhere in there will be a setting which makes the meter agree when switching between GR and +4, after setting a tone to 0VU output in +4 mode with no GR present. Increase the GR and set it so that it matches at around -5dB (5dB gain reduction). It will be maybe a little off at -3dB, maybe a little off at -8dB... a little off all over the scale, but I find that matching the meter at-5dB is usually an excellent compromise." 

  Am I just doing this with the front panel control knobs ??   where & when am I actually adjusting R25 ???   

  just cant figure out the steps ..,.  :'(
Title: Re: D-LA2A Support Thread
Post by: jplebre on March 26, 2013, 05:21:06 PM
Hey

Yes you use the front panel. Inject a +4dBu signal and set the gain so you get 0vu (+4dBu=0vu). No peak reduction.
swap to GR, adjust "zero adjust" for 0vu. raise peak until you read 3dB or 5dB of reduction (depending on your meter - as it said 5dB is usually a good compromise) and swap it back to 0vu and see if it matches (signal should have gone down as well.

If they are not matching, replace R25, turn peak reduction off, start over: zero adjust for 0vu in GR mode, raise peak reduction until you read 5dB compression, check o/p to see if it matches.

Just leave the gain static and just play with Peak reduction at each step.

set gain w meter on VU (o/p +4) then:
Zero adjust (meter=gr) with no peak reduction > Peak reduction until GR=-5dB > check o/p for consistency > adjust R25 > repeat
Title: Re: D-LA2A Support Thread
Post by: audiophreak on March 26, 2013, 06:31:05 PM
Thanks jplebre !! 

    just finished calibration  ;D ;D ;D   , stereo adjust tomorrow - Pix to come soon  ;D ;D ;D

Title: Re: D-LA2A Support Thread
Post by: audiophreak on March 27, 2013, 04:40:57 PM
Hi All,
        Well.. after two years I finally finished my D-LA2A ... and it sounds WONDERFUL !!!!!    :)

    Its kind of a "Russian" D-LA2A  ala Kingston style with some Russian PIO caps. Tele ECC83's , GE 6AQ5A's and RCA 12BH7A's , Sowter I/O transformers , Rondo PT, Kenetek T4B's  and of course [silent:arts] beautifully done PCB.

  Thanks to [silent:arts] , Kingston,  jplebre and all who post and make these wonderful projects available ... and the people that trouble shoot them with/for people like me.

    ... I have learned so much ... and have so much more to learn ...

 Thanks everyone !!

EDIT :    I used SS over braid on the mains wiring to the power switch on the front panel connected to the star ground as another member did for the "Kingston-duct"  ;D   

... here is a link to more pix  - https://goo.gl/photos/hHc82KsZmSgu3i1c6

ps.  noticed that the 6AQ5a's get REAL HOT  - and the Lytic caps next to them are getting hot from the tubes, not sure if this is something I should be concerned about, just thought I'd mention it... maybe a tube heat sink of sorts ?? 
Title: Re: D-LA2A Support Thread
Post by: Uhl on March 31, 2013, 11:48:08 AM
Hi,

I have just finished my LA2A and while measuring for shorts I noticed that I had a short in the HV rail at one side. I always can measure 0 Ohm between C171/C172 and ground. So I was thinking, maybe it is a bad cap. So i took them out and still I'm getting 0 Ohm. It also doesn't matter if tubes are installed or not. I have the white boards. Has anybody experienced something like this? Is there something I have missed?

Thanks
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 31, 2013, 01:26:38 PM
On both sides?
No problems reported yet with any board.

Check your Multimeter Batteries!
Title: Re: D-LA2A Support Thread
Post by: Uhl on March 31, 2013, 01:56:00 PM
No just on one side. The other side is working fine. I just powered it up, secondary voltages seem fine but one this side no voltage read and after 2-3 seconds it smells like a short to ground.
I'm a bit confused, what could it be if not the caps?
Title: Re: D-LA2A Support Thread
Post by: Uhl on April 01, 2013, 05:16:14 AM
Ah stupid. I have found it :) R136 had just a small connection to R135. Now it seems to be fine. Voltages are okay. I have to make the 5V connection to the VU meters and then calibration time.
Title: Re: D-LA2A Support Thread
Post by: rob_gould on April 14, 2013, 08:32:15 AM

Hi Silent Arts,

I have a load of this single strand wire which of course twists together and holds its shape beautifully which I'd like to use for the heater wiring...

http://www.rapidonline.com/Cables-Connectors/Rapid-Equipment-Wire-Single-Core-1-0-6-Red-Reel-of-100m-01-0335

It's rated 1kV RMS @ 1.8A.  is this underrated for the heater circuit?  I've seen 2A noted as the max current for this circuit elsewhere in the thread, but of course the voltage of 6.3V is very low compared to the high voltage rating of my wire...

Cheers

Rob
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 14, 2013, 09:01:46 AM
Rob, I'm not an expert with this, but I would use it with no doubt.
Title: Re: D-LA2A Support Thread
Post by: rob_gould on April 14, 2013, 12:06:41 PM

Thanks!
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 08, 2013, 10:39:47 AM
Anyone have 4 x 1N4141 switching diodes spare ??

Missing from my parts order for this :-(

Would be a great help, I can pay or swop something ?

Cheers,
Martin.
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on May 08, 2013, 01:55:02 PM
Anyone have 4 x 1N4141 switching diodes spare ??

The BOMs I have say that you can use standard 1N4148 for these.
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 09, 2013, 05:17:01 AM
Anyone have 4 x 1N4141 switching diodes spare ??

The BOMs I have say that you can use standard 1N4148 for these.

Ah, OK when I looked them up in the data sheet they were like a BIG 1N4007, 100v 3watt !!

I have hundreds of 1N4148, perhaps they are used in the bypass relay board then.

I just screwed up by ordering loads of parts that I have already from 3 years ago !  DUH !
Will have to use them on an additional single La2a, or sell them on.

That's what happens when you move house and have stuff buried in boxes !

M.
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on May 09, 2013, 06:06:07 AM
D101, D102, D201, D202 are 1N4148
D1 to D6 are 1N4007
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 13, 2013, 10:35:23 AM
Is this Omron G5V-2 relay correct ?

Thanks, Marty.

(http://www.pbase.com/image/150173171.jpg)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 13, 2013, 11:46:22 AM
Marty, looks cool  8)

(well, looks like 6V? should still work)
Title: Re: D-LA2A Support Thread
Post by: bernbrue on May 13, 2013, 11:56:14 AM
ho, ho, Marty is just back an already infected !! 8)
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 14, 2013, 04:30:53 AM
ho, ho, Marty is just back an already infected !! 8)
regards
Bernd

I know, I went from "Zero to Hero" in about 5 days !!!!

No, just trying to sort through parts, find what I have and what I don't have, just found that i repeated my
Farnell order for the DLA2A !   ... now have almost enough parts for 2 x !!

Well, many things can be used else where so it was only about a €40 mistake.

Thanks Bernd & Volker for the continuing friendly help :-)
You ROCK.
M.
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 14, 2013, 04:43:08 AM
Marty, looks cool  8)

(well, looks like 6V? should still work)

Just a "Blur" in the photo, they are indeed 5V  :-)
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 14, 2013, 05:54:48 AM
OK, struggling with my German and the RS site for Molex KK, which I know nothing about !

Found the 2,54mm headers in 2 and 3 pole  ... good

Have choice of either "Crimpgehause" OR "Ansclussgehause" for the 2/3 pole connectors to the leads ??

Which is correct/best and what is the name of the "crimp pins" that are needed ... is that all ?

I thought that I saw 5 pole and 8 pole headers on the drawing as well next to the traffo's!!

I wish these companies would offer header/ top / pins all together, why separate them ??

THX, Marty.
Title: Re: D-LA2A Support Thread
Post by: Kingston on May 14, 2013, 05:59:16 AM
I've found it a bit difficult to shop for the right ones, too. Until I found futurlec, they only have the bare essentials and very cheap.

Here's your one stop link: http://www.futurlec.com/ConnPolHead.shtml
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 14, 2013, 06:05:33 AM
I've found it a bit difficult to shop for the right ones, too. Until I found futurlec, they only have the bare essentials and very cheap.

Here's your one stop link: http://www.futurlec.com/ConnPolHead.shtml

OK, I'm with you but that's from the US of A and I have an RS account with free delivery.
Does that mean that I need a HUGE order or suffer some massive postal fees that make it a "no no" ?
( your experience required )
RS are 4 x as much in cost BTW !!

Oh and any idea on the AC connections, 3.92mm or 5mm ?
M.
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 14, 2013, 06:09:31 AM
OK, found EU ship rate is reasonable and there's no minimum order :-)
M
Title: Re: D-LA2A Support Thread
Post by: bernbrue on May 14, 2013, 06:35:22 AM
Hi Marty,
I bought these. Quite cheap and ready to go.
http://www.musikding.de/Wire/PCB-connectors:::163_158.html
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: Kingston on May 14, 2013, 06:37:00 AM
OK, found EU ship rate is reasonable and there's no minimum order :-)
M

Indeed. They are Hong Kong based if I remember right, lot's of other handy stuff they got too, usually significantly cheaper than elsewhere.

[edit]

Oh and any idea on the AC connections, 3.92mm or 5mm ?

http://www.futurlec.com/ConnTerm.shtml
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 14, 2013, 07:04:30 AM

Indeed. They are Hong Kong based if I remember right, lot's of other handy stuff they got too, usually significantly cheaper than elsewhere.

http://www.futurlec.com/ConnTerm.shtml

Thanks Michael, got 'em , done , ordered several types for a couple of other projects while I was there.
Some pots also, 28 bucks and 4 postage :-)
Quick calculation and RS was just over twice the cost !! WTF.

Thanks all for chipping in, now I have 100 molex connections to trim, crimp and solder !!!! :-(

( that's the part where I would pay someone else to do it !! )
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 14, 2013, 07:08:12 AM
Hi Marty,
I bought these. Quite cheap and ready to go.
http://www.musikding.de/Wire/PCB-connectors:::163_158.html
regards
Bernd

AH .... BUM, would have gone for that, pre-wired that is pretty cheap !!

I might try a few and see how they are, any problems with 'em ??

Thanks B.
Title: Re: D-LA2A Support Thread
Post by: jplebre on May 14, 2013, 07:32:37 AM
Holy crap goldmine! that's a good few hours saved!!

J
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 14, 2013, 07:45:22 AM
I ordered the prewired 2 pole / 3 pole and a few more besides.
That really saves some VERY boring wire-up time on Molex .... hate that stuff !!

Got the octal sockets and the small .022 solen fast caps too.

Thanks Bernd, you are a star :-)
Title: Re: D-LA2A Support Thread
Post by: Kingston on May 14, 2013, 03:32:26 PM
Now if only someone would come up with reliable replacement to all things Molex KK standard. Crimping tool or not my success rate is 9/10 good crimps at best, which is nowhere near reliable enough or even adequate. :(

I hate them with a vengeance. Of all things soldering and build related, they have caused me most grief.  >:(
Title: Re: D-LA2A Support Thread
Post by: jplebre on May 14, 2013, 03:34:38 PM
@kingston could it be your crimp tool? :)

I still apply a blob of solder afterwards just to be extra sure.
Title: Re: D-LA2A Support Thread
Post by: Kingston on May 14, 2013, 03:37:39 PM
I still apply a blob of solder afterwards just to be extra sure.

Me too.

I like the idea of prewired Molex KK. Unfortunately they don't cater for the common shielded cable scenarios, or thicker wire for more amps and/or less wire resistance.
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 14, 2013, 04:04:11 PM
I still apply a blob of solder afterwards just to be extra sure.

Me too.

I like the idea of prewired Molex KK. Unfortunately they don't cater for the common shielded cable scenarios, or thicker wire for more amps and/or less wire resistance.

Yes, that did cross my mind too, still for some duties it will be great, will still wire I/O with my shielded
cable, but it may well mean 40 + crimps I can avoid !
My vote goes for "screw terminal" though it takes up a little more space, tin leads - test = lock with nail polish.

Marty.
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on May 14, 2013, 05:14:18 PM
Crimping tool or not my success rate is 9/10 good crimps at best

What kind of wires do you use? 0.25 mm²?
Title: Re: D-LA2A Support Thread
Post by: Kingston on May 16, 2013, 02:12:21 PM
Crimping tool or not my success rate is 9/10 good crimps at best

What kind of wires do you use? 0.25 mm²?

Various sizes, but mostly the standard 0,22mm2 hookup wire. 0,5mm2 seem to give more grief, don't think the crimps are designed for that, even if the connector amp rating is.
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 17, 2013, 05:17:05 AM
Yup, my hookup wire is 2.0mm and I also add a tiny dab of solder to crimps.
They just take SOOO much time to do, which I don't have enough of.

BTW - the pre-crimped leads arrived and they seem pretty good. ( plastic housing is cheap though )
Will test 'em before installing though, just to make sure that i don't lose my mind chasing faults !!

MM.
Title: Re: D-LA2A Support Thread
Post by: baadc0de on May 21, 2013, 03:45:55 AM
Guys

any idea why my DLA2A is only stable with C14 bumped up to 22nF? Grid stoppers installed, shielded cable throughout. Anything below 4nF oscillates like crazy when you push "reduction" and "makeup". Tried with 12ax7 stock, then 100k plate resistors, then 6072A (love this sound). With 22nF it sounds "OK" and compresses well at first glance, but I thought to pick your brains on this if you have an inkling. If nothing else, what to check?
Title: Re: D-LA2A Support Thread
Post by: jplebre on May 21, 2013, 05:47:00 AM
Quote
Anything below 4nF oscillates like crazy when you push "reduction" and "makeup".
you have oscillation when you do reduction as well or just make up?

Where are your transformers (eg. near the XLRs) someone had issues with this and moving the transformers helped.
Title: Re: D-LA2A Support Thread
Post by: baadc0de on May 21, 2013, 08:51:26 AM
Quote
Anything below 4nF oscillates like crazy when you push "reduction" and "makeup".
you have oscillation when you do reduction as well or just make up?

Where are your transformers (eg. near the XLRs) someone had issues with this and moving the transformers helped.

If you push just makeup, there is no oscillation, even if you up the reduction quite a bit. Just reduction also does not oscillate, but push reduction to anything above about 1/2 and it will oscillate if there is at least some makup applied (not zero).

transformers are not that close to XLRs, are shielded UTCs and have shielded wire going to them. Any ideas mates?
Title: Re: D-LA2A Support Thread
Post by: jplebre on May 21, 2013, 10:06:43 AM
does it happen without the T4B installed?
Title: Re: D-LA2A Support Thread
Post by: baadc0de on May 21, 2013, 10:09:38 AM
does it happen without the T4B installed?

Nope, no oscillation with T4b pulled. I have several to choose from and they are all exhibiting this behavior, so it must be the compressor not the T4b.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on May 21, 2013, 10:13:26 AM
Nope, no oscillation with T4b pulled. I have several to choose from and they are all exhibiting this behavior, so it must be the compressor not the T4b.

Must be in the sidechain ...
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 27, 2013, 04:42:54 AM
Have just started the project :-)

Will take a while, as I do it whenever I have a few spare hours.

Mistake No 1 : ( and hopefully my last )

Fitted a 2,200uf cap at the 25v rail rather than a 3,300uf as spec'd !

It doesn't want to come off so I stopped before I kill the part & board !

Any issue with this? or should I dremel it off, remove the leads and fit the 3,300uf?
( possible but may mark to board a little )

Cheers,
Marty.
Title: Re: D-LA2A Support Thread
Post by: bernbrue on May 27, 2013, 04:50:32 AM
Hi Marty,
leave the cap where it is. It won´t hurt.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: MartyMart on May 27, 2013, 05:50:43 AM
Hi Marty,
leave the cap where it is. It won´t hurt.
regards
Bernd

Thanks Bernd = you're a star :-)
Was just worried about "ripple" but I have space to "tack on" a 1uf poly or something if need be.

Marty.
Title: Re: D-LA2A Support Thread
Post by: bernbrue on May 27, 2013, 05:53:08 AM
Hi,
the 5V rail is just for the relays and other stuff, it´s not in the audio path. The 2200uF will do the job fine.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: jonathanmorbin on June 06, 2013, 05:55:49 AM
Hi,

I posted a while back about my VU meter LED's Flickering/not turning on. I really dont know what could be causing this, I have tried new LED's, new VU meters. i have since built another D-LA2A and it has just happend to this unit. One VU now does not light up. all the flickering LED's I have still flicker when i try them in the new unit.

I am using Hairball Audio 8020 meter. I know that other people have used these meters fine with no flickering or anything. Can any body assist me? My second unit has all screened cabling inside.

http://www.hairballaudio.com/shop/product_info.php?cPath=25&products_id=86
Title: Re: D-LA2A Support Thread
Post by: Harpo on June 06, 2013, 07:11:59 AM
I posted a while back about my VU meter LED's Flickering/not turning on...
I am using Hairball Audio 8020 meter.
Two (maybe white, different colour has different parameters) LEDs connected in series, so double forward voltage drop at same current for your meter illumination.
These LEDs come with a max.allowed Ifwd of maybe 20mA that you don't want to exceed.
What is your raw DC voltage in front of the 7805 voltage regulator (regulators left side pin 1 or +side of C5, from where you pick your voltage feed for this LED string with current limiting resistor in between) in respect to  its reference voltage at PL2-2 ? ([this measured raw DC voltage] - 2* Vfwd for your two series connected LEDs) / maybe 10mA LED current that you decided to allow to not exceed parts limits and not to build a headlight = value of current limiting resistor needed. For example (9V - 2*3.4V)/0.01A=220ohm.
Title: Re: D-LA2A Support Thread
Post by: jonathanmorbin on June 06, 2013, 01:28:20 PM
on pin 1 of the 7805 i have 11.55 and at pl2-2 i have 4.94v. i take my 5v for the LED's from PL2-2. do you think i need to put acurrent limiting resistor in? the LED's are 2 in series and on the VU itself it labels it as 3.6-5.2v 20mA.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 06, 2013, 02:18:52 PM
do you think i need to put acurrent limiting resistor in?
yes!
Title: Re: D-LA2A Support Thread
Post by: jonathanmorbin on June 06, 2013, 03:07:19 PM
you'll have to excuse me but what value do you recommend i put in? what would my workings out be?
Title: Re: D-LA2A Support Thread
Post by: Harpo on June 06, 2013, 04:04:44 PM
you'll have to excuse me but what value do you recommend i put in? what would my workings out be?
Maybe reread my last reply?
Your 'on pin 1 of the 7805 i have 11.55 and at pl2-2 i have 4.94v' doesn't make sense.
When you measure between pin 1 of the 7805 (multimeters red probe wire) and pl2-2 (black probe wire), multimeter set for reading DC voltage, the multimeter will show a single voltage readout.
pl2-2 is the reference voltage for your +5V rail that has NOTHING to do with your audio reference voltage or ground.
If this readout would be 11.55V, current limiting resistor value would be (11.55V - 5.2V)/0.01A = X ohm. You do the math.
Title: Re: D-LA2A Support Thread
Post by: jonathanmorbin on June 06, 2013, 06:09:31 PM
Thanks for your help, i miss read your first post so got confused. all is ok now and working correctly.
Title: Re: D-LA2A Support Thread
Post by: Harpo on June 07, 2013, 04:52:03 AM
Thanks for your help, i miss read your first post so got confused. all is ok now and working correctly.
Thumbs up.

It would be helpful if you could measure and post the DC voltage between both meter illumination terminals and the colour of illumination for this type of meter, Mike at hairball is selling.

These Nissei meters come in various illumination colours. Depending on LEDs type and colour or even a colour mix used, this forward voltage differs a lot (red between 1.8-2.1V, blue 3.3-3.6V, ... per LED), hence the 'on the VU itself it labels it as 3.6-5.2v 20mA' for an all avail.colours universal housing.
Title: Re: D-LA2A Support Thread
Post by: mrdarwin on June 29, 2013, 03:59:31 AM
Hi!
I'm looking for informations and wiring guide about D-La2a.
I tried the links on the first page of the thread, but they redirect me to nrg forum, I tried to register me but never received confirmation... so I can't read the documents... Any idea? If someone has information...
Thanx
Title: Re: D-LA2A Support Thread
Post by: rob_gould on June 29, 2013, 04:02:38 AM
This should do the trick for you :

Quote
compiled informations from this thread in a single PDF by sonicwarrior
Title: Re: D-LA2A Support Thread
Post by: mrdarwin on June 29, 2013, 05:00:53 AM
This should do the trick for you :

Quote
compiled informations from this thread in a single PDF by sonicwarrior

Thanx! I saw this post... but where is the pdf???
Title: Re: D-LA2A Support Thread
Post by: rob_gould on June 29, 2013, 05:04:05 AM
Clicking that link takes you to sonicwarrior's post. The document is attached to his post. You should be able to see it just below it.
Title: Re: D-LA2A Support Thread
Post by: mrdarwin on June 29, 2013, 11:59:24 AM
Clicking that link takes you to sonicwarrior's post. The document is attached to his post. You should be able to see it just below it.
Thank you...and shame on me!!!!!
Each time i looked at this post i was logged off... so the link didnt appear...
Log in, and miracle link is here!
Title: Re: D-LA2A Support Thread
Post by: mrdarwin on September 02, 2013, 10:28:29 AM
Hi!
I finished my D-La2a.
It works perfect, calibrated etc... :)
I have two questions:

Here is a capture ofmy la2a's  frequency response:
(http://studioevolution.free.fr/la2a.jpg)
There's something like a low cut at 50Hz...  Is it because the tubes or the xformers???
I use Edcor xformer, Mullard 6bq5 and 12ax7(2), Electro Harmonix 12BH7 and Tung sol 12ax7(2).
Edcor WSM frequency response is: 20~20K Hz., <1dBu (datasheet)... I tried to swap the tubes, same result, identical on each channel.
any idea???

Later, I wish to improve this machine... but what first???:
more matched and expensive tubes?
sowter input or output?

thanx for reply
Title: Re: D-LA2A Support Thread
Post by: jplebre on September 02, 2013, 10:39:57 AM
IIRC this was discussed already on this post or on the LA2A post.
again, IIRC, you can tweak this with a zobel network.

But for the calculation, your HPF is at 30Hz (the frequency is given by the point where a 3dB attenuation has been achieved) not at 50Hz
Title: Re: D-LA2A Support Thread
Post by: mrdarwin on September 02, 2013, 12:20:46 PM
IIRC this was discussed already on this post or on the LA2A post.
again, IIRC, you can tweak this with a zobel network.

But for the calculation, your HPF is at 30Hz (the frequency is given by the point where a 3dB attenuation has been achieved) not at 50Hz

Thanx
Ok, I'll do some research about "zobel network"...
Title: Re: D-LA2A Support Thread
Post by: mrdarwin on September 04, 2013, 03:11:22 AM
So...
I found informations about zobel network on the net. I read differents posts on this thread.
But I can't find what I have to do exactly... continue searching
Title: Re: D-LA2A Support Thread
Post by: jplebre on September 04, 2013, 05:27:03 AM
http://www.groupdiy.com/index.php?topic=26119.0

I think this was the thread I read when building mine
Title: Re: D-LA2A Support Thread
Post by: bernbrue on September 19, 2013, 11:33:19 AM
Hi,
I would like to report my findings concerning oscillation. My input transformer is the original Sowter 1:4, Output is Edcor 10K/10K. I did the 25K pot 75K resistor mod for the input gain.

Background: My unit worked fine from the very beginning, except for the annoying 30kHz oscillation with higher gain settings causing meter pegging. I moved the output transformer farer away from the board and the xlr connectors which helped a bit. I consequently used moderate gain setting so that unity gain was almost achieved.

Today I tried various ideas to eleminate oscillation. I realized that the area around V1 and R11 (68K Feedback) is very touchy and that even moving my hand around V1 reduced oscillation a bit. CJ proposed to change the value of R11 in order to reduce negative feedback and gain. I finally put a 14K resistor in parallel to the existing 68K. That helped quite a lot but I still couldn´t crank up the gain to maximum without meter pegging.

Then I had a real "heureka" experience. The shielded wires for the gain reduction pot and gain pot were connected wrong, well not wrong but the shield was conducting signal and a red wire was meant to work as shield. What a silly mistake!!!! I rewired it and now I can set the gain pot to maximum without any oscillation at all. I measured the compressor with RMAA and the specs are more than convincing. With the paralleled negative Feedback resistor THD is 0,382 %. Not that bad. All other values including absolutely flat frequency response are excellent. I´m more than happy now with my Dual LA2a!!

People having these problems as well: CHECK YOUR WIRING (verify that shield is connected to ground!!!) and REDUCE FEEDBACK RESISTOR.


regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: desol on September 19, 2013, 08:10:35 PM
Nice work!

I've mentioned this and read it from many others as well. This build is extremely sensitive to wiring!

I had my freq response pot turned the wrong way for a while.  :o When I actually adjusted it properly, to flat...the high end and proper compression came back.  ::)


Title: Re: D-LA2A Support Thread
Post by: firfe on September 21, 2013, 03:02:20 AM
Hello .
I m buildind the d-La2a.

I change the neon by a zener

But i have a little question.

The zener is a 62V 5w and the hole is to small in the pcb.

I ve solder a paste of a resistor ( 1/4w) to the zener for put at the N2 emplacement.

It s good idea ? I look the orientation in pdf.

Thank you in advance and sorry for english.
Best
Jf
Title: Re: D-LA2A Support Thread
Post by: desol on September 21, 2013, 12:06:07 PM
5 watt is a bit too big...you could still use it, but then you need to modify it, etc.

1-3 watt would be good.
Title: Re: D-LA2A Support Thread
Post by: firfe on September 21, 2013, 02:57:01 PM
thank you for the reply.
i think my solver work in this case.
i would just to be sur that not a bd idea.
next step...the wiring.
the pcb is just perfect...
Title: Re: D-LA2A Support Thread
Post by: salomonander on December 04, 2013, 01:59:16 PM
hey
id like to use some big 10uf pio caps for c105 and c205. most come in 400v though. is this sufficient for this build? the ones in the bom are rated 450v. cheers
Title: Re: D-LA2A Support Thread
Post by: firfe on December 19, 2013, 10:10:05 AM
hello
i've a problem with my voltage.
i've a big noise with modulation in the gain pot.
no action for peak red  pot.
the vu looks working but nothing in gr mode.
my voltage are little strange.
i've found -15V diference beetween the good value and mine everywhere on the pcb.
I ve check my resistor...
i use a rondo trafo.
thank you in advance for help.
you can find my voltage in attachment.
Best

JF

Title: Re: D-LA2A Support Thread
Post by: firfe on December 21, 2013, 11:26:25 AM
hi
ok i've check all my resistor again...everything is ok.
but always same voltage problem...if it's a problem i'm not sur.

i've made a mistake when i 've put the tube.
i've exchange one 12AX7 with the 12BH7 .i hope the tube still working.(light is ok).

in the second channel i've the signal ( no strange modulation and noise) but zero gain reduction.
only the gain pot working.
all the other command look inactive.
and my voltage measure are same as the first channel.
i will solver my molex connection.
and have you an issu for check if the T4b work?
sorry about my fantastic english.
best and thank you .
jf


Title: Re: D-LA2A Support Thread
Post by: dipfrik on January 20, 2014, 10:02:01 PM
Just finished my build a few minutes before. But i can't get any compression on the baby? Gain works fine, bypass fine, tubes and NE2 are glowing (checked the heater wiring triple times). If i dial in the peak reduction fully clockwise nothing happend. Maybe a tiny little bit in my imagination ;), but the meter is not moving any mm in GR mode. (both channel acts the same)

Exchanging all tubes and T4B with different ones has no effect.

Any hints were i can start my search?

Thanks, Sven
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 21, 2014, 05:19:40 AM
Play around with RVX03 and RVX04 ...
Title: Re: D-LA2A Support Thread
Post by: dipfrik on January 21, 2014, 05:29:47 AM
Hi Volker,

thanks for 1st quick hints, but we are talking about the "STEREO ADJ" and the "ZERO ADJ" 1M VR's on the board right?
I definitely need to get a better understanding of the whole circuit, but how can these affect the compression (peak reduction) from nothing to "working"? ;)

Many thanks, Sven
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 21, 2014, 05:41:19 AM
Look at the schematic: if RVX03 (STEREO ADJUST) is set to "linksanschlag" it is set to ground = no compression.
The "ZERO ADJ" can be set to show no compression too (even if it does compress).
Sometimes the trimmers need some for and back movements to work / to conduct after long time storage.
Title: Re: D-LA2A Support Thread
Post by: dipfrik on January 21, 2014, 06:02:56 AM
Ok, i will try that later at home. If RVX03 is not linked at all (dual mode with no wires between the molex pins and the switch) it has still an effect on the compression for each channel?

Thanks, Sven
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 21, 2014, 06:15:16 AM
Yes. It is like a second "Peak Reduction" control.
Stell den auf Rechtsanschlag.
Title: Re: D-LA2A Support Thread
Post by: dipfrik on January 21, 2014, 07:37:59 PM
Yes. It is like a second "Peak Reduction" control.
Stell den auf Rechtsanschlag.

Ok, i got my right channel working after a few heavy rotations on all three guys RVX04 - RVX03 and RVX37 and i see and hear a good amount of gain reduction.
Then i checked the left channel again and again but no gain reduction. Maybe a tiny little bit if i crank it all up, but far away from the right channel and again no sign of any movement in GR on the meter.

I tested everything from the left on the right to make shure nothing is damaged on the left channel and also moved the "working" parts from right to left.

- T4Bs both fine in the working right channel
- all tubes fine in the working right channel

(all from the working right channel in the left channel has no effect)

Ok fine or not ;)

I measured the whole pcb on both side, but found at any point identical/very similiar voltages. I also replaced RVX03 and RVX37, because RVX04 is the only one on the left channel, that responded to trimmer movement (needle is moving and i can totally dim out NE2) and works like the one on the right channel. I checked both later and there were fine. I switched all the meter, front panel potententionmeter with no effect.

So what can i do now with my left friend? It's a stereo frontpanel. ;)

Cheers, Sven
Title: Re: D-LA2A Support Thread
Post by: firfe on January 22, 2014, 02:53:23 AM
hello
noboby can't help me...
 :(
Title: Re: D-LA2A Support Thread
Post by: dipfrik on January 22, 2014, 06:38:04 AM
Hey firfe, i would if i could but captured with my own problems ;)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on January 22, 2014, 03:48:08 PM
Sven, if the Cable length does allow it: cross check the peak reduction pot and look if the failure follows.

Mr. Firfe, did you cross check the tubes from left to right?
Title: Re: D-LA2A Support Thread
Post by: dipfrik on January 22, 2014, 07:15:56 PM
"Ohje"… did that the last three hours in any possible combination including all i/o transformers with no luck  :-\ (right = fine, left = no GR)

How should a channel sounds/act if:

(input/output = with transformers in the chain)

a1) only input  is connected - tubes - T4B
b1) only input is connected + tubes - T4B
c1) only input is connected - tubes + T4B
d1) only input is connected + tubes + T4B

a2) only output is connected - tubes - T4B
b2) only output is connected + tubes - T4B
c2) only output is connected - tubes + T4B
d2) only output is connected + tubes + T4B

a3) only input & output is connected - tubes - T4B
b3) only input & output is connected + tubes - T4B
c3) only input & output is connected - tubes + T4B
d3) only input & output is connected + tubes + T4B


e.g. on the working right channel i have in combination a2) massive!!! hum. If i did the same on not working left channel the hum is there but way-way quieter.
Do i need more hum on the left? ;)

OMG..this baby will drive me crazy..i know it ;)

Thanks again for any hints, Sven

PS: after so many successfully built units as "rookie" in in the last 2 month with no problems, Holger told me again and again: "the time will come my son…" yes, now! ;)
Title: Re: D-LA2A Support Thread
Post by: dipfrik on January 22, 2014, 08:03:04 PM
Update: please forget the hum stuff right now. i found out that the heater wiring was not optimal regarding "drilling" and i can get control of the hum on both channel with repositions the wire away from the gain molex connection. So the unit should be dead quit with no audio at the input in all combinations from a1 - d3.
Title: Re: D-LA2A Support Thread
Post by: dipfrik on January 23, 2014, 11:39:07 PM
…another update from my workbench.

I didn't solve the problem, but i completed a second pcb a few minutes before. An exact copy of the "no left GR" 1st problem board.
What should i say? Works like a charme from minute zereo ;)

What is wrong with the 1st board and the GR on the left channel? damn it...

This is not the way how i want to solve problems ;)

Night, Sven
Title: Re: D-LA2A Support Thread
Post by: dipfrik on January 24, 2014, 01:54:11 PM
"all clear" ;)

Ok, it was the heater wiring. I renewed the complete heater wiring on the 1st unit and now the left channel is back and i can start calibrating two units.

Thanks for all the help!

PS: will come back with finished assembled unit
Title: Re: D-LA2A Support Thread
Post by: frazzman on January 25, 2014, 06:34:24 AM
"all clear" ;)

Ok, it was the heater wiring. I renewed the complete heater wiring on the 1st unit and now the left channel is back and i can start calibrating two units.

Thanks for all the help!

PS: will come back with finished assembled unit

That's some epic wiring there!
Title: Re: D-LA2A Support Thread
Post by: desol on January 25, 2014, 08:11:28 PM
I built my unit years ago and I still have not been able to figure out why I'm unable to calibrate it like everyone else.

It seems to work and compress flat with the trimmers all the way to the left. I've looked at it under freq analysis and
the trimmers are mounted according to the silk-screening on the board. I have no idea.

According to the trimmer data sheet (on BOM), it looks like resistance is increased with clockwise rotation?

Title: Re: D-LA2A Support Thread
Post by: Studio Mollan on January 31, 2014, 10:16:45 PM
Yes, R37 is the high-pass filter. Has rather extreme effect on sound so like I said, put it on the front panel.

R11 is the global feedback resistor. LA2A make up gain amp is absolutely swimming in negative feedback with that 68k. It's a very linear amp, complete devoid of any recognizable tube distortion. You won't know it's tubes until someone tells you because the excess feedback removes all distortion.

R11 as a pot is basically an extra gain control. Try 50k in series with a 470k pot maybe. It will give you a lot of extra gain (and control), and you will be able make those 12AX7's sound distorted by removing feedback. But 12AX7 distortion sounds like crap and now you have a stupid amount of gain, so you probably don't want that. Harmonic distortion, yes, but not nice.

Solution: replace 12AX7 with 12AY7. You will lose some gain, but will be able to take it back by removing some of the excess feedback. Now the distortion sounds much better.

and NOW you have a tube amp!

Hi!
I'm going to try this on my la2a clone. The pot instead of the fixed 68k resistor. What taper should the pot have?
Thanks!
/
Emil
Title: Re: D-LA2A Support Thread
Post by: kml23956 on January 31, 2014, 11:10:47 PM
Does anyone have a copy of the US BOM? The link on the first page is dead?
Title: Re: D-LA2A Support Thread
Post by: firfe on February 02, 2014, 08:13:27 AM
Quote
Mr. Firfe, did you cross check the tubes from left to right?


hello
thank for help.
yes i've try to cross check the tube...and i've change all the tube by new one...same probl.

it's looks like the T4B don't work.
but i don't know how to test them.
i'v found some answer in the web but not clear for moment.
i have some freetime again to check my compressor this week .
best
jf
Title: Re: D-LA2A Support Thread
Post by: desol on February 16, 2014, 10:17:07 PM
BOM  is back up?  ;D
 
Title: Re: D-LA2A Support Thread
Post by: frazzman on February 17, 2014, 05:36:14 PM
Sorry to ask this question again... But I just wanted to check on the wiring of the primaries on the RONDO transformer...

With dual primaries - (2x White & 2 x Yellow) - For 230V operation - do I wire one yellow primary to the IEC connector & one white primary to the other side of the IEC connector and then join remaning yellow and white primaries together?

This is the first time i've had a toroid with twin primaries...
Title: Re: D-LA2A Support Thread
Post by: desol on February 18, 2014, 03:12:18 PM
High voltage operation should be in series...low voltage in parallel. So yes, yellow and white to mains, yellow and white joined together.

ie:
Title: Re: D-LA2A Support Thread
Post by: frazzman on February 19, 2014, 07:26:58 AM
High voltage operation should be in series...low voltage in parallel. So yes, yellow and white to mains, yellow and white joined together.

ie:

Thanks for confirming
I browsed through so many peoples build photos but couldn't really make out this detail to confirm my understanding of the 230v wiring, maybe lots of 115v builds
I'm just about ready to put this all together. If I need to crimp one more molex connector I will be insane
Title: Re: D-LA2A Support Thread
Post by: desol on February 19, 2014, 10:04:16 AM
Molex's can be a pain...  :)

- Obviously (just wanted to add) , on that 230v wiring, make sure that the joined yellow and white are from each one of the primaries. Just sayin...
Title: Re: D-LA2A Support Thread
Post by: frazzman on February 19, 2014, 03:44:47 PM
Molex's can be a pain...  :)

- Obviously (just wanted to add) , on that 230v wiring, make sure that the joined yellow and white are from each one of the primaries. Just sayin...

Oh yeah, of course.. You mean because there's a white and yellow/green wire in the secondaries ? The primaries have the black Heatshrink around then which makes them easy to identify. I've built about 4 pultecs in the past but I always find these high voltage circuits nerve-racking on first power up even though I know everything's as it should be, something about a 630v cap that is (and should) keep you on your toes
Title: Re: D-LA2A Support Thread
Post by: desol on February 19, 2014, 04:13:21 PM
Molex's can be a pain...  :)

- Obviously (just wanted to add) , on that 230v wiring, make sure that the joined yellow and white are from each one of the primaries. Just sayin...

Oh yeah, of course.. You mean because there's a white and yellow/green wire in the secondaries ?

No, just that somebody not in the know might tie one primary together (mistakenly) and put 230v across a single primary...  :o
Title: Re: D-LA2A Support Thread
Post by: frazzman on February 19, 2014, 09:44:15 PM
Molex's can be a pain...  :)

- Obviously (just wanted to add) , on that 230v wiring, make sure that the joined yellow and white are from each one of the primaries. Just sayin...

Oh yeah, of course.. You mean because there's a white and yellow/green wire in the secondaries ?

No, just that somebody not in the know might tie one primary together (mistakenly) and put 230v across a single primary...  :o

You mean my mistakenly joining yellow to yellow or white to white ?
Title: Re: D-LA2A Support Thread
Post by: desol on February 20, 2014, 01:08:46 AM
 ;D Yes... I suppose so.

I can't really remember if one is just yellows and one is white's...or if there's a yellow and white on each.. or...
We understand each other...that's the important part.

Title: Re: D-LA2A Support Thread
Post by: frazzman on February 20, 2014, 05:48:00 AM
;D Yes... I suppose so.

I can't really remember if one is just yellows and one is white's...or if there's a yellow and white on each.. or...
We understand each other...that's the important part.

Good good, I just wanted to make sure! There's two pairs of yellow, two pairs of white, each pair has Heatshrink around them. In the builds I've seen, I noticed a lot of people wiring them in parallel but I'm down under so it's 230v all the way. Thanks for your help
Title: n00b question concerning the revisions
Post by: finbase on February 23, 2014, 05:54:35 AM
Helo folks!

I've been trying to find the answer quite eagerly, but couldn't... My apologizes if this is already thoroughly covered.

I'm just wondering that in which la2a revision and production year this Volker's D-la2a/project schematic is based on? My la2a experiences are more or less based on UAD plug-ins, but as far as they're concerned I've found that the Greyface is sonically THE la2a for me. If I've understood it right, UAD's Greyface is emulated after the very first production batch and revision. So that's something I'd like to build also...

So my questions (one already asked..)
-In which revision this Volker's d-la2a is based on?
-If not based on the Greyface (revision 1), is this project easy to "modify" so that the result would be sonically equivalent?

Although I'm still a complete n00b as far as electronics are concerned, and I have a few more beginner-friendly projects on my to-do list first, the thought of building a D-la2a unit is darn obsessing... :) So why not start studying the topic already!

Thanks,
finbase

Title: Re: n00b question concerning the revisions
Post by: frazzman on February 23, 2014, 11:52:02 PM
Helo folks!

I've been trying to find the answer quite eagerly, but couldn't... My apologizes if this is already thoroughly covered.

I'm just wondering that in which la2a revision and production year this Volker's D-la2a/project schematic is based on? My la2a experiences are more or less based on UAD plug-ins, but as far as they're concerned I've found that the Greyface is sonically THE la2a for me. If I've understood it right, UAD's Greyface is emulated after the very first production batch and revision. So that's something I'd like to build also...

So my questions (one already asked..)
-In which revision this Volker's d-la2a is based on?
-If not based on the Greyface (revision 1), is this project easy to "modify" so that the result would be sonically equivalent?

Although I'm still a complete n00b as far as electronics are concerned, and I have a few more beginner-friendly projects on my to-do list first, the thought of building a D-la2a unit is darn obsessing... :) So why not start studying the topic already!

Thanks,
finbase

Hi finbase... it sounds like maybe you're looking at this the wrong way... trying to make hardware that models that sound of the software you like...I don't know what revision LA2A volker's design is from but I'd be willing to tip it sounds more faithful to the original than the UAD plugins do
Title: Re: n00b question concerning the revisions
Post by: finbase on February 24, 2014, 11:08:17 AM
Yes, I know that my question isn't too relevant...

Unfortunately a hobbyist like me don't have the access to all the fantastic hardware. I am a professional musician, but my sound engineering is more or less only a passionate and enjoyable hobby, like this DIYing is starting to be. Nevertheless, I know quite well "tonewise" what I like and what I don't.

So let's put it in other words: what are the main parts on the la2a circuit that affects the unit's "timbre"? Input and output transformers and tubes, of course, but I assume that some particular capacitors in the signal path too? If I want to emphasis the "low mid body" (200-400Hz), what kind of options do I have?

Hopefully my quesiton makes sense to someone. My intention is not to make the others tired with my daydreams...
Title: Re: n00b question concerning the revisions
Post by: finbase on March 01, 2014, 03:26:40 AM
Yes, I know that my question isn't too relevant...

Unfortunately a hobbyist like me don't have the access to all the fantastic hardware. I am a professional musician, but my sound engineering is more or less only a passionate and enjoyable hobby, like this DIYing is starting to be. Nevertheless, I know quite well "tonewise" what I like and what I don't.

So let's put it in other words: what are the main parts on the la2a circuit that affects the unit's "timbre"? Input and output transformers and tubes, of course, but I assume that some particular capacitors in the signal path too? If I want to emphasis the "low mid body" (200-400Hz), what kind of options do I have?

Hopefully my quesiton makes sense to someone. My intention is not to make the others tired with my daydreams...

Ok, I've been thinking about my questions more thoroughly...

Just forget my previous my messages. The answer to my question is quite obvious: "call it EQ, baby!"
Title: Re: D-LA2A Support Thread
Post by: melomane on March 01, 2014, 09:20:51 AM
crazy stuff! I will order soon a kit :):):)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 01, 2014, 10:17:26 AM
we do not have kits for this ;-)
just PCBs and PSU transformers.
with all the other parts, it is DIY  ;D
Title: Re: D-LA2A Support Thread
Post by: frazzman on March 12, 2014, 12:40:39 AM
I'm preparing for tonights grand unveiling... first power on. I think everything looks good, does this toroid wiring look correct?

PSU is Wired in series for 230v operation. The picture shows it all, but in case its not clear... There are 2 pairs of primaries, i've got the white of one pair tied to the yellow of the other pair. Then of the remaining 2 primary leads - white to IEC (L) and yellow to IEC (N)

IEC Earth tied to chassis as usual, and toroid earth wire tied to chassis as well.

One other thing I noticed, in silent-arts original picture of the toroid wiring, his picture shows a "brown" and a "brown/red" wire. On my transformer, there are only 2 pairs of brown wires. I take it these can be used interchangably?

Thanks a lot
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 12, 2014, 05:01:27 AM
I'm preparing for tonights grand unveiling... first power on. I think everything looks good, does this toroid wiring look correct?

Looking good!

One other thing I noticed, in silent-arts original picture of the toroid wiring, his picture shows a "brown" and a "brown/red" wire. On my transformer, there are only 2 pairs of brown wires. I take it these can be used interchangably?

this is fine. the "brown/red" and the "black/red" is my personal (red) heat shrink marking since I wanted the heaters to be "in phase" - but I guess this doesn't matter.

Time to power her up!
Title: Re: D-LA2A Support Thread
Post by: frazzman on March 14, 2014, 02:20:30 AM
Powered up... Worked straight away first time. I was surprised as there are so many points of failure with all these molex connectors and wiring.  First power on revealed that disconcerting kind of electrical burning smell but in absence of any smoke or concerning signs - it seems to be fine. I thought it was maybe the smell of the regulator heating up or the tubes. Anyhow, looks like I need to do the highly documented gain pot mod... Can't even crank it half way without the speakers exploding ... This is an amazing project
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 14, 2014, 05:15:54 AM
Great stuff!

The electrical burning smell is normal, the tubes burn away your fingerprints ...
Title: Re: D-LA2A Support Thread
Post by: frazzman on March 14, 2014, 08:54:00 AM
Great stuff!

The electrical burning smell is normal, the tubes burn away your fingerprints ...

I figured. The PCB layout is exceptionally good. I'm just so psyched that it worked first go. I'm waiting for my meters to arrive but so far everything sounds right to my ears.
Title: Re: D-LA2A Support Thread
Post by: frazzman on March 15, 2014, 04:39:25 AM
Great stuff!

The electrical burning smell is normal, the tubes burn away your fingerprints ...

Hi Volker,
 Quick question for you (that I need to hopefully finish the build...!). Sorry if it's been covered, I searched the thread but couldn't find a definitive answer.... If I want to use 12v lamps in the VU meters, where is the best spot to power from ? Or is it better to find an led powered meter and borrow some power off the relay psu ? I wanted to use some of the hairball HB-8037 meters. Thanks a lot
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 15, 2014, 04:46:03 AM
Don't know what kind of Lamp the 8037 uses, best would be to replace it with 5V Lamps.
Title: Re: D-LA2A Support Thread
Post by: frazzman on March 15, 2014, 05:08:23 AM
Don't know what kind of Lamp the 8037 uses, best would be to replace it with 5V Lamps.

Hi Volker,
It's a hairball meter, runs on a 12v lamp:
http://www.hairballaudio.com/shop/product_info.php?products_id=40

They used to offer a 5v led version but doesn't look like they do anymore
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 15, 2014, 05:22:31 AM
The lamp should be replaceable. Just replace it with a 5V version.
Title: Re: D-LA2A Support Thread
Post by: Palmito on March 19, 2014, 12:05:57 PM
Hi folks
I just finished my dla2a, it passes audio, is dead quiet, so that a good start. Bypass switch seems to be working since the gain pot gets active when compression is on. The vu meter seemd to work fine also, it shows the level and stays at 0dB on gr. The problem is that it doesnt compress.

Could my problem come from the relays ? Since i read that some models dont work... Did anybody used Omron G5V-2 ?
Thanks
Alex
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 19, 2014, 01:12:47 PM
Since "gain" is working the relays are fine (and Omron G5V-2 are the correct relays).
Title: Re: D-LA2A Support Thread
Post by: Palmito on March 19, 2014, 05:58:56 PM
Ok thanks.
Strange thing is that both sides arent compressing... i tried swapping tubes, t4bs, same thing... So maybe this could have something to do with stereo linking ?
At first i mistakely install the t4bs sockets the wrong side around, then i changed them, do you think i could have damaged them by powering the unit ?
Another hint: when i turn the gain reduction pot at max (fully clockwise) all i hear is a slight distortion. Maybe someone had the same problem ?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 19, 2014, 07:08:49 PM
Turn all trimm pots to far to the right first.
Multiple times.
Title: Re: D-LA2A Support Thread
Post by: Palmito on March 20, 2014, 03:11:09 PM
I tried this already...
I used Edcor xsm 10k/10k on input and xsm 10k/600 on output. Is that correct ?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on March 20, 2014, 03:46:23 PM
Transformers are fine.
Title: Re: D-LA2A Support Thread
Post by: Palmito on March 21, 2014, 04:48:19 AM
I used Kenetek T4B, with R25=33k. Is that right ?
Title: Re: D-LA2A Support Thread
Post by: Palmito on March 21, 2014, 07:29:43 AM
Sorry for all the questions, im trying to find where to search...
Could i have damaged the T4Bs by connecting them in reverse ?
Title: Re: D-LA2A Support Thread
Post by: Palmito on March 21, 2014, 01:04:58 PM
Ok i sorted it out, I had the center tap connected on the input Xformers, i disconnected them and now its working !
Thanks a lot Volker
Title: Re: D-LA2A Support Thread
Post by: frazzman on April 10, 2014, 09:22:26 AM
Hi Volker, and any other D-LA2A experts who still hover over this thread..!

My first D-LA2A is about 98% complete, I just have a few questions to help get me to the finish line.

Issue 1)I completed the stereo adjustment calibration, both channels show the same amount of gain reduction in stereo mode. The meters are spot on with each other. The problem is, to my ears it just doesn't sound like there is near as much compression going on as the meters would indicate. With peak reduction dialed in at max, the meters are pretty much hovering around -20db (GR). If I dial back the peak reduction, both meters respond accordingly... Rather than describe to you what it sounds like, heres some very short drum clips to explain:
- NO LA2A: https://dl.dropboxusercontent.com/u/108741277/LA2A/la2a-BYPASS.mp3
- LA2A, max peak reduction, gain about 50% - https://dl.dropboxusercontent.com/u/108741277/LA2A/la2a-STEREO-GR.mp3

For R125/R225 I have installed 100k trimmers pretrimmed to 'default' value of 33k....
If I don't adjust these for GR tracking adjustment , will GR metering or behavior be off?
Also the OPTOs are stereo matched.

I Just don't know if it sounds right! Are my eyes or ears lying to me?

Issue 2)
I completed gain pot mod - 25k pot+75k resistor in series.
>> On the left channel I can now dial max gain without issue.
>> On the right channel when I get to about 3/4 gain, the audio on right channel breaks into noise/static sound, if I dial back, the problem disappears. I've tried testing the pot from the Left side on the right to rule out the pot... no difference
As a side issue (maybe related, maybe not) the right channel has a little bit of hum, measuring about -65db noise floor (pretty noisy?). Grounding is fine... I'm guessing some noise from the toroid as this is closer to the right channel. Don't know if this has any bearing on the gain issue...

Sorry for the long winded post... so keen to get this build finished...

Thanks all for the support
Title: Re: D-LA2A Support Thread
Post by: frazzman on April 11, 2014, 09:41:32 AM
I think I might have answered 70% of my own questions .... In short, the fender jewel bezel light is satan! I had one in the center of my front panel, with it removed the noise floor just improved by about 10db, and now I can turn up my right channel gain pot without it crapping out into noise and distortion (the right channel already had a little bit of noise which seemed to be exacerbated by high gain setting). I have to work out a way to route this cabling without adverse affect. I haven't mounted the mains toggle switch to the front panel yet but I'm worried about the impact having those leads next to the pots could be...

So now with the gain pot and noise floor addressed, my only looming concern is a perceived lack of compression, stereo calibration is completed, limiter response set to full CW as per la2a manual. With the meter showing max GR it just doesn't sound like the signal is being crushed...

Reading other users reports, it sounds like turning the limiter response trimmer CCW increases compression ? The only thing I haven't done is the Gr meter tracking, trimmers are set to 33k, I can cope with the meter being slightly off as long as know that the compression is responding as expected... Appreciate any thoughts from other builders
Title: Re: D-LA2A Support Thread
Post by: frazzman on April 11, 2014, 08:08:56 PM
Sorry for the post overload... But this thing is driving me nuts! Everything is working... I have a useable gain range, stereo adjust is complete, meters show gain reduction and respond to changes in the peak reduction pot... BUT when I look at a wave form with the unit at max peak reduction, it just doesn't look very compressed!! Any ideas ? I've tried adjusting the limiter response trimmer but it's hard to tell if it's helping or not.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 12, 2014, 04:00:11 AM
feed in a +4 dBu sinus signal, 1kHz without any gain reduction
meter in VU mode should read 0 VU
change the meter to gain reduction mode, you should read 0 VU

now dial in peak reduction until your meter (still in gain reduction mode) reads -10 VU
change your meter to VU mode

should still read around -10 VU, and your output should be -6 dBu
Title: Re: D-LA2A Support Thread
Post by: frazzman on April 12, 2014, 07:07:33 AM
feed in a +4 dBu sinus signal, 1kHz without any gain reduction
meter in VU mode should read 0 VU
change the meter to gain reduction mode, you should read 0 VU

now dial in peak reduction until your meter (still in gain reduction mode) reads -10 VU
change your meter to VU mode

should still read around -10 VU, and your output should be -6 dBu

Thanks for the reply Volker!

What about gain what should that be set to? I assumed that it should be set so that the meter(s) read 0 VU with +4 dBU 1khz sine wave, is that correct??

Based on your steps, this is what I did:
- Feed in +4 dBU 1khz sine WAV - adjust signal to measure +1.228 vAC across XLR in pins 2+3
- Switch to VU mode, adjust gain until meter(s) read 0 VU (I'm not sure about this part...)
- Switch to GR mode, meter is reading 0 VU
- Dial in peak reduction using right channel PR pot (stereo mode) until reading - 10 VU
- Change meter to VU mode - meter then drops from -10 VU to -7 VU???

Confused about how to set the gain?

Thank you
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 12, 2014, 09:09:32 AM
yes, gain set to read 0 VU

the 3 VU offset might be because of stereo mode only using one side for PR,
or the meter is a little bit off in gain reduction mode.

I would say: all is fine with your unit  8)
Title: Re: D-LA2A Support Thread
Post by: frazzman on April 12, 2014, 09:25:02 AM
yes, gain set to read 0 VU

the 3 VU offset might be because of stereo mode only using one side for PR,
or the meter is a little bit off in gain reduction mode.

I would say: all is fine with your unit  8)

Thank you!
I will try the gr tracking adjust to see of that gets the meter more accurate in GR mode but I'm not too fussed.

I'm just surprised to see that looking at the waveforms of some drums that would appear to be getting heavily compressed, that the waveform doesn't look that way. Maybe it is that the LA2A style of compression is more subtle than say an 1176? Then I tried using some dynamic range meters to compare before and after of a drum track with heavy compression and then bypassed, it threw me off to see that the dynamic range had not been altered much with heavy compression applied.

This is my first opto comp, I have to say it sure does sound good but I wasn't sure about the gain reduction behavior
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 12, 2014, 09:45:06 AM
...
I'm just surprised to see that looking at the waveforms of some drums that would appear to be getting heavily compressed, that the waveform doesn't look that way. Maybe it is that the LA2A style of compression is more subtle than say an 1176?
Very different style of compression for sure.
To "hear" the D-LA2A, try it with vocals etc, sustained sounds, not with drums  ;)
Title: Re: D-LA2A Support Thread
Post by: frazzman on April 12, 2014, 09:55:14 AM
...
I'm just surprised to see that looking at the waveforms of some drums that would appear to be getting heavily compressed, that the waveform doesn't look that way. Maybe it is that the LA2A style of compression is more subtle than say an 1176?
Very different style of compression for sure.
To "hear" the D-LA2A, try it with vocals etc, sustained sounds, not with drums  ;)

I always hear about these shining on vocals... Well I guess I'm done now.. Thanks again for your help. Amazing project. I can't stop playing around with it
Title: Re: D-LA2A Support Thread
Post by: frazzman on April 15, 2014, 08:48:40 AM
I still have one annoying problem on my right channel. I thought I had resolve these issues but apparently not :(
My right channel has about a 10db worse noise floor when compared to the left channel. I'm guessing due to it being closer to the toroid. Moving the toroid doesn't seem to make much difference...

The other really annoying problem that I can't seem to resolve is when the gain on the right channel is at max or near max, it breaks into static/noise. I don't have this issue on the left channel. Swapping gain pots/wiring between the sides doesn't resolve the issue so I'm pretty confident it's not the gain pot. I'm using the 25k pot+75k resistor mod. Any ideas what could cause this issue on 1 channel only ?
Thanks!
Title: Re: D-LA2A Support Thread
Post by: rob_gould on April 15, 2014, 09:30:17 AM
Swap tubes and t4b one at a time between the channels maybe? Should be possible to isolate the issue that way...
Title: Re: D-LA2A Support Thread
Post by: desol on April 15, 2014, 03:18:16 PM
As far as reducing noise, I have wrapped toroid's in sheet mu metal and added additional shielding around them in an attempt to lessen EMI.
It did help to a noticeable degree.

To get really good performance...you would have to have a custom box made of thicker mu-metal for the transformer.

Come to think of it, there is a fellow in the white market with another solution...about 60% of the way down the page:
http://groupdiy.com/index.php?topic=38026.0
Title: Re: D-LA2A Support Thread
Post by: frazzman on April 15, 2014, 08:15:42 PM
As far as reducing noise, I have wrapped toroid's in sheet mu metal and added additional shielding around them in an attempt to lessen EMI.
It did help to a noticeable degree.

To get really good performance...you would have to have a custom box made of thicker mu-metal for the transformer.

Come to think of it, there is a fellow in the white market with another solution...about 60% of the way down the page:
http://groupdiy.com/index.php?topic=38026.0

Hi Desol,
Thanks for the reply, i've used mumetal before on past builds, on my gpultec's it made a huge difference. It's a shame its so expensive, but i've ordered some regardless.

Have you had any issues with noise/distortion sound when gain pot is maxed out? I've read a lot of posts from users who report oscillation at max gain, mine doesn't sound like oscillation but its annoying never the less. The weird thing it only happens on 1 side and it doesn't seem to be due to the pot itself, I just can't narrow down the culprit.
Cheers
Title: Re: D-LA2A Support Thread
Post by: desol on April 15, 2014, 08:34:47 PM
I don't think that I have noticed any distortion....but then again, I never turn it up that high.

I'd first try what Rob suggested above...
Title: Re: D-LA2A Support Thread
Post by: frazzman on April 15, 2014, 11:13:28 PM
I don't think that I have noticed any distortion....but then again, I never turn it up that high.

I'd first try what Rob suggested above...

Hi desol,

Thanks for the reply. I tried what rob said, and so far I can't get the problem to follow the components, so even when swapping gain pots/tubes/t4b , the problem is always on the right. I know having the gain at this setting is not practical, but I'm still trying to understand why it could affect one channel and not the other (all components are the same)...

This is what it actually sounds like, you can hear in the last 5 seconds when I turn the gain pot down a little, the problem immediately disappears ... Really weird...

https://dl.dropboxusercontent.com/u/108741277/la2a%20problem.mp3
Title: Re: D-LA2A Support Thread
Post by: rob_gould on April 16, 2014, 04:38:43 AM
Are your transformers on molex connectors? Can you move those between channels too?
Title: Re: D-LA2A Support Thread
Post by: frazzman on April 16, 2014, 05:10:51 AM
Are your transformers on molex connectors? Can you move those between channels too?

Yep they are, I'll give that a shot too. Will have to unscrew them from the chassis. Will let you know how I go.
Title: Re: D-LA2A Support Thread
Post by: DaTastenrasta on April 16, 2014, 05:38:39 PM
Hey guys,

sorry for interrupting the tech talk but I'm actually new to the DIY-forum though I've built an mnats-1176 before. The problem is that I've been searching through a lot of the posts so far and I can find posts going into depth in almost every thread but I can't seem to find some kind of beginning.

I would like to build an LA-2A in the original version, so with the turret boards and a non-PCB-style one. And to be honest I'm still at the very beginning apart from knowing what it is, what it does and a very undetailled knowledge of what a turret board is  :-[

Is there anyway you could help me get started? Would really appreciate that.

Thanks for your help!
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on April 16, 2014, 05:45:44 PM
http://groupdiy.com/index.php?topic=3278.0
Title: Re: D-LA2A Support Thread
Post by: desol on April 16, 2014, 06:13:15 PM
I don't think that I have noticed any distortion....but then again, I never turn it up that high.

I'd first try what Rob suggested above...

Hi desol,

Thanks for the reply. I tried what rob said, and so far I can't get the problem to follow the components, so even when swapping gain pots/tubes/t4b , the problem is always on the right. I know having the gain at this setting is not practical, but I'm still trying to understand why it could affect one channel and not the other (all components are the same)...

This is what it actually sounds like, you can hear in the last 5 seconds when I turn the gain pot down a little, the problem immediately disappears ... Really weird...

https://dl.dropboxusercontent.com/u/108741277/la2a%20problem.mp3

Yeah...somethings off there. If I was more well versed in theory (I more have solid Refrigeration electrical theory...with some electronics, I'm not a theory engineer) I could really help. Sorry man...

About the best I could offer is to trace the audio signal with a scope (carefully ~ 350v) and see where it starts getting messed up. Seeing as everything seems to work up until a certain level of gain it sounds like it could be a bad tube, poor connection, bad switch or wiring configuration.
Title: Re: D-LA2A Support Thread
Post by: frazzman on April 16, 2014, 06:17:28 PM
I don't think that I have noticed any distortion....but then again, I never turn it up that high.

I'd first try what Rob suggested above...

Hi desol,

Thanks for the reply. I tried what rob said, and so far I can't get the problem to follow the components, so even when swapping gain pots/tubes/t4b , the problem is always on the right. I know having the gain at this setting is not practical, but I'm still trying to understand why it could affect one channel and not the other (all components are the same)...

This is what it actually sounds like, you can hear in the last 5 seconds when I turn the gain pot down a little, the problem immediately disappears ... Really weird...

https://dl.dropboxusercontent.com/u/108741277/la2a%20problem.mp3

Yeah...somethings off there. If I was more well versed in theory (I more have solid Refrigeration electrical theory...with some electronics, I'm not a theory engineer) I could really help. Sorry man...

About the best I could offer is to trace the audio signal with a scope (carefully ~ 350v) and see where it starts getting messed up. Seeing as everything seems to work up until a certain level of gain it sounds like it could be a bad tube, poor connection, bad switch or wiring configuration.

Thanks Desol, I will see how I go. It's really weird because this issue literally occurs on the very last few millimetres of the gain pot, I can get it extremely loud,  but as soon as it's maxed out this issue occurs. My logic was that if everything works perfectly when the gain pot isn't maxed then it can't be a wiring issue etc
Title: Re: D-LA2A Support Thread
Post by: Sammas on April 22, 2014, 09:06:01 PM

Hey guys, I am in the process of ordering the transformers to complete my D-LA2A.

What are your thoughts on using Carnhill VTB2380's on the input and output? They are 15k:600ohm ungapped.

Shipping edcors to Australia is horrendously expensive. It works out the same to get 4 carnhills from Colin in the UK!


http://www.audiomaintenance.com/acatalog/CA-18-VTB2380_extended_info.html
Title: Re: D-LA2A Support Thread
Post by: frazzman on April 24, 2014, 10:17:41 AM

Hey guys, I am in the process of ordering the transformers to complete my D-LA2A.

What are your thoughts on using Carnhill VTB2380's on the input and output? They are 15k:600ohm ungapped.

Shipping edcors to Australia is horrendously expensive. It works out the same to get 4 carnhills from Colin in the UK!


http://www.audiomaintenance.com/acatalog/CA-18-VTB2380_extended_info.html

Hi Sammas,

I'm from Oz as well, I had a similar dilemma... The postage direct from Edcor in the USA is ridiculously expensive but the price of the transformers are ridiculously cheap...
The transformers for this project cost me $10usd each + $50usd shopping so $90 all up, I think that will still come in cheaper than the carnhills ...
Title: Re: D-LA2A Support Thread
Post by: dandeurloo on April 24, 2014, 10:42:12 AM
Here is a option.  If you plan on using one of my cases.  You can have the edcors shipped to me and I can ship the case and transformers to you to share shipping.  I have done that for a number of guys. 

 
Title: Re: D-LA2A Support Thread
Post by: Sammas on April 28, 2014, 07:40:22 PM

Hi Sammas,

I'm from Oz as well, I had a similar dilemma... The postage direct from Edcor in the USA is ridiculously expensive but the price of the transformers are ridiculously cheap...
The transformers for this project cost me $10usd each + $50usd shopping so $90 all up, I think that will still come in cheaper than the carnhills ...

Hey frazzman!

The transformers are just tacked onto an order of other parts, so I would be paying shipping with or without the transformers anyway.

I think I have found a nice chap locally that has some edcor 600:10k transformers for sale. I think I might just go with those.


Here is a option.  If you plan on using one of my cases.  You can have the edcors shipped to me and I can ship the case and transformers to you to share shipping.  I have done that for a number of guys.

I purchased the project half finished from a chap in Australia and it came with a case.
But thank you Dandeurloo! That is mighty nice of you to offer!
Title: Re: D-LA2A Support Thread
Post by: salomonander on May 02, 2014, 04:55:18 PM
hey
did anyone use the original utcs on this build? i need help with the pinouts. i have utc a10 and a24 and need to know how to hook them up. thanks!

ps: would it be smarter to mount them on the outside of the case (like back in the days) or inside? im wondering about shielding etc....
Title: Re: D-LA2A Support Thread
Post by: saxmonster on May 07, 2014, 11:37:49 PM
Where does one get a face plate like this at?

Title: Re: D-LA2A Support Thread
Post by: melomane on May 08, 2014, 12:25:03 PM
Hi there!

I have a problem with my D-LA2A.
I just done the assembly, but I have problem with my unit.

I made a video for convenience, check below the Youtube video please :)

Here is my configuration:
- T4B IGS
- Power Transformer from Silent Arts
- Audio transformer from Edcor

The problems:
- Left Channel: no sound, just a buzz...
- Right Channel: no compression G.R, problem with gain potentiometer when more than 50%...

I have double check the heater connection, and all connection (include for the 3 grounds connection + screen).
I don't know the problem  :(

Please help me  8) Thank you so much !

http://youtu.be/idRbu564NGs (http://youtu.be/idRbu564NGs)
Title: Re: D-LA2A Support Thread
Post by: Dr Gris on May 13, 2014, 01:01:42 PM
hey
did anyone use the original utcs on this build? i need help with the pinouts. i have utc a10 and a24 and need to know how to hook them up. thanks!

ps: would it be smarter to mount them on the outside of the case (like back in the days) or inside? im wondering about shielding etc....

I guess you've solved it by now, but I found this:

It appears that the 1968 schematic illustrates the A-10 (input tranny) primary labeling inverted - with tranny pin 6 hot. Older schematics as well as photos of reissue units illustrate tranny pin 1 hot.

If I'm correct, then this is the way to wire the input for XLR pin 2 hot:

XLR input pin 2 --> barrier strip terminal 1 (optional) --> HA100X/A10 tranny pin 1 (primary) HOT input to tranny
XLR input pin 3 --> barrier strip terminal 5 (optional) --> HA100X/A10 tranny pin 6 (primary)

(My layout reflects this, and this supports the reissue manual's instructions to use barrier strip terminal 1 for hot)

Now, the output side is always illustrated the same way in all the schematics (without the XLR) - barrier strip terminal 10 to tranny output pin 1 hot. However, photos of the reissues (with XLR's) indicate that XLR pin 2 is wired to barrier strip 8 (pin 6 of the output transformer), which would reverse the polarity from the output tranny.

This is how (in photos) the reissue unit's output is wired for XLR pin 2 hot:

XLR output pin 2 --> barrier strip terminal 8 (optional) --> A24 tranny pin 6 (secondary)
XLR output pin 3 --> barrier strip terminal 0 (optional) --> A24 tranny pin 1 (secondary) HOT output from tranny

(My layout reflects this too, and this also supports the reissue manual's instructions to use barrier strip terminal 8 for hot)

But, the trouble here is that pin 6 of the output tranny secondary is not the hot side.

Has the signal's polarity been flipped by the time it gets to the output transformer primary, so that reversing the XLR connections puts the signal back in phase on the way out?

If so, then it makes sense.

Best
//M
Title: Re: D-LA2A Support Thread
Post by: salomonander on May 15, 2014, 05:00:34 PM
thx! this helps a lot
Title: Re: D-LA2A Support Thread
Post by: salomonander on May 22, 2014, 03:28:58 PM
my pcb is already in the case so no way to check the backside. i have a question regarding the inputs and outputs.
+ and - are labeled left and right. so mass (pin1 on the xlr) goes in the middle of each molex ?

cheers
Title: Re: D-LA2A Support Thread
Post by: salomonander on May 22, 2014, 05:00:36 PM
ps: i did not insert any tubes or t4bs. but i measure around 370v on most tube sockets. seems wrong i guess.... any help..... thx!
i assume that something is wrong with r29? its certianly a 4.7k one in there... is the grounding the first starting point?
Title: Re: D-LA2A Support Thread
Post by: salomonander on June 04, 2014, 04:45:00 PM
ok so i sorted most things out. the unit works, compresses and sounds gorgeous. but my meter doesn't show the correct values in GR mode. i can clearly hear more than 15-20db of reduction while the meter never adventures further than 3-4db of reduction. no matter what i set the gain reduction to. anyone have an idea where i can start the search? i did replace rX25 with a trim pot.

cheers
Title: Re: D-LA2A Support Thread
Post by: salomonander on June 04, 2014, 04:51:30 PM
ps: if i may make a modest suggestion for the next revision of the board...
it would be amazing if the signal would travel to the t4b in bypass mode. switching out is great and clean. but whenever switching back into compression mode one gets a dynamic spike (a big one when doing lots of reduction) since the t4b has to catch up first...
Title: Re: D-LA2A Support Thread
Post by: Bowie on June 04, 2014, 07:56:19 PM
ok so i sorted most things out. the unit works, compresses and sounds gorgeous. but my meter doesn't show the correct values in GR mode. i can clearly hear more than 15-20db of reduction while the meter never adventures further than 3-4db of reduction. no matter what i set the gain reduction to. anyone have an idea where i can start the search? i did replace rX25 with a trim pot.

cheers
Sorry if I'm pointing out the obvious but triple-check all the resistor values that are in the path to the meter.  If it sounds like you're getting correct GR then something is going wrong between your sidechain and your meter.
Title: Re: D-LA2A Support Thread
Post by: frazzman on June 06, 2014, 03:13:06 AM
Hey Volker et. al,
Having some issues with one of my d-la2as... I had a bit of noise on one channel and had to pull the case apart to improve conductivity between all pieces. Anyhow in the process I've managed to mess up the output on my left side. I have a constant hum and very low distorted signal on that side. 

I thought perhaps bad molex crimp on output transformer leads but I've swapped it with working side and no difference. I have also tried known working pots / switches etc from working right channel but to no avail. GR metering is working properly on both channels and stereo link so I know input is ok but output is interrupted.

 Any pointers on where to look for areas that may interrupt output ? I am thinking a dry joint somewhere but I've avoided taking the whole thing apart as I'm not too keen on removing the PCB... Best to discharge all caps before taking an iron to the pads around the molex connectors ? I've been lucky until now with any tube builds I've done not requiring any surgery. I'm paranoid about residual charge in the caps....I was thinking of just reheating all the molex connector pads? Sorry for the long post, I've spent way too long looking at this, appreciate any fresh insight
Title: Re: D-LA2A Support Thread
Post by: band_master on June 06, 2014, 05:08:59 AM
Hi all,
Working on a re-build of my D-LA2A. It was my first project and the orientation of the PCB was not the best way to go. Changed up the layout and re-wired everything including the heaters. Was up too late trying to troubleshoot some hum in channel 2. It does that thing where the signal cuts out and the meter spikes if you crank the gain. Had the limit/comp switch wired backwards, fixed that. Had the unit on for a while and noticed that R234 started to smoke. Check the heater wiring? other ideas?

cheers,
BD
Title: Re: D-LA2A Support Thread
Post by: bernbrue on June 06, 2014, 05:45:03 AM
Hi,
I would like to report my findings concerning oscillation. My input transformer is the original Sowter 1:4, Output is Edcor 10K/10K. I did the 25K pot 75K resistor mod for the input gain.

Background: My unit worked fine from the very beginning, except for the annoying 30kHz oscillation with higher gain settings causing meter pegging. I moved the output transformer farer away from the board and the xlr connectors which helped a bit. I consequently used moderate gain setting so that unity gain was almost achieved.

Today I tried various ideas to eleminate oscillation. I realized that the area around V1 and R11 (68K Feedback) is very touchy and that even moving my hand around V1 reduced oscillation a bit. CJ proposed to change the value of R11 in order to reduce negative feedback and gain. I finally put a 14K resistor in parallel to the existing 68K. That helped quite a lot but I still couldn´t crank up the gain to maximum without meter pegging.

Then I had a real "heureka" experience. The shielded wires for the gain reduction pot and gain pot were connected wrong, well not wrong but the shield was conducting signal and a red wire was meant to work as shield. What a silly mistake!!!! I rewired it and now I can set the gain pot to maximum without any oscillation at all. I measured the compressor with RMAA and the specs are more than convincing. With the paralleled negative Feedback resistor THD is 0,382 %. Not that bad. All other values including absolutely flat frequency response are excellent. I´m more than happy now with my Dual LA2a!!

People having these problems as well: CHECK YOUR WIRING (verify that shield is connected to ground!!!) and REDUCE FEEDBACK RESISTOR.


regards
Bernd


R234 has to be 3W. Check value of R235 and voltage rating of C213 as well. Try changing the 6AQ5 with the working channel
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: band_master on June 07, 2014, 02:00:34 PM
I checked wiring and made sure polarity on the pots and molex connectors were good. tried moving around the audio transformers. checked voltage drop across r229 getting 350v before but only 216v after. checked heater voltages on 6AQ5A and am getting 6.7vac across 3 and 4 but also getting 6.7vac across 4 and 5. Double-checked the heaters and a solder joint was poking through the PVC coating on the heater wires causing a short. Fixed that and now it's not smoking anymore. Still getting more noise floor in channel 2 and audio cuts out and meter pegs if you turn gain past 8 or 9...at least voltages across r229 are good now. 350v before and 250v after.
Title: Re: D-LA2A Support Thread
Post by: bernbrue on June 07, 2014, 03:25:51 PM
getting 6.7vac across 3 and 4 but also getting 6.7vac across 4 and 5. Must be a short? will have to double-check heater wiring again.

ATTENTION!!!! pin 5 is the anode that means there is high voltage. When there is a short between 4 and 5 you found the reason why R234 has burnt.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: band_master on June 07, 2014, 04:41:59 PM
thanks, bernbrue. yep i edited my last post before i saw your reply. I fixed the heater connections to 6AQ5A. R234 and R229 still read good on my meter, but there is evidence of overheating on either side in the solder joints. do you think component failure caused by the heater short could be the cause of the signal drop out problem with the gain maxed out?

i tried swapping tubes and gain/reduction pots across channels. maybe i should try swapping transformers...attached is a pic of my current orientation. i have seen this work for other builds, but am considering moving the audio transformer to the left of the PCB on the opposite side of the toroid and out from under the XLRs as the left channel's noise floor is much lower than the right.
Title: Re: D-LA2A Support Thread
Post by: frazzman on June 08, 2014, 09:12:53 AM
Hey guys,

Still battling with my issue on the left channel of my D-LA2A. Everything initially worked fine but I developed a constant hum and low distorted audio on this channel. This is really weird and something I have never experienced on any other builds ... Tonight I found that if I press my thumb semi firmly against the PCB just under the "LIMIT COMP" Molex connector -- the problem goes away...!!! (see attached pic)

Audio then passes cleanly and behaves just as the right channel does. Once I release my thumb, the hum returns instantly and the problem returns...

I spent the last few days thoroughly checking everything on this channel
- I moved 'known working' pots/switches from the working side
- Tested in and out transformers across to the other channel - no issue
- Removed PCB and reheated all pads
- Removed powder coat on the casing around all switches / panel edges to ensure proper conductivity
- Checked for grounding with DMM, looks fine.
- Checked my working channel and found that audio passes cleanly with all pots and switches disconnected (and not just in bypass mode), so I can even eliminate all of those on the non working channel... problem still persists

I was initially convinced that this had to be a bad molex or transformer wiring issue but tonights finding disproves that...

The only thing I can think of is a bad connection on the heater wiring, the area I'm pressing is very close to the tube socket the heater wiring runs to. The confusing thing is, this wiring seems solid - can measure 0hm from the end of 100r resistors through to the end of the heater wiring.

I created an audio export as well so you can hear the problem too:
https://dl.dropboxusercontent.com/u/108741277/la2a-issue.mp3

I can create a video as well if it helps to explain.

You can hear in the clip, the hum is present, soon as I press down on the board, you hear a pop and the audio passes correctly, then 10 seconds or so later I let go of the PCB and the problem returns...

Really appreciate any ideas anyone has... does this sound feasible?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 08, 2014, 01:13:25 PM
Is the problem still there with only the LIMIT / COMP unconnected?
(anybody uses this?)

the LA2A is very sensitive to unshielded / untwisted cables!
Title: Re: D-LA2A Support Thread
Post by: band_master on June 08, 2014, 03:13:16 PM
@frazzman

Did you reflow the tube socket joints and the molex connector joints under the PCB? you should definitely use shielded wire for the limit/comp switch. moving that wire around and even touching the switch i have found it is noisy even with a shielded pair. have you tried replacing the female molex connector for the limit/comp switch?
Title: Re: D-LA2A Support Thread
Post by: frazzman on June 08, 2014, 07:59:09 PM
Hi guys,

The problem is still there irrespective of the limit / comp switch plugged in. The problem is present with none of the switches or pots connected.
As I mentioned, the working channel can pass clean audio with all switches and pots disconnected. That is not the case on the left side. No matter what, the issue is present until I press my thumb firmly against the PCB. I am thinking it has to be the heater wiring ...  I did reflow solder on all molex connectors
Title: Re: D-LA2A Support Thread
Post by: band_master on June 09, 2014, 02:20:47 AM
you might have a broken PCB trace. long shot but I had a hum problem with an access 312 build and it turned out that the solder pad had lifted and become broken inside of the solder joint.
Title: Re: D-LA2A Support Thread
Post by: bernbrue on June 09, 2014, 04:34:39 AM
Check grounding. Each channel and psu have individual ground planes. There is a nice pdf about this topic.
Regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: sonicwarrior on June 09, 2014, 05:12:26 AM
Btw.: All NRG Recording forum links in the OP are broken as it has moved to http://www.energyrecording.de (previously http://www.nrgrecording.de/nrg). So e.g. the link for the ground scheme is now:
http://www.energyrecording.de/viewtopic.php?t=405&postdays=0&postorder=asc&start=3
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 09, 2014, 07:22:48 AM
As I mentioned, the working channel can pass clean audio with all switches and pots disconnected.
There is something wrong.
With the "GAIN" (RVX01) pot disconnected it shouldn't pass any audio.
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 09, 2014, 07:35:53 AM
ps: if i may make a modest suggestion for the next revision of the board...
it would be amazing if the signal would travel to the t4b in bypass mode. switching out is great and clean. but whenever switching back into compression mode one gets a dynamic spike (a big one when doing lots of reduction) since the t4b has to catch up first...
A few solder bridges and you are done:
Title: Re: D-LA2A Support Thread
Post by: frazzman on June 09, 2014, 09:47:07 AM
Thanks for everyone's help... I stripped the heater wiring on my dodgy left channel and cleaned it all up and did it fresh and cleanly and problem is gone ... I suspect the wiring to the top left tube socket had a become a dry joint - then when I pressed on the PCB around that area the problem would go. Everything is back to normal now on both channels .. I could swear my working channel passes audio with no switches or pots connected... I could be wrong
Title: Re: D-LA2A Support Thread
Post by: salomonander on June 09, 2014, 10:35:44 AM
ps: if i may make a modest suggestion for the next revision of the board...
it would be amazing if the signal would travel to the t4b in bypass mode. switching out is great and clean. but whenever switching back into compression mode one gets a dynamic spike (a big one when doing lots of reduction) since the t4b has to catch up first...
A few solder bridges and you are done:

great thanks!
Title: Re: D-LA2A Support Thread
Post by: salomonander on June 09, 2014, 10:42:26 AM
ok so i sorted everything out. the meters not showing the right amount of compression was simply a wrong value trim pot in the R3 postition (somehow installed 100Ohms instead of 100k :)

there is still one problem though. my 5v regulator ic gets way too hot. i do have a heatsink installed. when touching it one can get a serious burn. plus my vu lights shut down after a while when it gets too hot (we had over 34 degree today - no problems last night). restarting the unit solves this.
im wondering if my heatsink is too low budged (it was some cheap one from an electric store around the corner) or if my lamps are the problem. i do have 6,3v 1,6W 0,25A lamps installed in my meters. not leds. i dont even know if there are "good" or "bad" heatsinks - so any help would be great. i want to close the lid on this and move on :)
Title: Re: D-LA2A Support Thread
Post by: frazzman on June 09, 2014, 10:46:22 AM
ok so i sorted everything out. the meters not showing the right amount of compression was simply a wrong value trim pot in the R3 postition (somehow installed 100Ohms instead of 100k :)

there is still one problem though. my 5v regulator ic gets way too hot. i do have a heatsink installed. when touching it one can get a serious burn. plus my vu lights shut down after a while when it gets too hot (we had over 34 degree today - no problems last night). restarting the unit solves this.
im wondering if my heatsink is too low budged (it was some cheap one from an electric store around the corner) or if my lamps are the problem. i do have 6,3v 1,6W 0,25A lamps installed in my meters. not leds. i dont even know if there are "good" or "bad" heatsinks - so any help would be great. i want to close the lid on this and move on :
Your regulator is going into thermal shutdown from overheating! You need to install a bigger heatsink, bigger the better... Get some thermal paste too. Should be an easy fix
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 09, 2014, 10:56:52 AM
connect it to the chassis (isolated). or use a better performing heatsink.

with the weather in germany today we have one further problem:
too much power, resulting in higher voltage, a result of our Energiewende (solar is working).
at the moment you even get money for waisting electrical power.
we are already selling to our EU neighbors with negative prices.

http://www.welt.de/wirtschaft/energie/article128800398/Extreme-Belastungsprobe-fuer-deutsches-Stromnetz.html
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 09, 2014, 10:58:00 AM
Thanks for everyone's help... I stripped the heater wiring on my dodgy left channel and cleaned it all up and did it fresh and cleanly and problem is gone ... I suspect the wiring to the top left tube socket had a become a dry joint - then when I pressed on the PCB around that area the problem would go. Everything is back to normal now on both channels ..

 8) Great you sorted this out!

I could swear my working channel passes audio with no switches or pots connected... I could be wrong

well, it even passes audio without power ;-)
without the "IN" switch connected (often misread as "bypass") the relays are in bypass mode.
look at the schematic, without the gain pot there can't be any signal.
Title: Re: D-LA2A Support Thread
Post by: frazzman on June 09, 2014, 11:01:36 AM
Thanks for everyone's help... I stripped the heater wiring on my dodgy left channel and cleaned it all up and did it fresh and cleanly and problem is gone ... I suspect the wiring to the top left tube socket had a become a dry joint - then when I pressed on the PCB around that area the problem would go. Everything is back to normal now on both channels ..

 8) Great you sorted this out!

I could swear my working channel passes audio with no switches or pots connected... I could be wrong

well, it even passes audio without power ;-)
without the "IN" switch connected (often misread as "bypass") the relays are in bypass mode.
look at the schematic, without the gain pot there can't be any signal.

Hey Volker - sorry of course you are right...! I should have said everything disconnected except for "IN" switches otherwise as you said it would be in bypass mode. But looking at the schem I can see what you mean about the gain pot. I know for sure audio passes without limit / comp switch connected. Not though I can even hear the difference with this switch (... True to the original ...) Geez who knows, I'm delirious after fixing this bad boy. Just glad it's working :) thank you for your help and all other members!
Title: Re: D-LA2A Support Thread
Post by: salomonander on June 09, 2014, 11:12:32 AM
connect it to the chassis (isolated). or use a better performing heatsink.

with the weather in germany today we have one further problem:
too much power, resulting in higher voltage, a result of our Energiewende (solar is working).
at the moment you even get money for waisting electrical power.
we are already selling to our EU neighbors with negative prices.

http://www.welt.de/wirtschaft/energie/article128800398/Extreme-Belastungsprobe-fuer-deutsches-Stromnetz.html

hey Volker

thanks. so basically connect a cable from the heatsink to starground? am i understanding this right?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 09, 2014, 11:20:43 AM
thanks. so basically connect a cable from the heatsink to starground? am i understanding this right?
no. mount the regulator + heatsink isolated to chassis.
chassis will be a further heatsink.
Title: Re: D-LA2A Support Thread
Post by: audiophreak on June 09, 2014, 11:58:04 AM

with the weather in germany today we have one further problem:
too much power, resulting in higher voltage, a result of our Energiewende (solar is working).
at the moment you even get money for waisting electrical power.
we are already selling to our EU neighbors with negative prices.

http://www.welt.de/wirtschaft/energie/article128800398/Extreme-Belastungsprobe-fuer-deutsches-Stromnetz.html

  sorry to get off topic , but is there a way I can convert/ translate that article in to English ??  would love to read it and hear about all the great clean energy the rest of the world is doing :)
Title: Re: D-LA2A Support Thread
Post by: salomonander on June 09, 2014, 12:08:46 PM
thanks. so basically connect a cable from the heatsink to starground? am i understanding this right?
no. mount the regulator + heatsink isolated to chassis.
chassis will be a further heatsink.


got it thanks. by isolated you mean detached from the pcb right? so simply drill an m3 hole and put the regulator plus heatsink there via three wires? sorry for new noob questions.... i am a noob :)
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on June 09, 2014, 12:14:49 PM
by isolated you mean detached from the pcb right? so simply drill an m3 hole and put the regulator plus heatsink there via three wires?
by isolated i mean electrical isolated:
http://www.aosmd.com/res/application_notes/package/AN101_TO220_Guidelines.pdf

wires are fine, or just solder to the bottom like I did:
(http://www.silentarts.de/DIY/D-LA2A/IMG_3981.jpg)
Title: Re: D-LA2A Support Thread
Post by: bernbrue on June 09, 2014, 12:19:53 PM
the plastic washer between regulator and heatsink is VERY important!!! If you look closer you will see that the metal screw is also isolated from the heatsink (ground).

(http://origin.dastatic.com/forums/gallery/data/500/IMG_20131223_193224_721.jpg)

regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: band_master on June 09, 2014, 08:07:53 PM
I am still experiencing that hum in channel 2. If the gain knob is turned up past 8 the audio cuts out and the meter pegs. i took another looks at R229 and R234 and although they both read good on a meter I am still suspicious. Would a compromised resistor due to a short in 6AQ5A in these locations potentially cause the problem? Since these are pretty beefy resistors I wonder if another component is blown.

Will have to probe around with my meter. I have a scope but have never really used it. Are there points in the circuit I should check first for the noise? Thanks, guys.
Title: Re: D-LA2A Support Thread
Post by: band_master on June 16, 2014, 03:15:52 AM
Update: I replaced R229 and R234 and am still getting the signal cutting out and meter pegging at 8/5 on the gain knob for channel 2. Looking at the back of the board i'm pretty sure the heater short was on the side of C206 that connects to R234. Reading the chain a bit more it seems that my issue may be a result of high frequency feedback? Wondering if RV237 may be compromised. Have read other posts where wiring issues were at fault...things seems fairly in order there. Will have to keep poking around.
Title: Re: D-LA2A Support Thread
Post by: salomonander on June 23, 2014, 02:01:29 PM
the plastic washer between regulator and heatsink is VERY important!!! If you look closer you will see that the metal screw is also isolated from the heatsink (ground).

(http://origin.dastatic.com/forums/gallery/data/500/IMG_20131223_193224_721.jpg)

regards
Bernd

thanks!
this totally solved my issue. i have one last question regarding this project. i have the original utc transformers installed. and im wondering if i should mount them isolated in order to not get any ground loop. is this correct thinking? or will it not matter?
Title: Re: D-LA2A Support Thread
Post by: bernbrue on June 23, 2014, 02:05:55 PM
When you haven´t got a ground loop it doesn´t matter!  ;D
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: Sammas on June 24, 2014, 08:58:28 PM
the plastic washer between regulator and heatsink is VERY important!!! If you look closer you will see that the metal screw is also isolated from the heatsink (ground).

(http://origin.dastatic.com/forums/gallery/data/500/IMG_20131223_193224_721.jpg)

regards
Bernd


I go as far as using nylon nuts and bolts as well. They tighten nicely, and make it pretty impossible for their every to be electrical contact to the heatsink.
It might be overkill, but it give me piece of mind particularly with gear that travels!

http://www.jaycar.com.au/productView.asp?ID=HP0160
Title: Re: D-LA2A Support Thread
Post by: michaelW. on June 29, 2014, 01:15:34 PM
i´m Going to order at edcor for some Transformers so if you´re located in germany and need smth from edcor send me a PM and we can share shipping


Cheers Michael ;)
Title: Re: D-LA2A Support Thread
Post by: saxmonster on July 06, 2014, 11:03:32 PM
What is the mouser part # for this?  Anyone know?

Title: Re: D-LA2A Support Thread
Post by: saxmonster on July 06, 2014, 11:08:38 PM
Also will this work for the ICI?

I'll just install in on it the chip and leave it in a vertical position so it doesn't touch anything.

Title: Re: D-LA2A Support Thread
Post by: saxmonster on July 07, 2014, 12:37:16 AM
In the Drip boards he calls for C8A to be .01uf and C8B to be .022uf both at 400volts.  What should we use?  .032uf?

I know the pdf says 0.1uf wima but is this correct?

Thanks.

edit: I have an extra one of these from another project will it work since its after the diodes and should only be in a 5volts area?  Its rated for 50volts.

http://www.mouser.com/ProductDetail/TDK/FK26C0G1H104J/?qs=%2fha2pyFadugcXy8xf4igHin1m%2fc0OvUEBPD1Rk13R4USHU6Mw11W9w%3d%3d



Title: Re: D-LA2A Support Thread
Post by: saxmonster on July 17, 2014, 01:04:33 PM
Ok Guys,

My D-LA2A is up and running no smoke or flames, hahahahah.

I have not calibrated yet and I still have to wire up the jewel Lamp and Meter lamps. 

I have a couple of questions that I notice just from running a quick drum loop through it

!.  First is the Right side gain pot since it is so close to the power switch has a buzz and I can change the sound when I move the AC wires, how do you guys deal with this.  The wires running to my pots are all shielded but I think the interference / buzz is coming from the solder connection areas cause when i touch it it changes again.  Should I twist the AC power wires?

2.  The left channel seems hotter (Gain wise) that the right.  I did do the 25k pot 75k resistor.  Didn't check if the resistors are matched would that matter?

3.  My ne2's that are on the pcb next to the t4b's are flickering the left side more than the right.  Is that normal?

4.  the output meter works on the left side however the GR meter doesn't move, I have swapped the two molex's on the pcb but still the GR meter doesn't work.  I do hear the compression but it just doesn't show on the meter.  Where can I look to fix that?  Right side work great for both output and GR.

I am so excited about this project.  I will have pictures coming very soon.

Also like to thank Josh aka (California Road) for selling me his 85% built kit.  Wait to you guys see this faceplate.  Killin!!!!


-Scott







Title: Re: D-LA2A Support Thread
Post by: saxmonster on July 21, 2014, 07:23:35 PM
can someone help me.

The unit passes audio just fine.

bypass works great however with the peak knobs unplugged from the pcb and no t4bs installed i have an issue.

The left pot seems hotter than the right one.

To get zero on the meter with a test tone the left pot is at 20 on the front panel and the right channel has to be at 35.

I have not calibrated the unit yet as I though it would be important for the gains to be equal first.

I measured the pots for ohm and they don't get the same reading in the same spots, i did off, 1/4, 1/2 and 3/4 turns i could see if they were a little off but they are not close.

Should / can I get "MATCHED" pots?

I have the ones that are in the bom for the 25k and 75k resistor mod.


errrrr. Thanks in advance.

-Scott



Title: Re: D-LA2A Support Thread
Post by: bernbrue on July 22, 2014, 09:41:34 AM
Hi,
I suggest to finish the unit completely before spotting any errors. Then you should calibrate the compressor. There are lots of information about how to do that.

http://groupdiy.com/index.php?topic=32677.msg553490#msg553490

Since we do not know which case and frontpanel you use, we can´t comment on your buzzuing issue. AC wires must be twisted.
regards
Bernd
Title: Re: D-LA2A Support Thread
Post by: saxmonster on July 22, 2014, 05:18:28 PM
Thanks for the info Bernd.  I have reread those posts and anything dealing with calibration. I have included a video of my issues.  I am getting closer but would like to get even closer and put the lid on this thing

Still having issues trying to calibrate this thing.

I don't think it should be this hard.

Everything seems to be working just not reading correctly on the meters.  Check out the video I think it explains a lot.

https://www.youtube.com/watch?v=VHM9MeaYZl0&feature=youtu.be
Title: Re: D-LA2A Support Thread
Post by: saxmonster on July 23, 2014, 03:17:23 PM
Ok So I have found a few things out that I must do.

I have to add a 3.6k resistor to my hairball meters.  This will hopefully adjust the 0vu in the meter so that when I get zero on the meter the incoming signal will be the same as the out in my DAW.

I will also add a 100k trimmer set to 33k for the RX25 resistors I guess the real 33k resistor are causing it not to track right so i need to either go higher or lower on these.

I have tested my pots with nothing connected to them.

Here are my results

Gain Pots set to      Left          Right       Difference
0                        24.63k        25.7k        1.07k
20                      24.25k       25.34k       1.09k
50                      21.94k       23.07k       1.13k
80                        7.01k         8.28k       1.27k
100                         30R          4.5R       25.5R


PR Pots set to        Left         Right        Difference
0                        103.8k      87.7k         16.1k
20                        98.7k      82.9k         15.8k
50                        88.8k      73.3k         15.5k
80                      23.86k     15.84k         8.02k
100                        1.8R        1.7R           .1R


Could the difference in gain pots be why my gain knobs have to be at different spots when sending a 1k tone through the la2a.

I ordered new bourn pots. 

http://www.mouser.com/Search/ProductDetail.aspx?R=PDA241-SRT02-253A2virtualkey65210000virtualkey652-PDA241SRT02253A2
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on July 23, 2014, 03:26:19 PM
The 3,6k Resistor is needed, for every VU Meter (not Hairballs fault).
This will help for sure.

For the Pots: they do have tolerance, especially log versions.
The new ones you ordered are specced to 15%.

So - all looks fine right now, don't worry.
Title: Re: D-LA2A Support Thread
Post by: saxmonster on July 29, 2014, 04:00:16 PM
Ok Boys and Girls I am real close I can smell it now.

I have installed the 3.6k resistors on the positive side of the meters and now when my meters read zero my daw reads the same input reading as the output.  DONE

I made the adjustment at RX04 for the GR to Zero Out on the meters.  DONE

I have installed new gain pots and I am still having and issues with one pot needing to be turned higher than the other to get equal gains returns in my daw and on the meters.

The left channel is almost at halfway up about 47 on the faceplate scale for the meter to read zero.
The right channel only needs to be turned up a quarter of the way to 25 on the faceplate scale in order for the meter to read zero.

I have installed new 25k pot with the 75k resistors.  Why are these not closer?  Is something happening on the left side that is cause a gain drop?  Could a tube be bad. 
How can i get these gains to track closer together?

 :-*OK BOTH POTS are now tracking the same both are about a quarter of the way up for the meter to read ZERO.  The problem was the resistor of the left must have became a cold solder from installing the new pot.  So now onto finishing the calibration.

Thanks
-Scott






Title: Re: D-LA2A Support Thread
Post by: saxmonster on July 29, 2014, 05:20:15 PM
OK, Its all done, HAHAHAHAHAH

Fully built and Calibrated.  The Pots and the wiring on them were the biggest issue I guess.

I suggest anyone building this to install  trimmers at RX25.

Everything works great. 

Gains settings are just a hair off from equal on both sides.
I am getting an accurate 5db of gain reduction on both sides and when I link them they are both perfectly equal.  But even without the link they are less than .25 of a db aways from each other.
Pretty cool.

One little issue remains and that is a hum in the right channel once I raise the gain above 65.  I have all the power wires twisted but I think it has to do with the pot being so close to the Light and power switch in the middle of the faceplate.
After I fix that all that is left to do if decide if I want to put in the zeners instead of the neon lamps
Find a setting for the limit response.
THEN PUT THE LID ON AND INSTALL IN THE RACK,hahahahha.

Thanks for a great project!!!!!!!!!
Title: Re: D-LA2A Support Thread
Post by: saxmonster on July 29, 2014, 10:46:35 PM
So I am going to leave the limiter response set to open (factory set)

The hum on the right channel is from the Limit/Comp switch so I will have to remake that with shielded wire.  I have move the wire out of the way of the power switch and all is quite now so I might just leave it but for those building I would use shielded wire for the limit/comp switch.

Now where did I put my lid?
Title: Re: D-LA2A Support Thread
Post by: weiss on July 31, 2014, 03:05:40 PM
just ordered a bunch of parts for my new la2a..

does anyone have some of the 3watt 4.7K resistors going spare? don't find it in any of the stores here in germany, even mouser backordered them..

i still didn't get the whole "zener diode" thing. what do i actually need? led's? only my meters?

thanks for your help!
weiss
Title: Re: D-LA2A Support Thread
Post by: saxmonster on July 31, 2014, 09:26:29 PM
Sorry I don't have any resistors.

You can replace the neon lamps with a 62v 5watt zener diode.  They are a bit quieter and will last far longer than the neons.  I have the neons in and will seed how long they last.  The neons are mounted on the PCB and tell you that the pcb is getting juice.  Nothing to do with the meters, they have led's in them.

-Scott



Title: Re: D-LA2A Support Thread
Post by: Harpo on August 01, 2014, 03:26:47 AM
does anyone have some of the 3watt 4.7K resistors going spare? don't find it in any of the stores here in germany, even mouser backordered them..
http://www.reichelt.de/5-Watt-axial/5W-AXIAL-4-7K/3//index.html?ACTION=3&GROUPID=3117&ARTICLE=2624&OFFSET=16&WKID=0& (http://www.reichelt.de/5-Watt-axial/5W-AXIAL-4-7K/3//index.html?ACTION=3&GROUPID=3117&ARTICLE=2624&OFFSET=16&WKID=0&)
Title: Re: D-LA2A Support Thread
Post by: jipsu on August 02, 2014, 04:18:11 PM
Hi list,

I've almost ready with my D-LA2A, just missing the vu-meters, audio-transformers, pots and switches (in other words: no cords in the molexes yet).
The board is ready with all components and tube wires.

Would it be safe to power on for a quick test and some measurements?
If "yes" what would be good places to measure?
Was thinking of the zeners for voltages (the neon replacements) and tube voltages. other i should try out?

Gotta say, this has been a great build, can't wait for the real test with audio!

ps: i'm looking for the audio transformers, so if anyone can help with the sh--ty high postals from Edcor, much appreciated :)
Title: Re: D-LA2A Support Thread
Post by: weiss on August 03, 2014, 08:37:33 AM
thanks saxmonster, thanks harpo!

i will try the zener diode. does anyone have a 2u template for the frontpanel?

weiss
Title: Re: D-LA2A Support Thread
Post by: saxmonster on August 03, 2014, 10:35:10 AM
This guy does

http://www.don-audio.com/Dual-LA2A-frontpanel-2HE-two-color-silkscreened

I almost went this way.
Title: Re: D-LA2A Support Thread
Post by: djfatum on August 04, 2014, 04:09:45 PM
hello where can I buy this kit to build ??
Title: Re: D-LA2A Support Thread
Post by: rock soderstrom on August 04, 2014, 04:25:04 PM
No kit, but good pcbs and transformers are here:

http://groupdiy.com/index.php?topic=39570.0
Title: Re: D-LA2A Support Thread
Post by: weiss on August 04, 2014, 04:26:22 PM
hello where can I buy this kit to build ??

there is no kit. you have to buy all the parts separately on your own.
but there is a bill of materials which includes a list of all parts. pcb (and optional transformer) is made by silent arts
Title: Re: D-LA2A Support Thread
Post by: djfatum on August 04, 2014, 04:27:51 PM
ok I understand thanks
Title: Re: D-LA2A Support Thread
Post by: jipsu on August 07, 2014, 03:36:51 PM
hello where can I buy this kit to build ??

there is no kit. you have to buy all the parts separately on your own.
but there is a bill of materials which includes a list of all parts. pcb (and optional transformer) is made by silent arts

Also in the b.o.m there are mouser order codes, so it's super easy to get correct parts (or replacements)...
Please note that one condensator is missing in the bom but it's mentioned somewhere...
Title: Re: D-LA2A Support Thread
Post by: saxmonster on August 08, 2014, 01:18:31 AM
Capacitor C8 is missing.
Title: Re: D-LA2A Support Thread
Post by: saxmonster on August 09, 2014, 01:08:36 AM
Hi Guys,

Having a slight issue with my unit.

I am seeing that my GR zero on the meters are walking.

I have set them a few times after the unit has warmed up and then put it back in the rack and then a day or two later the have moved off the zero line and to the left a little bit.

What is causing them to "walk" of off zero?

Thanks
-Scott

Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on August 09, 2014, 03:48:53 AM
Hi Scott,

this is normal, mainly caused by temperature drift.
Title: Re: D-LA2A Support Thread
Post by: saxmonster on August 09, 2014, 08:30:53 AM
Thats what I was thinking but just wanted to make sure. 

Enjoy your vacation!!!!!!
Title: Re: D-LA2A Support Thread
Post by: saxmonster on August 12, 2014, 01:30:36 AM
Would installing the zeners help with the drifting?
Title: Re: D-LA2A Support Thread
Post by: weiss on August 12, 2014, 10:28:41 AM
is there actually any wiring guide or a schematic? what means tbd resistor? and what modifications do i need to fit my tubes in the 2u case? all the links to the threads on nrg-forum in the opening post are down...
Title: Re: D-LA2A Support Thread
Post by: saxmonster on August 12, 2014, 10:50:15 AM
There is a PDF in the beginning of the thread with all the wiring for the front switches and a few threads that talk about the different transformer wiring.  You will just have to reread and copy and paste what you need, thats what i did.

THe TBD means "To be determined".  You use a trimmer to find the value that you need and then if you choose you can take it out measure it and then replace it with the correct resistor.

I don't have a 2ru case mine is in a 3ru but from what I remember  you have to shave the sides of the pins to the tube and t4bs sockets so that they fit flush with the pcb giving you the extra mm clearance you might need in a 2ru case.

HTHS.
-Scott

Title: Re: D-LA2A Support Thread
Post by: weiss on August 12, 2014, 11:16:26 AM
hey thanks for your answer!

You use a trimmer to find the value that you need and then if you choose you can take it out measure it and then replace it with the correct resistor.

and how do i know when the value is correct? what resistor do you have there?

weiss
Title: Re: D-LA2A Support Thread
Post by: saxmonster on August 12, 2014, 11:44:35 AM
When you set the gain reduction to zero on the meters you use the trimmers to adjust that and get them both on zero.  also you use them on RX25 to set the same compression levels on the meters.  I didn't replace mine yet with actual resistors.  I will probably just leave the trimmers in incase I have to readjust maybe down the line.

Title: Re: D-LA2A Support Thread
Post by: weiss on August 23, 2014, 12:29:21 PM
Here is my d-la2a. Currently using edcors. Panel made by frank. But still some wiring to do and not all parts arrived yet..
Enjoy.

(http://groupdiy.com/gallery/0/54909-230814122727-2261180.jpeg)

(http://groupdiy.com/gallery/0/thumb_54909-230814122727-258778.jpeg) (http://groupdiy.com/index.php?action=gallery;sa=view;id=259)(http://groupdiy.com/gallery/0/thumb_54909-230814122727-2591852.jpeg) (http://groupdiy.com/index.php?action=gallery;sa=view;id=260)(http://groupdiy.com/gallery/0/thumb_54909-230814122727-2601586.jpeg) (http://groupdiy.com/index.php?action=gallery;sa=view;id=261)(http://groupdiy.com/gallery/0/thumb_54909-230814122727-261533.jpeg) (http://groupdiy.com/index.php?action=gallery;sa=view;id=262)(http://groupdiy.com/gallery/0/thumb_54909-230814122727-2261180.jpeg) (http://groupdiy.com/index.php?action=gallery;sa=view;id=258)(http://groupdiy.com/gallery/0/thumb_54909-230814125605-2621301.jpeg) (http://groupdiy.com/index.php?action=gallery;sa=view;id=263)(http://groupdiy.com/gallery/0/thumb_54909-230814125605-263188.jpeg) (http://groupdiy.com/index.php?action=gallery;sa=view;id=264)(http://groupdiy.com/gallery/0/thumb_54909-230814125605-2642205.jpeg) (http://groupdiy.com/index.php?action=gallery;sa=view;id=265)
Title: Re: D-LA2A Support Thread
Post by: brewbacca on August 30, 2014, 06:51:20 PM
Hey all, I'm throwing my hat into the ring here

Just finished (ish) a "telronix" unit and it's working (ish). Here are some key parts I've used


The rest was mainly what was in the US BOM. It seems like that thing could use a bit of updating.

Some odd things to note that I was hoping to get feedback on:


(https://imagizer.imageshack.us/v2/1375x504q90/661/xCLUKI.jpg)
(https://imagizer.imageshack.us/v2/636x955q90/674/ps88Nt.jpg)
Title: Re: D-LA2A Support Thread
Post by: brewbacca on August 30, 2014, 09:36:49 PM
Also of note, I tried running a pair of guitar tracks, and when I turn up the compression, I can hear a lot of distortion (like a bad fuzz pedal). So obviously something is messed up in my build. Anybody know of some spots where this could happen? Could the t4s be backwards?
Title: Re: D-LA2A Support Thread
Post by: weiss on August 31, 2014, 06:37:52 AM
From where can i order the trim resistors when they weren't included with the t4b's? Ordered them from igs Audio
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on August 31, 2014, 06:58:26 AM
From where can i order the trim resistors when they weren't included with the t4b's? Ordered them from igs Audio
just use a standard 33K resistor

or use Mr. Andrews calibration:
http://groupdiy.com/index.php?topic=23253.msg276178#msg276178
Title: Re: D-LA2A Support Thread
Post by: weiss on August 31, 2014, 10:12:27 AM
just use a standard 33K resistor

or use Mr. Andrews calibration:
http://groupdiy.com/index.php?topic=23253.msg276178#msg276178

+1
Title: Re: D-LA2A Support Thread
Post by: saxmonster on August 31, 2014, 01:01:43 PM

  • First, using the 100K pots for gain, I'm getting +4dbu levels with barely turning up the gain. This is where the unit is at in the pictures. This thing is currently a hell of a mic pre ;). I'm assuming this gets more manageable with the 25K pot/75K resistor?
yes do this mod
  • When running a 1K tone at around +4dbu, I only get about 4 db gain reduction with the gr knobs cranked. It varies just a bit between compression and limiting. I assumed the limiting would be stronger than the compression setting, but I've never used a real la2a. In any case, my understanding is that this thing should be pretty noticeably compressing with the GR knobs all the way up. Any thoughts on what might cause this?
Check your wiring from the pots to the molex's.  Wiggle them and see if it affects the meters.  I had issues with the molex connectors. 
  • I'm getting around 280 VAC on the blue and red wire terminals (250V). Should I look into adding high watt resistors to get it down to 250V?
Not sure on this.
  • When I measure voltage on the heaters (at each terminal with the DMM common to ground), I'm getting around 3.5V AC. I've checked the heater wiring and it looks good so I'm not sure if there's a trick to measuring that.
as long as your tubes are glowing you should be ok
  • When I switch the VU to GR mode, the needle doesn't move at all and just stays at around -20 on the meter. My understanding is that it should move up to around 0 db (give or take)? Any thoughts there?
you need to adjust the trim pot to get GR to read zero on each channel, search this thread
[/list]

(https://imagizer.imageshack.us/v2/1375x504q90/661/xCLUKI.jpg)
(https://imagizer.imageshack.us/v2/636x955q90/674/ps88Nt.jpg)
Title: Re: D-LA2A Support Thread
Post by: brewbacca on August 31, 2014, 03:36:51 PM
Thanks for the response saxmonster!

Title: Re: D-LA2A Support Thread
Post by: brewbacca on September 15, 2014, 11:09:06 PM
So still no luck with getting this thing to compress correctly, although I've made a bit of progress with some of the other issues.
- I realized that I wired the dual switch incorrectly.
- I stuck a 33K resistor in R125 and R225 and am able to get the meter to zero in gain reduction mode,  but it doesn't move at all when it should be compressing (in theory).
- I went with the 25K pot with the 75K resistor, and yeah, that should be standard ;)

 I haven't been able to give this too much time for troubleshooting, but have been able to figure a couple things out.

Here's a video if anybody wants to take a gander: http://youtu.be/FLgo-2fwWRA

If you have a couple free minutes I'd love it if you could take a look at the video and let me know if you have any input.

Thanks!
Title: Re: D-LA2A Support Thread
Post by: saxmonster on September 16, 2014, 01:25:33 PM
A few things that I noticed

The lights flickering on the board are ok thats normal.

Does your channel two work?  The same?

You need to reread the pdf and setting up the meter section found in this thread just do a search.

It sounds like it is compressing but your r37 limit response might be set the wrong way try turning it all the way the other way.

Basically use your daw to send 0db out and an adjust your meter to read zero then feed it back into the daw and it should still be 0db

Then flip the meter to GR mode and it should still read 0db.  If not fix that its in the pdf.

Then turn the peak reduction knob till you get about 5db of gain reduction back into your daw.

Then adjust the meter to read -5db.

Thats is just for one channel do the same for channel two.

Then reread the stereo adjustment procedure to get the two channels to be fairly close around -5db.

You might have to put a trimmer in the r25 spot to get them to track properly.

You will have to do this process a few time cause one turn affects the other spots, hahahah

I know its a lot but just reread everything until you understand it.


Have fun.
Title: Re: D-LA2A Support Thread
Post by: brewbacca on September 16, 2014, 01:57:20 PM
A few things that I noticed

The lights flickering on the board are ok thats normal.
I thought so, but I wanted to check

Does your channel two work?  The same?
Yes, they both function exactly the same as far I can tell.

You need to reread the pdf and setting up the meter section found in this thread just do a search.
I'll be sure to give it another read through, but the meter stuff isn't really my main concern. I was going to hold off on that until I was sure it was compressing correctly

It sounds like it is compressing but your r37 limit response might be set the wrong way try turning it all the way the other way.
So it's only going down about 3 or 4 db with the compression turned all the way up. Is that normal? It seems like it should squash the signal more. The signal running into the compressor is a ~+4dbu 1K sine wave coming from my daw(as you described above) through my mixer which has meters . I have a 1meg pot on the front panel attached to r37(s) and adjusting that makes a slight difference, but not a ton.

Have fun.
Thanks ;)
Title: Re: D-LA2A Support Thread
Post by: saxmonster on September 16, 2014, 06:49:52 PM
Try using a 440 signal and see if you see anymore of a difference.

Sending a 1khz tone at 0db out of my digital performer daw I have to set my gain to about 20 (I did the mod also)

Going thru the la2a with the peak reduction at 50 I am getting a little over 5db of gain reduction back into my daw and the meter on the la2a says -5db even.

With the peak at 75 I am getting about -10.5 of reduction in my Daw and about -10 on my meter.

I don't think its an accurate science but its close.

I am using T4B's from drip.  Let me know how you make out.

Can you post  a photo of the outside of your panel and the inside so I can see how you did the R37 limit response pot.  I would love to do it but I am afraid I might mar my beautiful front panel.

-Scott
Title: Re: D-LA2A Support Thread
Post by: brewbacca on September 16, 2014, 07:02:22 PM
I'll try the 440 and see what happens. I'm also going to try downloading a LA-2A plugin of some sort so I can compare. I had an LA-610 and the compression on that would do waaaaay more gain reduction with grain reduction turned up, although I know that's different than an actual LA-2A.

You can see the pot/knob I'm using for r37 in the pics I posted above. I can get some more detailed picks, but basically I just drilled a 1/4-3/8" hole over the gain reduction  pot. If you haven't drilled a panel make sure you get a center punch of some sort and then start with smaller bits and gradually go to larger bits.
Title: Re: D-LA2A Support Thread
Post by: saxmonster on September 16, 2014, 07:16:11 PM
Sorry didn't see the pics, looks great though.

I think i am hearing harmonic distortion when you turn the peak reduction all the way up. 

Hopefully someone else will chime in to help you.

Maybe just double triple check all you connections and wiring.  It has to be something simple. It always is.
Title: Re: D-LA2A Support Thread
Post by: djfatum on September 20, 2014, 06:40:18 AM
HI is there a place where I order all the components can recommend something  ;)

Andrzej
Title: Re: D-LA2A Support Thread
Post by: weiss on September 20, 2014, 11:19:57 AM
Quote
WSM600/15K
1--Brown
4--Green
5--Blue
8--Grey

WSM15K/600
1--Yellow
4--Green
5--Grey
8--Pink

Does this also work for 10k/600 and vice versa? Can i combine 600/15k and 10k/600 audio transformers?
Title: Re: D-LA2A Support Thread
Post by: [silent:arts] on September 21, 2014, 05:35:55 AM
If I recall correctly all pinouts at Edcor are the same.

600/15K and 10K/600 you will have more gain, but it will work.
Title: Re: D-LA2A Support Thread
Post by: weiss on September 21, 2014, 10:02:08 AM
thanks!
Title: Re: D-LA2A Support Thread
Post by: djfatum on September 21, 2014, 10:49:46 AM
Hi, where can I buy good T4B cell to build D-LA2A  ??

Andrzej
Title: Re: D-LA2A Support Thread
Post by: weiss on September 21, 2014, 04:28:13 PM
Hi, where can I buy good T4B cell to build D-LA2A  ??

Andrzej

how about google?

IGS: http://www.igsaudio.pl/en/product/others/70-photocell-t4bx
Kenetek: http://www.kenetek.com/T4AT4BUnits/KenetekT4BModules/tabid/300/Default.aspx
Drip: http://www.dripelectronics.com/index.php?option=com_content&view=frontpage&Itemid=1
Title: Re: D-LA2A Support Thread
Post by: weiss on September 23, 2014, 07:33:39 AM
hey guys. i got some issues with my la2a. I think it is obvious, that i can't continue with calibration in this condition.
I made a video showing what doesn't work: http://youtu.be/Kdk6pENa4aY

To sum it up:

- Audio is going through while unit turned off (is this normal?)
- When turned on, only left channel works
- Potentiometers don't work properly, weird behaviour (shown in the video)
- No audio is being processed at all (compression, limiting etc)
- Left meter does not output vu signal

Here are some pictures as well:

http://www.imageupload.co.uk/images/2014/09/23/IMG0430.jpg
http://www.imageupload.co.uk/images/2014/09/23/IMG0431.jpg
http://www.imageupload.co.uk/images/2014/09/23/IMG0432.jpg
http://www.imageupload.co.uk/images/2014/09/23/IMG0433.jpg
http://www.imageupload.co.uk/images/2014/09/23/IMG0434.jpg
http://www.imageupload.co.uk/images/2014/09/23/IMG0435.jpg

Still need to power the led's btw.

thanks for your help
weiss
Title: Re: D-LA2A Support Thread
Post by: bernbrue on September 23, 2014, 10:20:50 AM
Hi,
would be nice to have bigger pictures of your built. The picture you posted cannot be found (Error 414). I had a look at the video. A few things to consider (maybe too obvious, but we have to start somewhere):

< Audio is going through while unit turned off (is this normal?)>
yes, we call this true relay controlled bypass

< When turned on, only left channel works>
In the video I saw that the meter starts to peg when turning up the gain . Check wiring of the potentiometers. The shield of the wire has to be connected to ground. Have a look at the pcb layout, which pin of the molex connector goes to ground. There is a complete wiring guide somewhere. Check this out.

< Potentiometers don't work properly, weird behaviour (shown in the video)>
wrong wiring, see above

< No audio is being processed at all (compression, limiting etc)>
Maybe a silly remark, but did you do the heater wiring underneath the pcb?
Try to make your left channel work properly. Then compare it to the right channel

- Left meter does not output vu signal
3K6 resistor installed? Toggle switch wired correctly? Molex connector plugged into the right place?

I bet there are some very simple things gone wrong! Read the wiring & calibration guide attached.
Bernd
Title: Re: D-LA2A Support Thread
Post by: weiss on September 23, 2014, 10:47:12 AM
Hi,
would be nice to have bigger pictures of your built. The picture you posted cannot be found (Error 414). I had a look at the video. A few things to consider (maybe too obvious, but we have to start somewhere):

< No audio is being processed at all (compression, limiting etc)>
Maybe a silly remark, but did you do the heater wiring underneath the pcb?
Try to make your left channel work properly. Then compare it to the right channel

- Left meter does not output vu signal
3K6 resistor installed? Toggle switch wired correctly? Molex connector plugged into the right place?

I bet there are some very simple things gone wrong! Read the wiring & calibration guide attached.
Bernd

thanks, i fixed the pictures. Yes i read that guide and i soldered all heater wires as the manual says. Voltages are okay.
What 3,6k resistor do you mean? Wiring is correct and molex as well.
Title: Re: D-LA2A Support Thread
Post by: bernbrue on September 23, 2014, 11:16:36 AM
So lets do some basic tests:

- Turn all pots to 0.  Switch bypass off.  Set meters in VU mode.  Sent a signal through the unit. You should hear nothing at first, then turn up 
   the gain pots. You should hear the signal on both channels, the VU meters should twist up.
- Set the unit/meters in GR mode. The meters should stick to 0dB. Turn up the gain reduction pot. The unit should start to compress, the 
   meters should go down.

The video is quite confusing, since you hear music all the time and it doesn´t get louder when you turn the gain pot.

General things to check:
- Are the relays the correct ones? Do they click when switched on/off?
- what about the grounding? In the picture I can see, that not all ground wires go to the same star ground
- did you connect ground of the 5V psu to main ground (jumper)?
- the vu meters need an additional 3K6 resistor on their negative side.
- check direction of the diodes, that replace the neon lamp.
- check the input/output transformer wiring, especially the molex connector on the pcb.
Bernd
Title: Re: D-LA2A Support Thread
Post by: weiss on September 23, 2014, 11:48:47 AM
Hey thanks for your reply Bernd!

- Turn all pots to 0.  Switch bypass off.  Set meters in VU mode.  Sent a signal through the unit. You should hear nothing at first, then turn up the gain pots. You should hear the signal on both channels, the VU meters should twist up.
I hear the same signal in bypass mode and non-bypass mode. Vu displays -20db all the time on both channels. Gain pots do nothing when turned up.

- Set the unit/meters in GR mode. The meters should stick to 0dB. Turn up the gain reduction pot. The unit should start to compress, the meters should go down.
Meters stick to 0dB but when i want to compress via the peak reduction pot, the signal stays the same and meters don't move.

- Are the relays the correct ones? Do they click when switched on/off?
Yes, they click when turning on and off. Type: Omron G5V-2 (5V)

- what about the grounding? In the picture I can see, that not all ground wires go to the same star ground
They do.

- did you connect ground of the 5V psu to main ground (jumper)?
Yes.

- the vu meters need an additional 3K6 resistor on their negative side.
Thanks for this. But everything else should work even if i missed this resistor!?

- check direction of the diodes, that replace the neon lamp.
I did. the round mark on the diode points to north to the top of the pcb.

- check the input/output transformer wiring, especially the molex connector on the pcb.
I did so as well, using this information:

WSM600/15K: 1--Brown / 4--Green / 5--Blue / 8--Grey
WSM15K/600: 1--Yellow / 4--Green / 5--Grey / 8--Pink
Title: Re: D-LA2A Support Thread
Post by: bernbrue on September 23, 2014, 12:51:05 PM
Very strange!
Are your voltages correct? Did you measure? You should have something like 120V after R113 (220K) and 220V after R117 (10K).
If the unit doesn´t pass audio and the gain pot does not influence the audio level, there must be something wrong either
- with the tubes (V101/102)
- gain pot
- B+ voltage
- bad soldering
- broken input or output transformer

I attached the original schematic for you to check the preamp (upper part of the schematic)
Bernd
Title: Re: D-LA2A Support Thread
Post by: weiss on September 23, 2014, 01:10:36 PM
Very strange!
Are your voltages correct? Did you measure? You should have something like 120V after R113 (220K) and 220V after R117 (10K).

- I think so, R113 has 118V and R117 about 215V
- V101 is JJECC83S tube and V102 Electro Harmonix 12BH7AEH
- For pots i used 100k log b by omeg
- my soldering was never bad during my last projects, everything worked from the first start
- transfomers are all new

how can i measure the heater voltage?
Title: Re: D-LA2A Support Thread
Post by: bernbrue on September 23, 2014, 02:03:17 PM
I saw in your video that the VU meter of the right channel starts to move when you turn up the gain pot. Thus the signal passes at least the circuit up to output transformer. I myself make sometimes very obvious mistakes, so there is no accuse meant in my assistance. I suggest to double check the right channel first:

- check xlr input/output wiring
- verify that both relays of each channel are working (I suppose here is something wrong)
- check the molex connector of the input transformer
- check the heater voltage at each tube (pins 4&5, 6AQ5 pins 3&4)
- check your test setup (I saw the RME meters of your input channels moving)
- even brand new transformers can be broken, especially the Edcors you are using

Bernd

Title: Re: D-LA2A Support Thread
Post by: weiss on September 23, 2014, 02:32:40 PM
how can i test the relay? i think as well that there has to be the issue, i really didn't find any wrong wiring until now.
All my heater voltages are around 3,25-3,28V. Is that correct? And i can say for sure that my setup works! :)
Title: Re: D-LA2A Support Thread
Post by: audiophreak on September 26, 2014, 03:57:03 PM
Hello All,
                    After having my D-LA2A up and running for a while now (  and sounding absolutely Fantastic  ;D  )   the 6AQ5A's get very hot and extremely close to C171/172 and C271/272 - so I found a couple of 7-pin test sockets ( as I used a 3u case  ) and those caps are much cooler now , ( how ever  C171 still is hot to the touch compared to the others )  I may have to replace that one.  She still sounds awesome , so I don't think this has affected operation in any way , heres a pic
Title: Re: D-LA2A Support Thread
Post by: brewbacca on September 29, 2014, 12:59:28 PM
I tried the test where I opened one of my t4b's up and ran the unit in a dark room. I didn't see any light coming from the illuminated panel, but the meter dipped a bit when on gain reduction mode. That was probably getting light from the meters or the neon lamps.

I'm wondering if there's a problem with my t4b's. Does anybody have any suggestions for testing the t4b or the socket for the t4b? Like, what voltages should be on what pins?

Edit: I'm getting around 3.5V on pin three of the t4b socket. Is this high or low? Also, should pin 1 and pin 2 both be connected to ground? I get continuity between pins 1 and 2 on both the socket and the t4b's I have.

This is the pin order I found earlier in the thread:
1   NC
2   GND
3   EL panel input
4   GND
5   VU meter LDR
6   GND
7   Signal LDR
8   GND

Thanks guys! I'm so close I can taste the happiness :)

Yet another edit: After some searches it seems that yes, pins 1 and 2 do connect.
Title: Re: D-LA2A Support Thread
Post by: offthewallstudio on October 01, 2014, 01:14:46 PM
Hi everybody. I want to build this unit. I need a mouser cart for this. I can buy the PCB for a Dual LA 2A.
and the  PSU transformer from Volker.

I can buy the metal box template from Dan. I NEED everything else! lol...

Much help would be appreciated!!!!! I am new to this website and not sure how it works so feel free to email me :)
[email protected]

This is for the DUAL LA 2A not a single, thank you!!!!!
Title: Re: D-LA2A Support Thread
Post by: brewbacca on October 01, 2014, 01:51:54 PM
There's a link to the BOM and other super useful on the first page of this thread. You can use that to make a mouser cart. The BOM is missing a few items and I think(?) has some extra items, so I recommend reading through the pdf and checking parts in the BOM against the PCB before ordering. Also, definitely go for the 25K pot in series with a 75K resistor for the Gain pot. The search at the top of the page is also super helpful for looking things up in the thread.

Also, don't do this late at night! Aside from the dangerous voltages, it's easy to make dumb mistakes. I just finally noticed that I wired my heaters incorrectly for the 6A5QA after about a month of scratching my head trying figure out why the compression wasn't working!

Good luck!
Title: Re: D-LA2A Support Thread
Post by: brewbacca on October 04, 2014, 01:53:33 AM
Hell YES! Got this thing working finally!  ;D ;D ;D

Sounds pretty good so far. I'm not hearing a ton of noise too so I must have done some things right the first time :)

Full disclosure: I wired the heaters incorrectly for the 6AQ5A sockets and thus ruined some tubes. Got some new tubes and fixed the heaters.  Now I feel much more confident about tracing voltages and reading schematics ;)
Title: Re: D-LA2A Support Thread
Post by: offthewallstudio on October 16, 2014, 04:07:58 PM
Hello everyone! I am getting ready to build a D-LA2A. I have one built 2 of the 500 series mic pres with very minor problems. Any tips or pointers would be most appreciated! Is there a list in order on how to build this?  :o
Title: Re: D-LA2A Support Thread
Post by: darkus on October 22, 2014, 04:28:33 PM
I just wired up my d-la2a but now i feel ive been getting mixed information.

Bernbrue said the meters need the 3.6k resistor on their negative side. In the wiring guide that i found from the compiled pdf i saw it was on the positive side. Which way is it?

Also the gain pot mod, is the resistor in series with the first pin or parallel between the two (im excluding the shield pin)

Someone said parallel earlier in this thread and on this page i read its in series, which way is it?  :o

Im still waiting my matched Kenetek T4B's but ive powered it up, all voltages look good, tubes are glowing etc. im so happy.
Title: Re: D-LA2A Support Thread
Post by: jipsu on October 23, 2014, 02:34:48 PM
I just wired up my d-la2a but now i feel ive been getting mixed information.

Bernbrue said the meters need the 3.6k resistor on their negative side. In the wiring guide that i found from the compiled pdf i saw it was on the positive side. Which way is it?

Morjensta :)

Taken from the La2a schematic, looks like the negative side.

Title: Re: D-LA2A Support Thread
Post by: saxmonster on October 23, 2014, 04:07:52 PM
I used the positive side
Title: Re: D-LA2A Support Thread
Post by: darkus on October 24, 2014, 01:38:40 AM
This is exactly what i mean. Wtf?!  ;D

The wiring guide said + so i have it there. Havent tested yet if it works.

What about the potmod wiring? Confused here....
Title: Re: D-LA2A Support Thread
Post by: softshoe on November 04, 2014, 04:02:18 PM
I'm wondering if anyone can help me. I've got audio being passed when the gain pot is at zero. (seems to be high passed audio). In trying to find the problem I began breaking connections to see if I could isolate the problem. I ended up with most molex connections removed and only 1 single 12bh7 tube and I was still getting audio.

General info:
* Both channels act identical and will pass audio with just 1 12bh7 and the input/output transformers connected.
* The channels otherwise function as expected. The gain and peak  knobs work as expected. T4bs light and will compress the audio.
* The peak reduction knob will effect the audio when gain is zero.
* input transformers are utc a-10

Things I've tried
* I tried connecting audio to the adjacent  channel to see if there was some type of short getting audio in the ground. no audio was passed
* I tried different 12bh7 tubes. (5-6) all same
* tried both channels. they act identically

I'm stumped at this point. Anyone have any ideas?

Also, should all 8 tubes be too hot to touch?
Title: Re: D-LA2A Support Thread
Post by: dmp on November 04, 2014, 04:19:23 PM
Quote
Bernbrue said the meters need the 3.6k resistor on their negative side. In the wiring guide that i found from the compiled pdf i saw it was on the positive side. Which way is it?

I don't think it matters. The vu meter is measuring current, and needs a 3.9k in series like other vu meters. It doesn't matter if the resistor is on the + or - side.
Title: Re: D-LA2A Support Thread
Post by: saxmonster on November 13, 2014, 09:32:33 PM
Hi Guys,
Having an issue with my D-LA2A now.  The left channel seems to have this high pass filter that comes on when no signal is going through the channel.  I have included an audio file of it.  Sorry for the TV in the background and the clicking clock, the wife was home hahahah.  What should I start looking at to get rid of this issue.  It doesn't seem to do it when I first turn on the unit.

I am running a elam251 clone into a 1073 clone which work just fine.  I have narrowed the signal channel issue down to the left channel on my la2a.  the right channel seems ok for now.   Thanks so much.

http://www.ehornstudios.com/media/LA2A.aif

anyone?  I got a visual on all the caps and everything looks great.
Title: Re: D-LA2A Support Thread
Post by: Rocinante on November 14, 2014, 12:37:06 PM
Ugg. 
I am so close I can taste it. 
Okay so I have read (and reread) this thread and have taken days (then weeks) off to meditate on it and work on other projects hoping I would come back to it and it would hit me.  Hit me it has not.
I have been reluctant to ask for help on this thread cause i figured somewhere, someone had already posted a problem similar enough to mine and that I just needed to find it but I haven't been able to.  I am sure it's in here somewhere since i am so close and I think I remember someone posting with a similar problem but just can't find it and I give up and need to ask for help.
Or at least a point in the right direction.
First things first; this has been my favorite project to date.   By far.  I have learned soooo much reading this thread and building this thing.  It feels like ten projects in one awesome one.   Thank you Volker and everyone else; it's been a trip.
Onto what's up;
So I have only built one side using  Edcor in and out (wsm 600/15k and vice versa) as well as using Kenetek's T4B.  I am currently saving up for Sowter in and outs but might just grab some more Edcors until then.   
I have also implemented the 25k pot mod using the required 75k resistor and 12ay7 tubes.
I have power and all my voltages are pretty on.  I ran shielded wire throughout except for lights and what not. 
When putting music through I have gain and not really compression or it feels like too much and it's drenched in low frequency I would even say there's a high frequency cut off.  Everything sounds like its in a reverb tank.  Vocals are almost non existent.   They are in the background.  It feels like a grounding issue but I have every ground in place, my star ground looks good and i have run wires to the front panel and sides.  I also have zero noise or hum.
Audio comes through and the bypass works perfectly.
The gain works but I have to crank it and reading this thread that should not be like that at all.
I would really appreciate it if someone could point me in the right direction.  Maybe its a wrong resistor value somewhere but they all look right after checking and rechecking a bunch of times.
Here are some pics of the inside.
(http://i.imgur.com/EJ6b0Lol.jpg)
In the above pic the bh7 and ay7 are in the wrong places which I noticed right after taking it. I have swapped tubes since then and still my problem persists.

Here's the side without the tubes or T4B in.
(http://i.imgur.com/aumZEMSl.jpg)
and during daylight
(http://i.imgur.com/cTIImfOl.jpg)

Finally, just look at how awesome that looks, this needs to get working.   ;)
(http://i.imgur.com/LuSdyFEl.jpg)
Please help me make it sound awesome too.
Title: Re: D-LA2A Support Thread
Post by: jipsu on November 15, 2014, 03:34:13 PM
Everything sounds like its in a reverb tank.  Vocals are almost non existent.
[/quote

Just a wild guess: the other channel is inverted at some point so there's some sort of "stereo without mono signal" combination?
Sometimes pluging a stereo jack about the mid-way in causes an effect that reminds your description...

But as said, just a wild guess...
Title: Re: D-LA2A Support Thread
Post by: darkus on November 19, 2014, 06:01:17 AM
Hi there!

I have a problem with my build. I just put my new Kenetek's in this unit and started to calibrate it only to see i have a problem with my meters.

Im feeding a 0.775V signal into it and when the unit is IN and i crank the gain i can hear the signal. My meters jump right to -7 and stay there. I can hear the attenuator working cause when i turn it the signal gets weaker. But my meters show no movement no matter if i put them on GR or VU.

The only way i can get my meters back down to -20 is to tap them. Are they broken? I have the resistor on the positive side and ive checked trafo wiring etc.
Title: Re: D-LA2A Support Thread
Post by: MountCyanide on November 19, 2014, 08:51:13 AM
Sounds like pressure. Loosen the screws if you've mounted them too tight.
Title: Re: D-LA2A Support Thread
Post by: Ro