D-LA2A Support Thread

[MicDaddy]

Lowfreq, try swapping T4bs see if the problem follows the optos?

 

[Lowfreq]

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.

 

[[silent:arts]]

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.

 

[andia]

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

 

[audiophreak]

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 :

 

[audiophreak]

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 ?

 

[[silent:arts]]

yes - no power to the relays = bypass.
this way the comp passes signal even if the fuse blows 

 

[audiophreak]

yes - no power to the relays = bypass.
this way the comp passes signal even if the fuse blows 

Thank You 

 

[audiophreak]

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  :-[

 

[MicDaddy]

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. 

 

[ethervalve]

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

 

[andia]

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

 

[desol]

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.

 

[abechap024]

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

 

[creature.of.habit]

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.

 

[desol]

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.

 

[creature.of.habit]

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.

 

[martthie_08]

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 ?

 

[[silent:arts]]

last question for today: what the hell happened to nrgrecording.de ?

use www.nrgrecording.de
without www. it doesn't work for me either ...

 

[[silent:arts]]

and congrats on the D-LA2A.
we want to see some pics, you know this ;-)