new la-2 pcb

[tomcat]

Thanks Gregory. Did you get my mail some days ago?

 

[tomcat]

I spoke to gregory about this and like to post this q here for discussion as well.

When building a stereo unit there are two possible configurations regarding the power xformer.

1. 2 seperate, one for each channel
2. 1 custom wound torrodial, for both channels (80mA / 4A)

Are there any possible problems to expect when you use just one xformer for two channels?

EDIT: maybe a stupid question :wink: Imho it should be no problem. But im rookie regarding tubes :?

 

[hejsan]

Hi there,
I can't seem to find info on this:
I have Drip Electronics LA-2A PCB REV10 LOMAYESVA 05

On the PCB R12 is marked 2.7k
On the PCB R14 is marked 470k
On the PCB R36 is marked 1k
On the PCB R34 is marked 2k 2W

In the partlists I have for originals, R12 is marked 220k and R14 is marked 2.7k and R36 is marked 470R and R34 is marked 10k 2w

So, what should I do?

Is there a partlist/BOM somwhere in this thread for this PCB?

Thanks,
hejsan

 

[dripelectronics]

oh no ,
the parts list that you have is wrong.

follow the pcb values.

ill try to pull togeather a new bom.

gregory

 

[hejsan]

Thanks, much appreciated.

 

[babyhead]

Greg-

I am having such a party with your PCB today! I am so working except for a few minor things.

I have a steady buzz :wink: . All kidding aside I will get back to you after I work on the grounding.

The other problem deals with the threshold. It seems way too low. Is the 22k 2w on the PCB not 10k as in the schematic for a reason? If it is to tame the threshold for a A10 etc, I am using jensen 10K:10k, so that might be that.

I added the Jensen ground lift switch for the input ala their Generic Tube Input schematic. I wonder if I should do this for the output as well.

Speaking of Jensen, has anyone here tried to implement the Jensen output stage?

First I lost my internet, so I built my G7. Next my converter dies and needs to go in the shop for 10 days, so I do my LA. What does that say?

:guinness: :guinness:

 

[babyhead]

Fixed the buzz, so on to the threshold. I'm picking up a 10k 2w resistor on the way lunch with mom.

This one is almost done. I'm waiting for my pilot lights to come in before the front panel gets holed up.

I'm beside myself, like saying my ABCs for the first time.

:guinness:

 

[safe as milk]

hi gregory
i sent you an email about some t4b's/boards
(in case it's in your spam)

thanks

 

[dripelectronics]

hi there ,

cool got the email and responded , thanks milk.

ive only tried the jensen wired up with out their mods ,
sounds pretty cool , but ill have to give the mods a try.

wich threshhold ?

the older la2's used a 22k as doed the mondern

if going to a 10k you might switch r36 to a 470 ohm as is in the schematic.

using a 22k brought all the voltages with in perfect range.

10k shoots up a few things here and there , but i doubt any problems
from it.

tell be about the threshhold.


hejsan , really sorry about the delay in the parts list ,

download the ver 2.0 manual , the parts list is virtually the same.

except for the pcb mount pots and fuse clips.

http://www.lomayesva.com/drip_opto_manual.pdf

best ,

g.

 

[guavatone]

Meter works in +4 mode
-doesn't budge in GR mode even when compression is so high it's distorting

-Resistor values are correct in that area. I double checked the switch connections. I followed alighnment instuctions for Zero input.

Any tips?

 

[dripelectronics]

email me a couple of pics of the project ,

[email protected]


ill take a look.
what type of meter ?

does it need the rectifier circuit ?

g.

 

[guavatone]

Thanks. It is a Beade meter that someone on BM sold me and said they were the propper ones for LA2a.

I am not sure if it needs a Rectifier. I am unfamiliar what the rectifier circuit is but if it's a couple of diodes, I could give it a try.

 

[dissonantstring]

hi charlie,
before you try to add a germanium rectifier bridge, try feeding the meter (out of circuit) with a tone generator. feed it 1KHz at 0dBu and see if you get that on the meter, then try lowering and raising the output level of the generator to see if it is reflected in the movement of the meter. i'll bet the beede meter already has a rectifier bridge if it is a VU meter. is signal passing when have it in GR mode? it may be a meter switch wiring problem rather than the meter itself if it works fine in +4 mode.
-grant

 

[guavatone]

re. last post, all is fine - -all is fine with meter

- found most of the mods for LA2A, makes me think it's much better for my use to mod them.


I do get distortion after 3dB of Gain Reduction. can someone confirm if this is normal. I used 1K tone and the distortion emphasised higher harmonics.
-I fixed this...it was an embarassing miswire of the limit adjust pot.

 

[mfdu]

[quote author="dripelectronics"]oh no ,
the parts list that you have is wrong.

follow the pcb values.

ill try to pull togeather a new bom.

gregory[/quote]

phew - that's a relief. i have two of your rev1.0 boards whic i have been accumulating the parts for. was just checking my BOMs to get started during the week.

please advise - is there a correct BOM?

i think i've given up converting them to australian suppliers - i'll just buy through Mouser and pay shipping. sigh.

chris.

p.s. any news on shipping of the t4b?

 

[Purusha]

Yes, the new bom would be really nice :thumb:

But too bad, I already ordered the parts for the PCB 1.0. Is there alot of changes?

 

[dripelectronics]

ill cross refrence the v.2 parts list ,

everything should be the same of course minus the
fuse clips.

resistors and caps are the same as in the v2.0 manual
.

 

[Svart]

anybody use trafos that weren't the originals? something like edcors?

 

[dripelectronics]

some one in the p2p la2a thread has , im not sure who ,
they said they worked great , no occilations.

best , g

 

[mfdu]

i've got a pile of strange old trannies which i plan on trialling.

the hardest thing is going to be determining the wiring, but i'll get there.

so yes, i'm going a bit strange on the trannies, but i can't say yet how it's worked out.

chris.