D-LA2A Support Thread

Are you sure this behavior is new?
Drifting is normal for tube gear between cold and warmed up,
and it might be the meter only.

[silent:arts] said:

Are you sure this behavior is new?
Drifting is normal for tube gear between cold and warmed up,
and it might be the meter only.

Click to expand...

Not completely sure. The meter doesnt shift from 0VU, it just shows less gain reduction. When no signal fed it still returns to 0.

Could I be losing gain at the input somehow?

-delete error-

Hi everybody,

I built my D-la2a 4 years ago. Easy built and every things worked fine from the first time.
But, Since a few weeks I can't have a good Vu tracking on the right channel. The meter show 2db less than what's really happened.
It'seems to come from the T4b cell. I've noticed that I also have more compression with this T4b cell (fixed with the stereo adjust trimpot).
My T4b cell came from Kenetek and I buy them matched.
Is it possible that my matched T4b cell become dismatched with time ?
Thanks for your help.

Components do age.
In a D-LA2A the T4Bs and Tubes will age similar (equal hours count, equal environment / temperature etc),
but not equal.
All fine with a new calibration from time to time.

I try to do  a new calibration of VU meter but I can't find the right setting with R25. It's happen only with one of my T4B cell The best things I can do is that the  GR meter show 2db less than the really compression. I don't think it's comming from tube or other components. Do I have to change the value of the R25 trimpot  (I use a 47K trimpot)?
Thanks.

Hey y’all! First time posting here. I built an la2a a few years ago from the recproaduio layout like many others have. It sees constant use in my studio, but after hearing others built from the same layout, the slight amount of top end that mine loses has started bothering me. My question to you guys is - is there a specific part of my circuit I can check (make sure no mistakes were made), or modify to give it better top end response? Thanks in advance! 

PS -don’t make fun of my rats nest wiring. This was the first thing I had ever built! Haha

It could be u need to adjust the value of the output transformer zobel capacitor for flat response. Think it's C4?

Make sure you have the limiter response trimmer turned the right way.

mrclunk said:

It could be u need to adjust the value of the output transformer zobel capacitor for flat response. Think it's C4?

Click to expand...

I did quite a bit of digging since I posted this, and I believe this is correct. For some reason when I built it I put a 47pf silver mica cap in the C4 position. From what I've read, and calculated, this is giving me a HUGE attenuation of frequencies above 2-3k. I have a 330pf silver mica cap on order, and I believe it will be the solution to my problem. I will report back. Thanks for your help!

TDJ said:

I did quite a bit of digging since I posted this, and I believe this is correct. For some reason when I built it I put a 47pf silver mica cap in the C4 position. From what I've read, and calculated, this is giving me a HUGE attenuation of frequencies above 2-3k. I have a 330pf silver mica cap on order, and I believe it will be the solution to my problem. I will report back. Thanks for your help!

Click to expand...

I use silver mica 150pf for a nice tone ;-)

Hi. I'm finishin one D-LA2A unit . I have two UTC O-1 units.... Can I use these in input?  seems to me that they are very similar to UTC O-10 but reversed... on paper. Maybe I'm wrong and I can't interchange them and must look for sowter modern version for LA2A? Maybe they are crap on that function? they seem  cheaper on internet... ???
Thanks for all! 

Hi,
I just finished one second Dla2a, or almost...because sound does not pass through it (except when unit is "off").
Some facts :
- I firstly forgot to connect the heaters, during first powering on..i do not know if Something can be broken by this.
- I also missconnected the 7805, it was in the wrong side..i do not know if it can broke something
- Sound passes when unit is not powered on, so no problem at the connection of xlr's
- When unit is powered on, no sound at all
- Neon are illuminated, so as tubes, vu meter find the 0 in "GR" mode.

In my opinion the Relay circuitry is involved there :

- With all Relays Molex disconnected, i have continuity between the 2 pins of "Relay 5V", like it is already switched..It is like this on 3 "Relay 5V" connections. I do not find any short under the pcb...

Looks like the relays are working fine.
If they wouldn’t work you would have the same sound with and without power.

[silent:arts] said:

Looks like the relays are working fine.
If they wouldn’t work you would have the same sound with and without power.

Click to expand...

Thank you for your reply. Could you please tell me if it is normal to have 2 pins of "5V relay" molex, shorted even with nothing plugged in ?.. I think it should be normal to have them disconnected when switch is "off" position.

The coil resistance of an Omron G5V-2-DC5 relay is 50R. There are two relays in parallel, giving you a resistance of 25R. Most Multimeters will see this as a short and „beeep“.

[silent:arts] said:

The coil resistance of an Omron G5V-2-DC5 relay is 50R. There are two relays in parallel, giving you a resistance of 25R. Most Multimeters will see this as a short and „beeep“.

Click to expand...

Thank you for saving my time..i will try to solve tonight.
Hugo

Check if your "GAIN" pots are wired correctly.
Assuming it is the same on both channels it is rather not a short are broken component.

[silent:arts] said:

Check if your "GAIN" pots are wired correctly.
Assuming it is the same on both channels it is rather not a short are broken component.

Click to expand...

Yes you are right.
I wired 25k log pots in serie with 75k resistors ( i realize now that i puted the resistor in the output lug instead of the input lug), i will check this. Great great support..awesome. thank you so much

Hi there.. just wanted to introduce my D-LA2A which I finished last night. I used Sowter 1449 input TXs and 1010s output Txs.
Thank you, Volker for this amazing project and thanks everyone for documentation within this thread.











Just have a question, when I dial in the Link between the channels, the GR backs up a bit. Is this the regular behavior of the compressor?

Cheers,
Falk