D-LA2A Support Thread

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poctop

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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,
 

college101

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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
 

poctop

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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,

 

college101

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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!
 

college101

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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 ??? :eek:
 

tmuikku

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college101 said:
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
 

poctop

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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,
 

poctop

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Please let me clarify a single details here i have the T4B from studioelectronics these are OEM universal audio.
D
 

electrisizer

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poctop said:
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?

 

poctop

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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,
 

poctop

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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,

 

poctop

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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.
 

Biasrocks

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poctop said:
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
 

poctop

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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,

 

poctop

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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..................................................
 

telefunk

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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.

 

Biasrocks

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telefunk said:
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
 

drgrateful

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Mar 31, 2010
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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!
 

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