D-LA2A Support Thread

[stereokillah]

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?

 

[tskguy]

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

 

[[silent:arts]]

HF oscillation. sorry for the tweeters
try the gridstoppers, or reduce the gain range (what I did).
you will never need gain past 5.

 

[tskguy]

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

 

[[silent:arts]]

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.

 

[tskguy]

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

 

[[silent:arts]]

in this case try the "gain mod".
better adjusting range as a benefit too.
(but before testing with your loudspeakers do with a meter)

 

[tskguy]

Very cool,

Thanks again for your help.

Eric

 

[tskguy]

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

 

[tskguy]

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

 

[tskguy]

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

 

[crisotop]

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

 

[bernbrue]

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

 

[[silent:arts]]

ah yes, I remember:
http://www.nrgrecording.de/nrg/viewtopic.php?t=405&postdays=0&postorder=asc&start=225

 

[tskguy]

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

 

[tskguy]

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....

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

E

 

[crisotop]

wohoo! congrats!

 

[tskguy]

Thanks man!

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

E

 

[rob_gould]

Nice work - looking good

Can't wait to get my one of these up and running...

 

[[silent:arts]]

congrats  ;D
great you featured out the oscillation 
is this a Gustav PCB ?