Need DAC w/output decoupling. Advice please
Jul 26, 2010 at 10:38 AM Thread Starter Post #1 of 10

maxxy

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Hi guys
 
Really need some assistance here.. breaking my head over this one. I have zero electronics knowledge so please talk to me in laymen's terms. Much appreciated :)
 
I have a Burson PI-100 integrated stereo amp. I watch movies on this thing, so I feed it DTS downmixed to stereo from my EMU 0404 PCI. I guess the downmixing codec isn't perfect, because it causes the amp to jump into protection mode, probably due to the subwoofer channel causing some kind of DC leakage into the amp (which shouldnt happen in a perfect downmixing situation).
 
I talked to Burson and they recommended I put some 10uF caps between the RCA and the PCB, which I tried and it didnt solve the problem (as input caps. I used Vishay MKT1813 I think if that matters). Does anyone know of any decent DAC that has output decoupling that will solve my problem? :frowning2: I watch a lot of movies on my stereo system and this really ruins the experience. It jumps into protection mode a lot (and I have to stop the movie and reset the amp).
 
Thanks in advance
 
maxxy
 
Jul 27, 2010 at 9:32 AM Post #2 of 10

ROBSCIX

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You just said you installed some output caps and it didn't help your issue.
Are you sure you installed them correctly?
 
Output caps or inputs caps are exactly the same thing in a different circuit position.
 
Jul 27, 2010 at 11:18 AM Post #3 of 10

maxxy

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Hi ROBSCIX
 
Well, Burson didn't really send me any schematics. They were archived and retrieving them would take "a few days" or so they say (hmpf...).
 
I connected the caps like this (didn't solder 'em because I wanted to make sure they work before soldering stuff to the amp):
 
RCA cable > 10uf cap > RCA cable  > Amp (Left channel)
and the same for the Right channel
 
According to the photos I sent Burson of my amp, that's the way they told me to connect it. Enclosed is the "detailed description" of how I should connect the amps (the arrows were added by the Burson techy):
 

 
When connecting one channel to the amp (either left or right), the dc protection wouldn't kick in. Connecting both (with or without caps) would cause the amp to jump.
 
I would still appreciate any solutions regarding either fixing the amp (I know this isn't the right forum for that, sorry) or if anyone can recommend a decent DAC which will solve my DC problems :frowning2:
 
Thanks in advance!
 
Jul 29, 2010 at 1:29 PM Post #5 of 10

joe_cool

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Quote:
(didn't solder 'em because I wanted to make sure they work before soldering stuff to the amp)


You have to disconnect the white wires and replace them with caps to do this test.
smile.gif

 
Jul 30, 2010 at 5:22 AM Post #6 of 10

maxxy

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Hi
 
Thanks for the input. But why do I have to disconnect the white wires? Isn't doing what I did going to give the same effect?
 
Aug 3, 2010 at 2:30 PM Post #7 of 10

ROBSCIX

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The decoupling caps go right in the audio signal path.  The will block all DC and allow AC(audio signals) to pass through.
 
They are bad for the signal but sometimes needed.  However, doesn't your next device have decoupling on the inputs?
Many people will remove them from their sources as the receivers, amps..etc will in many cases have input decoupling caps so they are redundant and your just degrading the signal quality for nothing.
 
Aug 5, 2010 at 2:10 PM Post #8 of 10

joe_cool

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Quote:
Originally Posted by ROBSCIX /img/forum/go_quote.gif
 
However, doesn't your next device have decoupling on the inputs?
 


If I understand correctly, the Burson amp IS the next device and it was recommended that he install input coupling caps to remove DC offset and ultra-low frequencies coming from the DAC. For this to work, he has to REMOVE the white wires and replace with caps.
 
Aug 6, 2010 at 7:55 PM Post #9 of 10

maxxy

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Hi
 
Thanks for the replies. I was hoping that perhaps there is a DAC that will solve these issues for me and clean the sound for the amp (currently using a PCI EMU 0404).
I will try to install the caps instead of the wires and update.
 
Thanks
 
Aug 8, 2010 at 1:16 AM Post #10 of 10

joe_cool

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IMO the PCI EMU 0404 is a good sound controller and DAC, but the software is not up to my standards. I don't know the true nature of your problems, but the cap mod is a good recommendation.
 

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