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My buffalo32s has been performing flawlessly until today I noticed that the right channel is significantly quieter than the left, sometimes it crackles a little louder and then back to quieter. Maybe a connection is weak? I narrowed the problem down to the buffalo. I have also:
-- Double checked to make sure I had good power voltage before I even wired it to the buffalo
-- Checked the entire right channel for shorts with a multimeter and found none
-- Rewired and checked outputs
-- Checked DC offset, it was nearly zero. 0.2-0.3mV maybe.
-- Tried resetting DAC
-- Tried without volumite
-- Tried USB I2S, USB SPDIF, and normal SPDIF inputs with different sources
Any suggestions? I have been extremely careful with this build and I don't know what could have possibly gone wrong!
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Possibly a dead opamp on the right side?
I would especially suspect the AVCC opamp. But it really could be any of them.
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Thanks, Russ. That would make sense given that there aren't any shorts/bad solder joints. Is there a way I could test the opamps to figure out which one might be faulty? Also sorry, which of the opamps is the AVCC opamp?
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I would simply measure the voltage (very carefully) at the output of each of the opamps while running.
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I've just returned from a very long trip abroad and have time to work on this again. I never got to measuring the voltage on the opamps, but before I do I have a couple questions. Please, forgive my ignorance on this subject, but I really do not want to mess something up: 1. To measure to measure the voltage of LM4562 would I just put one probe on Pin 1 (output) and another on AGND? then again for Pin 7 (output) and AGND? And for the OPA1632's, do I measure the output voltage the same way? (Each output with AGND?) 2. What kind of voltage am I looking for on each opamp? 3. Which specifically is the AVCC opamp on this diagram? http://www.twistedpearaudio.com/images/digital/buffalo32s_layout_11.jpgThanks for your help!
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Please, please, somebody? I have to go back to college in a few weeks and I really want to take a (functional) ass-kicking DAC with me. I am fairly good at electronics, but I don't know much about opamps and I don't want to make any mistakes.
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You have the right idea. Measure the voltage at the outputs(as per the datasheets) in relation to GND. You need to measure the all but the OPA1632 for now.
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I just measured the OPAMPS with the exception of the OPA1632's, here are the results. The LEFT channel is the working one, and the RIGHT channel is the quiet/defective one.
LEFT:
IC3 (LME49710) output = 1.0V
IC13 (LM4562) output A (pin 1) = 4mV
IC13 (LM4562) output B (pin 7) = 522mV
RIGHT:
IC2 (LME49710) output = 3.27V
IC14 (LM4562) output A (pin 1) = 3mV
IC14 (LM4562) output B (pin 7) = 1634mV
So do you think the LME49710 or the LM4562 is causing the problem? Or both? Thanks!
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It looks like just the LME49710 on the left side is dead, or has a short or open near it. I would concentrate around that opamp.
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No visible signs of shorts or opens around LME49710. Replacement opamps are on their way! I'll post again when they arrive and I've tried them out.
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You might try touching the pins with your soldering iron just to be sure.
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Well, my sample opamps came in from national semiconductor today and I got busy. But before I started I decided to give Brian's advice a shot and touched my tip to each of the pins... and that fixed the problem! I was just using my crappy headphones but will try my speakers tonight, I am SO pumped! Thanks again Brian and Russ!
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