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I got my Buffalo32 v1.0 running two days ago, it plays music wonderfully on both channels fine, however, when the music level drops to 0 (ie paused, or between tracks), the left channel plays a very harsh static noise. I can provide oscilloscope images.
A few notes:
- It does it on two different spdif sources (Sony DVD player and a M-Audio Audiophile 192)
- It does it with both the internal firmware and the volumite
- With the volumite, the noise volume goes up and down with the volume setting
- It does it with the case lid on and off, also a previous post suggested untwisting the spdif cable between the connector and the PCB, this had no effect.
- The Lock LED remains constantly on (Checked with oscilloscope)
- When I change the sample rate on the M-Audio soundcard (from 44.1k to 192k) the frequency of the static noise goes up. Also setting the spdif bits (consumer/pro, scms) has no effect
- The onboard switch settings seems to have a minor effect on the noise, but not much.
- PS voltages are stable on the scope.
I'm fairly concerned at this point, it seems that the DAC chip is decoding the idle spdif signal incorrectly. The right channel is fine, only the left channel has the issue.
Any help would be appreciated
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Is is possible to post a picture of your implementation? It can help rule out simple physical layout issues.
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Do you have the output traces cut were specified in the manual?
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Yes, all tested at 22ohms. I'm pretty sure it's not an analog stage thing. I'll post pictures later tonight of the DAC build. I have images of the scope trace - 0.2V/div 0.1ms/div Edit - I've sent an image to your TP email address 2nd Edit - Thanks for letting me know how to do attachements! Edited by user Tuesday, September 15, 2009 6:59:25 PM(UTC)
| Reason: Not specified abrough attached the following image(s):  Left channel - static noise.JPG (66kb) downloaded 568 time(s).You cannot view/download attachments. Try to login or register.
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Posting picture is kinda different here, You will see an attach button on the top right of your post after you post. You can then attach images to your post.
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Hi res-images have been emailed directly to Russ White. For the benefit of the forum, here are some of the images in reduced size. nb - Some of the connections are currently disconnected... Edited by user Tuesday, September 15, 2009 9:46:11 PM(UTC)
| Reason: Not specified abrough attached the following image(s): WholeDAC-Front-Reduced.jpg (114kb) downloaded 562 time(s). WholeDAC-Side-Reduced.jpg (123kb) downloaded 562 time(s).You cannot view/download attachments. Try to login or register.
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Yo tenia este problema, y lo solucioné poniendo un condensador de 100-200 nF en serie con la entrada spdif.
I had this problem, and I solved it with one capacitor 100-200nf in serie wiht spdif imput.
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I added a 220nF in series with the spdif input, but it did not work. :-( I have a TP toslink adaptor which I can hook up to my Sony DVD player, I'll try that. I'm open to suggestions as to how to diagnose the issue as I'm short of ideas on this one. 
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Attached are two traces of the spdif signal. First is with no music playing, second with music playing. A few notes: - 0.1V/div approx .48V p-p - 0.1uS/div for approx 2.8MHz (Correct for 44.1kHz) - The trace is DC coupled, so the signal is balanced around 0V, ie it must be AC coupled at the source. - Note the faint traces between the bright traces on the idle images, that is presumably the preamble which comes along every frame (32 periods) Edited by user Thursday, September 17, 2009 1:54:45 PM(UTC)
| Reason: Not specified abrough attached the following image(s): Spdif - Idle.JPG (56kb) downloaded 519 time(s). Spdif - Playing.JPG (50kb) downloaded 515 time(s).You cannot view/download attachments. Try to login or register.
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Here is the trace at R6, as it goes into the DAC chip. 1V / div for 3.3v p-p Nothing really looks out of place Edited by user Thursday, September 17, 2009 2:06:08 AM(UTC)
| Reason: Not specified abrough attached the following image(s): Spdif -idle at R6.JPG (27kb) downloaded 512 time(s).You cannot view/download attachments. Try to login or register.
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The digital shots look fine. I have to say I am stumped myself.
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I just wired in the toslink module, same results. Audio plays fine until volume is reduce to 0 (or music paused etc.), and then the left channel plays a harsh static type noise. Just to confirm, the rightmost regulator should produce 1.2V, and the other two 3.3V? Unless anyone has any suggestions, shall I return it to TP for further diagnosis? Edited by user Friday, September 18, 2009 1:57:39 AM(UTC)
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abrough:
sorry to go off subject here but that is one of the better SPDIF signals I have seen, do you mind me asking what is your source?
There is lots of buzz about the quality of the SPDIF signal and many ways of implementing them after the chip and before the coax connector out.
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It's from a M-Audio 'Audiophile 192' Soundcard. I posted them to show there's nothing really wrong the the digital source that could cause the problem I'm still having.
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Can you check the output of the S/PDIF comparator to see if there is any noise on it's output with no signal?
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Hi,
I will post the images when I get a chance. I'm moving house right now and I'm sure Brian understands the calamity that goes with that.
Cheers
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Hi, Sorry for the delay but moving house really takes it out of you. Attached is the scope trace on the output of the comparitor with no signal. There is no noise, and the thickness of the line is simply as sharp as I can focus it. Please help, I'm open to any suggesstions as it's unusable as is. Adrian abrough attached the following image(s): Input to DAC - No signal - Resized.jpg (43kb) downloaded 232 time(s).You cannot view/download attachments. Try to login or register.
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Hi,
Is there anything anyone can suggest as how to diagnose or resolve this issue. I paid a lot of money for this DAC and I'd like to see it functioning properly. I've email Brian and Russ directly a while back but there seems to be no reply from them.
Cheers, Adrian
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anything to do with one psu VERY close to the BUFF32 pcb? I would try and move the B32 pcb further out to the side of the chassis
best
Leif
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