[holland]

running SPDIF coax (doesn't really matter) to the Buffalo DAC with IVY (v1.0), when playing, pull out the SPDIF. I'm interested in the DC offset. Does it zero itself with a loss of signal or is there DC?

I noticed a problem with my computer motherboard feeding SPDIF to the Buffalo DAC, that there's DC. It seems when it stops playing the DC remains and doesn't drop down to idle levels, if I play a digital silence file, the DC goes back to idle voltages. Upon poking around, I found that if I pull the SPDIF, I can get similar results.

I was just curious if anyone else saw that. I was initially thinking blown opamps, but now I'm not so sure.

Thanks much.

 

[FallenAngel]

IVY has 0 DC offset, it uses a good quality opamps for I/V stage, therefore, no DC.

How are you measuring DC?

 

[rds]

I'm wondering the same thing. It doesn't seem possible for the IVY to put out DC.

 

[holland]

Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif How are you measuring DC?

How else do you measure DC? At the jacks and on the IVY. SE to G. IVY does not have 0 DC offset. The idle voltage has DC and is measurable. Sure, it's small, just like a CMoy has small DC.

Play a track, DC will jump around (this is normal). Pull out the SPDIF. Do the experiment and report back, please.

 

[rds]

Yeah, any amp will have some DC of course. You didn't say how much DC. Are we talking fractions of a mV?
Just a thought that is probably wrong, but could the signal be bouncing in the internal spdif pathway of the DAC? There was a signal and then one end became an open circuit. I wonder if that would cause bounce?

 

[holland]

I see, yes, I'm talking mV, not fractions of mV. My idle is ~1mV on one channel and ~2.5mV on the other. When I play tracks it normally bounces around sometimes up to 60mV on a DVD player or a CD player. I have, under some conditions hit 1.5V (with my soundcard which I'm trying to figure out). I'm trying to track this one down, and in doing so, I noticed that if I pull the SPDIF, the IVY out stays at where the DAC was playing and doesn't "disconnect" and go back to idle voltages. If I play a silence track, it resets. With a real CD or DVD player, if I hit stop/pause, it resets back to idle. With my integrated soundcard, if I hit stop, it doesn't reset (I think that's soundcard issues). I noticed some popping when changing tracks in foobar2000.

The oddity I'm wondering about is what happens when you pull the SPDIF in the middle of playing.

I haven't figured out the high DC offset I initially saw, but I suspect it's my integrated soundcard (I blew up my soundcard and have to resort to the integrated). When I connect to a CD and a DVD player it seems OK. I initially suspected the opamps have gone bad when I saw 1.5V DC, but putting it under different stimulii, it doesn't add up. That is DAC idle overnight, DC stays put at where it is on first power up (some minor thermal drift in fractions of mV). I think the 1.5V may just be where I "stopped" the track and the soundcard not "resetting". It is a bit worrisome though, so I'm still poking around. I don't want to blindly replace the opamps. I'll ground the inputs into the IVY at some point to see what happens when I hit the high DC state, but I want to make sure about the SPDIF disconnecting abruptly case.