Interference Issue Perhaps?

[RichardHolbrook]

Hi Everyone -- I'm having systems issues and wonder if anyone has had a similar issue or advice.

 

I run a Mac Mini into my DAC (Audio Note) through an external bridge, the Human Audio Tabla, which is a self-powered USB bridge (very similar to the M2Tech HiFace Evo + Evo Supply that Elberoth wrote about in his USB/SPDIF shootout thread). From the DAC I go straight to a tube amp. After generally 1-2 songs, the sound starts to fade out, then gets a lot of fuzz / fog sounding over it and goes very quiet / plays very quietly, but periodically comes back a normal level for a few seconds periodically -- if I flick the DAC'S power switch off and on for just a second, I hear a his, like there is discharge going on, and when I turn the DAC back on, it plays again correctly for another song or two before the issues start repeating. I can generate the same result by flicking the switch on my amp off and on.

 

My amp's had the tubes checked recently, so I don't think that is the issue, and the DAC / amp were matched together by my dealer, so I don't think the mismatch lies there. I plug both the amp and the DAC directly into separate wall outlets.

[flatmap]

Do you happen to have a CD transport where you can take optical straight into the Audio Note DAC? And just as a double check, do you have another source you can plug directly into the amp?

[sandyk]

Have you tried a different USB port ? It sounds like it may be a possible compatibility problem with the USB to SPDIF adaptor.

 

Flatmaps suggestion is good too.

[pooger]

As has been mentioned, you need to isolate each piece of equipment (by trying aaa different source, etc.) to see where the problem is. But it seems like you can correct the issue (for a song or two) by switching the DAC off, so that does point to the problem being there. If I were to take a wild guess, I'd say it's a power supply cap going bad in the DAC, most likely in the I/V stage. Does the noise and fading, etc. come to both channels pretty evenly? Is the audionote a tube DAC?

[dc2bluelight]

AIf I were to take a wild guess, I'd say it's a power supply cap going bad in the DAC, most likely in the I/V stage.

+1