Built my Crack, but have some buzzing I can't figure out.

[BaksideAttak]

Update:

So the crackling stopped, but the buzzing continues. It has changed in character, though. When the potentiometer is all the way down, I get a louder buzzing in the right channel only. As I turn it up, the buzzing fades into both channels. I have no idea what this could mean.

• I tried unplugging each cable from the power strip individually to see if it stopped the buzzing. No luck.
• I unplugged each peripheral from the computer one by one. No luck.
• I switched the computer to a different power strip. No luck.
• O2 works fine fed from ODAC plugged into the USB on my desktop (using this now)

So it seems like those tube sounds have gone away (like you said could happen, Doc), but now the buzzing is louder and behaves differently.

Given the channel weirdness, could this be an issue with the cabling from RCA inputs to the potentiometer? I've seen some people use Cardas Star Quad to replace the braid... would this help? I'm by no means an electrical engineer, and I wouldn't even know how to do that.

[MDFreaK76]

I have the same problem. I'm pretty sure its due to a Ground Loop. Essentially, the ground from your laptop/USB/DAC/Audio Out and the ground from your Crack have different potentials. This creates interference between the the two circuits, which presents itself as a hum in the 50-60Hz range. Give the youtube link below a listen (its what 60Hz sounds like).

I'm still trying to find an adequate solution for this. Some suggestions i've heard are:

• Try a different plug, maybe on another circuit/breaker (Tried this; somewhat works)
• Use TOSLINK from Source to DAC (Not tried yet)
• Clip the ground on the NEMA 5-15P connector (included for completeness, but a terrible idea. Please DO NOT try this!)
• Clip the +5v and GND leads on the USB cable (Not tried yet)

On a somewhat related note: I've also had CPU interference if my amp is plugged into the same surge protector as my laptop, which creates a much higher pitched buzz/hum that goes away if i keep the CPU busy enough.

Info on Ground Loops: http://en.wikipedia.org/wiki/Ground_loop_(electricity) [nofollow]
YouTube Link to 60Hz Hum: https://www.youtube.com/watch?v=SVZ2P0KsLic [nofollow]


Good luck!
  -Rick

[Doc B.]

Ground loop hum is usually 120Hz and buzzy sounding, not 60Hz. 60hz is usually due to magnetic coupling and soft sounding.

[Jim R.]

Don't cut the power lines on your usb cable -- the usb receiver chip needs those to bootstrap even if the dac uses internal power instead of usb power.

-- Jim

[Paul Joppa]

The ultimate solution to ground current problems is to eliminate the ground current from the signal lines. That means a transformer, an optical link, or the traditional balanced line. Naturally all of these are compromises, one way or another. Pick your poison!

Non-ultimate solutions involve reducing the resistance of the signal-ground line in which the current is flowing, or reducing the current itself. Naturally, "reducing the current" means sleuthing out the source(s) of that current - never an easy task, but sometimes an interesting challenge!