DAC USB Hum

Hello cetla416!  If you decide to replace some of the components in your system, look for units that allow you to use optical cables. I solved a hum problem in my big system that way. Good luck otherwise!

@cetla416 , I have the same streamer and Orchid DAC pair (super happy and impressed).  Connection is of course USB via a Supra USB cable.  For comparison I also have a CDP and phono pre-amp out  connected via the RCA inputs.  For this test all units' PCs were kept plugged and hot, and the interconnects kept in place mainly for my ease and the simplicity of variables.  I cannot confirm without work, all of said components or which if any, share the same power bank and ultimately which outlet on the same wall (same to breaker box though).  I ran out of them on same/same and may explain the TT hum.  So here us what I observed as far as hums. 

The turntable/pre-amp has the most.  I think I can run that down (different banks/outlet than amp) but it's not a bother to me as Im about 5% vinyl these days.  The CDP/RCA is the least and WAAAY less than the TT.  As a reference the volume on my Raven is at 12:00 and takes being pretty close to speaker to hear it. 

On to the Zen/Orchid pair.  When the Zen is on, and the Orchid is both plugged in and in warmup mode, the hum is the same from the ZEN/USB as the CPD/RCA. Again, way lower than the vinyl.  Interestingly, when the Orchid DAC warmup is done and there's an audible click, the hum drops considerably for the RCA/CDP and is really hard to hear without ear in front of speaker.  It remains unchanged for the Zen/USB.  Using a very sophisticated technique of my phone corner on the baffle between the drivers and some freeware, I get that drop as 57db to 47 db (the house central forced air was also blowing) for the CDP/RCA pairing.  Someone smarter than me could perhaps comment on this change at warmup.

So to summarize the hum is acceptable (to me at least) for the Zen/Orchid pair and the CDP/RCA when the Orchid is warming up  OR running,  but becomes nearly inaudible for the CDP/RCA once it reaches running status. Does this confirm the USB's hum issue and would those filters make the USB circuit as quiet as the RCA's?

Maybe this helps, maybe it confuses the situation.  Just a field report from a user with same.  Your post and possible cure may ultimately make mine better yet! 

The hum from the DAC itself does not travel throughout the chain to my speakers. Last night I taped over the Ground Pin on the USB cable. No hum from the DAC. I ordered an iFi USB isolator which is supposed to cancel the hum. 

Sorry everyone, but I got my 2 inputs wrong at the amp.  It's the Zen/USB that quiets down when the DAC hits warmup.  The CDP/RCA is the one that doesn't change after warmup.  So perhaps someone can explain why warmup on the DAC silences the small hum from the Zen/USB.

So what did taping do for that if you know/can speculate?  Did it insulate the ground out and therefore break up the ground loop difference?  Not sure I asked that right.  I can hang with acoustic wave and wave theory, some DSP (geophysics degree) but EE makes my head hurt!