Ground loop noise when powered off - emitted via Out 1-2

CorOS Version: 1.3.2

Describe your issue:
When unit is powered off but connected using Outputs 1&2 I get a very loud buzz (ground loop) feeding whatever mixer or audio interface and I am forced to disconnect the cables to stop the signal. If the QC is in standby this does not occur ony when selecting power off - seems to be like an earth / signal leak rather than entirely muting the outs after powering down.

Steps to reproduce your issue:
Happens everytime I keep the unit connected and power down.

I expected this to happen:
When I power down and leave the QC connected I’d expect silence - no output or ground loop

I have tried the following things:
New XLR cables, Isolate Out 1 and 2 no change.

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Make sure you contact support about this at

I agree to email support but have you also tried changing your signal grid output to multi, out 1/2 or out 3/4? Also when diagnosing, please disconnect everything (e.g. USB, sends/returns etc.) and just use XLR outs 1/2 etc.

I have had a similar issue since the very beginning. When first contacted, NDSP indicated that they had identified and would be providing a different power supply. No recent update on that…

I have been able to eliminate the noise that occurs when the unit is off (and when it is on) by connecting the USB port to something that is grounded. YMMV, but has worked for my unit.

Same issue here, brand new QC, XLR outs 1&2 hum when unit is off. TRS 3/4 Seem to be ok.

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NDSP recommends to use the QC standby feature instead of turning the unit off. Although I have never experienced any noise/hum, others have resolved via utilizing an alternate PS and or power conditioner. If you still have issues with the unit in standby, please reach out to and they will get you sorted.

standby will mute the outputs but doesn’t turn the unit off like it does with a laptop. I’d say your best bet is to look at a ground lift of some kind or find a different PSU that is grounded.

This is a good grounded solution that won’t break the bank. It works great for me:

Power supply from Parts Express w/reverse polarity adapter cable off Amazon: