Wiggling the PSU power cord eliminates USB noise.

[viivo]

Corsair HX1000i.

I've been troubleshooting a noise issue coming through USB to an external DAC and separate headphone amp for a month now. As a last resort, I put on the headphones and turned the amp's gain to maximum and started fiddling with cords and cables while it loudly buzzed, and discovered that moving the PSU power cord at the PSU completely eliminates all noise, at least for a few moments until it seems to settle back down in the socket. I am using the 14ga cord that came with the PSU, but I have tried others, both 14ga and 16ga, all which exhibit the same behavior, so I'm certain it's not the cord itself.

What is going on here and is there any way to make this "fix" permanent? The PSU is touching the metal of the case and is plugged into a properly grounded outlet. A few more symptoms in case they are helpful: moving the mouse modulates the noise, and putting a load on the GPU dramatically increases the noise.

 

[Luke M]

Does the noise go away if you use a "cheater" plug (3 pin to 2 pin adapter)?

 

[viivo]

Does the noise go away if you use a "cheater" plug (3 pin to 2 pin adapter)?

It does if I use one on the amp without grounding the tab. I haven't tried one on the PC and don't feel comfortable using one long-term.

 

[Luke M]

I'm guessing that your wiggling is disconnecting the grounding pin.

If you use a cheater as a workaround, protect it with a GFCI.

 

[viivo]

I'm guessing that your wiggling is disconnecting the grounding pin.

If you use a cheater as a workaround, protect it with a GFCI.

Could it not be caused by a short in the power supply or elsewhere in the PC? It has shutdown or restarted more than a few times when I was blindly fumbling to plug something into the USB type c port in the back. I assume that's because of a short.

 

[Luke M]

I doubt anything is truly wrong, other than the audio gear not being well-designed.

 

[pendragon1]

Could it not be caused by a short in the power supply or elsewhere in the PC? It has shutdown or restarted more than a few times when I was blindly fumbling to plug something into the USB type c port in the back. I assume that's because of a short.

yes it could be that or the cords are not seating deep enough. look at the end of the power cords you have and use the one that has the metal connectors closest to the edge of the plug. you can even sand down the end a little to make sure it connect deeper. if the system still keeps shutting down rma it. if the system stays running and the dac noise continues I would try the dac on another power circuit/plug, try that either way.

 

[GiGaBiTe]

I would suspect the PSU is faulty and needs to be replaced. Try another known good PSU to see if the problem goes away, defeating the ground isn't safe for electronic equipment because it's often used as a noise path for shielding and other decoupling applications.

A GFCI to defeat the ground won't save you in all fault conditions.