NUC Incessant Passive Speaker Feedback - how to eliminate?

All - hoping you can help me with annoying issue that impacting my ability to enjoy Roon in one room.

I have a NUC8i7BEH running ROCK that I am also using as the server and endpoint with one USB port going directly to a Schitt Modi Multibit DAC. The DAC then connects to a Schiit Sys passive volume input switch, then into Schitt Magni headphone amp which I am using a preamp that goes to a Reisong A10 tube amplifier. The amp is powering two 6 ohm Wharfedale Diamond 10.1 speakers. (NUC -> Schiitt Modi DAC -> Schiit Sys -> Schiit Magni amp/pre-amp -> Reisong A10 amp -> Wharfedale Diamond 10.1 Speakers)

Since hooking this up I have had incessant feedback into the speakers - crackling, high frequency buzzing (not a hum). This occurs whenever the NUC is on, and the USB cord is connect between the NUC and DAC.

I have tried a variety of “fixes” but none have been successful. This includes:

  • USB Jitterbug and iFi iPurifier3 USB endpoints on USB cord
  • Using a very short high quality USB cable
  • Placing Ferrite chokes on both the USB cable, and the power cable to the NUC
  • Plugging the NUC into TripLite ISO Bar surge protector that is the amp is also plugged into
  • Plugging a powered USB hub into the NUC, and then connecting from the hub into the DAC

None of these has been successful in eliminating the speaker feedback. The only other options I I have come across in my research is removing the ground plug from the NUC switching adapter (seems slightly dangerous), getting a linear power supply for the NUC, or quit trying to use the NUC as endpoint - and leverage a different endpoint solution.

Any other thoughts or ideas that I should try? Thanks much!

Have you tried taking the headphone amp or the switch out of the circuit?

Yes, same feedback is present if I take the DAC straight into the AMP. Thanks for the suggestion though.

What about nuc, DAC, headphone amp, headphones as a chain?

No noise when using headphones, seems isolated to when speakers are in the chain. I assume that is due to the amp/speakers being more sensitive to the what ever interference is being generated by the NUC/USB.

How can you be sure that the interference is not generated by the tube amp? That by all means would be my first suspect…

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Which bits of the chain were in use before and what was feeding them?

I have had a NUC directly connected to a Modi Multibit for years without the issue. However, eventually the USB input on the Modi died.

Seems to be a common occurrence for a certain generation of that DAC. Schitt told me to get a new one. I just repurposed it and used the coax input instead as fed by a DigiOne.

Yes, very dangerous, and would only be effective if the issue were a ground loop, which would result in a hum audible even when nothing was playing, rather than distortion.

Are the HPs plugged in to your Magni? If so, I would think the issue is after that point, with a loose speaker connection or something off with the tube amp.

Is there any change if you physically move things around - specifically putting as much distance as you can between the amplifier and the NUC and it’s power supply?

(And - just checking - is the NUC power supply actually grounded, or is it double insulated?)

I have had the amp in place for a while, with a turntable at one point directly input to it, and then with the turntable going to into the Schiit SYS -> Schitt Magni -> Reisong A10 AMP - and there was not any interference. The interference feedback was first noted when I put the NUC into the chain.

Thanks tried that as well - move the NUC into a separate cabinet away from the rest of the components in the chain with a longer USB cable. That still gave me the interference feedback into the speakers.

Yes, the power supply is grounded through a three prong plug that connects to the switching adapter.

Thanks for the suggestions

Thanks for the input. Yes, the HPs were connect directly to the Magni.

To your other inquiry, as a part of this overall hunt to eliminate the feedback - I actually replaced the speaker cables and double checked all connections.

I never have had this issue before - so that is why I thought the NUC’s usb port, etc- was/is the culprit.

Do you have a laptop or PC to temporally switch to a Roon core on another device? This should help with finding out if the culprit is really the NUC as you think, or some problem further down the chain.

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Yep, just tested running Roon core on a MacBook Pro into the DAC - no feedback at all. So, I think the NUC is the culprit.

Thanks for the suggestions.


Everything was in the chain before with the exception of the NUC.