I use a NUC10i3, and have the exact same issue. Tried just about everything, different DACs, USB cables, PSU from my other NUC, you name it, all to no avail.
Sometimes my NUC won’t boot and I have to dis- and reconnect the PSU before it’ll boot up (maybe also because the grounding issue?) and this only happens when a DAC is connected…
I’ve also removed the ground from the cable and this resolved the issue! Will report later if this also fixed the booting problem.
As the originator of this thread I want to update where I’m at now.
It does seem to be a ground loop between the NUC and the DAC through both the AC power ground, and the USB cable 5V ground… I can reduce the noise to near inaudibility either by cutting the AC ground with a cheater plug, or cutting the 5V USB cable power (pin 4, and 1 for extra measure). I figure cutting the USB ground is the safer option, so I put insulating tape over the USB cable pin1.
It seems that this noise issue only occurs with some DACs. Some seem immune. I have one that’s noisy, and one that’s not. BTW- the noisy DAC is powered off an external smps with no separate ground. On top of that, I tried my battery powered DAP in DAC mode, and it was noisy as well.
The DAC I have that doesn’t experience the noise has built in ac power supply, and cost it bit more than the others. Anyway, it all seems a little hit and miss. I still want to come up with a better solution.
EDIT:
Going to try something different. I just ordered a new DAC with balanced outputs. I’m hoping that a balanced connection between DAC and pre-amp might stop the noise.
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Thanks for this thread. Just wanted to share that I’m having the same issue with a Topping D90 MQA DAC and a NUC8i3BEK1. All signs point to a ground loop based off of what I’m hearing–particularly the fact that it seems to vary in noise with the power draw/load on the NUC itself.
I find myself agreeing with many on this thread that input isolation of power problems for USB interfaces should be a priority for DACs, especially when we’re talking about MQA transport as that should be all digital data going down to the system.
For what it’s worth, on my model of NUC the noise is louder on the USB C ports vs. the USB A ports (the latter of which have lower power capabilities).
I’ve already tried an iDefender+, which lowered, but did not fully eliminate the noise. Unfortunately, it seems like using optical or HDMI sound output is not supported by Roon (which makes sense most notably for MQA), but it’d be nice to be able to output via a connector that is inherently less noisy than USB.
For next steps, I’m going to clean and isolate the power source. I’m curious from @denydog if balanced outputs end up working–it should make some difference. Also curious if anyone has any specific low noise/no ground power supply suggestions for the NUC. Cutting the ground from the NUC power supply and then also cutting the USB power out of the cable both seem like they should work to eliminate the literal ground loop, but it’d also be nice if the DAC or the NUC isolated this noise overall 
Me again, just wanted to share that I’ve gone through my next steps and got all balanced (TRS/XLR) cables through the chain, as well as put in a power cleaner, and even tried an iSilencer+.
Hopefully this helps people avoid trying to fight against the ground loop and/or other noise in this situation by merely neutralizing/cleaning it–it’s not enough. Next steps I’ll try are to cut the ground from the NUC power supply and then the power wire from the USB cable. I expect both of those solutions to work, they’re just not as satisfying… I may also just give up on the Topping D90 DAC and buy a different one that properly isolates its USB input because this entire class of problem is just stupid–it’s digital data going over the USB cable (at least it is when we’re talking about MQA encoded music), for power on the line to bleed in is just poor DAC design.
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That’s some good information in the last two posts, much appreciated.
As for my attempt to use a balanced connection from DAC to pre-amp, well it turns out I don’t have a Pre-amp with balanced inputs. It has balanced output, but I knew that, just momentary confusion.
So I connected the new SMSL SU-8 V2 the usual way, only to find it wasn’t recognized by the ROON/NUC until I restored the USB cable’s ground pin, which I had disabled to break the ground loop. Also sad to report that this SMSL DAC is no more resistant to this noise issue than my other SMSL DAC, even though it has an internal power supply. So I have now reverted to disabling the ground pin on the NUC’s power brick again.
That does get rid of the noise, but seems a shame to have to loose the ground pin, though the risk seems low of any negative repercussions.
I’m glad you had a chance to use the iDefender+ as that was something I was also going to try. Sounds like it wasn’t a complete solution. You mention you went to balanced cables and a Power Cleaner. Were they effective? I also agree with all your conclusions regarding the problem and potential solutions. It seems we have the same problem, and have arrived at basically the same place. Good luck, I’ve not given up yet.
I do have the one DAC that doesn’t suffer the noise, but unfortunately I’m not that thrilled with its sound signature.
This may have been answered…
I experienced the noise described by many here: Glitchy audible noise when my Pro-ject DAC is connected to an Intel i3 NUC running ROCK via USB. Connect the USB-noise. Disconnect the USB-no noise.
I added a 3-prong to 2-prong adapter for the AC brick, and the sound stopped with the USB connected.
Question: Is this safe? Or should I stick with grounded AC connection and add something like this: iFi iDefender-External Ground Eliminator?
Officially it’s not safe to bypass equipment ground plug. What is the chance that an ungrounded power brick could send AC power to the NUC chassis? I don’t know.
Try the iFi device and share the results. I’ve heard of mixed results.
SMSL, and many many many DACs, use a XMOS USB chip. This chip requires power from the USB host to function. It’s also not my favorite because of the “noise” issues referenced in this thread. Seems plenty of manufacturers implement this chip in a way that doesn’t provide proper isolation.
If you’re looking to replace a noisy USB DAC, and your current DAC has a XMOS chip, don’t buy another DAC with a XMOS chip as you are almost guaranteed to not resolve the issue.
So, its been just over two years since starting this thread and I no longer have a noise problem. I never identified the actual cause, nor a solution, I just decided to avoid the problem.
The cause seemed like some kind of ground loop, allowing noise from the NUC8 into the USB connected DAC. But for a while now my main system consists of just the NUC, the DAC (with volume control ability), and a power amp feeding the speakers, so not much flexibility there. I thought about trying some kind of USB noise filter, but it felt like a band aid fix to me, and I didn’t feel the confidence from user reports that I read on some of the noise blocking devices.
So what I did do is create a proper Roon endpoint with a Pi 4 in the Flirc case running Ropiee. Also got a switch to split the ethernet connection from the router, to the Roon Core and the PI 4, and no more noise… So I don’t know if the PI 4 just injects less noise via USB than the NUC8, or if it was something else tha went along with this configuration change. I’m just happy to get rid of the ground cheater plug.
All for under $100
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This is what I was about to recommend.
The RPI4 is the best solution, IMO.
Opens up affordable power supply options too.
I know there is nothing novel about this latest setup. I think it’s even the preferred method recomended by Roon.
I feel like I should go all the way with an ethernet connected DAC, and be done with USB, but I’m good for now.
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