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Solved a USB buzzing issue


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So, I have a Focusrite 2i2 that I use for connecting a Mic and Guitar and producing through simulators, and I have a Teac UD-301 strictly for listening to WAVs. Both of them are dead silent, no buzzing, hissing, or any other annoyances. I then purchase a Nuprime DAC-9, thinking I would improve on the excellent performance of the Teac (regardless of its digital volume). Unfortunately, I've been through hell and back trying to eliminate the buzz that the new unit exhibits once a USB cable is connected.

 

I've gone through isolation transformers on the power cord, I purchased a standalone PCIE USB card, tried a new Pangea CU USB cable, updated drivers where possible, disconnected fans within the PC chassis, unplugged all drives but the OS (Win 10), and I pulled out my video card and ran off of built in video on the MB.

 

Then I connected the unit to a laptop running on battery. That last step eliminated the noise. Plugged in the power supply and the noise returned. So, I decided to reconnect it to my PC once again, but I plug it's (the DAC) power cord into a cheater plug (removes ground), and the noise disappeared.

 

So, sorry this was long, but no other device needed a ground lift, so I'm of the opinion that there's an issue with the new DAC. Does this sound about right?

 

Thanks!

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Ground loop?

Sent from my SM-G900F using Computer Audiophile mobile app

 

Yep, that's what I'm assuming, but only happens on one device and goes away with a ground lift.

 

Sounds like the Teac has (better) galvanic isolation. Or does the new dac have a ground plug but the teac does not?

Nope. Teac is grounded:

 

Exactly right, and thus why I'm baffled by the problem, unless there's something going on inside that new DAC.

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The photos for the Nuprime don't quite reveal the type of the USB B connector. It 'looks' as though the shell connector is crimped onto the frame of the DAC, which is grounded to safety earth. That's where the ground loop comes from.

 

The Teac uses a plastic shell, which insulates the USB cable shell from the frame and safety ground. This is also the practice for Grace Design m920 USB connector, and just looked at Yggdrasil, hard to tell, but looks like a layer of plastic around metal too.

 

From here? Return the Nuprime as unsuitable or buy an Intona or just keep using the Teac.

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The photos for the Nuprime don't quite reveal the type of the USB B connector. It 'looks' as though the shell connector is crimped onto the frame of the DAC, which is grounded to safety earth. That's where the ground loop comes from.

 

The Teac uses a plastic shell, which insulates the USB cable shell from the frame and safety ground. This is also the practice for Grace Design m920 USB connector, and just looked at Yggdrasil, hard to tell, but looks like a layer of plastic around metal too.

 

From here? Return the Nuprime as unsuitable or buy an Intona or just keep using the Teac.

Good sleuthing. Still interested in whether the ground loop expresses itself with the Teac in other ways - like a flatness in soundstage & reduction in dynamics

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Holy moly, I'll try this today. I've been allowing this to slide this week since I put a HumX inline with it's power cord.

Edit: I couldn't wait to try this, so I tried electrical tape, just 1 wrap of Scotch Super 33+ and it wouldn't fit. Then I tried Teflon tape, but the noise still existed. It's not overbearing, but it's clearly audible. Reinsert the HumX and it goes away. Everything is plugged into the same out via a power strip, Tripplite Isobar.

 

 

ype of the USB B connector. It 'looks' as though the shell connector is crimped onto the frame of the DAC, which is grounded to safety earth. That's where the ground loop comes from.

 

The Teac uses a plastic shell, which insulates the USB cable shell from the frame and safety ground. This is also the practice for Grace Design m920 USB connector, and just looked at Yggdrasil, hard to tell, but looks like a layer of plastic around metal too.

 

From here? Return the Nuprime as unsuitable or buy an Intona or just keep using the Teac.

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Thanks Middy. I think the HumX is getting the job done, and I'd rather not mess with the USB signal. I've read up on the CMX though, and it does seem nice if I needed multiple device filtering. My Fluke is a fairly new 87 model, and it's measuring 0 to negative values on DC on the outlets, so I doubt offset is a problem. While not the top of the line, the 87 is still a fairly decent unit.

 

So, it looks like I need to suck it up and keep the HumX in line, or swap the DAC9 for a new one (as they've offered, unless is a design defect).

 

Thanks for everyone's help! I'll keep the thread updated if there's a change!

 

https://pooraudiophile.com/2015/03/how-to-fix-dc-offset-and-transformer.html

 

If your US based

 

I use this

This is cheap and we'll made

 

 

DC Blocker Trap Filter – Assembled in Case | ATL Hi-Fi Audio Company

 

Intona is nice...

 

Sent from my SM-G900F using Computer Audiophile mobile app

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Ok, update. I opened the case on the DAC9 and started poking around with my MM for continuity to ground. The chassis ground lug and the unit's receptacle ground are intact. However, using either the receptacle ground or the chassis ground, I do not obtain continuity to the USB port shell, which is metal.

 

 

More oddly, I DO obtain continuity between the chassis ground or receptacle ground and the positive lugs on the XLR and RCA outputs. Why would the hots be grounded?

 

Does any of this sound odd to folks here as well?

 

Thanks!

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I have a similar USB buzzing issue though in a different part of the chain. I recently purchased an Minix NEO Fanless PC (MINIX NEO Z83-4) to use as a HQ Player NAA. It comes with a 12v 3A switching power supply (planning to purchase a LPS later). When I connect the USB to the DAC, immediately a ground loop type buzz comes on. I've tried both a powered and a non-powered USB cable since my DAC has the Amanero board that doesn't need power from the USB. I also tried plugging the adapter into the HumX (which I had lying around from before) and the buzzing still shows up.

Any suggestions on how to fix this (or if it's worth fixing) or should I just return the Minix and find a similar alternative?

Oh - my DAC has no hum/buzzing issues when a different PC, Mac or the Sonore Microrendu is connected.

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