Shielding usb audio signal from PC

[Mossshine]

Hello, I would like to ask for some advise for "balancing/clearing audio signal" (can't describe it better).

I get that "good old" electric fuzz, mainly when under load. This gets better (but still present) when I literally take copper wire, put it under one screw holding the motherboard to the case and grounding the other end to the outlet (EU). I had different motherboard before and it was even worse (surprise surprise, shielding is better on rather expensive motherboards). I did try unplugging other stuff from PC, like peripherals and having only pc, monitor and amp in the outlet, but no luck.

Is there anything I can do to fix it, other than making it less annoying with a cable sticking out of my case ?

Audio setup:

From Windows 10 and MusicBee (ASIO or WASAPI shared) player,
to SMSL Sanskrit 10th MKII DAC via single USB cable plugged from the back of my motherboard,
then taking nice and chunky RCA cables to DarkVoice 336 TubeAmp,
outputting to my DT-990 PRO 250ohm.

PC:

• ryzen 3600
• asus x570 tuf
• amd rx 470
• 2x 8gb ram corsair
• 4x hdd
• 1x samsung m.2
• evga SuperNOVA 850 G3
• no other pcie cards

Edit:
When DAC is plugged to my phone, no more fuzz comes out, which means, it's really coming from PC.

 

[Yasuo]

Have you tried with another amplifier? I remember DarkVoice has a noise buzz issue, sometimes it goes away after many hours, there is also a fix by removing or changing some caps.

 

[Katji]

I had different motherboard before and it was even worse (surprise surprise, shielding is better on rather expensive motherboards).

That much is clear to me, the best bet is a high-end motherboard, like ASUS or Gigabyte, and [afaik cautionary] the problem is much less likely with a good laptop.

 

[Mossshine]

Have you tried with another amplifier? I remember DarkVoice has a noise buzz issue, sometimes it goes away after many hours, there is also a fix by removing or changing some caps.

Oh no, it's not the AMP, I have had noisy tubes so I know how that sounds, it's really electric kind of noise - plugging the DAC to my phone doesn't have this issue. It's when it's plugged in to PC

 

[Katji]

Have you tried with another amplifier? I remember DarkVoice has a noise buzz issue, sometimes it goes away after many hours, there is also a fix by removing or changing some caps.

Yes, and on one channel. There is some major audiophool bs on it on some forums. valve burn-in bs.

 

[AnalogSteph]

Oh no, it's not the AMP, I have had noisy tubes so I know how that sounds, it's really electric kind of noise - plugging the DAC to my phone doesn't have this issue. It's when it's plugged in to PC

...which completes the ground loop that is giving you issues. Classic case of unbalanced connection between two IEC Class I devices. The fact that the ground loop is running over USB ground back to the PC power supply is not making things any better.

I don't even think you're the first to complain about this model amplifier. My guess is that the construction dates from the '90s or something, when you could generally arrange a floating source like a CD player (kind of like your phone now). In the days of PC sources, it's just a bad design that will require adding a line-level isolator at the input. You wouldn't want to see Amir's measurements of one either, but that's not the point of such an amplifier anyway, it's just a flavor cannon. Ha, he has actually measured one. If not even the Audio Precision with its galvanically isolated inputs and outputs can get clean results, there may actually be some internal ground loop issues going on as well, which is in no way helping matters. (At least I wouldn't assume they'd be using half-wave rectification, but you never know.)

EDIT: Posted just earlier today...

 

[somebodyelse]

As AnalogSteph says, you need to break the ground loop, or at least minimize its influence. You can try powering the DAC from a separate psu (phone charger, Pi psu etc.) and using an optical connection to the motherboard - there's still a chance of leakage current issues via the new psu, but its cheap and easy to try, and will probably work. Beyond that you get into USB isolators, or audio isolation transformers between the DAC and the amp, and have to decide how much you want to spend. One of the reasons pro audio uses balanced connections almost everywhere is so that they don't have to try to sort these ground problems every time they hook up a new piece of kit.

 

[Mossshine]

As AnalogSteph says, you need to break the ground loop, or at least minimize its influence. You can try powering the DAC from a separate psu (phone charger, Pi psu etc.) and using an optical connection to the motherboard - there's still a chance of leakage current issues via the new psu, but its cheap and easy to try, and will probably work. Beyond that you get into USB isolators, or audio isolation transformers between the DAC and the amp, and have to decide how much you want to spend. One of the reasons pro audio uses balanced connections almost everywhere is so that they don't have to try to sort these ground problems every time they hook up a new piece of kit.

If I use optical out from my motherboard port to the dac and power the dac from separate power adapter (phone's charger ?), won't that degrade audio quality in some sort? I guess this is a stupid question, but please bear with me.
Also will any optical cable do, or are there some "better" ones.

 

[hyperplanar]

If I use optical out from my motherboard port to the dac and power the dac from separate power adapter (phone's charger ?), won't that degrade audio quality in some sort?

No

Also will any optical cable do

Yes

 

[somebodyelse]

Hyperplanar has the essence of it, but there are details and corner cases.

Optical won't degrade the signal so long as it's in spec and the DAC is decent, but it will limit the maximum sample rate you can use. That limit will depend on the transmitter on the motherboard and the receiver in the DAC - probably 96kHz but maybe 192kHz. If you have anything higher then the OS (Windows 10?) or the player app will most likely take care of resampling and is unlikely to be audible. There's a recent thread covering what Windows gets up to. Regarding the DAC being decent, amirm seems to have stopped testing all the digital inputs separately as there was rarely a significant difference, and it multiplies the work needed to do the tests. WolfX-700 kept going a bit longer but seems to have stopped now too. Having said that, the measurements of your DAC do include jitter performance for the coax input and a note about the toslink (optical) being slightly better than coax, which looks bad but is probably still inaudible.

Any optical cable should do so long as it's not broken. If anything's wrong it'll almost certainly be very obvious. Spending more will get you a prettier sleeve and connectors, but that's about it.

 

[Mossshine]

Fixed ! yay

Got myself the optical cable - pc to dac and instead of using the usb connection for audio and power I am powering my DAC with a spare phone charger. No more ground loop.

Note: sounds different, almost like soul left the sound, like uptight, it's hard to describe, I guess the ground loop "noise" in usb was adding some color or something

 

[hyperplanar]

Check to make sure the output sample rate and bit depth is the same as before (would recommend 24 bit/44100 Hz for general use) and all audio enhancements/EQ are disabled on the motherboard audio.

 

[Mossshine]

Nope, everything was disabled.

I went ahead and ordered iDefender+ (ikr, half the pirce of my DAC), plugged in in with external power and now I can enjoy USB with no hiss (it definitely is better via USB than optical cable). I could make something that does exactly what the iDefender+ does with scraps laying around me and my 3d printer, but I got lazy.