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Cleaning USB for Bus Powered Audio Devices: Discuss

L5730

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#1
Some of you guys may be aware of my posts and other's in the Topping D10 review thread. It seems that this DAC, like many audio devices that get their [power from the USB Bus, suffer from some noise coming from the USB port itself.

From my own experience, plugging the DAC into a Raspberry Pi 3B (+5v PSU and Ethernet connected) dropped the noise considerably compared to any port on the PC. However, I think it can be lowered still.

One user was having a terrible time with noise, and so made their own solution:
Take a USB cable and cut the +5v (red) cable. Run an external +5v power supply into the device-side of the UBS cable red wire that has just been cut.
Take the ground (black) cable and splice into it the ground lead from the PSU. Do not break continuity of the ground lead in the USB cable.
This approach takes the +5v power from elsewhere, whilst leaving everything else connected.

There seems to be some devices knocking around the auction sites consisting of an ADUM chip and a small PCM board, with or without a barrel connector for external power. The spec. indicates that these are meant for the lower old USB v1 data speeds and not USB 2.0 480 mbps or USB 3.x.

I can appreciate my topic is a bit messy here, but it might be nice to try and compile a number of possible solutions that folks can try.
It might also be good to list devices that do and do not suffer from USB power noise.

How do the Bus powered audio interfaces fair with regards to USB noise?

EDIT:

Devices with clean USB power:

Raspberry Pi Model 3B
May have issues with current draw, but as along as it is USB spec. (<500mA) and nothing else it drawing much power then things should be fine.
Do be mindful of connecting HDMI devices as there could be a source of noise.
Ethernet connection seems to be free from carrying noise through a wired LAN via router.
(U:Create kit with Keyboard, Mouse, 2.5A PSU, Case etc. Plug n Play kit )
 
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Krunok

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#2
Some of you guys may be aware of my posts and other's in the Topping D10 review thread. It seems that this DAC, like many audio devices that get their [power from the USB Bus, suffer from some noise coming from the USB port itself.
As it was shown in measurements @amirm made with D10 it doesn't have any issues with them.

DAC which was designed to be powered over USB link should withstand any garbage coming from the port. D10, and other well designed DACs do exactly that.
 

L5730

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#3
..but folks seem to be having issues with power coming from USB, so something is up somewhere.
I can see, from my limited testing (I confess to just fumbling in the dark) that there is less noise when plugged into the RPi. I also hear mouse movement and when windows are dragged around the screen - but I have to crank the heck out of the amp to hear it.

As said in the thread linked, for me it's not troublesome, even though it is there. At -72 dB it's well below the noise floor of the room I am in and at the levels of amplification I am using it just isn't audible.

I can't seem specifically where @amirm shows that the D10 isn't affected by USB power. I know he showed a Schiit product falling over with rough USB, and I'm trying to find that.
 

Krunok

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#4
I can't seem specifically where @amirm shows that the D10 isn't affected by USB power.
D10 was powered by USB port of his PC when he did that test and noise floor level was at app -140dB.

Of course, it may very wel be the case that your USB port is particularly noisy.

When I crank volume of my D10 to 100% I have to get app 5cm to the tweeter to hear the noise and that is probably coming from my amp, not from D10. Now it's connected to Dell PC but it was the same with RPI.
 

solderdude

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#6
A different Mobo, a different source power supply, a different amplifier, different cables, different mains conditions and you have a nice mix of ingredients that can cause 'problems' in one setup and less in another when the only constant is a specific DAC.

The problem may not be in the DAC but combination of other components.

Galvanic separation may be the easiest way out of such problems.
It does not have to be the +5V supply of the source but could be if the +5V dips below that of the internal regulators in the receiver chip.
 

solderdude

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#8
The question is whether the problems are caused by a 'dirty' 5V or by a 'dipping' 5V.
In case of the latter 1000uF may be more effective than 10uF.
Could also be that there are other problems than the 5V from the source in which case the filtering may do nothing.
There is also the data lines which may or may not be 'afflicted' as well and is not addressed by the filter.
'Crap' could also come via the common (0V) line and a ground loop may be the problem.
 

L5730

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#9
I value you folks' input.
So what kind of cheap devices or hacks/mods can be performed to see if it makes a difference?

I'm going to have to try the RPi again, disconnecting the Ethernet cable and HDMI and see what comes of it.

For what it's worth, I took the left channel audio only from the D10 and fed it into the left channel audio only on the motherboard ADC to see if the noise was somewhere in the ground that way. Used an RCA>TS on both cables and just hooked the two tips together, leaving the ring (ground) unconnected. Basically running a line level mono signal without ground. No difference really.
 

solderdude

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#10
You could possibly record the 'problem'.
 

Blumlein 88

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#11
It is probably hidden in one of the various Schiit modi test threads. In one of them Amir compared the sensitivity to the USB of the Schiit vs the Behringer DAC. At one point he used powered USB hubs between the Schiit and the PC. This did in some cases clean it up fairly good. Some hubs did this better than others. That is a cheap solution to try if you are hearing mouse clicks and screen activity coming through. If you'll search and find that info maybe you can buy the exact one that worked best for Amir.
 
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#12
i tried one of the chinese cheap USB filter.

onestly i stopped using it because it brought no hearable improvement, but for less than 10$ you can try. unless you want to try something more expensive like ifi or audioquest filters
 

L5730

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#13
You could possibly record the 'problem'.
http://www.filedropper.com/d10noise

30seconds @ 192 kHz / 24 bit. Added 36 dB of gain so it's more audible.
0-10s: D10 is connected via audio cables, but not to USB - no power.
10-20s: D10 powered on, display bright.
20s-30s: D10 powered on, display dim.

If you want the original, non boosted file, I can provide that instead.
 

solderdude

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#14
What is the exact chain and which devices are connected to mains and to each other with what kind of wires.
What mains is used with or without safety ground for what device ?

Is this recording made with nothing but the D10 RCA output connected to the input of the PC soundcard and merely switched on ?
Any mains power supply used ?

When the D10 is connected in someone else's chain does it do the same ?
 

L5730

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#15
UK 240v 50Hz AC > 3-pin UK plug with Earth > Desktop PC > (any) USB 2.0 or 3.0 to D10 > 2x RCA to 3.5mm TRS stereo > (same) Desktop PC Motherboard ADC.
PC is connected to a TV via HDMI and to a monitor via DisplayPort, as well as Router via Ethernet cable, desktop speakers via 3.5mm motherboard sound out, a printer via USB. I'd hope all that crap isn't causing the issues :S

Oh yes, and the old electrical wiring in the house means we have one ring main, and I heard a small pop through desktop speakers connected to motherboard, when someone switched a 240v outside light off! I think our house wiring is craptastic.

The recording is with the D10 connected, no audio playing through it, and Windows set to use something else for output. Absolutely no sound is being played through the D10, it's purely it's own noise.

It's strange but the amplitude of the noise is lower when the Raspberry Pi is solely connected to the D10 - which indicates that the noise can be attenuated depending on what the DAC is plugged into.

I have a second D10, and that behaves identically as this one, so I don't think I have two faulty units, that'd be really strange luck. I think my issue lies somewhere in my setup.

I've got a Masterplug MVA1200 switch-mode PSU that has a 5v option. I'm going to check polarity tomorrow and try using that to power the D10 with the suggested T-GND / cut +5v custom USB cable.

I don't have another ADC, except for in a laptop with a TRRS thing (mic/line in and hp/line out in same jack socket), and I don't have the cables to faff with that. There is a netbook somewhere I might be able to dig out for testing, try that on battery power.
 

solderdude

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#16
When your laptop is connected to the D10 (+ its power supply) only is it quiet ?

When your PC is only connected to the D10 (and its power supply) and all other connections are removed is it quiet then ?

What is connected to the RCA output of the D10 normally ? desktop speakers ? headphone amp ? Stereo system ?

What happens when the D10 is out of the loop and the audio-out of the PC is connected to whatever the D10 is feeding ?

You could try to use it the way you do now and unplug each device connected to the PC one by one, listen if it cleans up after removing certain parts.
 
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L5730

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#17
3. What is hooked up normally to D10 is a pair of active monitors - and I had to turn them up, but I could hear these same buzzing sounds. Not audible at normal volume levels I actually use.

4. The motherboard sound is fine, no noises above a small background hiss.

As for 1. The laptop is not used portably, all cabled are tethered to a board it's on. D10 hooks up by USB when required and then on to Integrated Amplifier. I'll have to turn the amplifier up and see what noise I hear.

2. I am going to have to unplug a bunch of stuff and see.

For the heck of it, probably a bad idea, but I used the left channel into the motherboard ADC (tip on TRS) and touched it against (1) D10 > RCA pin (2) D10 RCA shield (3) D10 case. Both the signal and shield connection from the D10 have exactly the same buzz sounds, the case does not, that is dead silent. I do not know if this helps. D10 connected via USB to desktop PC.

As said, it's really not an issue in use, because it's low enough down I don't hear it, but still, it shouldn't be there and for the sake of completion I should try to remove the buzz. It's good to learn something along the way too.
 

Krunok

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#18
UK 240v 50Hz AC > 3-pin UK plug with Earth > Desktop PC > (any) USB 2.0 or 3.0 to D10 > 2x RCA to 3.5mm TRS stereo > (same) Desktop PC Motherboard ADC.
Does the same issue happen when you route signal to a different audio device?
 

L5730

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#19
Yeah, instead of going to motherboard ADC, go to active monitors - same sounding buzz, same change in frequency when the display dims.
 
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