Journal: hunting down and trying to fix USB electrical noise in an audio path.

[AnonymousGuy]

I rarely ever see this sort of thing documented so here we go.  Long story short: my laptop is 75 feet away and I wanted to be able to get audio out of it to my office so I can easily toggle between laptop audio and desktop audio on the same set of speakers.    My desktop is running a JDS Labs Atom Amp that has a 3.5mm input jack that I'm going to use for the laptop.  The desktop is fed by the RCA inputs from a JDS Labs Atom DAC and is completely silent.  My laptop is running a JDS Labs Element which is a very good combo usb DAC/Amp that has a AC power supply for its op amps.  I've connected the headphone jack on the Element to the Line In on the GoXLR.

 

So through a combination of cranking the gain on the Amp or doing some fuckery routing the audio through a GoXLR and Voicemeeter I can see and hear what noise we're talking about.

 

Here's the cool GoXLR routing setup.   The important part is the line in is being connected to the broadcast stream mix, so then I can hook that in Voicemeeter and get a dB measurement.

 

Here's the noise floor.

 

 

This is what it sounds like coming out of the Atom Amp with the gain absolutely cranked.  It's obviously less audible at normal volume levels but you can still hear it by ear.   -55dB noise floor is not good....-70dB would be good enough to be inaudible.

 

 

There is a literal fuckload of products that claim to be able to fix something like this.  Oh it's ground loops.  Oh it's USB jitter.  Oh you need an independent USB power supply.  Blah blah blah.  The only thing I'm going to say is *it's not the cables*.  75 feet isn't that long of a cable run and I'm using my own built 1/4 to 3.5mm cable with shielded cable.  It's never the cables unless you're doing some weird shit like coiling a cable around a power wire with a really shitty cable with a really long run (hundreds of feet like at a concert).

 

 

So here's the kitchen sink we're going to throw at it and return what doesn't work.  I'm not going off the deep end and spending $1000 on various "audiophile" products that claim similar things:

 

 

 

 

 

All of the ones that have independent power plugs (iFi, Nobsound) I'll try with and without an external power brick.  I don't have a fancy 5V power supply to work with so I'm going to use a normal phone charger deal from the wall and a battery bank to see if either one helps.

 

<Links will be inserted here to followup posts with result summary>

[da na]

I have seen older integrated soundcards (this happens much less nowadays) but on the old motherboards I work on (2000s-2010s) often the integrated sound is quite distorted. The squealing sounds increase with CPU load. Digital noise with things like that is pretty common. Sound Blaster cards always fix that. 

If you don't care too much about quality you could use a USB sound card.

[AnonymousGuy]

4 minutes ago, Mel0nMan said:

I have seen older integrated soundcards (this happens much less nowadays) but on the old motherboards I work on (2000s-2010s) often the integrated sound is quite distorted. The squealing sounds increase with CPU load. Digital noise with things like that is pretty common. Sound Blaster cards always fix that. 

If you don't care too much about quality you could use a USB sound card.

The JDS Labs Element basically is a USB sound card with an AC power brick for the amp section.  The USB ports on this laptop (Elitebook G8, 2021) are noisy as fuuuuck.  I didn't mention it in the first post but I also see similar noise profile when I connect a USB XLR interface with a line-in as well (Focusrite Scarlett)

[da na]

1 minute ago, AnonymousGuy said:

The JDS Labs Element basically is a USB sound card with an AC power brick for the amp section.  The USB ports on this laptop (Elitebook G8, 2021) are noisy as fuuuuck.  I didn't mention it in the first post but I also see similar noise profile when I connect a USB XLR interface with a line-in as well. 

Yeah, USB especially on laptops don't get super well noise isolated and all that. They expect few people will actually use audio over USB is my assumption. 

[AnonymousGuy]

19 minutes ago, Mel0nMan said:

Yeah, USB especially on laptops don't get super well noise isolated and all that. They expect few people will actually use audio over USB is my assumption. 

I'm waiting on a 1/4 to 3.5mm adapter so I can also check out how well the built in audio jack is on the laptop.  I'm going to guess they really didn't give much shit though about it and whatever noise is in the USB ports is probably everywhere since it's just a noisy ground plane somewhere with everything dumping their switching noise into it.

 

(I found it funny that I didn't already have a 1/4 to 3.5mm adapter.  I've got a whole bin full of cables and adapters but until now I've never needed to upsize 3.5mm to 1/4, only ever needed to downsize 1/4 male to 3.5mm female)

[AnonymousGuy]

 

Did absolutely nothing.  No change in the noise in dB or subjective profile.

 

 

-20dB change in the noise floor.  -70dB is mostly inaudible without having the gain cranked to absurdly loud levels.  The sound profile is still buzz-y (maybe 60Hz hum?) but it lost a lot of the "data" fluctuation sounds and is a lot more consistent.

 

 

Basically completely fixes the noise.  I can split hairs and say that -84dB isn't complete silence but I barely hear it with the gain maxed out and have to have my ear next to the speaker.

 

With a Monoprice USB power adapter providing external power (there's a switch on it to change internal vs. external power)...no difference it is still -84dB.

 

 

This only does anything when it has external power, it changes the hum to a slightly higher pitch than the "Compact Hum Eliminator" and similarly filters out the data fluctuation sounds.  This thing cost like $60 though sooooo.....nope.

 

 

OK what if you completely change to a different USB interface?  Well...exact same noise outcome of -50dB, same sound profile.

 

Conclusion:

 

Nobsound really won this thing.  I don't what it's doing but whatever it is by far worked the best at cleaning up the sound.  And for only $25 which is cheap compared to a lot of the other "solutions".  I'm not going to sit here and say it'll fix every audio issue because god only knows how many things can create noise in an audio path, but  at least from what I observe it really cleaned up USB based noise.