Weird usb audio noise spikes

[Kapparino]

Hello,

I noticed a very high pitched hiss going through my speakers and headphones that is driving me crazy, I can't figure out wheter it's coming from my pc or my dac (or something else?!)

So first of all, here's my setup : 

MSI Z170a gaming pro carbon mobo -> mackie big knob studio+ interface -> speakers/headphones

So I made some measurements with my phone mic and it is cleary visible.

Here's the graph where you can see the spikes at around 8 and 13khz coming from my pc.

 

So I then tried using another computer (my laptop) and came up with these results:

The spikes are still there but there are more of them at different frequencies.

 

Some considerations :

- Changing windows sound level does not affect the noise

- When no sound is playing the noise will stop after some time

- Using a 3.5mm jack coming from built-in soundcard to the stereo input of the interface makes the noise disappear

 

Any help would be greatly appreciated

[Majestic]

The laptop test is with the laptop speakers or using the laptop to power the speakers?

 

Do note that when you're testing this type of feedback, placing the microphone only an inch differently can give you a totally different graph. So if you want to do an actual AB test, you need to completely fix the MIC in place and don't move the speakers.

[Kapparino]

@Pangea2017 I unplugged everything but the usb audio cable and I've unfortunately seen no change. The problem is that the noise is also hearable through my speakers.

@Majestic The laptop test was the same but with the usb cable plugged into the laptop. The mic was jammed between my headphones. The whole graph isn't important, it's just those spikes that matters.

[Majestic]

What app did you test that with? Just seeing how reliable it is.

[Kapparino]

The app is called Spectroid but once again this is just a super non professional way to show the noise that I'm hearing.

Using the interface to record the audio output through audacity and then boosting the gain also highlights the noise.

[EsaT]

If lrouting already analog signal through audio interface doesn't have that noise, then DAC of it obviously takes some noise from USB port/its power.

(with noise varying between USB ports)

No input signal for some time could make that audio interface go to some idle/sleep state explaining noise stopping after some time.

[Kapparino]

So you're implying that the noise is coming directly from my pc? Any way to solve this besides buying a new motherboard?

 

Oh, and I forgot to mention that I'm currently using an Ifi Idefender 3.0 (usb ground loop breaker) because of ground loop problems (GPU coil whine going through speakers) 

but I noticed that this hissing noise was amplified a bit when I had the idefender plugged in. That doesn't make any sense ?!

 

[Kapparino]

Hello,

So I made some more measurements today using my pc line out (analog connection) as the input, the results were quite surprising.

If someone has an idea of the real source of the problem, any help would be highly appreciated.

https://imgur.com/a/GFwn6ca

 

[GrandFatMan]

it could be "dirty power" 

[Kapparino]

How? ifi iDefender cuts off usb power and my psu is tier 1.