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Studio speaker noise

Per W

Per W

n00b
Joined
Jun 17, 2016
Messages
2
I have a bit of a mystery.

I bought a pair of KRK Rokit studio speakers, and they will not cooperate with my stationary PC. They work well with my macbook.

When connected directly to the PC, I get a hiss noise from the speakers. I thought it was electric noise, so I try connecting the speakers via en external USB soundcard - digital signal so no electric noise - but same noise.

When I then plug USB soundcard into macbook - noise is gone.

How is it that noise from desktop PC gets to the speakers even when using external USB sound card?
 
Per W said:
How is it that noise from desktop PC gets to the speakers even when using external USB sound card?
Click to expand...

There is nothing about USB that isolates from electrical noise, as it's still a cable with metal wires that can conduct electricity. Coax digital (S/PDIF) won't fully isolate either, for the same reasons. The only digital format that fully isolates electrical noise is optical, as electrical interference simply cannot travel over the rubber and glass cable.
 
was the macbook running on battery or plugged into the wall? if it was on battery, plug it into the wall where the PC is and see if the sound comes back, may be electrical noise caused by the ground.

I had noise from my M-Audio BX5 speakers, swapped out the speakers, swapped out the PC, and finally just lifted the ground from the speakers.
 
GotNoRice said:
There is nothing about USB that isolates from electrical noise, as it's still a cable with metal wires that can conduct electricity. Coax digital (S/PDIF) won't fully isolate either, for the same reasons. The only digital format that fully isolates electrical noise is optical, as electrical interference simply cannot travel over the rubber and glass cable.
Click to expand...
Using optical solved any sound issues I ever had.

Op- sounds like a ground loop issue.
 
With electrical noise I was thinking noise added to the signal by analog components on internal audio - with USB audio, the original digitally computed audio data is sent to an external device, digital data unaffected by any PC internals.

So the issue may be like, both devices connected to the same power outlet?
 
Per W said:
With electrical noise I was thinking noise added to the signal by analog components on internal audio - with USB audio, the original digitally computed audio data is sent to an external device, digital data unaffected by any PC internals.
Click to expand...

And what makes you think that the same electrical noise can't simply travel over the USB cable and still be present at the time of the digital to analog conversion?
 
Per W said:
With electrical noise I was thinking noise added to the signal by analog components on internal audio - with USB audio, the original digitally computed audio data is sent to an external device, digital data unaffected by any PC internals.

So the issue may be like, both devices connected to the same power outlet?
Click to expand...
Yes this is what I meant. Dirty AC power... or a AC ground loop. Simple things like certain lights etc can cause this.

I highly doubt it'd be the cables or speaker wire.
 
Low quality (or broken) RCA cables can cause audible hiss especially if it's a longer pull. RCA cables don't cost much so if nothing else works, try a higher quality cable.

Ground loops usually manifest in a 50-60hz buzz instead of a hiss.
 
PCs are noisy, PC power is noisy, therefor a USB DAC without good power circuitry will be noisy. You can add a USB power filter like this Schiit Audio, Headphone amps and DACs made in USA. at $99. If you have a powered hub, you could try that, but a lot of DACs don't like to play nice with hubs.

To help us narrow down the source of the noise, does the sound change pitch and loudness if you fire up a game, or is it a constant 60hz like this:
 
Mine was hiss and hum as well as you can hear noise when the hard drive and mouse move.

Here is a video I just recorded.


Using a 3prong to 2 prong adapter makes the noise go away.

I also had a 20a circuit installed just for the PC setup and the noise is still there. Really strange.
 
Last edited:
B00nie said:
If the adapter makes the noise go away it's a grounding problem. 2 prong is not grounded.
Click to expand...
Yep, couldn't figure out the cause of the issue. 2 different PC's, 2 sets of speakers, 3 different sets of cables. Pulling the ground to the speakers was the only thing that worked.
 
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