Ferrite cores and audio lines (stereo)

[faekjarz]

Hi!

I'm noticing some audible, as far as i can tell w/o an osmelloscope, high frequency interference on my 2(+1 subwoofer) stereo PC speakers (Logitech X-210). It sounds like tinnitus, and yes i double checked, it's not my actual tinnitus. I already galvanically decoupled the signal line without improvement.

Adding a ferrite core, straight on, or double through, didn't improve the situation.

1) Is there an actual application of ferrite cores on analogue stereo audio feed lines?
2) Why, or why not?
3) Should i take the thing apart and look for worn out components, something obvious like caps and stuff?
4) Should i re-route the audio feed line, and separate it from digital cables, like Ethernet, HDMI/DVI, or even mains power supply lines? (Why?)

[tszaboo]

Ferrite works in the MHz range, audio is in the KHz range. Unless you can prove that the noise is RF interference, it is not going to do anything with the audio.

[JS]

Did you tried the speakers with a different source than your computer?

Onboard audio cards are well known for introducing all kind of noises, some of them could be reduced decoupling the signal as you did but some can't. If that's the case getting a USB card could help. Expending a bux more for a good known audio brand one would be even better if you want low noise.

JS

[faekjarz]

Did you tried the speakers with a different source than your computer?

Good point!

The noise persists with a different source (my smartphone), and even without any source. So, it's just a noisy speaker system, i guess. It's a fairly old one, and i bought it pre-owned, a few years ago.

I'll probably turn it off and take it apart; any recommendations what i should look for?

[BergRD]

osmelloscope = AvE?

[faekjarz]

 

[JS]

Did you tried the speakers with a different source than your computer?

Good point!

The noise persists with a different source (my smartphone), and even without any source. So, it's just a noisy speaker system, i guess. It's a fairly old one, and i bought it pre-owned, a few years ago.

I'll probably turn it off and take it apart; any recommendations what i should look for?

Short the input and see what happens, does the noise go away or gets lower?

Hard to tell without knowing the nature of the noise, could be a PS issue, caps going bad maybe, not rare in old stuff. You can know with the DMM measuring AC across the DC output of the PS.

Or, less likely and harder to find without osmelloscope, something bad with the input stage.

JS

[coldfiremc]

like tinnitus? if it varies with load(and power stage signals) could be a whining iron echo from the power source, those "noises" are 3rd harmonics, if not, in some place, the slower modes of a clock are trolling you. Is not easy to get around that. Check ground paths, and clock sources nearby.

talking about ferrite, depends how is the winding made. if is an isolator, anything AC will pass it flawlessly, obviously if power does not exceed the nominal values of the iron , or if its frequency is far beyond its nominal values. With just winding the cable on it and not cutting anything, Another uses are to create hystheresis in DC power lines, that supress not so high frecuency noises (khz).