[sdiy] (OT) Preventing digital noise in audio out of a "2 PCs -> 1 audio amp" with USB box

[sleepy_dog at gmx.de]

> What happens if you connect the audio through the box and not the USB

Oh! Excellent question. I somehow didn't go down that route because I 
remember not hearing noise from the newer PC with just onboard sound 
(which I checked for that reason), but now that I think of it, I did not 
amplify the sound after that, I plugged headphones in directly. The 
computer at work does manage to have noise with that setup.

Well, long story short. the noise is still there with all USB plugs 
unconnected from the box... so I guess it does come from the PC's 
onboard sound chip when amplified. It is rather quiet, but audible when 
I crank up the amp more for some quieter audio/video file.


Steve


Am 19.03.2017 um 21:03 schrieb mskala at ansuz.sooke.bc.ca:
> On Sun, 19 Mar 2017, sleepy_dog at gmx.de wrote:
>> All audio jacks are screwed into the metal case rather close to each other, so
>> I guess there should be very direct GND paths between those? They would
>> certainly not have to go through "USB territory", judging from my naive
>> understanding of such things.
> What happens if you connect the audio through the box and not the USB
> (just make a USB connection through a separate cable)?  Checking that
> could verify whether the noise is really coming from the USB connection or
> from something else.
>