100KHz garbage coming out of my Focusrite Scarlett 2i2 v2

[restorer-john]

So, my M-Audio Audiophile 24/96 and M-Audio Audiophile 24/192 don't make noise like this at ~100KHz when idle, so why does the Focusrite? Do I have to fix everything?

DSO. (same with BW limit) The freq is 100Khz, not 133KHz as indicated...

Confirmed on the old CRO (HF REJ will kill it):

It seems to be USB related as I tried a different PC and the noise was worse! Output in parallel with a 10K load. Idle, no signal, monitor level turned down. Turn it up and residual noise fills in the gaps, but the spikes are still there.

 

[pma]

Yeah ..... , is there any DC/DC converter in the card, John? Like the one to make 48V phantom or anything else? If the analog scope does not have SMPS, then it definitely comes from DC/DC, SMPS of the soundcard/PC or USB. In such cases, I am trying battery power or isolation transformer for the PC (my ISO tr. has 150pF stray cap.).

 

[restorer-john]

is there any DC/DC converter in the card, John? Like the one to make 48V phantom or anything else?

You're right. For sure there will be a buck/step up in there someplace for the 48v phantom power- it's probably active even though the switch is off...

The analogue scope is a proper old girl (no digital and no SMPS) and I turned off everything except it, in case the DSO was being naughty. To its credit the Rigol SMPS is really good as far as I can tell. But it should be, it's inside a scope!

I've been having a hell of a time in the last few weeks with noise. Everything from LED SMPS supplies to PC power supplies, routers to air conditioners.

Honestly, I'm a bit over it.