USB Input causes noise across whole amplifier - Musical Fidelity M5si

Yes, I know exactly what this is.

Unfortunately, even today, DAC makers still don't universally use galvanically isolated USB inputs. << insert big sigh here>> and this is 100% what happens.  Especially when your PC and audio are on different AC circuits.

The solution is really simple and cheap though.  You need a USB isolator.  Make sure it supports the bandwidth you need.  Here is a good one.

This is a bad situation because there are a number of situations where a ground loop occurs and it's not this obvious.  Usually listeners "only" suffer from elevated jitter, but it is detrimental to the sound quality.

Hi tony1954,

"From what is says in the manual, I would check that the driver your computer (either Mac or PC) is using is compatible "

My manual doesn't mention drivers, that I could find anyway. All USB devices are working, and those that require drivers are up to date.

I didn't mention but I also tried different USB busses.

The M5si is recognized, is set as default. And it works as expected.

It is only the noise, regardless of whether USB is selected as source.

Hi erik_squires,

Thanks for the info and link.

Alas, for the $$ I'd like solutions inherent in the device, sigh.

I'll look at the isolator though.

@photon_arts You can find them from around $30 I think.  Just make sure it supports high speed 2.0.

It does stink, especially when I have seen some mega-buck DAC vendors sell this as a huge upsell. 

And it's also upsetting because 90% of the time there  is a USB ground loop problem it is NOT audible hum.  It's really bad jitter which listeners may never know about.  They'll hear it in lack of clarity, focus and harshness, but without a jitter analyzer they would not know they had an issue.

It is only a very small amount of USB ground loop issues which show up as audible humm.