most likely. It is all in your head
But if not you can measure it wit REW or something and show us...
You can try grounding the USB hub "Ground".
But over all very disappointing to hear another "high end" product being so susceptible to noise from the USB port.
And also sad There is no testing for this USB port "isolation" in the reviews.
No one hears the difference between SINAD of 115 and 120dB but this problem is kind of obvious and annoying for many customers.
Yet it would be very easy and cheap for the manufacturer to make the DAC (mostly) immune to noise form the usb port.
Selling an Separate USB isolator is a strange after thought.
This could and shuld be included in the devices for cents.
The same Conclusion he had for USB isolatos
and for cables...
don't know how he can make this conclusion if he was not able to reproduce the problem many experience.
You don't need an "linear" power supply You need an Low noise power supply with low common mode capacitance or High impedance.
It just happens to be many linear power supply's are low noise and have high impedance to mains.
As OP is experiencing the DAC is clearly not doing well with noise coming from the USB port.
A USB Isolator with an Low noise power supply would help.
Better RCA cables would maybe Help.
Are the USB ports properly grounded to the PC case? is this a DIY pc or from a big manufacturer (who actually dose EM compliance testing)
Nice argumentation, the usb ports were on a basic usb hub powered by a DC powersupply, so I don't think i can do much there, I think I could try to ground the PC USBs and connect the dac to them. I changed the powersupply to a phone chargher and connected the toslink, the noise isn't there at all, so now I just have to check the USB.