The mic preamps are most-sensitive to noise since they are high gain and they amplify noise along with the signal.

"Because of the severe power constraints of USB bus powering, the headphone outputs, and often the phantom mic power (mic current capability) are limited to power levels that are far less than ideal"

Externally powered hubs are nice since you can pick the power supply.  Usually doesn't matter, but for really sensitive instrumentation I've used low-noise linear power supplies with hubs before.

is there any truth to the notion that mic preamps,phantom power ,  headphone outputs etc will perform worse on bus power?

Quote from: theoctavist on 2023-02-07 09:50:03

is there any truth to the notion that mic preamps,phantom power ,  headphone outputs etc will perform worse on bus power?

That depends on how well the device filters noise from the bus power and how much power the bus allows it to draw.

I would guess it's probably cheaper to rely on an external filtered power supply than it is to build adequate filtering into the device, especially if there's no guarantee that the bus can provide enough power in the first place. (Although USB-C might solve the bus power issue, now that there's a standard for supplying up to 240W!)

With care USB can be fine. There is enough power for headphones and noise can be filtered. But it's often easier to just use a cheap external power supply at a higher voltage rather than clean up USB+5v.