Dedicated 20 amp circuit. 10/2 or 10/3?

If the device count is modest and the power low, 10/2. If you want multiple outlets and really want 2 dedicated circuits, 10/3.

Also, consider running 10/2 at 220V to a step down, balanced transformer in the room. If this is a long run this can be especially beneficial.

10-4 that is what I had installed.

my friend is a master electrician and Audiophile 

you have live ,neutral and 2 grounds a common ground ,and a insulated isolated ground in its own conduit , then has its own smaller buzz bar the 20 amp 

breakers are industrial silver over Copper which means like regular breakers that are copper should be replaced every 4-5 years because of oxydation,

and use gold plated Copper outlets ,  breakers were made by Siemens Germany 

I tried getting them for my friend very hard to obtain since covid.

underwood Wally has a plug in device Puron ,buy the better ones with the Furutech 

gold copper $350:, the cheaper ones $250 and 3x less conductive Brass, check them out they truly clean your line further ,even if you have a very good line conditioner.

I have a 20 amp dedicated line and I believe it’s its a 12/3 cable on two duplex boxes.  One has the power conditioner on it and the other has the amps plugged into it.

 I haven’t changed outlets mostly because if I ask five people about it, I get five different answers.

One can run 10/3 romex for 220 single phase to a location, and run with it a 12g. green ground with it.  Perhaps not 'according to Hoyle' but at the business end one can 'split' into 2 - 110 circuits and still have the 'safety' mechanical ground....

Label what you've did/done....at each end.....

It's not nice to 'leave mousetraps' like that, and keep your amp loads balanced.

Cooking one side generally takes the other with it...just to make the point....;)

Oh...and if you move/sell and/or bust the lease with your 'loud *ss music'....restore it to a 'normal' 220....With the correct f/m plug....