What receptacle for 240V 20A in the States?

Not to through a fly in the ointment. But it is possible you may effect the sonics of the Amp. For better, or worse??

From the mains of the U.S. 240V you will essentially be feeding the Amp from a balanced power system. Also the voltage may be closer to 250V + . You may want to have that checked first. Also check what the maximum input AC voltage rating is for the Amp.

As for the NEMA 6-20R receptacle that would be a good choice. If you already have an extra 120V dedicated circuit by your audio system all you will need is a 2 pole 20 amp breaker installed at the electrical panel and the two insulated conductors of the dedicated branch circuit terminated on the 2pole breaker.

Angus80808, You will need to reconfigure one of the existing 120V dedicated branch circuits to a 250V dedicated branch circuit. At the electrical panel the 250V branch circuit must be connected to a 2 pole breaker. If the wire is #12 awg and the receptacle is a 20 amp then the breaker must be a 2 pole 20 amp breaker.

As in regards to phasing the power that feeds your home is fed from a split phase secondary winding of the power company's utility transformer. Single phase, only one phase. Two hot ungrounded conductors with a center tapped grounded conductor, the neutral.

03-03-07: Angus80808
Yes, as you mentioned, I will connect to a 2 pole breaker (2x 120V). The wire is #10 awg and will use with a 20 amp circuit...(or maybe 30A??) This makes sense to me.

Do not think of it as 2x 120V. It is single phase 240V. And no you will not need the neutral conductor. Just the two hot 240V conductors and the equipment grounding conductor.

As for the wire size being #10 awg, because of the 20 amp receptacle you are using the branch circuit over current device, (the 2 pole breaker in this case), must be 20 amp. Not 15, not 30, it must be a 2 pole 20.....

And as Ngjockey said in his post have an electrician do the job. 240V will kill you just as dead as 120V
Jim

I would exchange the receptacle and plug for 30A if I go that route.

Mike I would not recommend doing that. You will be fine with a 20 amp branch circuit. 240V X 20 amps = 4800 VA...
Jim