If the plug on the power cord is a NEMA 5-20P 125V 20 amp rated plug then per NEMA, UL, and NEC code the amplifier continuous FLA (Full Load amps) cannot exceed 16 amps.
20 amps X 80% = 16 amps. Continuous is 3 hours or more.
Per NEC electrical safety code the required branch circuit size is 20 amp. Also because of the FLA, imo, the 20 amp branch circuit should be a dedicated circuit strictly to power the amp.
If it were me I would have #10awg wired installed. The breaker at the electrical panel has to be 20 amp. Receptacle, 20 amp.
IF the amp does not have a soft start circuit for start up and causes the circuit breaker to trip once and awhile due to high inrush current you may need to have a 20 amp HM (High Magnetic) breaker installed. A HM breaker has a longer lag time for inrush current.
DO NOT install a 30 amp breaker.
Example of a 20 amp HM breaker:
20 amps X 80% = 16 amps. Continuous is 3 hours or more.
Per NEC electrical safety code the required branch circuit size is 20 amp. Also because of the FLA, imo, the 20 amp branch circuit should be a dedicated circuit strictly to power the amp.
If it were me I would have #10awg wired installed. The breaker at the electrical panel has to be 20 amp. Receptacle, 20 amp.
IF the amp does not have a soft start circuit for start up and causes the circuit breaker to trip once and awhile due to high inrush current you may need to have a 20 amp HM (High Magnetic) breaker installed. A HM breaker has a longer lag time for inrush current.
DO NOT install a 30 amp breaker.
Example of a 20 amp HM breaker:
Standard QO115 and QO120 circuit breakers are manufactured to have a magnetic trip point at approximately 8x to 10x the breaker rating. There are some applications, however, in which a load has an inrush current high enough to cause these standard circuit breakers to trip. Examples of these loads include area lighting for athletic fields, parking lots, or outdoor signs. To allow the high inrush current without tripping the circuit breaker, a high magnetic breaker should be used. These high magnetic breakers have a magnetic trip point set much higher than the standard circuit breakers. They can be identified by the HM suffix on the catalog number (QO115HM). Current production HM breakers are also identified with a "High Magnetic" label on the side of the breaker (see photo).http://www.schneider-electric.us/en/faqs/FA96714/
NOTE: The above explanation comparing the standard breaker to the high magnetic breaker applies to 1-pole, 15A and 20A, QO, QOB, QOU, HOM and CHOM breakers only. Other ampere 1p breakers, and all 2-pole and 3-pole versions are already high magnetic as standard. (Breakers with suffix GFI, AFI, CAFI, or DF are not available as high magnetic).