Hi
A 4B can draw 7 amps and preamps and such draw very little amperage so a 15A/120V is fine for most single amp/assorted sources audio systems. 
I'm a little confused on this, given what the Bryston manual for the 4B-SST2 states - as quoted here:
"The circuit feeding the 4B SST2 should be sufficient so as not to cause the circuit breaker to trip. For example, the 4B SST2 when operated with both channels delivering maximum power into 4 ohm loads will consume all the available power in a normal North American residential circuit (15 Amps), therefore a dedicated electrical circuit may be necessary with this situation."This implies that the 4B could draw a full 15 Amps, which is backed-up by the detailed power consumption specifications, quoted in the manual, as follows:
2 channels @ 300W into 8 ohms: 1280 Watts - this equates to 10.7 Amps at 120 Volts
2 channels @ 500W into 4 ohms: 2100 Watts - this equates to 17.5 Amps at 120 Volts
Recognizing that these consumption figures would be on a unfluctuating input signal that would result in a constant output at the above level - which would likely never occur in real-life given the constant fluctuation in the input signal due to corresponding music signal, this does beg the question as to where the 7 Amps consumption figure comes from and why it's not quoted in the manual or specifications. As well, why is there such a statement suggesting a dedicated 15 amp circuit in the manual?
I'm just trying to make sense of this since I've been building a dedicated listening room and purposely wired a dedicated 20 amp circuit for my 4B-SST2 to ensure I would always have enough current and more to spare.
