When using two (2) Bryston 7B-SST2 mono power amps, can these be connected to the same 15A electrical power outlet via a high-end powerbar (along with Bryston sources like the BP-26, BP-1.5, BCD-1, BDA-2 and BDP-2)?
Same power outlet or not does not mean anything when you have let's say total of 6 outlets in the room and they all run with only one 15A breaker. You cannot only change the breaker to 20A either. If you do it is not safe, and if you push hard your wire will catch on fire before the breaker trip.
Unless you change all the wires from #14AWG to #12AWG but again, are you going to do it and use few breakers for only one room.
How about if someone live in an apartment that does not own and cannot change anything?
Usually the safe and correct way is, to use only 80% of the maximum capacity under continuous load.
Let's say for only one 15A:
120v x 15a=1800w this is your maximum capacity
1800w x .80=1440w your 80%
7BSST2 draw 250w each at idle and even if you play loud but I hope not full power, you would use around 650w each and you have 5 source components which I would say each one would use 30w at max. (I only have the BDP-1=30w and BDA-1= 10w)
If you do not connect any thing else to this outlet, you are using 1450w which is your 80% and you should be fine.