electrical phase

Agree with most of AP's post except that many 240 Volt breaker panels are manufactured so that first/third/succeeding odd horizontal rows are on "A" phase and second/forth/succeeding even horizontal rows are on "B" phase. Use a voltmeter to verify construction.

Lighting dimmers can be added to the list of noisy devices to be located on the non-audio phase.

Great post Albert! I am pressing print on this one.

If you should decide to rearrange your household loads in the distrubution box, don't get so carried away that you wholly unbalance the loading of your drop transformer. You want basically equal current loads on both phases, when all loads in the house are operating. I measured all the loads with a clamp-on Amprobe & then put the noisiest ones on the other phase from the dedicated line, maintaining an overall balance as secondary objective. This becomes even more important when commercial power fails for a long time & we have to fire up the backup generator.

Thanks, fellows.
Albert, great explenation.
I have a 60 amp panel into the sound room.
I asked my brother inb law (he's an electrician) to explain to me how he'd wired it.
I now understand that half the outlets are one one phase, half on the other.

KP

I'd like to point out one error in Albert’s post. It has two do with two 120volt phases one row on the left side one row on the right.

A panel is configured so that a (full size) breaker and the breaker directly underneath it are on opposite phases. That way a two-pole breaker can be plugged into two spaces right next to each other (or one on top of the other) producing 240volts.

To truly isolate one half of a residential panel 120/240 volt. You would have to configure your breakers top to bottom skipping every other space.

I hope that makes sense. In all practicality there is no possible way to isolate any one phase for audio unless you have a three-phase panel with no 3-phase loads present in that panel.

My best advise is to always pull a dedicated neutral (white wire) with every hot. In addition add an isolated ground and I.G. receptacles

While I'm on the subject I'd like to mention that there is no such thing as two phase power. 120/240 is derived from a single transformer and is refered to as single phase power in the electrical trade in general.

3 phase power can only be 120/208, 277/480, or 120/240 with a high leg(Not very common except where lots of motors are present) These are standard 3 phase voltages used in the USA