Crazy 9.5 Fingers wrote:there is a buzz you can not get rid of, no matter what you do, and your amp's ground is either lifted or not but you can't get rid of it.
Modern electronics and digital recording have pretty well eliminated 60 cycle hum.
If you are into vintage guitars, amps and effects, you will always live with a little of it.
Ground "lift" switches actually open the ground to an amp, which is damgerous and un-necessary. Power reverse switches swap neutral and hot to try to eliminate hum, but were more used in 60's vintage amps in live performance situations (if you got a shock when you touched your strings and a mic at the same time.)
In my experience, hum comes mainly from cheap cables and pickups and poor shielding. An isolation tranformer would be expensive overkill in my opinion.
Rather than spend hundreds on a transformer, here are my suggestions:
1) If you haven't already, invest $40 in a high quality guitar cable. I've had good luck with Planet Waves. This goes for mic cables, patch cords, etc. as well Also be aware that single-coil pickups are more susceptible to noise than humbuckers. All the metal on your axe, expecially the bridge, should be grounded behind the pickguard. If you hear more hum when you're hands are not touching the strings, this could be a problem. Get a guitar tech to check it.
2) If you are re-wiring the room, it would be worth having a dedicated circuit. A home studio shouldn't use too much power, one 20 amp circuit should be enough. But you might want to over-size the wire, especially if the run is long. Please get an electrician if you don't know what you're doing. Also have the electrician make sure you have a good ground at your breaker panel. A lot of grounds in old houses are clamped to a water pipe when they should be using a copper rod driven into the dirt.
3) You are correct in wanting to keep the lights and the power circuits separate. Two of the biggest hum sources are dimmers amd fluorescent fixtures. Don't use them around a studio.
4) Computer monitors are another big source of hum. Keep your distance when the record light is on.
Just one old guy's opinion.