AC Line Noise. Please Help.

[DavenPaget]

I harp on this a lot, but gigging musicians need to either take an outlet tester or an isolation tranformer with them to gigs.

If you are building your own amplifier or a power supply for all your pedals, it may be a good idea to build in the outlet tester so you never lose it.  It consists of three neon lights that should show hot to neutral is on, hot to ground is on and neutral to ground is off.  Double pole switching and circuit breakers are good ideas.

Many amplifiers have a capacitor from line to ground that may be switchable from one side of the line to the other.  This should be replaced by a line-to-line filter using class X or class Y capacitors which are described here:

http://www.justradios.com/safetytips.html

or L-C filters using these components.

At some point, someone should suggest using MOV's (metal-oxide varistors) or semiconductor spike suppressors.  Noise caused by a bad neutral connection can easily cause up to double the voltage to appear at the power input.  I would put the suppression after the breaker just to ensure that continuous double voltage trips the breaker.

Ooh i'm interested in TVS diodes , how much should i get for 240V supply ? (1phase)