Newsgroups: rec.arts.theatre.stagecraft
Subject: Re: Sound settings???
References: 
"Plus net"  writes:

> A) During quiet periods (When a SFX is not been actioned and the system is
> idle) there is a unacceptable hum from the FOH all our speaker which is
> distracting to the audience (or at least myself but others agree when asked
> is it distracting  to them) They have the Amps (positioned Backstage) FULL
> UP and between Cues leave the desk faders up and only activate the SFX by
> starting CD/Cassette / Mini disc etc.

I have put up a specific web site hon solving this kind of problems to
http://www.hut.fi/Misc/Electronics/docs/groundloop/
There are lots of information how to solve this kind of problems.

The basics of heeping hum out of the system:
- power everythign from same power source which is different that dimmers use
- use well shielded balanced cabling in all long runs
- keep cables away from lightin related power cables
- use well designed equipments 
- if the topics above does not solve the problems use signal cable ground
  lifting or audio isolation transformers where needed

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/