I guess the first thing to do is make sure you know whether it's the amp or the mixing board introducing the noise. I don't know what connectors you have on them but I imagine the line levels are standard so could you either try running the mixing board out through a receiver/amp from your stereo system or try running some stereo kit (maybe a CD player) through the studio amp and speakers ?
I haven't touched a mixing board in 25 years but my first thoughts would be :
- start with a can of compressed air from rat shack or equivalent to blow the dust out of all the controls (probably want to blow from the inside out rather than blowing it further into the innards)
- wiggle all the controls which have signal going through them when the noise is happening and see if any are crackling implying a loose (high impedence, more noise prone) connection. Hit them (or maybe all) with some cleaner. Alan has an article on cleaner selections :
http://www.axiomaudio.com/tips_cleaning_staticy_controls.html
Is the noise on both/all channels or just one ?
