guitar interference

[madmuso]

HI guys,

I have a question regarding electric guitar and amp interference. A friend of mine has built a separate studio behind his house and I have been helping him plug in all the outboard and other various units.
The studio has its own electrical sub board, which gets its power directly from the house main board. The power and lights in the studio are on separate lines coming from the sub board, and each room in the studio also utilizes its own line from the studios sub board. So far, everything is dead quiet, no electrical noise or interference of any sort. The console, outboard, tie lines are all dead quiet.

However, today we plugged an electric guitar directly into a marshall amp head and box and we were getting some sort of electrical interference, regardless of whether we were using single coils or humbuckers. To eliminate the amp and box as the cause, I plugged a keyboard into it (Jon Lord style!) and it was dead quiet, even cranked all the way. Strange thing is, if the guitar is facing east or west, the noise goes away, if it faces north or south the interference is there, to the point where we wont even be able to record quiet stuff. With the guitar plugged in and noise present, we turned everything in the studio off one by one to see if any of the other devices were causing this, but nothing, even with everything off it remained the same.
The only thing I could think of is that there are 2 pairs of massive mains monitors in the control room, could it be possible that the magnets are doing some funky stuff? I dont know, im not a guitarist, is this just nature of the beast that is guitar! I hope not. Its hard to describe the noise but it reminds me of the days of CRT computer monitors and single coils where you would have to move to one side otherwise it would produce noise/interference.
There was one thing I noticed, if you turned on certain light switches you could here a very very slight click coming from the quad box, but this only happens when its the guitar thats plugged into the amp, not the keyboard.
If anyone can suggest where to begin trouble shooting that would be greatly appreciated, i really want to sort this out!
Thanks,

[Speedskater]

OK, get a long extension cord, one end to house power the other to the amp. Position the guitar for most noise. Turn the studio breaker off. Or turn each light and component off one at a time or turn them all off then back on one at a time.

[Soundman2020]

Have you tried with a different guitar? It could be a problem with the guitar itself: maybe a faulty potentiometer, or shorted wiring inside.

Have you tried swapping cables? It might be a flaky cable from the guitar to the amp.

Have you tried going through a passive DI box, with good Jensen transformers in it? Those are usually good at stopping some types of hum.

- Stuart -

[BriHar]

Did you also turn off your lights? Are you running florescent lighting?
Even in major studios this can be a problem, and sometimes the only solution is to find a place and orientation where the noise is at it's minimal, and just record it (usually the S/N will be acceptable in the final recording ). EQ and gating would also be applied. Sometimes a volume pedal can be put to good use in these situations.

[madmuso]

thanks for the replies guys, I will try everything suggested to get this sorted out. let ya know how I go.
We did try 5 different guitars, different leads, different legnths, etc. All the same issue.
Keep you posted.

[AntoinetteDolly]

I completely agree to Speedskater's suggestion.

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[cuankorsten]

I know it might be a bit after the fact but I found this article of John's that might explain the Marshall amp interference as it relates to audio wiring: http://johnlsayers.com/Recmanual/Titles/Acoustics4.htm