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Re: Guitar / Keyboard noise in new facility

Posted by Bill Fitzmaurice (P) on September 24, 2003 at 11:38:13

In Reply to: Re: Guitar / Keyboard noise in new facility posted by AlvinH on September 24, 2003 at 06:23:34:

When you're getting noise into pickups the source may be in the electrical lines. Amp power transformers, being magnetic by nature, serve as fine EMI emitters of AC line noise your pickups, also EM devices, detect and send into the amp. Take the AC out of the loop by using a battery powered amp and remaining noise sources are either RFI or EMI from sources other than your own amps, which you can't do much about. If the noise is gone then the culprit definetely lies in your AC.

If the noise is powerline sourced on both 110 legs of the 220 line, which are out of phase with each other, then the two noise sources will cancel each other out when you use a transformer to feed your amp with 55 volts from each of those 110 legs rather than 110 from only one leg, and your ground leg grounds your amp chassis but does not act as an actual conduit for current, eliminating it as a possible noise source as well.

I suspect an industrial noise source as there isn't that much household stuff in the homes around you likely to be making that much noise, and if you're getting noise into both of the 110 legs of your 220 line then whatever is making the noise is a 220 device as well, again making the case for an industrial source, or perhaps a whole- house air conditioner. Then again, it could be a household device that's contaminating via your ground, which again would be controlled by a 55-0-55 AC line that removes the ground as a current carrier.

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