Hum when connected to power supply? - Jemsite
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post #1 of 3 (permalink) Old 04-26-2013, 03:50 AM Thread Starter
 
Join Date: Nov 2011
Location: Vienna, Austria
Posts: 9
Unhappy Hum when connected to power supply?

Hey,

I just installed a pair of EMG Pickups in one of my guitars. I'm playing through a M-Audio FastTrack, which is USB powered and connected to a MacBook Pro.

Here's my situation:
- When the MacBook power supply is plugged in, I get a really loud electrical kind of hum, which STOPS when I touch any metal parts in the control cavity (jack, switch, etc.)
- When the power supply is NOT plugged in, the electrical hum disappears, but theres a hissing sound (like hiss from a high-gain amp), which gets LOUDER when I touch some metal in the cavity

It doesn't matter if the volume pots are open or closed, behavior is always the same. I think it's some kind of grounding issue, but I don't know where I should start looking, as to my eyes the wiring seems perfectly fine. I have another guitar with factory installed EMGs, which doesn't show this behaviour. Also I have installed them myself in two other guitars and never experienced this problem.

Thank you for any help or ideas,
Alex

Last edited by AlexFinger919; 04-26-2013 at 03:57 AM.
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post #2 of 3 (permalink) Old 04-26-2013, 03:58 AM
 
Join Date: Jan 2005
Location: Canberra, Australia
Posts: 9,233
Reviews: 120
Re: Hum when connected to power supply?

Did you leave a ground wire on the bridge? EMGs don't require this , and can cause issues if you do have the ground in place.
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post #3 of 3 (permalink) Old 04-26-2013, 04:09 AM Thread Starter
 
Join Date: Nov 2011
Location: Vienna, Austria
Posts: 9
Re: Hum when connected to power supply?

No, the bridge ground is disconnected on the guitar which hums. It's also not connected on the other guitars I installed them myself in, which don't have this problem.

On the guitar with factory installed EMGs the bridge ground is connected...?
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