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I have a JBL JRX SP118 Powered sub and it has a terrible hum. At first I thought it was a ground issue with one of the cords but I have disconnect everthing I could think of and the hum is still there.  Has anyone ever experienced this if so what could it be? I was thinking it might have something to do with the built in crossover.  :thinkin:   Thanks

It's most likely your power cord is too close or touching your sound cord from either your mixer or crossover.  Try separating them.

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Thanks Timerlea, I have disconnect and moved everything I could imagine. This hum has been there the past two nights and at seperate venues.  :shock:

Is the hum there with the input disconnected? Try plugging in the power with a ground eliminator adapter. If it is a 60 or 120 hertz hum then the filters in the power supply are bad.

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In fact I'm working on a jbl eon amp right now The 2 large round black filters on the left are in the 38 volt supply the 4 smaller blue ones are in the +&- 70 volt supply.

Jbl schematics are availible on the net schems
and they have very good tech support.

amp

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Thanks