Question about JBL PB12 Subwoofer
Hi, I have a JBL PB 12 sub and have a problem, when it turns on automatically it produces a humming sound, just in the instant the leds go from red to green, then it runs fine with no audio distortions. I know it has a delay circuit just before the final amplification stage to prevent it to damage the speaker when turned on at very loud volumes and it seems to be a problem with this circuit. My guess is the zener circuitry just before the power stage, but I'm not 100% sure. Does anybody has an idea on where to check?
Have you checked your music source? Some systems like computers have a sort of output first before normalizing, which isn't your powered subs or powered amps problem. Try plugging in a regular solid state player like an ipod if the humming is still there when automatically turning on or off...
Posted on Dec 09, 2007
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