I had a 20x20 car amp hooked up to a 12V PS on my bench runing into two cheap speakers and the high level inputs of an AR 8" home subwoofer. It played fine for two and a half hours. I shut it down and moved it around tp make things more neat and now I get hum regardless of whether there is any input and there is also almost no output from one channel. I can reduce the hum somewhat by rearranging the componants but I haven't been able to eliminate it or get the other channel back.
Then it hit me to check the resistance between the speaker grounds so I disconnected the amp and measured across the negative sides of the speaker wires (this includes the wires, speakers and subwoofer inputs). I got 112 ohms. Would that be close enough to a common ground to blow the amp after a couple of hours? Did I likely blow the chip on one side?
If this is the problem is there any way to get around the problem and still use the subwoofer in this setup?
Then it hit me to check the resistance between the speaker grounds so I disconnected the amp and measured across the negative sides of the speaker wires (this includes the wires, speakers and subwoofer inputs). I got 112 ohms. Would that be close enough to a common ground to blow the amp after a couple of hours? Did I likely blow the chip on one side?
If this is the problem is there any way to get around the problem and still use the subwoofer in this setup?
Never mind
It was indeed an interaction with the subwoofer inputs but I didn't fry the amp. I tapped into the preamp level inputs to the amp and ran those to the low level subwoofer inputs and all is well.
It was indeed an interaction with the subwoofer inputs but I didn't fry the amp. I tapped into the preamp level inputs to the amp and ran those to the low level subwoofer inputs and all is well.
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