Earth loop hum - peculiar problem
julianj
I have an older surround system - bought from Maplins (UK). It is Jazz
Speakers system, J-9941B. The subwoofer in its metal cabinet has
always had a bad ground hum, but it is only now I have got round to
investigating it as I am upgrading my system.
Basically the decoder box and the subwoofer are in separate metal
cabinets, and both have separate mains plugs. I thought that this would
be the source of the problem so I opened up both 3 pin plugs, and to my
surprise found there were only live and neutral wires in them.
No Earth grounding wire! The manual (I guess aimed at the usa?) also
shows two pin plugs with no grounding. I am thinking:
a) surely this is dangerous?!
b) this must be the source of the problem - if I properly put in an
earth wire to one or both of the metal cabinets that will solve the
problem?
any help will be appreciated.
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julianj
Kele
ground pin; this is to avoid potential ground loops.
The hum is most likely coming from your TV cable line. Disconnect the coax
TV cable and see if the hum (buzz) vanishes. If it does, a resistor in the
line often solves the problem. I can't say if all power strips with coax
jacks include a resistor, but in my experience, APC brand power strips do.
Coax in /out of power strip will insert a resistor in the line and has
worked for me to eliminate buzz heard through the speakers.
Note: depending on your AC wiring, and where a TV tuner is connected, the
resistor may need to be inserted up-stream on the TV coax cable line.
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