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Old 30th December 2011, 11:14 AM   #1
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Default Hum in RC cable


I have a subwoofer connected to about 20 feet away from my main system. The subwoofer is driven by a Focal Car amplifier with dual RCA inputs and 12V , 120 A SMPS , its a 400 Watt amplifier in bridged mode.

Now there is no way to reduce the cable length as it is tucked away in a corner , but there is LOUD hum in the system. i have a small ferrite isolation transformer may be used at line level , it have few turns about 20 on each side its 1:1 and very small size about 1.5 cm x 1.5 cm.

Can it be used for Hum isolation.
How can it be used for unbalanced to balanced convertor ?

please advice
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Old 30th December 2011, 11:30 AM   #2
dhaen is offline dhaen  Europe
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Not enough turns by far.
The hum is most likely magnetically induced or by earth current. Try powering both bits of kit from the same wall socket. That should fix either.
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Old 31st December 2011, 02:17 AM   #3
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Are the un-balanced RCA interconnects a co-ax type with a heavy braided shield?
Does the subwoofer amplifier run on AC power rather than a battery?
If so is this amp powered from the same AC power wall outlet as the rest of the system?

If necessary a small power transformer can be used as a subwoofer audio isolation transformer.
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