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Old 17th December 2011, 04:52 PM   #1
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Default Amp hum when RCA cable is connected

Hi,
I have two amps: one (mono) for subwoofer and the second (stereo) am trying to connect to the same psu.
One case houses the mono amp and the transformer. The stereo amp has its own rectifier and filter caps and connected to the power transformer inside the case.Both amps are silent with no RCA cable connected. There is a hum when the cable is connected without the source.When I connect the source(pc)and break the ground loop between the inputs of the two amps,there is a hum from one of the amps(the one whose ground input is disconnected).
How can I solve this problem?
Regards.
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Old 17th December 2011, 05:03 PM   #2
jcx is offline jcx  United States
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Ground Loop Isolator - RadioShack.com

or for 10x the price:

JENSEN TRANSFORMERS, INC. - ISO-MAX® CI-2RR Stereo Audio Input Isolator


Whitlock's seminar handout paper is really good intro to the issues:

http://www.jensen-transformers.com/a...%20seminar.pdf

Last edited by jcx; 17th December 2011 at 05:12 PM.
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Old 17th December 2011, 08:17 PM   #3
magnu is offline magnu  Sweden
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Try rotating the power plug, switching the AC input pins. In a few cases can this remove the problem.
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Old 17th December 2011, 08:23 PM   #4
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Quote:
Originally Posted by magnu View Post
Try rotating the power plug, switching the AC input pins.....
Swapping Active For Neutral?
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Old 17th December 2011, 10:00 PM   #5
jaycee is offline jaycee  United Kingdom
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Ian, there are some countries that dont have polarised power outlets. However in these countries, neutral and ground are usually never bonded together, and neutral is treated as a "live" line. Neutral to ground shorts will trigger an RCD in such cases.
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Old 18th December 2011, 01:42 AM   #6
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Quite so...We are not all MEN system but a little qualification is in order -hence the "shock horror" rather than objection.
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Old 18th December 2011, 02:31 AM   #7
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Ok - now you have me curious but couldn't locate the details of Kenya's earthing system. The system is officially using UK outlet fittings,
so it will require a little work to swap connections over but that also suggests a good reason not to try it.
Is this reference info correct in Kenya, Xeclipse?
Leads Direct - Mains Wiring
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Last edited by Ian Finch; 18th December 2011 at 02:34 AM.
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Old 18th December 2011, 05:35 AM   #8
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Originally Posted by Ian Finch View Post
The system is officially using UK outlet fittings,.......
Is this reference info correct in Kenya, Xeclipse?
Leads Direct - Mains Wiring
That's correct,a three pin plug but I have connected only two:live and neutral(the amp is in a wooden case). The pc has all the three connections.
Regards.
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Old 18th December 2011, 07:57 AM   #9
Lavcat is offline Lavcat  United States
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I second the suggestion of the Jensen ISO-MAX. I have an ISO-MAX between my computer and my preamp. I'm currently building a box that will have four more Jensen transformers in it for isolation.
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