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Speaker hum - ground loop problem...


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Old 10-05-2003, 16:04
biddenden_sue
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I originally added a comment on the thread "Problems with home cinema system", then realised I could now start my own threads.

Check my comment there for all my equipment and connections - can anyone advise me on the best way to eliminate speaker buzz/hum in quieter scenes? I think it's down to this "ground loop" but don't know how to overcome it.

I don't intend to change my equipment. Overall, I am very happy with all of it. This is a minor problem and I am sure it can be eliminated. I hope there's a nice helpful person out there who can tell me which leads or whatever need changing, and what I should go for.

Cheers

Sue
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Old 10-05-2003, 16:06
biddenden_sue
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"Need help with home cinema", sorry.
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Old 10-05-2003, 19:43
magic
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Check the connections, sometimes if the connections are poor and a short circuit occurs, it can cause hum. Try unplugging everything, and reconecting it again.
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Old 11-05-2003, 08:10
biddenden_sue
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I've probably done that at least 10 times. Who wouldn't?

Any other ideas?
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Old 12-05-2003, 09:38
iain
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have a look over at www.avforums.co.uk - perhaps a bit more techie over there, so you might get more joy.

iain
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Old 12-05-2003, 13:26
RedEarth
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Originally posted by magic
Check the connections, sometimes if the connections are poor and a short circuit occurs, it can cause hum. Try unplugging everything, and reconecting it again.
As a follow-on from this, try disconnecting all source equipment so you're left with just the amp and speakers. Does it hum now? Is the hum on every input source or just one? Then plug each item in, one by one, and this should help you to pinpoint which area the problem is in.

Also have you tried swapping your speaker cables for different ones.
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Old 12-05-2003, 14:26
davep
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Have you got any loops in your cables? I had a very expensive fully shielded co-ax lead that was about 2 metres too long so, to make it tidy, I coiled it up in a loop about 6-8" diameter. It acted as an induction coil and boy did that make the sub hum!

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Old 13-05-2003, 18:19
dodgygeeza
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Hmm, surely if your co-ax lead was fully shielded the coils couldn't have created a magnetic field

It is defiantely a good idea to check for looped leads though.
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Old 17-05-2003, 22:37
hop
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If it's really a ground loop that's causing the hum, make sure all your system is plugged into the same point on your ring main (ie: sourced from the same socket outlet - single or double).

This may fix this issue, I've seen it work very well before.
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Old 17-05-2003, 22:43
davey_do_little
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I have NO idea what I'm on about here , but is it possible to 'earth' or 'ground' one side of all the speaker terminals to a common point (say an electrical earth)?

ok shoot me if you like, or get me to try it on my kit
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Old 18-05-2003, 23:29
Jim Rae
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You could do that - and join your speakers to the washing machine earth ...

I'm with the people who suggest disconnecting things to see if the noise goes away.

Garbage in equals garbage out, is as valid with HiFi as it is with computers.

Is the buzz from the source, or put into the system later in the connection chain?
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Old 19-05-2003, 08:04
biddenden_sue
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Well it's my buzz, and I simply haven't got around to checking all the source connections out yet. I'll let you know how I get on when I've done it (hopefully today)

Sue

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Old 22-05-2003, 19:07
oldie
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As a very new member, I hope I am doing this right! If you haven't had any success yet with your hum I can sympathise. Having had over 30 years in audio equipment and system design, hum, clicks, pops and radio breakthrough can be a nightmare to fix. The suggestion to remove all connections except, obviously the mains and speakers, is a good start. If the hum is still there with all the volume controls down, try physically moving the mains leads around and see if any difference. Then, if the leads are long enough, move the equipment around in relation to each other. Mains transformers in one item can induce hum into another.
I don't think changing speaker wires will help but you could try physically moving them around. Don't try earthing the speaker connections. You could do much damage if you don't know which wire is earthed. With some amplifiers neither wire is earthed even if the terminals are black and red. If the above hasn't helped and the hum is still there with all connections off, volume controls down and with all other equipment mains leads disconnected, the hum may be inherent in the amplifier. If it really is loud there could be a fault.
Good luck, but do be careful when moving the mains leads in case there is a problem in a plug. Is the hum a deep low frequency hum or is it more of a buzz - there is a difference.
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