Ground Loop Hum

[Ashmore]

Help!

I've just sold my REL to a nice chap form the wam. It worked perfectly well in my house but he's called me up to tell me that no matter what he does it hums.

Obviously I don't want to have to take it back (but I will of course because I have a conscience). I've advised him to plug it into the same socket as the amp and that there's an illadvised 'fix' to remove the ground in one or other of the devices. I've asked him to check the connections.

What other options are there?

[Reid Malenfant]

Ground loop isolating transformer (http://www.ebay.co.uk/sch/i.html?_nkw=ground+isolation+transformer&_sacat=0&_odkw=ground+loop+isolation+transformer&_osacat=0&_trksid=p3286.c0.m270.l1313) in the line level input.

Mains isolation transformer is another...

[Ashmore]

Ahhh thanks. Presume this thing would do the job then:

http://www.amazon.co.uk/Behringer-MICROHD-Hum-Destroyer-HD400/dp/B000KUD2G4/ref=sr_1_1?ie=UTF8&qid=1337468513&sr=8-1

[YNWaN]

My Rel has a ground lift switch on the back panel, does this on not have this feature? To be honest, it's not the Rel that is at fault but it is highlighting that his system grounding is inadequate. If the worst comes to the worst he should try disconnecting the mains earth to the sub.

[Reid Malenfant]

Ahhh thanks. Presume this thing would do the job then:

http://www.amazon.co.uk/Behringer-MICROHD-Hum-Destroyer-HD400/dp/B000KUD2G4/ref=sr_1_1?ie=UTF8&qid=1337468513&sr=8-1
Yes that'd do the job.

As Mark says though, lifting the earth in one bit of kit will probably get rid of the hum. While it's not an ideal situation if the there is hum because of a loop, the kit would still be earthed by the screen in the audio connection.

It's not something I have ever had to do myself though in all honesty :scratch: Obviously not ideal either :(

[YNWaN]

No, I've never had to do it either. To be honest, I have absolutely no hum and lifting the subs earth makes no difference to system hum (although it does sound different).

[Barry]

Ahhh thanks. Presume this thing would do the job then:

http://www.amazon.co.uk/Behringer-MICROHD-Hum-Destroyer-HD400/dp/B000KUD2G4/ref=sr_1_1?ie=UTF8&qid=1337468513&sr=8-1

Isolation transformers are not the panacea they claim to be. I had a slight hum problem connecting a Quad 33/303 amplifier to the audio channels of my TV 'digi-box'. Fitting a 1:1 isolation transformer to provide a DC break did not help.

In the end I replaced the amplifier with a Mark Levinson/ Quad 520f combination (somewhat of an over-kill!) and the problem vanished.

[Spur07]

has he tried to isolate the cause/problem by methodically disconnecting/deconstructing his system? As Mark says its probably not a fault with the REL, although it may be causing the problem. I had a load of gunk, hum and shit going through my speakers after I recently moved my sub, I traced it back to a couple of crossed cables.

[pure sound]

Disconnecting an earth wire & relying on the ground connection in the interconnect cable is not a safe solution.

[Elephantears]

I've had issues with both ground loop hum and radio interference when using sensitive amps. My main system is a mass of crossed wires. I experimented in my office system (using screened RCA cables into the pre) and found that the first thing to avoid is crossing speaker wires and mains cables. I've eliminated the RF interference but still have a certain degree of hum.

[Ashmore]

Thank you all for your comments. We've agreed to work through with a new cable, then an isolation transformer.

If that doesn't work I'll take it back.

Simon

[YNWaN]

If this Is in the UK you really shouldn't need an isolation transformer (I doubt a new cable will do anything either to be honest). I suspect that the system contains one (or more) components that do not have a proper mains earth.

[Ashmore]

I accept the cable may not make a difference, but the buyer said the hum varied in intensity when he wiggled it and I have a spare around so it's no bother to try it.

We'll see.

[Ashmore]

This is now happily resolved. Apparently a behringer hum destroyer and some screened cable did the trick. Thanks for all the advice.

[Reid Malenfant]

Good news :) Hum is always annoying :rolleyes: