Sub-woofer Drone/Hum

[Big Aura]

Hello all - I posted this problem before as a sub-issue on another thread about calibration/Audyssey, but it didn't get to the bottom of the problem (older thread is here : http://whathifi.com/forums/t/217377.aspx for those interested); Andrew hope you don't mind a fresh thread?

Basically, I'm having a bit of a Sub issue and wonder if anyone can help...

Recently I upgraded my sub-cable from a no-name cheap offering to a Chord Crimson (both 10m).

However, with the Chord, I'm experiencing a constant droning noise. The noise manifests whether the amp is on or off, and even when the cable isn't plugged into the amp. I've tried laying the cable out flat running in a straight line away from any power or other cables to see it it's picking up interference, but it hasn't made any difference.

My sub is a Jamo E4 (not the fanciest in the market, but it's never given me any trouble) and the volume setting has six notches. At "1" there's a drone that can be heard/felt within 5 feet, at 2 it can be heard on the other side of the room (15ft away) and above 4 you can hear it in the hall with the door closed. I've also tried to change the cross-over freq, but that's not assisted or hindered in any way.

There's no reason I can think of for this. The old cable, flimsy as it is, doesn't cause any such issues.

Is the cable faulty? I don't fancy having to throw away a £40+ cable without a fight!

Any advice as to what could be wrong with it, or what I'm doing wrong would be greatly appreciated.

 

[Anonymous]

Hi,

When you say '...even when the cable isn't plugged into the amp' do you mean the Crimson or the mains cable? What happens if you plug the Crimson into the sub and the amp but unplug the amp from the mains (be sure to unplug it rather than just switch the socket off). Have you moved anything recently or started using a different socket for either sub or the amp? What happens when you unplug all of your sources from the amp?

ÿ

 

[Big Aura]

Thanks for the response - some clarifications below!

beaverme:
Hi,

When you say '...even when the cable isn't plugged into the amp' do you mean the Crimson or the mains cable?

ÿ

When the sub is plugged into the mains, and the sub-cable is plugged into the sub only, i.e. not the amp.

beaverme:
Hi,

What happens if you plug the Crimson into the sub and the amp but unplug the amp from the mains (be sure to unplug it rather than just switch the socket off).

Haven't tried that yet - and will do - but given the hum still exists when the sub-cable isn't plugged into the amp, I didn't think it would make a difference?

beaverme:
Hi,

Have you moved anything recently or started using a different socket for either sub or the amp? What happens when you unplug all of your sources from the amp?

Recently moved the sub as a builder needed access to where it sits, but when I replaced it, it works fine with the old sub-cable - only the new one causes problems. Haven't unplugged all sources (the only other recent change is adding a Copperline Alpha for the amp, but that's unlikey to cause more distortion!!). Given the sub hums even when the crimson is only plugged into the sub (i.e. not the amp) and the crimson is trailed off in a straight line in a completely different direction, it's unlikely to be any of the other sources?

Thanks again for responding.

 

[Anonymous]

could it be the earthing in this cable is different? I had a loud humming in mine and had to flick the 'ground' switch from in to out (or the other way round).

 

[Big Aura]

Ground switch? What does that mean (not very well versed in techy stuff). On the back of my sub, I only have a vol ***, a cross-over *** and a fuse dial (which I need a screwdriver to turn).

 

[Anonymous]

Hi,

First off, I think it's mains hum rather than just extra noise being picked up by the new cable. It's likely a result in the change in cable construction. The Crimson uses a twisted pair and floating shield design. The old one was probably a simpler coax design.ÿBoth cables are terminated with RCA phono plugs at both ends, aren't they and not XLRs or a mixture?ÿ

The quick answer is to pop the Crimson on eBay and buy a good quality coax subwoofer cable (try Mark Grant).

Not ready to give in just yet? Try flipping the ground lift screw or switch, if your sub has one. Are your sockets properly earthed? I recently discovered that some of mine weren't.ÿHow many prongs do the power connectors for your sub and receiver have? 2 or 3?ÿ

 

[Big Aura]

Yikes - it really quite loud, could mains hum really be that bad??! Why would it not make the noise when the older cable was in use - the mains is coming via the same hardwired mains lead, and I'm using the same socket (standard three pin plug, by the way).

Both cables are terminated with RCA.

Is the "ground lift" switch the fuse dial that I need a screwdriver to turn? Do I just turn that until the hum subsides?

 

[Anonymous]

Do you have three pins at the equipment end as well as the wall socket end? Check the sockets on the sub and the amp, rather than the leads. My Velodyne sub and Denon receiver both have two pins instead of three.

I think the 'fuse dial' is just there to provide easy access to the fuse in case you ever need to replace it. I'd leave it alone.ÿ

 

[Big Aura]

ahh, the mains cable is hardwired to the sub.

 

[Anonymous]

Is it a round (probably three core) cable or a flattened / oval shaped (probably two core) one? How about the amp?

 

[Big Aura]

Can't recall - will take the top of the plug tonight to see.

Amp is earthed at the mains end, but as the problem exists whether or not I have the sub-cable plugged in, that shouldn't be an issue?

 

[Anonymous]

Good point. Your cable is a decent length so I suppose it could be EMI noise. But improper grounding of the sub or a faulty cable (a short) sound more likely.

 

[Big Aura]

Hello all

Took me a while to get back to this thread, but I told the supplier of the Sub-Cable (Synergy AV) and they asked me to send it back. They tested the cable and sent it back to Chord, who sent me a new (I think!) cable, and it now works perfectly. I'm a happy lad.