Hum from speakers?

[admin_exported]

Any opinions on what could be causing a slight hum from my speakers? Some information:

Amp: K2

Speakers: MA RX6

The hum is present in both channels, but more pronounced in the right channel, and also extends higher up the frequency range in this channel - it's clearly audible from the tweeter as well as the mid driver on this side.

The hum through the speakers seems to match the frequency of the hum from the amp when it is powered on.

What I've tried:

Swapping speakers + cables - the more pronounced hum moves to the other channel.

Unplugging all the inputs - no change

Unplugging the amp from my Tacima and plugging it straight into the wall - no change.

Turning off potentially noise-inducing household appliances - no change.

Any thoughts gratefully received.

Edit: the hum is not affected by the volume setting, and is also present through headphones

 

[wireman]

Almost certainly sounds like an earth loop to me, but can be caused by a poorly made transformer or phase shifts on the mains supply. Visit some power conditioner web-sites like Isotek or Isol-8 (or google "earth loop") where there's plenty of advice on how to reduce/eliminate earth loops and other causes of mains-induced hum (transformer problems etc).

 

[Anonymous]

Wouldn't any kind of loop issues affect both channels equally?

 

[wireman]

tractorboy:Wouldn't any kind of loop issues affect both channels equally?

Not necessarily. I don't know the K2 intimately, but it has a large 500VA transformer which feeds 4 regulated rails so it's likely to have seperate windings on the transformer - hum may not be equal. You say the unit itself hums: this could be poor transformer winding, loose fixings into the chassis, loose plates in the core, or phase shifts. If the unit is earthed, double check the connection at both ends of the cable in the plug(s) - a loose, disconnected or dirty earth can cause hum if the unit is intended to be earthed but isn't properly. Mains cables running close/parallel to audio/speaker cables can also induce audible hum. There's lots you can check and try...

 

[Anonymous]

Hmmm, I see. Thank you for your detailed reply. I have made sure that the power lead is clear of the speaker cables, and tried swapping out the power lead, to no avail. I'll try running it from a different socket in case the earth off the one I'm using is shoddy - but that will have to wait until tomorrow.

 

[Anonymous]

Well, swapped over to another socket, just the same.

One other thing I have noticed, the flourescent light in the kitchen hums at exactly the same frequency, which I guess suggests it is indeed mains related?

Can anyone else who has the K2 comment on how much hum they get from the amp (mine is quite loud) and whether this finds it way through to the speakers?

 

[Anonymous]

before spending money, see if it's possible to take your speakers (and amp) to a local hifi dealer ... connect the speakers to some of their kit in their listening room, and see if you get a hum through the speakers ...

if none, then try connecting the amp ... you will then know that your equipment is fine (or not), then can narrow it down to other causes

 

[Henley]

It sounds like a mains induced hum which could be from anywhere in the system. Have you tried the amp in another system/room? If this fails then pop into your dealer with your amp and speakers (if poss) and ask them to check it out - that's all part of the service.

 

[Anonymous]

Henley:It sounds like a mains induced hum which could be from anywhere in the system. Have you tried the amp in another system/room? If this fails then pop into your dealer with your amp and speakers (if poss) and ask them to check it out - that's all part of the service.

My dealer? Service? You don't remember me, do you?

 

[Henley]

tractorboy:
Henley:It sounds like a mains induced hum which could be from anywhere in the system. Have you tried the amp in another system/room? If this fails then pop into your dealer with your amp and speakers (if poss) and ask them to check it out - that's all part of the service.

My dealer? Service? You don't remember me, do you?

Why I always say, buy locally. If you choose to move to the middle of no-where........... ;-)

 

[Anonymous]

Well, Nottingham isn't quite out in the sticks... but yeah, as regards buying locally, that's a lesson I learnt the hard way and put into practice when I bought my speakers recently.

I'm moving house shortly, and we're having the electrics overhauled and a new consumer unit put in. If after all that the hum persists, I guess that amp is going back to Roksan at some point in the future for a check up.

At the moment, however, I simply can't face the prospect of going through all that again.

 

[Henley]

Nottingham? and we have dealers there as well!

Try the tests I suggested and mail Catherine if you need help. If there is an issue then we'll sort it out at our end.

 

[Henley]

You havem't said, what's the source?

 

[John Duncan]

...and is it sitting on top of the amp, and does the hum still exist when you turn the source off?

S'what happened to me, I found that having the CD player sitting on top of the amp created hum.

 

[Anonymous]

Thanks for the suggestions all. As I mentioned earlier, the hum is present even with all sources disconnected, and also turned off.

Henley - thanks for your offer, but having just got an amp back in my rack after months of hassle, a process which was helped greatly by your Catherine of course, I can't bear to send it back off just yet. If it doesn't sort itself out, I'll come back to you in the New Year.

 

[Don Jr]

It's caused by the earth ground in your home. You should be ok after the move.

 

[zappa 100]

maybe take amp amd speakers around to a neighbours house and see if same problem occurs on their mains spur..

 

[Anonymous]

Well, more fiddling, without success. I'd swapped back in my PM6002, which is quiet as a mouse.

Back on the K2, a strange thing - as I said, the hum is audible through the right hand channel, including headphones. But when I put the amp on standby, the hum through the headphones gets much louder and deeper, and comes through both channels. Then after a few seconds there is a sound like an air raid siren starting up, back in the right channel, then a few seconds later it sputters out, although the louder hum is still present.

All quite odd.