sub hum

[bigdunc]

Can anyone help?
I have a MS208 sub which has started to emit a
fairly loud humming noise for the last 2 weeks or
so.

I've had it for about 3 months and haven't had
any problems until now.I've plugged the amp and sub into
the same socket and changed the lead but no joy

Any ideas?

 

[chrisgeary]

presumably the hum disappears if you disconnect the line level feed to from the amp to the sub? if so, you may have a ground loop. You don't say what your AV amp is, but the chances are that it needs to be earthed. Your AV system should have one system earth somewhere. Many components are only wired with 2 core mains cable as they dont need to be earthed for electrical safety.
I had this a while back - what I did was make up a single core lead (a bit of bell wire will do), wired it into a standard 13A plug to the earth pin. Plugged it in (this is safe as you are only using it as an earth!) and connected it to the phono grounding point (my 3803 at the time had a phono input with ground poing) and hey presto the hum disappeared.

 

[tuftus]

I also have a humming MS308 sub, I have replaced the phono lead for a better quality one but it has made no difference.

My AV amp is a Yamaha DSPAX640SE but I cannot see anywhere additional earths can be added.

Any clues on this one as I would love to get to the bottom of it?

Tuftus

 

[chrisgeary]

first, let's be clear. does the sub only hum when connected to the AV amp? how loud is the hum, is it background or is it as loud, or louder than the audio its being fed with?

 

[mw3cdj]

I to use to suffer from 50Hz sub hum , i solved it by running a separate earth to a new earth rod i drove into the ground just outside my room. A little OTT maybe , but i have nearly all my av rack earthed to it now.

Daran

 

[bigdunc]

My amp is a Denon 2802,if I disconnect
the lead the hum disappears

 

[chrisgeary]

right-o. does the hum disappear if you have the sub connected to the denon, but the amp is off?

also does it disappear if you turn the volume on the amp down to infinity?

also, does it disappear briefly whilst changing sources?

 

[bigdunc]

A- No

B- No

C- No

If I switch the sub off at the back the main
humming noise disappears but a very faint hum
can be heard from the rest of my speakers.
Only if I disconnect the lead does all hum disappear

 

[rozzar]

use a proper screened subwoofer lead
like Black Rhodium First Base or Ixos Gamma XHW406

next, buy a good quality Mains cable. Start from £50

 

[chrisgeary]

hmm, sounds like your sub is the source of the hum. with the sub off, does it disappear if you disconnect it from the wall completely?
might be a bad earth on the subs mains connection. other than that, im outta ideas.

 

[bigdunc]

Not sure if you misread what I said.
If I take the phono lead out of sub the
humming stops,switched on there is no problem.

Not sure if this is a factor or not but when I
got my sub a few of my cable channels were off air.
I wasn't too bothered so left it for a couple
of months.An engineer eventually came and fixed it, but later
that day the humming started.

Could this be the cause of the problem and if so
what do I do?
Thanks for your time.