I have an ageing home cinema surround sound set up and the amp/sub woofer has a nasty hum.

Checked all the speaker wires and electrical inputs and I cannot see anything that could be causing interference. Does anyone have any suggestions as to what the fault could be?

Thanks, JT

Usual cause is a ground loop, can be difficult to resolve. Does the hum stop if you remove the interconnecting audio cable? or get louder.

When you say ageing how old are we talking?

Thanks for the replies.

Usual cause is a ground loop, can be difficult to resolve. Does the hum stop if you remove the interconnecting audio cable? or get louder.

  

If I remove all audio inputs the hum remains the same.

When you say ageing how old are we talking?

No sure, at least 5 but more like 8 years.

is it wound up properly

 

I had a similar issue on an amp sub combo a few years back. I took the back off and blew a load of dust out which helped a lot.

Is the hum coming from all the speakers, the main speakers, or just the sub. Hum is USUALLY earth loop as above, but badly designed/built power supplies can also cause it - well actually it amplifies mains hum through poor rectification and smoothing.

Things to check.

The earth pin on the plug is clean, if using a multi-block, make sure the earth is actually connected properly, check plugs to make sure the earth cable has not pulled out; check your house earth is connected and working correctly (can be a problem for some after all the flooding), both at the earthing rod and in the consumer unit.

If it is an earth loop problem, disconnecting the earth on one of the unit usually works, but leaves you at slightly higher risk of electric shock - the sub is the best one to remove as usually there are few exterior metal parts that might become live.

Sounds like capacitor degradation either in the filter/amp circuits or could be a noisy PSU due to capacitors again.

 

Dust can also cause noise so give it a good dusting off/hoover (unplugged of course).

 

What make/model is it?

Thanks all

Shall give the unit a good hover later in the week and check the earths when I have a little time.

The unit is an Acoustic Solutions unit so not the greatest thing in the world, as to the model, I can't really find what this is.

When ours did similar one of the caps in the PSU wasn't far from blowing.

Might be worth seeing if any are bulging rather than having flat tops.