Diesel

Just a little shot on Scoobynet, but I probably have a hard fault…

It’s just that my living room's woofer has started humming (there is such a gag there – DO feel free - mines with extra cheese).

The woofer is connected to the left channel of my Cambridge power amp (the one the new fangled 5.1 one made redundant) and this amp is connected to the sub-woofer line out of my Sony 5.1 Tuner/Amp.

Woofer speaker is quite hummy now – interestingly it stops when you unplug the 5.1 sub line out connection, but gets MUCH louder if you leave it connected but simply switch the 5.1 amp off on the front panel…

I also connected the two amps together using the ‘phono’ ground wire (slightly less hum) and have replaced the phono lead that connects them line out to line in.

Anything else I could try chaps? Remember this just happened out of the blue on a system that has been fine and in situ for a couple of years.

Cheers (& who should I take the 5.1 Sony amp to be fixed to!!!!

unclebuck

Sounds like earth problems. Doubt if it is faulty equipment.

UB

ajm

Have you changed the location of any mains wires in the vacinity, extension cables etc?

Diesel

Hmm yes - there is a lot of clay soil around Surrey here. Maybe I should try some B&Q compost around the mains plug...

Seriously though, should I check both amp's earth continuity from the amp internally to the 13A wall socket?

It's drivingmmmmmmme pottyhmmmmmmmmmmmmmmmm!!!!

andrewdelvard

Do any of the lines cross over one another? Are tangled? If so make them as straight as possible, no contact and try that.

ajm

You could try that

....or you could see if there are any mains wires near to your signal wires because you can get induced voltage in the signal wires that can cause a 50Hz mains hum.

Also, do both amps have an earth point on the back? If so try earthing them together.

[Edited by ajm - 12/14/2003 6:51:53 PM]

paulr

Why have you got an extra amp between the av amp and the subwoofer?

[Edited by paulr - 12/14/2003 9:19:47 PM]

workshy_fopp

Could be an earth loop. Try plugging the sub and amps etc. into the same socket (via 4-gang whatever) and un-plug anything unnecessary.

mart360

Make sure no cables have been neatly coiled by the other half,,

looks neat, but creates an induction field and the byproduct is Hum...


Mart

Diesel

Ho Hum...I guess the the recent cable neatening operation may be to blame - although I noticed the hum seceral days AFTER that. Didnt think things may be so sensitive to simple mains cables...

I'll re-plug both amps to the same gang too...Doesnt tidying up always causes problems!!!!

In response to the other kind replies - I HAVE grounded both amps together using the 'phono' ground peg (the one next to record player input on both amps). And the reason that there are TWO amps is cos there is rarely a high wattage 12" subwoofer POWER o/p on these 5.1 amps. Its just line out for yer sub, but power out for yer back/MID/side ETC.

d