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View Full Version : annoying electrical hum pon the Hi-Fi



john eden
12-08-2009, 12:40 PM
My stereo has started humming, it is a pisser.

I've tried twidling with the wires and all that but to no avail.

Does it just mean my amp is fucked?

droid
12-08-2009, 12:54 PM
Tsch.. first the dodgy decks, now this.

What kind of stereo? Separate amp etc..? Do you get the hum through your headphones?

john eden
12-08-2009, 12:59 PM
yeah it's maddening.

Doesn't come through headphones.

Hi-Fi is separates - amp, decks, mixer, etc.

droid
12-08-2009, 01:24 PM
OK - if its not coming through your phones it could be the speakers?

Otherwise it sounds like a ground loop. Have you plugged anything new into the same sockets the amp is in? Try plugging the amp into its own separate socket that has nothing else going into it and also into the same socket that everything else is going into. You might need an isolation transformer to eliminate it though.

droid
12-08-2009, 01:26 PM
http://www.audioholics.com/tweaks/connecting-your-system/ground-loops-eliminating-system-hum-and-buzz


Start simple. Troubleshooting ground loops involves taking things in order and checking a few basic, common elements to see if the problem is simple, or complex. For example, if adjusting the volume on your processor/receiver does not alter the hum level, then the problem must be occurring after that point. It if occurred prior, then the receiver/processor would typically raise the overall level of noise. Make sense?

Work in the following methodical manner:

1. Start with the processor receiver to determine if the hum/buzz is source-related or due to a ground loop occurring after the amplification stage
2. Note any recent changes to the system that brought on this problem. Chances are, you can more easily isolate a problem if it just starting with the addition of a new piece of equipment.
3. What can you do quickly and easily to isolate or identify the problem and point to the proper solution (i.e. unplugging the cable from the wall to see if the Cable TV is the source of a ground loop.)

One other test to eliminate your receiver or processor is to see if the hum changes based on what input you have selected (DVD player, Cable TV, etc.) Does the hum change or go away when selecting a different input? No? Then your problem is occurring at a later stage in the system (most likely a ground loop caused by the addition of an amplifier or powered subwoofer with a 3-prong power cable.)

The final test is to unplug your Cable TV cable from the wall. Does the hum go away? It did in the case of Reference System 3. Eureka ! There must be a ground loop in the system involving the Cable TV line.

john eden
18-08-2009, 10:23 AM
cheers for this

it seems to go away after the amp has been on for a while...

Edward
18-08-2009, 05:29 PM
Did you fix it?

If not, tell me, is the hum coming through the speakers or is it something else actually vibrating?

When transformers get old they hum sometimes, can be quite loud, doesn't affect the signal path....

john eden
18-08-2009, 07:18 PM
Droid - nothing new plugged in afaik, but everything is plugged into two 4-ways because the actual socket is on the other side of the room.

the input channel doesn't seem to make any difference in general. It's a bit muted when I press the "direct" button and quite a bit louder when I press the tape/record channel.


Did you fix it?

If not, tell me, is the hum coming through the speakers or is it something else actually vibrating?

When transformers get old they hum sometimes, can be quite loud, doesn't affect the signal path....

yeah it's definitely coming through the speakers, even when everything apart from the amp is turned off.

I guess I've had the amp for well over a decade, so yeah might be that.

I'll try unplugging everything when I get a minute but it's all spaghetti junction innit...

thanks folks!

Bang Diddley
20-08-2009, 09:41 AM
Droid - nothing new plugged in afaik, but everything is plugged into two 4-ways because the actual socket is on the other side of the room.

the input channel doesn't seem to make any difference in general. It's a bit muted when I press the "direct" button and quite a bit louder when I press the tape/record channel.



yeah it's definitely coming through the speakers, even when everything apart from the amp is turned off.

I guess I've had the amp for well over a decade, so yeah might be that.

I'll try unplugging everything when I get a minute but it's all spaghetti junction innit...

thanks folks!

hum pon sound - very poor pun

Anyway have you tried to seperate the speaker cable out from the spaghetti junction. Might be picking up 'stuff'. Or maybe the turntable earth connection is not true.

john eden
24-08-2009, 09:41 PM
okay I was being a dick - it wasn't coming through the headphones because the headphones were plugged into the mixer.

When I plug the headphones directly into the amp, the buzz is there.

Tonight I've unplugged the amp from everything else and plugged it into a different socket in another room. Buzz is still there in the headphones.

I guess this means it's fucked.

Fair play though, I have had 15 years of fun out of it.

john eden
24-08-2009, 09:59 PM
hmmm

http://www.avforums.com/forums/av-amplifiers-receivers/770627-loud-humming-noise-sherwood-amp.html

25 years since I last did some soldering. :o

nomos
25-08-2009, 02:27 AM
:( hope you don't have to put it out to pasture.

just a word of caution - caps in a power amp can hold a huge (lethal) charge. which you probably know, but i'd personally be hesitant to go inside despite being fairly handy with an iron. plus, to test caps you have to take them out of the circuit which can get messy.

john eden
25-08-2009, 09:44 AM
I think I'm going to take it to a geezer in the back of a shop to see if he can do it. :cool:

john eden
27-09-2009, 09:33 AM
I think I'm going to take it to a geezer in the back of a shop to see if he can do it. :cool:

No doubt everyone will be thrilled to hear that the amp is now fixed!

Thank you man in crazy electrical shop which smells of incense and has a cat wandering around in it. :D

crofton
16-10-2009, 12:45 AM
this shop should presumably have a thread of its own...