Amplifier hum

Allen Longcor · 10-04-2005, 01:28 PM

So just recently my amplifier has begun to hum. I came here yesterday and did a search and found some info, but I'm still stumped as to why it just recently started humming. The amp in question is a HK Signature 2.1 that I purchased off of ebay over a year ago. I have changed nothing in my setup. Yesterday I plugged it directly into the wall instead of the power strip, removed the cable feed to the television, and even unplugged my sub which is on a different outlet but none of it helped. The amp uses a two pronged connector so I guess I can't use the cheater plug I see mentioned in many posts. My next step I suppose will be to run an extension cord from somewhere else in the house and plug my amp in. I'm not sure what else to do. Is my amp just showing signs of age? The humming is coming from the very front of the amp and while not very loud, is very audible in my bedroom system. Any help would be appreciated.

Kevin C Brown · 10-04-2005, 09:06 PM

Probably the screws or bolt(s) holding the transformer have come loose. If it's not in warranty any more, you could try opening it up, and tighten down every screw and bolt that you can find. I also think that capacitors can hum too, but only when they are going bad...

Another thread talking about something similar:

http://www.hometheaterforum.com/htfo...hreadid=243360

Allen Longcor · 10-05-2005, 12:09 AM

I seriously doubt it is still under warranty. I'm not sure when they stopped producing them, but I'm guessing it's been awhile. This is assuming the warranty is transferable. In any case I guess I will try it in another room and see if it still hums. If it does I can try tightening any screws I find. If not then I guess I can just live with it.

Chu Gai · 10-05-2005, 08:37 AM

Kevin's suggestion sounds reasonable. Also, there may be rubber grommets that have gone brittle or simply fractured. If that's the case, a good hardware shop ought to have something you can rig up.

Allen Longcor · 10-05-2005, 01:10 PM

I've been busy the last few days so I will have to open it up tonight and try these things. If they should not work, is it a good bet that the capacitors are going bad? If so, will this damage my equipment if it goes bad in the middle of The Incredibles? I don't want to play a guessing game with my amp and have it bite me in the ass when it finally goes.

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Chu Gai · 10-05-2005, 05:05 PM

Well Allen, as always, excercise due care around the unit when you open it up. Myself, I'd look for a way to rig up a makeshift stethoscope (some vinyl tubing and a funnel or get something at an auto place or even a kid's toy) and use it to isolate the sound. As far as your other concerns, let's deal with one thing at a time. If you've got insulated gloves and the problem is indeed related to the transformer, then pressing down on it will affect the sound and may even mute it. If that's the case, then how you attack it is up to you.

Kevin C Brown · 10-05-2005, 08:17 PM

It is most likely the transformer. Capacitors do fail, but that is sort of rare.

Chu's suggestion is a good one. Try to operate it while it's open, and then try to find the exact source of the hum.

Allen Longcor · 10-05-2005, 09:09 PM

Well I physically moved it to a different location in the house, plugged it in, and no more hum. Well if I placed my ear directly to the case I could hear something, but not the hum I can hear in my room. Before I moved it I removed everything from it and it still had the hum. Something in my room must be causing it, but it doesn't make sense to me since I have changed nothing in my setup and it has only been doing this for about two weeks now.

Kevin C Brown · 10-06-2005, 03:25 AM

Maybe something from your local power company has changed. You could try some power conditioning a la Monster, Panamax, Tripplite, etc, if you don't already have something like that.

Chu Gai · 10-06-2005, 10:18 AM

Perhaps the physical act of moving it jostled something inside. Now move it back and see what happens. You may have to ask the Magic Eight Ball.

Allen Longcor · 10-06-2005, 02:19 PM

When I moved it back and re-attached everything the hum returned. It's still warm enough that I run the fan which blocks most of the hum during a movie, but come winter with no fan I'm guessing it will probably bother me. I guess at that point I'll have to decide how far I'm willing to go to remove it, or if I can live with it. I'm really of the set it and forget it type so I'll probably end up forgetting it