Amp Hum

Also: Be very careful if you open up the amp. Caps etc. can hold current for long periods of time. I just recieved a suggestion from a gentleman at AA in regard to me popping open one of my amps for a look, which was: "Only use one hand at a time, this way if you do get a shock it will not travel from one hand to the other through your body" (which would be straight through the heart). I have been shocked in the past by electronics that have been unplugged for days and even weeks (I am also not very technical, so this is all that I have to offer:-).

Sailor, given that your amp is older, I would guess that the transformer is the culprit, either de-lamination of the plates, or mounting ... but given what I have read here, I would bet the transformer is the problem. And not a problem that should case you to dump your amp either.

If you do a search in the forums on just the word "hum", you will find probably 50 different threads. Several recommendations for use of isolation pads between the transformer and mounts seems to have provided positive results for some posters. Certainly read the threads though, because external factors have been attributed to be problems as well.

My opinion, for what it's worth.

the actual amp hums not the chassis or through the speakers, and it is constant

Could this just be transformer noise -- i.e. mechanical hum? I just pulled out my old Adcom GFA555 (original version from the early 80's) for use as a sub amp. Works great but has a hum that's only audible when my system is off and it is dead quiet (except for the amp). It's not a major problem, since I can't hear it when listening, but I was planning on pulling the top and trying to tighten the transformer. Maybe lay a sheet of sorbothane under it?

These old amps are such work horses. Do they ever die? The only other glitch is that the power on/off switch just broke. But, as I've seen reported elsewhere on Audiogon, it broke in the "on" position. Even when they break, they work.

Sailor, contrary to the above post, don't give up the ship yet! Is the hum from the amp chassis or the speakers? Is the hum constant, or intermittent? Is it source dependent?

How about throwing the amp away and buying a decent one?

Have you tried using a ground cheater. Ace hardware sells them for $1 and it converts a 3 prong plug into 2. I have some tube monos which need them, and a pair of SS monos which dont.

I cannot take the credit, but someone on another thread suggested a way to stop an amp humming. Teach it the words.

Try unplugging every appliance in your house one by one. I had an amp that hummed. The hum stopped when I unplugged my waterbed heater. I bought a new waterbed heater and the problem was solved.

Well I actually have two older adcom amps and when I got them they humed like it was no ones bussiness. I found that it was due to several factors: first of all have the power cables been modified? in particular the male ends? Second are they equipped with a three or two prong male power cord, if it is a two prong that is probably your problem. Also your home wiring could cause the problem, it would be more noticeable if it is a power hungry amp ie lots of power. In my case they were GFA-565 mono blocks(300 watts @ 8 ohms) and made all of the lights in the house dim when they were turned on, heh heh heh. I assume the hum your hearing is a 60Hz ground hum all of those things could cause that hum. If you are willing to modify the amps at all (which I did) you can upgrade the gauge of all power/ground related wires and at that time add a better power cable and that should take care of all of your humming, even if your house has power wiring(which my house also has). If you upgrade everything and it still hums the amp just might not know the song you are trying to play, just kidding!! If you have any questions just let me know, I have used the amps a lot for around 3 years and they have not hummed a peep since there upgrades. Best of luck :-) TIM