Amp hum problems

[Luca1979]

I have two amps, an old Fender and a '90 Mesa and I need a little help.
Well, the Fender is really quiet, no hum, but the Mesa has a noise/hum that disappear when I touch the strings on the guitar or any other metal part (I hear a "pop" when I touch).
Of course I tested both amps with the same guitar, in the same place.

Where is the problem?
Thanks.

[electroid]

Also make sure no one has removed the ground pin from the power cord. Sometimes an ungrounded chassis can make this worse.

[billm408]

I'm not sure what Mesa you've got, but all high gain amps hum to some extent. Does it happen on the clean channel as well? And I agree... the "popping" sound doesn't seem normal.

[brambosman]

I've had the same problem when still living at my parents' place. The sockets weren't grounded in my room.. Try touching a radiator with your elbow, does it feel uncomfortable ?

[Luca1979]

Yes, it also happens on the clean channel.
The power cord ends with two prongs, and I use an adaptor with three prongs to plug into the wall.
The chassis was redone in wood, how can I tell if the problem is there?

[chrisgraff]

Originally Posted by Luca1979

The power cord ends with two prongs, and I use an adaptor with three prongs to plug into the wall.

Don't you mean your power chord ends with three prongs?

Either way, it's a grounding issue. Take the amp somewhere with grounded power; Betcha it doesn't do it then.

[Ud Reks]

Yup, a grounding issue. I live in a house with old knob and tube wiring, and sometimes I can hear "radio stations" come through. Imagine that. I wish I could dial in a rock station and play along, but noooooooooo....

Anyway, here's the weird thing, and I hope someone can explain it to me. The radio signal does not come through when I'm playing straight into the amp. Nor does it come through when I'm playing through a pedal with its own AC adapter. But when I'm playing with a pedal with 9 volt batteries, I get the radio.

That's weird, no? The pedal isn't connected to electrical power, so where in the heck is it conductng a radio signal?

(Yes, I'm taking care of the hum in my new amp by buying a Pedal Power unit soon).

[electroid]

You're picking up RF (radio frequencies) either from the pedals or from the extra length of cables that connects the cables. The RF goes away when using the adaptors because the adaptors create an RF ground for the pedals or they at least change the combined length of ground cables which are acting as an RF antenna. The best solution would be to have an electrician hook up a grounded outlet for your amps.

[justonwo]

You need to ground that puppy. My Fender hummed like crazy until I grounded the outlets in my (old) house.

[Ud Reks]

Originally Posted by electroid

You're picking up RF (radio frequencies) either from the pedals or from the extra length of cables that connects the cables. The RF goes away when using the adaptors because the adaptors create an RF ground for the pedals or they at least change the combined length of ground cables which are acting as an RF antenna. The best solution would be to have an electrician hook up a grounded outlet for your amps.

Thanks for the info. That explains it.

Unfortunately, with knob and tube wiring, it's impossible to ground the outlet, unless you redo the entire electrical line to modern wiring. The previous owner redid the outlets all over the house, and my electrician laughs at it because it's really to no effect with knobs & tubes. The house needs the electric system to be entirely modernized, but it will never happen as long as I live here.

I had my electrician redo the kitchen and bathrooms. He did a good job, but after that experience, I'm done. No more.