Weird amp hum

[Doctor Jeff]

Here's a mystery I was told you guys on this forum could figure out.

I recently moved to a house in Omaha that was built about 1940, as far as I know has reasonably up to date wiring. I set up my guitars (Godin Kingpin, Epi Joe Pass, Alvarez classical A/E) and amps in the "music room" where my fiancee keeps her baby grand. However, I have had a lot of trouble with annoying hum.

Here's what I've observed: it affects both my amps, an Epi Valve Jr. and Ibanez Troubadour 20. It occurs with or without effects, with single coil and HB pickups. On the Valve Jr. when the volume is at 9 o'clock there's little hum but it goes up if I dial it either direction. All outlets in the room produce the same hum. Using an EH Hum Debugger has no effect at all on the hum.

Now here's the really interesting part--one day I noticed the faint sound of NPR coming through the VJ amp. I thought it might be picking up a signal from one of my radios, but changing stations had no effect. The NPR station, BTW, is at least 2 miles from my house.

Any thoughts?

[Enzo]

Yes, you pick up the NPR station because it is the closest one to your house.

Most homes wired in the 1940s did not have grounded outlets. Someone may have installed three wire o utlets in the walls, but that doesn;t make the grounds appear.

Go to radio Shack or a hardware and get one of those little outlet testers. It is a little thing you plug into an outlet, and it has three neon bulbs in it. Some will light up and some stay dark. The instruction sheet will tell you what each pattern means. It specifically will tell you if the grounds are wired and if the hot and neutral are reversed, or whatever.

Picking up radio stations is a CLASSIC symptom of poor grounding.

Google outlet tester or go here:
Receptacle tester - Wikipedia, the free encyclopedia

[Bruce / Mission Amps]

Besides finding out if you have a correct grounding at the outlets/switches and a proper Earth ground at the distribution panel, another thing to check is, did the guy/gal who did any electrical updating use aluminum wire with the incorrect outlets/switches built to be used exclusively with copper wire.
There are outlets and switches made for Al and Cu.
If you find Aluminum wire in those outlets/switches made for Cu..... they can get hot and start to oxidize forming all kinds of terrible problems, some of which will cause a fire, the least of which is rectification of strong AM radio signals.

[olddawg]

Get a ground lift adapter, the kind with a floating ground lug. Connect a length of wire from the lug to a cold water pipe (or a copper stake driven into the ground). Then plug a power strip into the ground lift adapter and plug all of your amps and stuff into the power strip.