Can't Stop the Hum

[Pnewsom]

This happens quite often, and its likely caused by a television, or some other electrical device that is plugged in on the same leg of your house electrical system. Try different rooms of you house to see if it disappears.

[cattzap]

A hum is usually a shielding issue. Not a ground issue. There is a very good chance that your guitar is picking up rf noise that you cannot see, that was not present in your previous location. Very few guitars are properly factory shielded. Use an ohmmeter and see if you have continuity from the bridge to the outside part of the output jack. I would be surprised if you did. You can get shielding tape from Stew Mac. Remove the strings and clean it then cover every spec if the inside of the cavities and the entire back of the pick guard. Make sure everything is connected to the ground lug of the guitar. Including the tape. This may mean that you need to add a wore with an eye screwed to the body so it it touching the tape.

As this is an acoustic place, the same thing applies, only it's a little more difficult to accomplish. You can wrap the outside of the wire going from the pickup to the preamp, and you can cover the outside of the preamp with the tape. If the battery is not inside the preamp, wrap its wire and cover its little box. Then make sure all of the copper foil tape is connected together and to the ground lug on the output. It's not an easy job because of having to work thru the sound hole, but it can be done.

[LouieAtienza]

If it is indeed interference, simply attaching a ferrite choke to your cable could help.

[sterling]

Originally Posted by MBDiagMan

You need to make sure you have a good ground in the outlet you are in plugging the amp into. This can be a safety issue. You can get a simple little plug with LED’s that you simply plug into the outlet and the different colored LED’s tell the story. When I helped my son do a few Gig’s when he was a teenager, I kept one of these in the gig box and checked outlets before plugging anything into the outlet. I was protective of my son and wanted good sound too.

I think it is called a ground fault tester. You can probably get one at the hardware store or Home Depot. You should never play electric instruments when wet or damp, but durn sure don’t do it if you haven’t confirmed a proper safety ground.

I have one of those orange ground testers. I tested all the outlets in that room. None of them showed an open ground or any other issue.

[MBDiagMan]

Great! Good to have that eliminated! I will study the thread and try to catch up.

[MBDiagMan]

I have a bad habit of quickly perusing posts before responding. Sorry for posting before seeing that you had already done that.

Since you get the same result with multiple instruments and amps, it pretty much has to be a magnetic field in the house or a wiring problem that the ground tester is not identifying. Do you know if it is 60 cycle hum? Are you near a high voltage high wire? Have you turned off every breaker in the house except the one feeding power to your equipment?

[MiG50]

I'm starting to lean toward farraday cage, but that could be a budget-buster.

[MBDiagMan]

Faraday cage would certainly be a good troubleshooting step.

[sterling]

I spent some time today moving my champ and guitar to different rooms. It was dead quiet in the upstairs bedroom. Still more prominent in the downstairs. I ran the tele and LP through their paces today. The teles hum
is not as loud as the LP. As a matter of fact I can live with the tele hum. The LP was much louder. I think the problem
Is a ground in that guitar. I don’t think it’s the amp and I don’t think it’s a ground problem with the house but I am going to have it checked
sincea I’m having electrician out to do some work anyways.

The hum was much worse with the LP and an OD pedal
with the champ and high gain settings with the mustang. Not a surprise though.

[Gmountain]

Could be a Dina Moe Hum.

[Bob Womack]

One more possibility: Noise on the A.C. power leg. In P.A. applications we deal with this quite often. As others have discussed, it is caused by another appliance on the power leg that puts out a secondary frequency that ends up being superimposed upon the 60hz frequency of the A.C. mains from the wall. Lighting dimmers are notorious for this because they chop normal power into variable duty cycles to reduce the light output of a bulb. In doing so they squirt a stream of square waves into the power line. There can be other sources of this noise but the results can sound just like induced hum.

The way to get that off your line is to use a power conditioner. Use of a power conditioner is also the cheapest way to diagnose it.

Bob

[clintj]

Another experiment, if you are interested. Try placing the amp in a couple of different spots within the room, and facing it a few different directions. Also, while holding your guitar turn around slowly while listening to the hum for any change. That may help clarify whether the noise is wiring based or from the surrounding environment.

[Dru Edwards]

Originally Posted by paulp1960

I wouldn't buy a noise suppressor pedal (AKA noise gate) to try to solve this problem. Also I wouldn't run an old amp like a Fender Champ without a proper earth connection.

It does sound like it could be an earthing issue and I would get that checked out before buying something that probably won't really fix the problem.

+1.

Sterling, I think you can confirm that it is strictly related to the house and you get no hum outside the home?

[Mr Fingers]

As others have suggested, you need to eliminate the hum at its source, not suppress it. It's terrible to have to run a rig that requires noise suppression because of constant background hum! Since the problem occurs in every room and with different rigs, it's unlikely to be a tv or other appliance since that is not present everywhere. I'm guessing either "dirty" power or, yes, a grounding fault. Just because a tester says your lines are grounded doesn't mean there can't be a ground fault in the system! I would try some other cords to make sure you don't have a fault in that part, and if that doesn't do it, bring in some one qualified. We all have our opinions, but as you can see from the variety of ideas posted here, we're not all experts, and many of us ar ready to just make guesses -- because we're not going to get fried if something is dangerously wrong.

[KevWind]

Originally Posted by sterling

I spent some time today moving my champ and guitar to different rooms. It was dead quiet in the upstairs bedroom. Still more prominent in the downstairs. I ran the tele and LP through their paces today. The teles hum
is not as loud as the LP. As a matter of fact I can live with the tele hum. The LP was much louder. I think the problem
Is a ground in that guitar. I don’t think it’s the amp and I don’t think it’s a ground problem with the house but I am going to have it checked
sincea I’m having electrician out to do some work anyways.

The hum was much worse with the LP and an OD pedal
with the champ and high gain settings with the mustang. Not a surprise though.

OK making diagnostic progress . It seems to me you have determined it is in fact "location specific" in your house, if it disappears in the upstairs bedroom.

One suggestion since obviously as you said not a surprise the high gain and OD increase the hum, being simply a volume increase so don't use them in testing for now. Best most efficient diagnostic procedure it to eliminate variables for testing. So while the LP may be louder (but if it also disappears upstairs ) and since you indicated in the OP the hum is present with the other guitars as well, seems to me the primary issue is not grounding in the LP, that strikes to me as a secondary additional issue .

Also you might try ( befor the electrician gets there ) as someone suggested setting your rig up down stairs wherever the hum is most noticeable, and then try shutting off adjacent downstair circuits at the breaker panel .