Hum and RFI That Will Not Die

[dshlapak]

Honest, this is about to drive me nuts.

I have an old, old, old house, with new (<10yrs) wiring. There've been problems with 60hz hum ever since we moved in, but I've finally had it. I bought a new guitar amp that is close to unusable b/c of the hum and the friggin' radio station that's coming in over it. It's not the amp--I took it back to the store and it's perfectly, beautifully, blissfully quiet when plugged into their AC. And it's not a bad cable or noisy guitar pickups or interference from a computer monitor 'cause the noise is there whether or not anything is plugged in, with or without a computer in the immediate vicinity.

I tried one of those "hum-buster" wall plugs. No good.

I tried a Furman rack-mount power conditioner. Nothing.

I tried a 3-to-2-prong adapter. No good.

I bought a PowerVar power conditioner (toroidal isolation transformer thingie) from Bobby at Mr Patchbay. No joy.

I tried all combinations of the above. No improvement.

I've tried plugging the amp into one of the dedicated, short-distance, straight-run lines we have in the house. Repeat after me..."no joy."

We're having some renovations done on the house and had an electrician in this AM. I asked him to check the main panel's grounding, hoping that maybe the whole damn house was screwed up. Well, he reports that it's "perfect." His word, not mine. Fully code-compliant, etc.

I'm not an electrician or a physicist or even particularly clever, aparently. I just want to be able to play my guitar and record without having to deal with a noise floor that's more like a ceiling. Any ideas on what the heck is going on? Anyone know a good exorcist in the Pittsburgh area?

Thanks in advance for any help.

Cheers.

--- das

 

[Tifstorey]

I'm trying to rack my brains here because i was once using a bass amp at a home studio and i could hear the radio and people talking from next door, through the amp. Very strange, but there was a reason behind it and the next time i went round it was sorted...

.........................Watch this space...

 

[kessel]

Well its looks like you've tried almost every method to remove the hum caused by ground. Do you have any fluorescent lighting or dimmer switches in the room where you are playing the amp? Also have you tried playing the amp through a UPS? Also, as far as the radio station is concerned, how long is your guitar cable and is it shielded?

 

[toyL]

Go here http://www.rfiservices.com/tips.htm to find out if the interference is within your own residence.
Reply, and I'll get back to you.

 

[toyL]

I have at least a few ideas as to the source(s) of your problem(s), but I need more info. The RFI (or EMI) may or may not be related to what you've thus far assumed is a 60Hz hum issue. EMI can sometimes possess characteristics that the ear may perceive as "hum".

I'd like to address the RFI issue first. You describe your house as very "old", which may indicate that the entire structure is functioning as an antenna. First, tell me about the design and location of your house--is it a flat?, a flat with a basement?, two-story?, bi-level?. Is it in the city?--near a radio-transmitter?, or in the sticks near a major highway? What is the approximate elevation of the land of your property?
You mention "the friggin' radio station"--can you ID which friggin' radio station it is? Are you sure it is a radio station?--and NOT a television station or some other form of EMI? If you're sure it is a radio station, is it always the same one? Is it AM or FM? Is the house wired for cable-TV? If yes, do you subscribe and "use" cable-tv? Is the house wired for cable-TV from a second cable-TV provider that you're not subscribed to? If yes, are you sure that this second cable service is NOT still "active" even though you don't use it. Do you use a satellite dish service to watch TV? If yes, how many outside DISH antennas are located on your property? If you have more than one, are they from the same provider?--and are they both active? If you have more than one DISH antenna and they're from different providers, are you sure that the one you're currently NOT subscribed to is "inactive"?

Go here http://www.kyes.com/antenna/antennatypes/antennatypes.html to read up on "antennas".

Am I correct to assume that you're 60Hz hum and RFI/EMI issues occur with & without your guitar plugged in? Is there "any" noticeable difference between when your guitar is plugged in and when it's not? Is this a problem for "every" amp you bring into your house?
As for the 60Hz hum: Try shutting down the power (at the circuit-breaker) in various other parts of the house one at a time to see if the hum goes away; it could be that "one" particular circuit (i.e. laundry-room) is causing the problem.

If you live in a rather dry climate, you might go outside and pour about a gallon of water on the house-ground spike. See if this corrects any "hum".

Other RFI/EMI concerns: I'm guessing you live near an RF-transmitter or maybe some other signal generator or relay station.

Do you have the amp on the floor?...on a stand?...etc.
Have you tried repositioning the amp vertically?--i.e. raising it up variously--a few inches at a time (NOTE: probably best to only try this while the amp is powered OFF). Maybe use some 2x4 or 4x6 scrap wood to do this; or place it even higher--maybe on a shelf, or a sturdy wood crate.

Getting tired right now...reply, and I'll think on this some more.

 

[toyL]

5/16: This site has detailed info, incliding links to the design and application of inexpensive circuits that can broadly or selectively cancel RFI: go to
http://www.dxzone.com/catalog/Technical_Reference/Radio_Frequency_Interference/
Again, I believe that if you can eliminate the RFI/EMI you may very well find that what your ears perceive to be 60Hz hum will also go away. Afterall, you have mentioned NO other audio devices in your home that suffer from a 60Hz hum problem.
Would really appreciate a "detailed" reply from you whenever you find the time, because I'm pretty sure I can fix this problem.
Have you had the chance to go to http://www.rfiservices.com/tips.htm to find out if the interference is within your own residence?

 

[Dani Pace]

Just wondering if you have ANY aluminimum wiring? That stuff is notorious for causing all sorts of noise and often works like an antena for radio signals.

 

[TimN]

How is the electrical grounded? (The house that is.) Do you have
a ground pole sunk outside? Is your power coming in above or below ground,
and do you possibly have any old pipes under the house that could act as
a loop. Finally, what are the houses around you like? Are they old, and do they possibly have issues with wiring/grounding?

 

[TimOBrien]

Ever think that you should be calling an electrician to see what else is wrong before your house burns down in the middle of the night while you're sleeping????

A $100 might not only save all your equipment and toys but your life!!

(When I sold my last house I found that half of it had been wired wrong when originally built and I'd been living for 10years with a grounding problem that could have burnt down the place....)

 

[toyL]

dshlapak stated--"...had an electrician in this AM. I asked him to check the main panel's grounding, hoping that maybe the whole damn house was screwed up. Well, he reports that it's "perfect." His word, not mine. Fully code-compliant, etc."

OK, there's apparently NO ground issue; and dshlapak hasn't mentioned ANY other electrical problems--given that the wiring is less than 10 yrs old...so, we can move on from there...

dshlapak--you still out there?...I'm confident that I can fix your problem, but you need to reply in "detail" to the things I have thus far covered. Hope to hear from you soon.

 

[johnnymegabyte]

I have a similar problem and it is from the Cable TV.

In my basement, my guitar setup is also integrated with PC via Mixer (to Line In of PC and CD input of my stereo) The VCR (cable connected) is also connected to my stereo. What a hum. Unplug the cable from VCR --- silence.
OR, if I unplug the CD input instead of cable. --- silence

So, I tied a short wire connected to my stereo stand to the cable wire. So when I unplug it, it doesn't fall to the floor, it just drops a few inches, and I can pull on that wire to pull up the cable and re-connect when I wanna watch TV.

You never mentioned whether you had other devices connected, so I thought I might pass on this experience.

However, I don't know if it's the cable that doesn't like the PC (or monitor)

 

[boingoman]

I have a similar problem and it is from the Cable TV.

Good call as something to check. Ungrounded cable can cause all kinds of problems. Many people never notice, because they don't hook up all kinds of sensitive audio stuff. If that turns out to be the problem, the cable company may come and ground it for free. Around here, it's a requirement.