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Resolved: Guitar hum driving me crazy

Discussion in 'Guitars' started by RobyG, May 23, 2004.

  1. RobyG

    RobyG Guest

    Hey guys,

    I don't know if anyone remembers this topic. I posted last year around this time because I was having problems with noise on my guitar in my home studio driving me crazy. I finally got it solved and wanted to post the results for everyone.

    After stumping the power company 4 times they referred me to the regional director for EMF. I don't know why, they said there was an avg 3.0mG in the studio room, which was "emanating from the audio equipment" and was perfectly normal according to them.

    The regional guy sent me a book (authored by third party) that discussed building wiring problems and what could cause problems. I got my hands on a gauss meter and went to town.

    The first thing I noticed was that there was from 20 - 80 mG on the cold water pipe in our bathroom. Yikes! 100mG = 1 amp. There shouldn't be current on the water pipe unless there is a fault somewhere. Other buildings that I measured all had 0.2mG on the cold water pipes.

    Other disturbances found included an average 1.0 - 4.0 over our bed (depending on whether tenants downstairs had thier lights on. Also measured a similar 40 - 80 mG along side our bed, realizing that there were power, water and gas lines intersecting at one corner and dispersing in right angles.

    After delving into the book the first thing I checked was for a grounded neutral....and that's what it was. Turning the light on in the bathroom caused the field on the cold water pipe to go up over 110 mG indicating the neutral was taking the ground path to return to the transformer.

    To isolate the problem I turned off the power at the mains and verified the bond from neutral to ground right at our units (breaker) subpanel. Sure enough it was exactly as the book described.

    In those panels there is a screw that grounds the neutral bus bar. This screw is shipped installed which is the correct configuration for the mains drop. However, when the box is used as a subpanel such as a breaker box in an apartment that screw is a violation of NEC code and must be removed. Of course it causes a ground loop.

    As soon as I removed it I verified the bond was broken with an ohm meter, then turned the power back on at the mains. Everything was as it should be. The current dropped on the water pipe (around 6 mG, still high), and the guitar had no more noise. I could crank that thing up using the highest gain I could find....even the single coils were clean!!! Fantastic! The reading over our bed was down to 0.5mG almost all the time. After a month of use the actual reading on our power bill was down by 25% or 100kW too!

    After that we went around the building with an electrician and had him break the bond on all the units and things got progressively better overall on the water pipe. However, 2 units didn't see improvement indicating there are other problems there. One unit, the unit I used to live above when this started, had a reading of 2.5 mG everywhere in the apartment at 3 feet above the floor. Main level, concrete floor. The reading at the subpanel was 95 mG. That unit is the only one in the building that hasn't had it's outlets changed and there is likely some arcing going on.

    Hope that helps out someone else that's had problems with noise on their guitar. Don't go messing with power if you don't know what you are doing though - it's deadly! Hire a qualified electrician or EMF consultant to take readings and make repairs.

    It was a long haul, it was a year. I started out knowing nothing about residential wiring and now I feel a little wiser. I won't be shopping for a residence without a gauss meter anymore though!!

    Thanks to everyone who gave me advice in this matter. You all helped me solve this.....
     
  2. ElGio

    ElGio Active Member

    RobyG,

    Im glad you fixed this problem. I have a similar one but I already lifted the amp ground to eliminate the ground loop from my variables. As I move around the Hum seems to change in intensity. I already tried my guitar-amp setup in a different place and it worked just fine. Any suggestions?
     
  3. moonbaby

    moonbaby Mmmmmm Well-Known Member

    You should really avoid lifting the ground on any guitar amp's AC connection!! This is a safety concern, as a non-grounded amp can KILL you! If your hum changes in intensity as you move the guitar around, it sounds like a shielding issue at the instrument end. Are there CRT screens, TV's, and/or flourescent lights in your environment? Single coil pick-ups?

    BTW, the post you replied to is 7 years old...:)
     
  4. ElGio

    ElGio Active Member

    LOL! I just noticed that. I stumbled upon this thread while researching the problem. I'm aware of the dangers of lifting the ground on the amp. I did it for a quick test plus its a 4w amp. I already turned off all the breakers in the apartment exept the ones dedicated for the outlets. Its a Fender american telecaster so yeah, single coil. The hum its more than the usual single coil hum. Im not sure that shielding my guitar will completely solve the problem. I dont wanna open the panel for inspection since its a main lug only panel. My next step is buying a real good noise canceling pedal or have the electric company inspect the distribution panel.
     
  5. dvdhawk

    dvdhawk Well-Known Member

    Your 4-watt amp is still plugged into 120-volts (that's what will KILL you if a ground goes bad), regardless of output.

    Does your Strat have a 5-way switch? Is it just as noisy with the switch in the 2 & 4 position?

    If not, I'd say it's the shielding and grounding in the guitar causing your noise in 1, 3, & 5.
     
  6. ElGio

    ElGio Active Member

    Its a Tele. The noise is there regardless of the switch position. Its coming either from the ambient EMF or a bad neutral connection somewhere. Both guitar and amp are fine since I've play in different places without a problem. Where I'm stuck right now is diagnosing the problem. I'ts hard to tell without tearing the whole wiring apart.
     
  7. Link555

    Link555 Well-Known Member

    Current Kills. 120VAC at 4W -> 4/120V = 33mA

    Electric Current Needed to Kill a Human
    So why turn off all the other breakers, how does that help? Your breaker likely trips at 15A? If your concerned put 100mA fuse inline with the power cord.

    If you remove the ground, where does the noise go? Removing the ground is the absolute last thing I would do. What else is on the circuit? Light Dimmers, CRT's something is making noise. Is your house wiring correct? Did someone mix up the hot and neutral in the box? A simple outlet tester would help...
    http://www.aemc.com/products/pdf/2121.02.pdf

    Do you have a bad cable ?
    can you record the noise and post it?
     
  8. BobRogers

    BobRogers Well-Known Member

    Sometimes literally.
     
  9. Link555

    Link555 Well-Known Member

  10. ElGio

    ElGio Active Member

    Turning off all the breakers will remove all the loads from the main Bus. In doing so I can garantee that there's no contamination getting into the electrical system from other loads. This of course if the contact reistance in the breakers its good. Turning off the breakers has nothing to do with the ground loop problem.

    If I remove the ground the noise is still there. This makes me think that somehow there's something going through the neutral that's not supposed to be there. The circuit only has other receptacles and my amp. Nothing more. I already measured the voltage at each outlet and tested for reverse polarity. I even tested for voltage drop and ground impedance on the lines.

    I've tried with 4 different cables including new ones.

    I will record the noise tonight so that you guys can hear ir.

    Thanls for the replies.
     
  11. ElGio

    ElGio Active Member

    BTW,

    I also tried a UPS, direct box with gound lift and isolation transformer, humx, and filters.
     
  12. Link555

    Link555 Well-Known Member

    Gotcha ....so do you have dimmers? are the hot neutrals wired correctly through out the circuit, the house?
     
  13. ElGio

    ElGio Active Member

    The hot and neutrals appear to be good. Then again, with all the breakers off (leaving any other bad connection (hots only) out of the equation) the noise is still there. So its probably a neutral thing back in the panelboard which Im not going to open since its a MLO panel. I dont have dimmers.

    Again, the problem is ambient EMF. I move around and the noise change in levels. I will record the noise with me walking around so that you can appreciate what I mean.
     
  14. ElGio

    ElGio Active Member

    Send me your email. The file is to large to upload it in the forum.
     
  15. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

    Except that the output wattage of the amp has nothing to do with it.
     
  16. Link555

    Link555 Well-Known Member

    Boulder: Yes sir, Worst case you are correct, best case he would blow a fuse on the power supply of the amp and that would save him.

    are all your hots and neutral correctly wired, i.e., not criss crossed from one outlet to the next? Have you taken off face plates to confirm this?
     
  17. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

    I would tend to assume the worst with power. If the power ground is energized and the waterbag holding the guitar is a path to a real ground, like a wet stage, would the fuse be in the circuit at all?
     
  18. Davedog

    Davedog Distinguished Member

    No. But like ALL AC circuits, it would be on the bottom half of the cycle and the chassis should be bonded to the neutral through the wiring in the house....if it has a grounding conducter....So this would be detected by using a circuit tester....But he has stated that hes already checked the polarity throughout his circuit. With everything else off there will be no backfeed from another circuit being crossfed or sharing a neutral connection somewhere else. Understand that only the loads on the same phase will have any effect on the one he's using, unless its a heavy ballasted lighting load and the breakers are next to each other in the panel.

    This is a shielding problem with the guitar. Yeah, I know.....some places are different than others and a single coil guitar will accent that. We run 3 isolation transformers onstage and its still not enough for the Strats in some venues. A lot of this has to do with the position of the building on the power grid, the type of transformer feeding the line, the amount of other loads and the type of loads upstream from the building....its a lot of math....
     
  19. mdb

    mdb Active Member

    That's crazy. I hope I never have those kind of problems. I probably wouldn't know where to start and just live with it. Isn't having the common wire running through your copper water pipes a little dangerous? Maybe make your shower experience a little electrifying?
     
  20. Link555

    Link555 Well-Known Member

    I would think the amp would be fused. what is the amp model and brand?
     

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