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Flamesong

Am I causing my amp to hum?

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I have not been on here for a while as I have not been well for some time but recently picked up my guitars again and bought a new amp.

I seem to be having a problem with hum and it is happening with all amps and all guitars combinations to varying degrees and I found the Diagnosing Wiring Faults in Guitars thread below but it is three years old so I thought I might not be thanked for resurrecting it.

However, although my problem seems closest to the second scenario listed, the amps hum but it is reduced when I touch the strings, it does not go away completely, it isn't the full story.

As I mentioned, I have the problem with all my guitars and I have checked the earth/ground on them all. According to my (Hilka) multimeter, there is about 1.5Ω between the shell of the input jack and the strings on the worst guitar and 0.8Ω on the best, a Fender Stratocaster and 0.9Ω on a Squier Stratocaster (neither of which I have ever touched, electrically); however, there is 0.3Ω when I test short the multimeter probes so I am not sure how to factor that into my measurements. I thought this was odd so I replaced the battery but it changed nothing.

Anyway, I accidentally discovered that the hum only occurs when I am within a few feet of whichever guitar is connected - which is kind of annoying. If the guitar is as close as two feet away from me it hums. If I touch the foot switch on any of my pedals, it stops.

It it possible that I am the source of the noise? As far as I know, I have no alien implants (surgical or extraterrestrial) but I do feel like I get more than my fair share of static shocks.

 

 

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Just a quick bit of additional information.

I was a bit perplexed by the meter readings so I checked with another unbranded multimeter and got pretty much identical results so I thought something was amiss. I started checking the resistance of random things like the steel shaft of a screwdriver (0.8Ω), guitar cable (sleeve to sleeve 0.5Ω - tip to tip o.4Ω) then I checked the length of the brand new strings on the 'worst' guitar (when I said worst above, I was only referring to ground resistance, it's actually my favourite guitar), top E 1.1Ω B 1.2Ω bottom E 0.8Ω. One end of top E to the other end of bottom E 1.0Ω.

These measurements are consistent between two multimeters which are both digital though the unbranded one automatically adjusts the unit scale. I got the impression from what I have scoured from online discussions that there should be 0.0Ω between the strings or bridge and the ground at the jack shaft so either everything in the measurement department is wrong or all my guitars' earths/grounds (including two Stratocasters) are bad and I can't imagine either, to be honest.

Edited by Flamesong
Correct weird formatting

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Sounds to me like you could have a earthing problem on your mains installation. Does this only happen at one venue or everywhere? With different amplifiers or always the same one?

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Most electronics questions are arcane to me......and Keith just beat me to the response. My own house is the cause of similar humming. It clears up at other locations.

SR

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@Scott: I strongly suggest you get your earthing checked on your house. Bad earth dangerous! I can tell you a few horror stories about bad earthing and the damage it can cause.

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I live in a pretty remote place and I don't gig so it hasn't really been possible to test anywhere else so far but I am going somewhere at the end of the month which should give me an opportunity to do so.

When I got the e-mail notifications, I just did a quick double-check in another room with two amps and a couple of guitars and got very similar results. One guitar I tried which I hadn't previously was noticeably quieter but when I did a ground check on it, it was actually higher across the board than the others and unlike the others it has no humbuckers (I realise the limited relevance of that if they are not selected but still).

The house is rented and it has had at least two electrical inspections in the nine years I have lived here and I have a multitester which says that the earth is okay. It makes me wonder about things like carpets - they were laid before I moved in and I have no idea what they are made from. Anyway, I am not going to be doing anything drastic as far as this house is concerned as I am hoping to move in the next year or so. Hopefully my test at somebody else's house will exonerate my body.

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46 minutes ago, KeithHowell said:

@Scott: I strongly suggest you get your earthing checked on your house. Bad earth dangerous! I can tell you a few horror stories about bad earthing and the damage it can cause.

Thanks Keith. It passes inspection...but there are definitely some outlets that have cleaner power than others. It probably wouldn't hurt to have them all checked individually.

SR

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