Strange "Static Noise/Bridge Ground" Mystery (not an issue!)

[Baloney Balderdash]

First I like to point out that I am not really seeking to solve an issue here, but rather curious about solving a strange mystery.

 

So I got an EMG Geezer Butler P pickups installed, which is shielded internally, and with the ground of the pickup wired running as a braided shield all along the insulated hot wire, so to start with the noise picked up/generated by this pickup in minimal, and not really an issue at any point, however at the moment I am rearranging my usual pedal board completely, so I use a temporary simplified pedal setup that run off a daisy chain, rather than the isolated power supply of installed on my pedal board, which does cause slightly more noise than usual.

 

Now to the mystery, as you would expect the noise gets less when touching any metal parts of the bass, thanks to the bridge ground wire, however while the noise almost entirely disappear when touching the bridge directly it is reduced notable less when touching across the strings, regardless if this happens above the body, above the pickups, above the fretboard, or above behind the nut, ever so slightly more when combining two of these positions by using both hands, but now for the really strange part, I recently installed some copper shielding tape on in the nut slots (a thin piece the width and approximate length of the nut, going across it, and then by the strings pressed down wrapped closely to the sides and bottom of the four slots), to compensate for the thinner strings I have installed to accommodate the tenor bass tuning I currently use this bass in, and when I touch the tape on the nut it removes just as much noise as when I touch the bridge directly, that is the noise almost entirely disappearing.

 

What on Earth (pun fully intended) could the reason for this be?

 

I mean I guess it is to expected that the ground connection might be more effective when touching the bridge, to which the ground wire of the electronics of the bass is connected, directly, than just touching the strings, especially cause since these specific strings are coated Elixir Nanoweb ones, but why then does the ground connection seem to be just as effective when touching the shielding tape applied to the nut, but not when touching the strings just in front or behind the nut (I mean the ground connection of the copper tape has to come from the strings, which again got it from the bridge)?

 

Edited September 7, 2023 by Baloney Balderdash

[dannybuoy]

What are you plugging into? I get a lot of ground noise if I plug certain preamp pedals in between my bass and my battery powered Phil Jones Bighead headphone amp… but that noise disappears when I plug in the charging cable, and I don’t get any noise through my amp either.

[Baloney Balderdash]

57 minutes ago, dannybuoy said:

What are you plugging into? I get a lot of ground noise if I plug certain preamp pedals in between my bass and my battery powered Phil Jones Bighead headphone amp… but that noise disappears when I plug in the charging cable, and I don’t get any noise through my amp either.

You never got further than the headline did you?

 

Nothing to do with my actual question whatsoever.

 

But I guess thanks for at least taking a guess on a possible help.

 

 

I suppose I can try to condense the main essence of this mystery and my question a bit more, though I am not sure whether the reader would understand the nature of the mystery fully then:

 

The noise almost entirely disappear when touching the bridge directly, but there is less noise reduction happening when just touching strings, but not the bridge, at any point, however when touching the nut (lets just say it's a metal nut for ease of understanding the phenomena) and nothing else, which only connection to ground could possible be through the strings, again the noise almost entirely disappear, just like when touching the bridge directly.

 

What could the explanation for that possibly be?

 

Might also be worth mentioning that the strings in question are coated Elixir Nanoweb nickel roundwounds.  

 

 

Edited September 7, 2023 by Baloney Balderdash

[ahpook]

Could the copper tape in the nut be making a better connection to the strings than your fingers ? The strings will be earthed at the bridge via their windings I guess, but aren't a good connection along their length as they're coated. If the copper nut grounds to the string cores...?

 

Just a thought, seems odd that soft copper would cut the windings, but I have no experience of coated strings. Possible late night thinking going on here

 

 

Edited September 7, 2023 by ahpook

[Baloney Balderdash]

28 minutes ago, ahpook said:

Could the copper tape in the nut be making a better connection to the strings than your fingers ? The strings will be earthed at the bridge via their windings I guess, but aren't a good connection along their length as they're coated. If the copper nut grounds to the string cores...?

 

Just a thought, seems odd that soft copper would cut the windings, but I gave no experience of coated strings. Possible late night thinking going on here

 

 

I suppose the obvious answer would be that the copper tape at the nut somehow makes better contact with the strings than my fingers against the strings, would definitely perfectly explain this phenomena, however the strings at that point are still their full thickness and fully coated, and there is no possible way the copper tape could cut the strings, if anything the copper tape cause less friction than the bare nut, heck I couldn't even cut my fingers on that copper tape if I did an effort to do so.

 

Then again I suppose the strings would press harder against the copper tape in the nut slots than my fingers do against the strings under normal circumstances, so I'd say it is still a quite plausible, and probably most likely, explanation. 

 

Guess I just never gave the fact that the strings are actually fully coated much thought myself, and that pressure might change the degree of conductivity/quality of the connection, since there is still definitely some conductivity/connection happening even at low pressure, as some noise reduction is actually happening just by touching the strings lightly. 

 

Certainly a more scientifically plausible explanation than it being shielding tape and just living up to it's name. 

 

Edited September 7, 2023 by Baloney Balderdash

[dannybuoy]

Sorry if I missed the finer points of your post, it was a bit late for me to absorb a wall of text!

But yeah, my guess would be string coating acting as an insulation, but the nut makes a firmer contact which forces more metal-on-metal contact.

 

My P bass doesn’t make any noise whatsoever now that I’ve sorted the earthing issue out further down the chain, so this whole conundrum of touching nuts doesn’t even come into question. Hope you get to the bottom of it!

[Andyjr1515]

Well, as always with me I am probably  may be wrong - but isn't it that the bridge earthing might be causing this effect?  How I always understood it was:

- that when touching the strings or bridge any potential current present at the strings or bridge basically grounds through your body

- but if your bridge is already fully grounded, then there is no potential current because that potential is always being fully dissipated through the bridge to the earth of your jack

- On the other hand, if your earthing of the bridge is weak then, when you touch the bridge or strings, that potential earths through you - stopping the mains buzz.

 

**I am aware that the grounding of the bridge is not primarily a shielding action - it is very much a safety step to stop fatality in the event that a short somewhere renders the strings and anything metallic touching them becoming electrically live.  But I think the above logic holds good even accepting that?

 

   

   

Edited September 7, 2023 by Andyjr1515

[KiOgon]

A little exercise 🤪 with a amp connected to a 'good' mains supply, speaker/s connected to the amp and a instrument lead plugged in, switch the amp on and you will surely hear a small amount of hiss and hum, touch any metal part of the amp or the earth part of the lead and this will diminish as it is using your body as 'further earthing'.

 

Same when you plug the instrument lead into the bass, given a good connection you will probably still hear a tiny reduction in background noise when you touch conductive and earthed parts.

 

Anything more significant means you're not getting a good earth to your bass/guitar whatever.

[tauzero]

14 hours ago, Andyjr1515 said:

Well, as always with me I am probably  may be wrong - but isn't it that the bridge earthing might be causing this effect?  How I always understood it was:

- that when touching the strings or bridge any potential current present at the strings or bridge basically grounds through your body

- but if your bridge is already fully grounded, then there is no potential current because that potential is always being fully dissipated through the bridge to the earth of your jack

- On the other hand, if your earthing of the bridge is weak then, when you touch the bridge or strings, that potential earths through you - stopping the mains buzz.

 

**I am aware that the grounding of the bridge is not primarily a shielding action - it is very much a safety step to stop fatality in the event that a short somewhere renders the strings and anything metallic touching them becoming electrically live.  But I think the above logic holds good even accepting that?  

 

Isn't it actually the other way round? The great big wobbly bag of dirty water that is you acts as an aerial and retransmits all sorts of gubbins from the environment which is picked up by the pickups and electronics, and when you touch the strings or the bridge you're earthing yourself.

[Hellzero]

Thanks @tauzero, I'm so tired explaining this phenomenon again and again and again.

 

Just make a real shielding with everything star grounded, so you'll stop acting as an antenna and suddenly everything will become dead quiet.