Shielding AGAIN I hear you say

[Oliwally]

I'm sorry, could I please resurrect this thread and ask some more noob questions? Here it goes:

Assuming that I correctly use copper shielding tape in all of my cavities and on the back of the scratch plate (grounded at the jack or volume pot housing, and overlapping at joints to have complete faraday cage) and the pots make contact with the shielding at the fitting holes …

… do I then still need to ground my pots by soldering wire from housing to housing or is it a complete waste of time?
… if I connect the housings anyway, does it do any harm? Will I create a ‘ground loop’ that will give me trouble?
… should I still use shielded wire and connect the shielding to the back of pots, or is this a complete waste of time?
… if I use shielded wire anyway, would it do any harm?
… if I use shielded wire anyway is it correct that I only ground one end of the shielding to avoid a ‘ground loop’?

Thansk a in advance for your thoughts.

Oli

[Marcel]

I'm sorry, could I please resurrect this thread and ask some more noob questions? Here it goes:

Assuming that I correctly use copper shielding tape in all of my cavities and on the back of the scratch plate (grounded at the jack or volume pot housing, and overlapping at joints to have complete faraday cage) and the pots make contact with the shielding at the fitting holes …

… do I then still need to ground my pots by soldering wire from housing to housing of is it a complete waste of time?
… if I connect the housings anyway, does it do any harm? Will I create a ‘ground loop’ that will give me trouble?
… should I still use shielded wire and connect the shielding to the back of pots, or is this a complete waste of time?
… if I use shielded wire anyway, would it do any harm?
… if I use shielded wire anyway is it correct that I only ground one end of the shielding to avoid a ‘ground loop’?

Thansk a in advance for your thoughts.

Oli

Grounding is often misunderstood... even by the so called experts..

... 1/ A soldered ground wire jumping from pot to pot helps to ensure a reliable ground connection under almost every cicumstance. You may have fully shielded your control cavity but that loose nut on the volume pot will make an awful noise if nil wire is used to permanently bond the earth connections together. And we all know how often volume pots become loose...

... 2/ Ground loops. Ideally we want to connect earth's or grounds in a star pattern, with all the 'radials' coming back to a single central point which is then subsequently connected through to our pedals and on to our amp. Any 'earth loop' you create anywhere only becomes a problem when a real and tangible AC or DC current passes through any portion of that loop, so in the case of earth loops in the shielding within the body of a guitar there is nil real DC or AC current in that copper shielding you so carefully fitted so there should be nil problem. Between your pedals and your amp, yep there is AC (your guitar signal), and then there is DC in the daisy chain power cable feeding power to your pedals so there is plenty of opportunity for the problem of earth loop or ground loop noise.

... 3/ Shielding when done correctly is never a waste of time.

... 4/ Over shielding (shielding everything in existence simply because you can) can lead to some issues. The biggest issue being the loss of high frequencies. Every shielded cable has capacitance from the centre conductor to the shield. The more shielded cable you have the more capacitance is there to suck away your higher frequencies just like your tone knob does when wound out down. There are times you need shielded cable to protect your (unbalanced) signal from interference so you will need to use it, the rest of the time try to avoid it if you can so that the higher frequencies of your awesome axe will actually be able to get to your amp.

... 5/ Grounding one end. This is a huge topic, bigger than this reply should go, but within a guitar the grounding of only one end of a shielded cable is generally not needed or preferred. You do need to have a circuit for things to work so you will need to be able to chase a continuity path from the centre pin of your guitar jack through all the parts of the guitar and then back to the sleeve connection of the guitar jack, and if that means using the shield of a cable to get from one place to another within the guitar then it must be done. On a shielded balanced line microphone cable used in a PA it is often done that only one end of the shield is connected (usually the source end), and inside a guitar amp the technique is quite often found to minimise stray signal pick up from other active components inside the amp, but inside a guitar it is rare and only done in certain cases due to very specific issues and if nothing else works.

As I said before there must be some DC or AC component on a part of any earth/ground loop for any negative issue to manifest. If you wire your earth/ground from your jack to a conveniently located pot, and then wire from that pot out to each location that requires an earth/ground connection then you will maximise your protection from 'interference' and minimise all those other issues. And follow the KISS principal ... 'Keep It Simple'...

[Oliwally]

Grounding is often misunderstood... even by the so called experts..

... 1/ A soldered ground wire jumping from pot to pot helps to ensure a reliable ground connection under almost every cicumstance. You may have fully shielded your control cavity but that loose nut on the volume pot will make an awful noise if nil wire is used to permanently bond the earth connections together. And we all know how often volume pots become loose...

... 2/ Ground loops. Ideally we want to connect earth's or grounds in a star pattern, with all the 'radials' coming back to a single central point which is then subsequently connected through to our pedals and on to our amp. Any 'earth loop' you create anywhere only becomes a problem when a real and tangible AC or DC current passes through any portion of that loop, so in the case of earth loops in the shielding within the body of a guitar there is nil real DC or AC current in that copper shielding you so carefully fitted so there should be nil problem. Between your pedals and your amp, yep there is AC (your guitar signal), and then there is DC in the daisy chain power cable feeding power to your pedals so there is plenty of opportunity for the problem of earth loop or ground loop noise.

... 3/ Shielding when done correctly is never a waste of time.

... 4/ Over shielding (shielding everything in existence simply because you can) can lead to some issues. The biggest issue being the loss of high frequencies. Every shielded cable has capacitance from the centre conductor to the shield. The more shielded cable you have the more capacitance is there to suck away your higher frequencies just like your tone knob does when wound out down. There are times you need shielded cable to protect your (unbalanced) signal from interference so you will need to use it, the rest of the time try to avoid it if you can so that the higher frequencies of your awesome axe will actually be able to get to your amp.

... 5/ Grounding one end. This is a huge topic, bigger than this reply should go, but within a guitar the grounding of only one end of a shielded cable is generally not needed or preferred. You do need to have a circuit for things to work so you will need to be able to chase a continuity path from the centre pin of your guitar jack through all the parts of the guitar and then back to the sleeve connection of the guitar jack, and if that means using the shield of a cable to get from one place to another within the guitar then it must be done. On a shielded balanced line microphone cable used in a PA it is often done that only one end of the shield is connected (usually the source end), and inside a guitar amp the technique is quite often found to minimise stray signal pick up from other active components inside the amp, but inside a guitar it is rare and only done in certain cases due to very specific issues and if nothing else works.

As I said before there must be some DC or AC component on a part of any earth/ground loop for any negative issue to manifest. If you wire your earth/ground from your jack to a conveniently located pot, and then wire from that pot out to each location that requires an earth/ground connection then you will maximise your protection from 'interference' and minimise all those other issues. And follow the KISS principal ... 'Keep It Simple'...

Hi Marcel,

Thanks very much for taking the time to write this comprehensive reply - fantastic stuff and makes a lot of sense.

I am planning to have a 9V preamp built into the RCA-4 Bass I'm building (just because...), so I guess that would qualify as a DC component that could give me grief.

I will have a go at your suggestions (as much as my humble electronics understanding allows) and not "shield everything in existence simply because I can" (love the way you put that - exactly what I was planning to do).

I'll try to keep it simple and use the star pattern grounding, probably using a small screw through the copper shielding in a convenient place and then branching out from there.

Awesome help folks, thanks so much! I'm not quite up to the wiring yet (just making sure I'm ready when I get to it) and I'm sure I'll come for more help when I have a go.