Modified Quiet Beast - Theory

[kidmag]

Hi yall.

New to this board, and to guitar electronics (and gtr assembly). I'm making my first guitar and it is very much my own thing all the way down to the electronics. I stumbled upon Quieting the Beast, and now I am rethinking the wiring I had spent a month thinking about!! Bear with me, my language will be layman.

So without going into too many specifics I just want to make sure I understanding some things about QTB because I would like to minimize hum! (by the way, my wiring is for a Humbucker bridge, P-90 neck, 1 vol, 2 tones, a 3 way-toggle for bridge/both/neck, and a on on/on/on DPDT mini-switch for the humbucker only, series, parallel, split, there is also a on/on mini-switch for a bass cut on the bridge pup).

So, here is what I think I need to incorporate in my wiring:

1. the shielding in the control cavity, and the around the individual pick-up slots are connected together and together they represent the Chasis Ground.

2. I will not be grounding the bridge or my strings.

3. All grounds from pups, pots, switchs, etc should be isolated and should all go back to one central grounding ring, which is then grounded to the Chasis Ground through the .33uf cap. Meaning no matter where it's coming from, it goes through this cap before hiting the Chasis Ground.

4. Since my output jack comes into my shielded control cavity, I don't need to use the shielded wiring to this jack?


Anything I'm missing, or just totally wrong about here? Thanks - this little project is proving to be pretty challenging, but the rewards will be sweet!

[UnklMickey]

kidmag said:

...

2. I will not be grounding the bridge or my strings.

...


4. Since my output jack comes into my shielded control cavity, I don't need to use the shielded wiring to this jack?


Anything I'm missing, ...

hi Kidmag,

welcome to GuitarNuts2.

2 -- i assume you mean you won't ground the bridge or strings to the signal ground. you will ground them to the shielding instead.


4 -- it won't hurt to use shielded cable here, and is probably a good idea if the distance is more than a few inches.

also, the ground of the ouput jack must not come in contact with the shielding, or the .33uf cap will not be able to do it's job of shock protection.


missing... one thing not mentioned: determine which coil of the HB has the opposite magnetic polarity to the P-90.

make sure that is the coil which is active when the HB is split.



cheers,

unk

[kidmag]

Hi Unk, thanks for the reply.. so sounds like I'm on the right track.

2 -- I guess I've never understood why you need to ground the strings in the first place. Will it make much of difference?

extra - how would I determine the polarity? I had assumed since the HB I have was a bridge pup, the furtherest south coil (one with the adjustable poles) would be the opposite polarity of any pup designed for the neck (ie.it's a SD neck vintage p90).

Thanks

[UnklMickey]

you're welcome Kidmag.


grounding the strings allows you to ground your body.

although in the case of QTB, it's through a cap, for (DC) shock protection.

your body will have a tendency to re-focus the EMF, usually right into the pickups and wiring.

grounding your body through the strings, will minimize that.

and yes, it definitely will make a difference.


to determine relative polarity, just get any small magnet, and (carefully, so it doesn't slam into the pickup) bring in near the P-90.

one face or end of the magnet will be attracted to the front of the pole pieces on the P-90.

make a note of which end or face this is.


place the same magnet near each coil of the HB.

whichever pole pieces (screws or slugs) attract the same face or end of the magnet to the front, is the coil you don't want to use when split.

using the right coil, will make hum-canceling (instead of hum-reinforcing) occur when the split HB and P-90 are used together (in-phase).


cheers,

unk