both series & parallel pup vol control

[sharkfin]

Ok, don't laugh at me now, I know pretty much nothing about electronics, but I was thinking about a way to mix the middle pup of my strat with the bridge & neck - not unlike the S-tastic mod.

The idea is to use the neck tone pot as a master tone, and the third pot as a blend (?) for the middle pickup, so it can be mixed in at any volume...

...so far so good...

...but here comes the problem: Can the pot be the type that has an indent in the '5' position, so turning the pot from 5 to 10 (clockwise) fades the M pup in series and turning the pot from 5 to 0 (counter-clockwise) fades it in parallel?

Please don't hit me - I'm just uneducated in the ways of wiring!

If this were to work, then the 5 way would function:

blend pot at '5' (M pup off):

1: N
2: N+B
3: N*B
4: -N*B
5: B

--------

blend pot at '0':

1: N+M
2: N+B+M
3: (N*B)+M
4: (-N*B)+M
5: B+M

--------

blend pot at '10':

1: N*M
2: (N+B)*M
3: N*B*M
4: -N(B*M)
5: B*M

--------

Can it be done? Opinions anyone?

[UnklMickey]

sharkfin said:

...Can it be done?...

no

[sharkfin]

How about not using some imaginary pot i dreamed up, but maybe a push-pull pot, pushed down fades the pup in parallel and pulled up fades it in series...

would that work? Sorry again for sounding like a retarded chimp.

[UnklMickey]

sharkfin said:

...Sorry again for sounding like a retarded chimp.

not so much, just a bit uninformed about the limitations of series and parallel configurations.


so here's a way to look at it that will help understand the difficulties involved.

when putting 2 coils in parallel, if you want to reduce the output from one of them you can add resistance in series with that one (or using a voltage divider). putting resistance in parallel with that one also puts it in parallel with the other (so they BOTH get quiet).

the opposite is true of putting them in series.

to make matters more complicated, the connection that used to be made from the "low" end of coil A to ground is SWITCHED to new connection at the "high" end of coil B which PREVIOUSLY was connected to the output.

so switching between series and parallel configurations is easy, because we can move more than multiple connections, to multiple destinations.

but doing that with a pot? not so much.


your idea about a push-pull pot and having the switch part doing the configuration switching, and using pot to fade is do-able. but even that gets a lot more complicated to do "right".

so, maybe one of the other members might be interested in working something up with you.

as for me, i prefer the simplicity of keeping the switching separate from the volume.

[sharkfin]

I have another question; I've heard that a pup that gets blended in series reaches its top volume very fast, not smoothly fading in as blending it in parallel. Is there a way maybe with caps or resistors to 'spread out' the series vol increase, to match the parallel vol increase?

sorry again for my lack of brains

[JohnH]

This stuff is really difficult.

The ToneMonster2 (see schematics board) tackles volume changes in series and parallel with a blender rather than seperate controls. You can get blending in a series system with a pot in parallel with a pickup that gradually bypasses the pickup being faded. Sharkfin - you are right that the fading can happen very suddenly at the ends of the pot travel. For that reason, it needs a much lower value pot than normal. I use 100 k linear, and the blending is smooth. However, the trouble with a pot that low is that putting one across your pickup slightly diminshes treble even at maximum. So I remove a section of carbon track to disconnect the pot as it reaches the central 100%100% position.

In parrallel, a seperate pot is needed (as part of a dual gang pot), and it needed bypass resistors and capacitor to keep treble and volume in reasonable balance.

What I did was fairly specific to that switching arrangement, but it might give a clue

John

[UnklMickey]

johnh said:

... I use 100 k linear, and the blending is smooth....

i would have guessed 25k would have been the magic number for the value of the pot. but you've actually been there, so that trumps a guess any day!