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log / linear pots advice and wiring configuration ideas please


Solomon
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No, I'm afraid wiring two volumes in parallel won't at all do what you want. You'll see that when you think through the scenarios you've described:

Scenario 1: you roll off the 250k pot. Then the hot output on that pot is connected directly to earth. So you'll get 0 output, no matter what the 500k pot is doing.

Scenario 2: you have both fully open. Then between the hot and the earth you've now got 2 resistors in parallel, giving an overall resistance of 166K, i.e., less than either of the two resistors on their own.

You could get round this by having a switch to select between the two volume controls, but I'd recommend just buying a single 500k and a single 250k, wiring one in and seeing how you like it, and then swapping for the other, seeing how you like that, and then choosing one. There's a reason why you never see stock basses with 2 master volumes on - it's just not worth it! :)

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Touche!

Right then... I'm pretty much there now. After barking up a tree for a while I've decided to drop the 4-throw switch idea... mainly because it'll just be too painful to pay £12 from Mouser to get the part I need because they appear to be the only people in the known universe to sell such an item!

So, because my plan is to get as much versatility from a single humbucker pickup as possible, I still want to get the series/parallel/north/south options from the pickup... and I've been bashing my brains to figure out how this could be done on two DPDT switches but for the ilfe of me I can't figure it out... I've got very close but not got it nailed. I'm prepared to believe it can't be done! Now my plan is to have 2 SPST switches - one for each coil. Then a DPDT (on/on) for a series/parallel selection. Clearly the series/parallel switch won't do anything if one of the coils is deactivated. Beyond this arrangement a standard volume and tone control... then (just for fun) a kill switch (DPST on/off/momentary).

[attachment=118798:wiring-final-pots.JPG]

Assuming this wiring idea is sensible and will work I would like to entertain the notion of changing the switches for pots... I don't see any reason why that shouldn't be OK but that might just be my lack of experience talking! So, with that in mind I've thought about swapping over the pickup selection switches (so we now effectively have a volumn control for each coil... clearly the normal volume pot would be redundant in this situation). In principle I reckon this is OK but I can't predict if this will trip up when we start fiddling with the series/parallel switch.

If the coil volume controls idea works then I'll certainly imlement it. Beyond that I've started thinking about using a dual pot for series/parallel instead of a switch. Now my O-Level physics knowledge assumes that this won't work... call it a gut feeling... but I have nothing more than a hunch to go on. Is it a stupid idea or is there some mileage here?

[attachment=118797:wiring-final-switches.JPG]

Actually... while I'm here, one last question... I know it's common practice to solder the earth to the back of the volume pot - but why? Does the pot chassis itself need earthing? Is it just for the convenience of having some kind of earth "hub"? I've been trying to draw up my diagram in a more "real world" type scenario and I probably wouldn't solder anything to the backs of pots - if I need some kind of hub I would probably just twist all the wires together, solder and heat shrink. Am I missing something?

Edited by Solomon
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