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I'm basically putting together a new guitar with an old body.
I got a combination of Seymour Duncan Hot Rails and Cool Rails and now I'm figuring out the potentiometers. (1 of them has to be push/pull ).
The wiring scheme says 250 Ohm, so I got that (though I don't know what the difference 250 vs 500 actually does), but there is also a difference between a logarithmic ("audio") and a linear potentiometer. I read you should use the logarithmic ones since they don't "cut-off" at the end. Is that both for volume and tone (I need 1 volume and 2 tones) ?
Any other advice I should take in account for the potentiometers, eg how do you know what knobs will fit on those meters?
Any advice on the switch itself (5 way switch)?
Volume pots should be log taper, otherwise all the action is in a few degrees at the bottom end. Remeber that loudness is essentially logarithmic. Tone, it depends on the circuit. If you fit a linear one and all the effect is concentrated at one end, then go log (or antilog, which can be hard to obtain).
Knobs: Most older pots had a 1/4" dia shaft with a flat for a grubscrew. Newer ones (here, at least) have a nominal 6mm dia, splined to suit push-on knobs. You can't put a splined knob on a 1/4 shaft, but you can do the opposite, and it's all horrible and wobbly.
Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012
(though I don't know what the difference 250 vs 500 actually does)
If I recall correctly it affects compatibility with amps. If you have a 250 ohm apparatus on one side and a 500 ohm on the other you would get noise and reduced volume since there would be reactive power on the line (which also creates static or semistatic waves).
OK, use logarithmic pots for volume and for the tone circuit use logarthmic as Pete said, as your hearing is logarithmic, you can very quiet (pin dropping) to very loud (jet take off). The actual values 250K ohms is what Leo Fender used in the bass designs (I would be very supprised if he didn't use them in the Strat & Tele guitars). Actual value is a way of matching impedance, Gibson tended to use split coil humbuckers which needed a 500K to balance the impedance. I would install them to there final position and measure the height and width of the stem sticking out of the body/scratch plate before embarking on the quest to find them. As for the switch Fender used a three way but plays found sticking between position (usually taking a spring out) they could get more tones as the pickups would blend differently. So 5 Way for my view (saves on having to repair switch). Sorry its a bit long but you asked a subject I know some things about!
If you haven't checked it out have a look at Daves World of Fun Stuff on YouTube he's always doing something like that!