Major headache, RE pot taper (log linear)

[fompsweeva]

Hello guys,

Please excuse my newbieness.

I've been reading around the internet on Log/Linear pot taper as I want to do my guitars right.

The most confusing thing for me is pot taper.

I've tried many different sites, but it's very confusing. Some schematics don't show pot taper, and some suggest to use all audio taper, some suggest 2 audio taper and two linear taper... I just don't know who to believe!

Then I went and looked in the back of my Tokai Les Paul (which is very new and I know it's unmolested) and it has two B500k's for volume and two A500k's for tone, the opposite of what I'd expect to see?!

So I'm wondering if anyone can point me in the right direction. I have 3 different Les Paul style configured guitars to re-wire and I'm getting very confused.

[JohnH]

fompsweeva - welcome to GN2.

Both linear and log will give you the same overall range - and it is a matter of opinion. The difference is the rate at which they take effect as you turn them down from 10. I have a les paul copy, and it came with lin for volume and log for tone. I think this is right on an LP, particulary the linear for volumes. In my rewiring efforts, I first tried log for volumes, and I have recently changed back to linear. With a two volume setup, it is much easier to set mixes of pickups with linear taper for volumes. I think you'll see both on different guitars however.

I don't have such a clear opinion about the tone controls, since I don't use them

John

[UnklMickey]

hi Fompsweeva,

personally, i prefer log tapers and single controls for volume and tone.

John mentioned the use of linears for volume, on 2 volume wiring, and he's absolutely right.

in that case, if one pickup is dimed, and you dial down one just a pinch, the series resistance on the dialed down control will have a HUGE effect because of the loading caused by the other pickup.

so, log taper would be very difficult to use in this case.

it would cause the difference between '10' and '9' to be excessive. (when BOTH pickups are selected.)

even with 2 tone controls, i'm almost certain the tone controls should still be log taper.

i'll reason this out and see if i can find any why they shouldn't.


unk

[UnklMickey]

hi Fompsweeva,

i've spent some time thinking about this issue.
whether a single, or separate tone controls, they should be AUDIO TAPER.

after much delliberation, i've determined it's EVEN MORE IMPORTANT for the tone control to be log taper, than it is for the volume control..... even on 1-volume, 1-tone schemes.

so, don't let anyone tell you to use linear pots for tone controls. you won't like the result.


cheers,

unk

[JohnH]

Unk - why do you think that?

I would agree, and my reason would be that I think most of the action on a tone control happens from 0 to about 100k, but you need a much higher value pot than that to get the tone cap completely out of action. So a log pot lets you get to the 'active' range quicker, with more of the pots travel devoted to the range where the greatest tone differences occur.

John

[UnklMickey]

johnh said:

Unk - why do you think that?...

John,

i think you did a great job of stating that in simple direct terms.

i don't have the Pspice advantage that you guys do, but i decided to crunch a few numbers manually.

if you ignore the capacitance and inductance,
and only consider the internal resistance of the pickup,
lets say 6k, and use a 250k pot, here's the comparison between the attenuation of the frequencies that are well above the 'knee' of the curve,
vs the resistance settings of a volume control for the same amount of attenuation.
this a$$umes that the capacitive reactance of the tone cap is so small as to be negligible.

Attenuation	Tone Control	Volume Control
0	NA	250k
-0.2	250k	244k
-0.5	100k	236k
-1.0	50k	222k
-3.0 dB	14.5k	177k
-6.0 dB	6k	125k
-9.0 dB	3.3k	89k

so even with this crude analysis,
it looks like a tone control begs for an even greater exponent in the taper than a standard audio taper pot provides.
my guess is you Pspice guys will be able to verify this to some degree.


cheers,

unk