Are the pots in wahs typically Log Or Linear?

[slotbot]

I looked up some crybaby schems but none of them specified. Does anyone know off hand if they are Log or Lin?

thanks!

s

[R.G.]

They're often linear, but the whoopie! Big Name! pots have an S taper that's really neither log nor linear. Linear works OK for starters.

[slotbot]

Ok thanks

im actually trying to develop something as a crybaby pcb replacement but i haven't got a wah yet to gut.

[Processaurus]

Ask around your friends, almost every guitar player has a crybaby they don't use!  I'd get ahold of one and make sure that the pot works for your application before getting too deep into the planning process, because 1) it is a weird taper, and 2) it is very difficult to replace with a normal taper pot.

Someone posted a company selling linear taper pots with the pinion gear on them a while back, and I bought some, but the rotation was wrong (they were just normal pots).  $20 lesson there.

[Hides-His-Eyes]

I thought there were serrated shaft to std conversion kits; in which case just use a std. pot twice what you need... Would that work?

[Joe Hart]

I thought there were serrated shaft to std conversion kits; in which case just use a std. pot twice what you need... Would that work?

I believe they are "heavy duty" type pots because they get QUITE a workout and "normal" pots would wear out too fast.
-Joe Hart

[Astronaurt]

It depends alot on the circuit really. I actually just finished building this Clyde McCoy clone: http://fuzzcentral.ssguitar.com/mccoy.php

which I'm super proud of, It was actually my first pedal project ever! anyway, this one uses a 100K ohm ICAR taper pot that I bought off the interwebs. It's not the same site I bought mine from, but you can trust Small Bear if you're looking to buy one and have it shipped:

http://www.smallbearelec.com/Detail.bok?no=934

there's yer Wah Pot, choose the value

[tubelectron]

Hi,

I have buit and serviced many wahs and I have found and used almost everything in values and taper : lin, log, reverse log, from 10K to 500K... But this is not the answer you're waiting for. Having several crybabies and voxes these times, I will have the curiosity to check them more accurately.

One thing is sure : if like me, you design yout proper circuit, or create a personal variation of a known design, the value and the taper of the pot will be a function of your tatse (vocal or wide band, kind of progression), of the circuit itself and of the allowed travel of the treadle pedal. There is no reliable rule there : it's a matter of trials.

A+!

[slotbot]

ok thanks for the replies. I got a hold of a dead crybaby octave-wah and from a quick measurement this particular pot appears to be ~ 100k log. The circuit im making is dsp based and i am sampling the voltage at the wiper, so in this case the value is not super important but the taper is quite. I decided what i will do is just add 1 or 2 jumpers on IO pins to dictate different LUTs as a sort of whatever taper to linear converter.

Also i agree with tubelectron in that it might come down to taste anyways. So having the ability to alter the taper pot might be good for experimenting even if i *think* i want linear at this point.

-s

[slotbot]

maybe i spoke to soon about it being a typical log. Heres a graph of 12 equal angular increments. Im assuming the results imply that a the crybaby does not rotate the shaft through the whole range since the last 1/3 of the rotation shows a constant value. The Y axis is in kilo ohms. The resistance was measured from the CCW lug to the wiper as the pot is rotated CW in 12 equal increments.

[tubelectron]

yes slotbot, you're right.

I forgot to mention it : all the travel of the pot is not used, there is a "dead" section, usually mainly on the bass side (pedal up). For example, on my original SolaSound wah, the pot is a 100KB (lin) but measures 81,2K (disconnected) and the value travels from 20ohms (treble = foot down) to 34K (bass = foot up) between wiper and gnd. But I was speaking for analogue wahs, so as you're in on a DSP wah project, indeed, the requirements are probably different.

A+!

[new]

This is the result from my test.Wah POT vs Linear POT.

[tubelectron]

Hi new,

Your diagram shows typically the "S-taper" like R.G. told us a few post before. On which wah (or pot reference) do you have found this taper ? I will have to check the ones I have...

A+!

[new]

It is  DIVA   A100K POT

[Govmnt_Lacky]

Have a look at the 5B taper here:

http://www.alphapotentiometers.net/html/taper_curves.html

[Paul Marossy]

They're often linear, but the whoopie! Big Name! pots have an S taper that's really neither log nor linear.

Never thought about it much, but I would have guessed an "S taper". I have found that a linear taper works OK. I just work around whatever I end up sticking in my wah pedals, it's not hard for me to adapt.

[Joe Hart]

I believe Mr. Teese said that you can mess with the "perceived" taper by adjusting the cap that goes to the pot. I think if you make it .33uf it imitates an ICAR taper from a linear pot. If I remember correctly.
-Joe Hart

[tubelectron]

@Govmnt_Lacky : Thanks for the useful link to ALPHA pots tapers +++

@Joe Hart  : yes, it tested it. Increasing the cap going to the wiper drom 0µ22 to 0µ33 usually smoothen the bass to treble transition, but it's not always the rule...

@new : it's probably an european norm pot, where A means linear, instead of Audio (log, US norm). But it is poorly linear in fact...

A+!

[Joe Hart]

@Joe Hart  : yes, it tested it. Increasing the cap going to the wiper drom 0µ22 to 0µ33 usually smoothen the bass to treble transition, but it's not always the rule...

Interesting. I always thought an ICAR taper made the wah sharper, and I avoided that mod. So I had it backwards?
-Joe Hart

[tubelectron]

Hi Joe,

Sorry : what do you mean here by "So I had it backwards ?" ?

(Sometimes current language subtilities do not match my "academic foreign" english...)

A+!