Pot taper for volume pedal?

Hi, all, I have an old Ernie Ball volume pedal that has a 100k linear taper pot.
I am trying to replace that with a higher value (250k) pot, and I'm wondering what taper I should use for a smoother transition than the linear taper is affording.
The circuit puts the wiper as the input (guitar) end, one end goes to the amp, and the other end goes to the ground. The pot is situated such that full clockwise is off.

The question is this: do I need a normal audio taper, or a *reverse* audio?

Also, the pot I get needs to have at least a 3/4" long shaft to mate up with the little pulley properly. The usual sources (Digikey, Mouser) are not replete with this configuration. Any suggestions for where I might find such an animal are welcome!

Thanks in advance for suggestions.

George Reiswig
Song of the River Music

That's not how it's usually done.

The input (guitar) is usually at the top of the pot, the output (to amp) is at the wiper, and the bottom is grounded.

Jameco. Look at the Clarostat RV-4 series, which are the equivalentof the
Allen-Bradley Type EJ, commonly found in wahs and vol pedals.
Note that none of the ones listed are audio taper (or 250K, for that matter) but Jameco is one of the few places which still offers great pots like these - give 'em a call, maybe they have (or can order)
exactly what you need. At only $8, these are a killer deal. Eyeball this:
http://www.jameco.com/cgi-bin/ncommerce3/ExecMacro/ jameco/searchResult.d2w/report?sort=BKW& search=Clarostat&Go.x=22&Go.y=7

Here's how to work it out for yourself...
A normal volume control (e.g. on an amp, Hifi etc) has zero volume when turned hard left when looking at it from the front panel.
Now, depending on which side of the pot you're looking at, that usually means that the signal is bled off to earth (completely) in this position.
An audio taper increases in resistance gradually at first and then more dramatically later - which is the way our ears respond to volume - logarithmically.
That's a plain audio taper.
A reverse audio taper can be looked at as pulling the knob off one side of the pot and sticking it in the back.
i.e.
Dramatic changes in resistance at first with much smaller changes later on.
If viewing the pot from the side the shaft's on your zero is hard anticlockwise - that's a plain audio taper you'll be needing.
Hard clockwise - reverse audio.
You want small changes in volume at the beginning of the "travel" and bigger ones later on (hence the problem you're experiencing).
To put it in another context - every time you double the power that you're getting from the speakers, you equate it to an equal change in volume.
i.e. changing from 1W to 2W is the same as changing from 100W to 200W.
You'll never guess - that's why those pots are popular in audio equipment...

I always say that helping someone solve their own problems through understanding is far better than dishing up a prefab solution...

I think that the problem LV might have with this is that he's interpreted the schematic - and not the circuit in itself...
Something that the manufacturer could have also done by not using a logarythmic pot in the first place...

Hope this helps

cb

Yes, that certainly looks like expert advice from where I'm sitting.

By all means, "wewerthe".

I apologize if I'm wrong. But with the pot full off at full clockwise then that's a reverse taper no?

Thanks for the tips, LV!

George Reiswig
Song of the River Music