how to create a psudeo Linear Pot from a Log pot

[stubish]

Hi all,
       I've seen plenty of schematics and guides on how to create a psudeo log pot from a linear pot, but I need something to go the other way. I've got a volume pedal I want to turn into an expression pedal (essentially emulate a 10k Linear pot with the installed 50k Log pot). has anybody got any idea of how I can do this? If so it would be a great help!

Cheers
Stuart

[PBE6]

Try putting a 12k resistor between lug 2 and either lug 1 or 3 depending on which direction you want the resistance to increase in. Not perfect, but not a bad approximation either way.

[GGBB]

Try putting a 12k resistor between lug 2 and either lug 1 or 3 depending on which direction you want the resistance to increase in. Not perfect, but not a bad approximation either way.

Only one of those two options works, and only if the pot it used as a variable resistor.  If you connect the resistor between lugs 2 & 3, this kind of works - at least the taper is more flat between 2 & 3.  But if you connect the resistor between lugs 1 & 2, you get the opposite - the taper is actually more curved between 1 & 2.

[stubish]

Thanks all for the advice. Here's an update.

The volume pedal has two 1/4 jacks, my plan is to build a cable that is two 1/4's to a TRS jack at the other end. One jack directly taps the center lug the other taps one of the outer lugs (I'm assuming it does not matter which, as the result is a log style curve). I took a look at the pot last night and it's actaully 250k. What value resistor would I need for that (I've got a few values here).

My plan is to just solder in the resistor on the TRS jack. That should do that trick, right? The end result I'm aiming for is the 250k Log pot to emulate (approximate) a 10k linear pot... if I can achieve that with one resistor all the better as I can probably stuff it into the trs jack...

Thanks!
Stuart

[GGBB]

One jack directly taps the center lug the other taps one of the outer lugs (I'm assuming it does not matter which, as the result is a log style curve).

It does matter - read my previous post again. You wrote that you are aiming for a flat taper with a log taper pot. If you parallel lugs 1 and 2 with a resistor the taper will become LESS flat, i.e. even more logarithmic. If you parallel lugs 2 and 3 the taper will become flatter. You also need to bear in mind whether resistance will increase or decrease as the pedal toe goes down.

It sounds like you are trying to do this with a cable only - in other words not modifying the pedal.  That COULD work, but there's no way to know without knowledge of how the pedal works (schematic) currently.

As for the resistor value with a 250k pot - a 10k resistor will give you a 9.62k pot, a 12k resistor will give you an 11.45k pot.  You choose.