pot taper for diy expression pedal

[allsavy]

I'm not sure if this is the right place to post this but I'm building a midi foot controller for guitar rig 3 software out of several momentary stomp switches and what will be either a wa or volume pedal (pot operated) interfaced to guitar rig via a usb gamepad and 2 software apps. 1- "joycur" to map static midi messages to keys on my laptops' keypad (which are in turn assigned to various preset effects switching functions in guitar rig) and works fine.

2- "MidiDriver" to handle CC# continous control. Temporairly I've removed the center stop 2 axis jotstick pot from the gamepad and connected a 100K audio taper pot to try things out. I got it to work marginally well although there is a portion in the middle of the pots travel that seems to lag in the responce curve somewhat like what a center return of the origional pot. In other words there is not a smooth transition throughout the new pots travel.

Since the App I'm using was intended for use with a joystick that the problem is with the software response curve. I have tried other software apps that allow configuration of either center point upward or center point downward that might be usefull but I forget what app that was.

Could choosing a different taper (reverse taper ?) help with the center lag issue?

Is there a proven app out there that can be configured to work out this bug?

[madmanmike777]

hey man, i know this sounds obvious, but maybe a linear taper instead of audio taper? that makes the transition less drastic and should smooth things out...i know ive seen plenty and built a bunch of 100k linear taper expression pedals for stuff like moog pedals, boss pedals, whatever....with boss they can actually make the AW-2 auto wah a REAL wah pedal...but i heard you say "reverse" taper, in ALMOST ANY case a linear taper pot may be used where a "reverse" or "reverse log" pot would be with NO loss of performance....hope that helps

[Steve A.]

... maybe a linear taper instead of audio taper?

Amen! I have an article brewing called "The Myth of the Audio Taper". It is one of those things that we keep hearing so that we assume that it is true: "the ear hears volume logarithmically so we need to use audio taper pots for an audio volume control".

In my experience if you are turning a volume control up from 0 you do want an audio taper pot but if you are turning the volume down from 10 I think that a linear taper pot is more appropriate. I think that reverse audio might even be better. (By adding resistors to a linear pot you can simulate an audio/reverse audio taper.)

If we go back to the early days of audio, some of the devices could get pretty loud (since amplification was brand new) so we would want to turn up volume very gradually- so as to not blast out ear drums. So in that application an audio taper pot was very appropriate.

Fast forward to today and if you are on the bandstand you pretty much set the controls on your amp to the maximum volume you plan to use and then turn down the volume control on your guitar to an appropriate level. Turning down from 10, you have a lot more control if you are not dealing with an audio taper.

If you are into volume swells (like Roy Buchanan) then stick with the audio taper. That is something that doesn't sound right with a linear taper.

This thread is about an expression pedal that sends a voltage back to the device depending on the setting of the pot. In an application like that you usually want a linear pot. But I had to rant about audio taper pots a bit.

Steve Ahola

P.S. Another myth we hear is that linear pots are okay for tone controls. It all depends on the guitar and pickups, the value of the tone cap and the tone pot and whether the pot is linear or audio. If you are not satisfied with the way your tone control works you experiment with different tone caps and tone pots until you find something that works for you.