adding resistors to improve taper of pan pedal

[tempus]

Hey all;

I've been doing some reading (and experimenting) on adding resistors to a pot to change the taper. I've got an Ernie Ball pan/volume pedal that works pretty well, except that the volume decreases as you get to the centre of the travel. IOW if I'm panning between 2 pickups (I've got a piezo in my Explorer), I can start with a healthy amount of volume when, say, the piezo is full on, but as I move the pedal up (bringing in the magnetic pickups) the volume of the piezo gets quieter before the magnetics get loud enough to make it sound like a smooth transition. There's a spot in the pot's travel near the middle where the volume gets quieter as you pan between the 2 sources, then it gets louder as the magnetic pickups take over. This is different from a balance control on my stereo or mixer, where the volume more or less stays the same as the sound swings from 1 side to the other.

I hope I've explained that well enough.

Are there any tricks I can use with resistors to change the taper to correct this issue?

Thanks

[R.G.]

Yes, you can tinker with tapering resistors, but you will probably only get to a compromise. This is a classical problem with passive pan pedals - it's hard to get them to sum to a constant audio loudness. That's one reason I like the two-opamp approach that I wrote about in "Panning for Fun" at Geofex. That one works well with only a single linear taper pot.

[tempus]

Thanks RG

I read that article as well, and it all looked fairly easy to implement. The problem is the mechanical part, i.e., building or modding an existing (quality) expression pedal to control the panning. That's how I ended up with the Ernie Ball, which, although it is built like a tank, suffers from this very problem (also, the stereo jacks are out of spec, so you have to stand on your head to get them to make a good connection). I don't know if there's any way to build the opamp circuit into the pedal I'm currently using, and taking out the existing dual ganged pot and finding a suitable replacement (with the right shaft size and length to be turned by the foot pedal)...

[R.G.]

I don't know if there's any way to build the opamp circuit into the pedal I'm currently using, and taking out the existing dual ganged pot and finding a suitable replacement (with the right shaft size and length to be turned by the foot pedal)...

IF it were me, I'd use my ohmmeter to figure out if one section of the existing pedal is a linear taper. Some of them are. If so, I would use the existing pot and scale the resistors in the opamp panner to match the existing pot and use only one section of it.

[ubersam]

Could it be because of the piezo's higher impedance? Which, IIRC, it is much higher than passive p-ups. Maybe buffering the piezo before the pan pdl. could help even out the mix/transisiton volume.

[tempus]

Thanks Uber, but I've already got a buffer on the guitar. It's not a question of different outputs or volume levels (the piezo goes to the PA, which can be turned up plenty loud) it's the transition from one pickup to the next.