How do I turn a volume pedal into a pan pedal?

[joegagan]

 i like the way you are thinking mark, with one excpetion. i understand why you would want the tone to change on the one side as it fades, but given a signal's propensity for treble loss as it gets attenuated ( even if the effect is psychoacoustic), i think the sound would just get muddy and weird using your method.

given that most players, when presented with the possiblity of an actual working morph pedal, one of the first things they would want to do with it is find settings that are a little of both. if one side has highs attenuated in the middle of it's sweep, this might not sound right to the player in the between settings.

[Mark Hammer]

The "mud" is a function of several things.  First, losing volume makes for a signal that seems less treble-rich; that is, of course, the very basis for the classic "loudness" switch on stereos, for that Fletcher-Munson curve compensation that ups the treble and bass as the volume is turned down.  In this application, the user wishes to NOT hear the deselected side, so any additional treble loss is perhaps more useful here.

Second, it results from loading.  Of course, in this instance, unlike true guitar volume pots, the segment of the pot between input and wiper does not increase in resistance as the  ground leg decreases.  Here, we are attenuating by only varying the ground leg of that resistive divider with the linear pot shared between the two sides.  My sense is that little loading would occur.

So, I'm gonna say I like YOUR thinking, Joe, but I still like my original suggestion.  Do note, though, that I am by no means suggesting a strong treble cut.  Just a little trim off the top.

[joegagan]

good point about the high possibility of not much loading, axg has stated there will be a buffer in line.

i am interested in hearing about any of the results of experiments.

[Paul Perry (Frostwave)]

I'm not convinced that you need a non-linear pot in this case.
When you are making a "effect" the key thing, is to be sure it is noticed. So long as you go from full left to full right, the effect will be obvious.

[axg20202]

Thanks all. Interesting reading. I'll be trying some things out today so will report back. I have to say I really like the design of this pedal, which has obviously stood the test of time to be reissued. The left to right tone control of the pedal is screaming out to be modified into another task, so my inital idea to make it a panner is proably the tip of the iceberg. I was just thinking that my Neovibe could have been housed in there, for example, allowing sumultaneous foot control of speed and depth. The only potential downside of this pedal for some (though not for me) is that its huge! Designed in a day when draft-dodgers with dirty great size 14 boots plugged a strung plank into an amp with cloth covered power cables and tubes as big as your head.

[axg20202]

Update:

OK, I rewired the volume/tone pedal into a volume/pan pedal and it works like a charm without having to replace the existing tone pot. The pedal has a tuner out (in thru to out), so there are already two jacks on the left side of the pedal to become the left and right outs. For anyone else wanting to try this, simply remove the direct connection between the in jack and the tuner out jack. Remove the tone capacitor. Then move the connection at the output (wiper) of the volume pot to one of the outer lugs of the tone pot. This cable runs to the original output jack and will form one of the L or R outs. Then run a new cable from the other outer lug of the tone pot to the tuner out jack, completing the complement of stereo outs. From the now disconnected volume pot wiper, split the signal off to two 50K resistors (as per RGs post) and connect each to one of the two outer lugs of the tone pot. Voila.

[joegagan]

cool news, thanks for posting that.