I recently built a Carlin Phaser, from the kit from Moody Sounds. It's a foot-contolled 8-stage phase shifter (kind of like a wah pedal) with an LED control feeding the 8 LDRs. (green LED if that matters) It's got a nice sweet sound, despite having no feedback or anything, but the pot that came with the kit doesn't seem to be right. It's a 100kA. All of the sweep (where the phase shift is noticeable) seems to be confined to about 20% of the treadle movement. (mostly when the LED is dark or near-dark) The rest of the treadle movement does nothing.
Would changing the pot to a different value, larger or smaller, or a different taper, make any difference? Could I fix things by adding a resistor in series with the pot? I don't know the specs of the LDRs that came with the kit. (dark resistance, etc..) I really like having a foot-controlled phaser. It has a nicer tone than the foot-controlled phasers I tried in the `70s. but I would really like to get the sweep problem sorted.
Have you got schematics? The Carlin Phaser google brings up is modulated with lfo or sweep by 10k antilog pot (this could be your problem) and uses a light bulb with the ldrs?
http://www.experimentalistsanonymous.com/diy/Schematics/Phasers/Carlin%20phaser.gif (http://www.experimentalistsanonymous.com/diy/Schematics/Phasers/Carlin%20phaser.gif)
Thanks. I'll give a 10k linear pot a try. I just used what came with the kit. (which came with a similar, incomplete schematic, minus the LFO part and with no value mentioned for the pot)
The original Carlin Phaser from the 1970s apparently used a plastic shade that was mechanically lowered (by moving the treadle) over the bulb to vary the light that was reaching the LDRs.