Variable Capacitor?

[anyuser00]

Is there any way to get a variable non-mechanical Capacitor.  I mean is there something like a LDR for capacitors?

[Tim Escobedo]

There are varactor diodes. But they tend to be useful for rather small capacitances.

[Brian Marshall]

i've never tried them, but there are switching caps....   i dont know much about them, except that they exist, and i believ require some external components to control

[ExpAnonColin]

You know, you can probably get the same effect with variable resistance.  You can get a somewhat similiar or very much comprable effect by basically making a LDR pot between 2 capacitors.  What you do is make one LED driven by some waveform, the other by an inverted form of the same waveform, and then 2 photcells of near exact values for each.  You then wire the "middle" to a junction of the 2 photocells and then either side of either photocell to the 2 "top" and "bottom" capacitor values you want it to go up and down to.  This would work better in a tremolo/LFO sort of setting than an envelope setting.

-Colin

[anyuser00]

Thanks guys, this is actually for a tube fuzz wah.  http://www.ax84.com/fuzzwah.html

I am building an amp and have a few extra tubes I can use, so I want to integrate this within my amp and control it from an external pedal.