Help understanding variable resistance and JFETs

[phector2004]

Hi everyone,

I've been trying to make a simple phase shift stage with LED/LDR controlling the resistance, with little success. I figure a JFET is a lot more practical, so I ditched my original design in favor of the MXR design. Here's my attempt at singling out one stage from the phase 45:



The LFO works fine, and the shifting works as expected, but I don't think I've got the JFET part right. I'm trying to understand what each part does, but it's got me stumped.

Why is there a 2x 10k voltage divider + 10n cap? What's the point of the top rail, with the 470k, 1M and 50n? Why not just feed the sawtooth wave into the JFET's gate with a series and a parallel resistor to set min and max resistance?