I wondered if I could swap the LED/LDR (or opto) for a FET, mosFET or 4049 gate (inspired by the PUP phaser series).
Here's the original: http://www.runoffgroove.com/phozer.html
I wanted to add a buffer, and that leaves me one opamp left on a quad, so I thought: "What if I add dry non-inverted signal to the inverted filtered signal? The other frequencies should cancel out and the peaks should get "peakier", right?
LTSpice kinda agrees:
("r" being the resistance from point A and B to GND, where the opto is originally)
And a sweep through the "r" range:
The thing I noticed is: The phase goes from: -90, 0, -360 to... WILD negative values.
Does it mean auto-oscilation and weird behavior?
Any suggestions on this one?