Shifting LFO range in Phase 90

[Mark Hammer]

I should probably know this, but unfortunately don't.

I am trying to adapt a Phase 90 to envelope control.  This will involve placing an LDR half of an optoisolator in parallel with the 500k Speed pot***.  Depending on the properties of the LDR, and resulting parallel resistance, I may have to nudge the speed in one direction or another, up or down, to get a suitable feel and responsiveness out of it.  Given that there is a much bigger choice in cap values than there is in pot values (or certainty in selecting LDR values), I was wondering which of the two caps in the LFO - the .01uf feedback cap, or the 15uf cap to ground - is the chief determinant of the speed.  My gut says the .01uf sets the range, and the 15uf shapes the waveform, but I'd like confirmation.

Alternatively, if there is a different means of tweaking the LFO rate, by all means, bring it to my attention.


(***The same LDR will also be switchable to being placed in parallel with the 50k pot in series with an 11k fixed resistor in the feedback loop, for more resonance as you pick harder.)

[earthtonesaudio]

The big cap determines the speed.  The small cap just slows down the output when it switches.