# Circulator LFO Reset



## ach (Mar 29, 2020)

I would like to modify the Circulator circuit such that the LFO can be reset via a secondary momentary footswitch. The main idea is that I would like to be able to set a very slow rate and trigger a long filter sweep by hitting both footswitches. I think it would also be a cool way to 'stutter' the LFO waveform.

My understanding of the LFO circuit may be off, but I believe C13 and C14 are the caps that fill/drain to set the LFO voltage.

Would placing the momentary switch across C13/C14 with a small resistor to discharge the capacitor be sufficient to reset the LFO to the lowest frequency position?
Would instead going across the negative terminal of C13/C14 (to charge the cap) set the LFO to the max sweep position?

Do I have the two reversed?

Thanks kindly for any assistance.




Edit. Made a correction to mod circuit drawing.


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## Chuck D. Bones (Apr 2, 2020)

Unfortunately, neither switch will work correctly.  The voltage across the timing capacitor swings between approx 2.3V and 6.0V.  Resetting to something outside this range will push the phaser into unknown territory.


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## ach (Apr 3, 2020)

@Chuck D. Bones - Thank you kindly for the information and review. I will think some more about how this might be achieved. If you have any suggestions they would be much appreciated.


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## Chuck D. Bones (Apr 3, 2020)

The bottom end of the capacitors is driven by IC3.1.  It acts like a current source.  What you need is a low impedance voltage source to force the bottom end of the capacitors to either just below 2.3V, or just above 6.0V.  That will hold the capacitor voltage to one end of the sweep or the other. When you open the switch, IC3.1 will start sweeping the capacitor voltage like normal.  you will need a vero board, a dual opamp and a few resistors to accomplish this.


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