[sdiy] Lowpass gate using H11Fx photofet optocouplers instead of vactrols

[Aaron Lanterman]

On May 3, 2010, at 3:27 AM, Dave Manley wrote:

> Aaron, for this and the vactrol filter it might be interesting to trigger the scope
> with the LFO square wave output and watch the decay of the envelope of the filtered
> output.  I think this would show the turn on/off delay characteristic of the
> vactrol, and maybe the H11Fx as well.  You might have to zoom in on just
> the leading or falling edge of the LFO output.

I thought about that exact experiment... as I was driving home after taking the video. ;)

Masahiro is building the perf board soldered version of his H11Fx circuit now. If he gets it working, I'll do that experiment. I am curious. 

For the four-pole-with-feedback-with-vactrols demo, at some point I did modulate it with a square wave, just as a lark; at the time I wasn't thinking about checking out the vactrol decay, but I noticed it when watching the video later. You could see it pretty clearly on the scope when the resonance was cranked.

- Aaron