Another Route To Repeat Percussion

[smallbearelec]

I remembered that Ampeg used a photocoupler to do this in the old Rockets and Geminis. Since I now have four (count 'em!) devices that could be used for the LFO, I wondered if I could make an LDR work as the modulator. Here is what I have going on the breadboard:



It's just another way to get that very hard trem. I have tried several photocouplers: VTL5C1, 2, 3, 6; Macron C, D, E, F, NSL-32. They all work, with varying degrees of hardness. I like the VTL5C2...YMMV.

I did not get the LFO to work with a regular UJT; the LED remains illuminated between beats and does not fully extinguish. This is probably due to something I don't know about how the device works. Comment from one of the analog gurus welcome, and thanks to Moosapotamus for the basic idea from the Skippy.

[pinkjimiphoton]

that looks cool!!  what kind of oscillator is it that you use? if it can do that real harsh kinda stutter like david gilmour gets on money, thats something i'd love to try.
thanks for posting it.

[smallbearelec]

what kind of oscillator is it that you use? if it can do that real harsh kinda stutter like david gilmour gets on money, thats something i'd love to try.

Basic relaxation oscillator, generates a sawtooth. For sound samples, check out the Skippy at Moosapotamus.net

[R.G.]

Yours is working on a slightly different principle than the original. It used the sawtooth on the timing cap for a pulse-trailoff. You're whacking the LED with a big pulse of light, and then listening to the speed of change of the LDR resistance in both directions.