Sample + Hold without a noise transistor??

[chicago_mike]

  Hey gang,

Upon reading some PDF's on OTA's, I see a circuit for both ramp and hold and sample and hold...

Im wondering if these are the same as on keyboards or similar.

If they are, then Its easy to make a good FSH-1 without a noise transistor, it would involve another LM13700, but you could adapt the unused ota for a 3rd stage in the filter section, making a 3rd pass band or low pass..

No, I haven't smoked anything today..just a thought,.

[soggybag]

I'm not sure what you are suggesting. But, you could use just about anything in place of the noise source. An oscillator of some sort, the ballgame from an AM radio. This sample source is going to determine how random the samples will be and is just providing a voltage to sample and hold on to until the next sample.

[slacker]

If you look at the GGG schematic of the FSH-1, Q5, Q6 and C9 are the actual sample and hold circuit, so the LM3700 circuit just replaces those. You still still a noise source or some other signal for them to sample.
What you could do, which is something I've been thinking about for a while is replace the noise source with a half an LM13700 set up as a VCO and the other half as the sample and hold. If you run the VCO really fast then you'll still get a random output from the sample and hold. Make the VCO speed variable and you could make something similar to the Sub Decay Prometheus pedal.

[chicago_mike]

I wonder how easy it would be to make the circuit switch between sample+hold and ramp+hold....more uselss junk.