[sdiy] PT-80 delay for Synth Modular

[Tom Wiltshire]

On 30 Jun 2008, at 14:15, Dan Snazelle wrote:

> tom
> can you explain a bit how you have made chorus with this chip? i  
> havent seen any schematics for doing such a thing and have always  
> wondered if its possible

Ryan Williams page is the definitive resource on this:

http://sdiy.org/destrukto/vc-echo.html

He describes three ways to make this variable: Vactrols(or LDR/LED),  
a current source, or FETs. His page includes a circuit for the  
current source with limits applied to avoid blowing the chip up.
Here's an alternative example that uses the LDR/LED technique:

http://home.comcast.net/~sbernardi/elec/og2/og3_echo.html

Myself, I've played with the FET idea on the breadboard, but haven't  
got much concrete to show for the experiments. I was thinking of  
combining this with one of my PIC LFOs to produce a chorus circuit  
that would have a much wider range of modulation waveforms than the  
usual triangle, triangle, or triangle selection.

Regards,
Tom