[sdiy] expo circuit

Dave Manley dlmanley at sonic.net
Sat May 24 03:35:14 CEST 2008

I was looking at JH's String Filter schematics 
and the resonance expo circuit with the transistor (Q4) connected as a 
reverse biased diode seemed similar to something I'd seen before (lower 
right on the schematic).  A little digging shows it is very similar to 
the synthi expo (as seen in the schematics on the Hinton site: 

So...what exactly is the function of Q1 and Q4? Does it give better 


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