[sdiy] How does the MS-20 ESP pitch extractor work?

[Aaron Lanterman]

For his final project, one of my students wants to build & compare some 
pitch extractors.

He's breadboarded up the chunk consisting of the four op-amps, BJT and 
various bits of goo between the circled numbers 3 and 5 on p. 4 of the 
M-20 service manual. I suggested that he just do that part and put in a 
sine wave and see what came out; then he could go back and put on the 
filters in the front end later.

But, he can't get it working. I'm having a hard time helping him debug 
since I have no idea how the circuit actually works. Could anyone give us 
some pointers on how it works?

Also, if he made up a circuit board of the ESP, would anyone else be 
interested in one?

- Aaron

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Dr. Aaron Lanterman, Asst. Prof.
and Demetrius T. Paris Junior Prof.    Voice:  404-385-2548
School of Electrical and Comp. Eng.    Fax:    404-894-8363
Georgia Institute of Technology        E-mail: lanterma at ece.gatech.edu
Mail Code 0250                         Web:    users.ece.gatech.edu/~lanterma
Atlanta, GA 30332                      Office: Centergy 5212