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

[Harry Bissell Jr]

oooh (waving hand)

I know, I know...

Its a tachometer circuit.  There is a three pole
LPF, a one shot multivibrator (that is REALLY
clever btw) and an averaging circuit with the
fourth pole of the LPF

(it uses a four gang potentiometer).

As you make the input cutoff lower, it increases
the filtering on the output at the same time... you
can get a trade off between ripple and settling
time.

The unique feature of the one shot is that at low
frequencies it outputs a narrow pulse, but at high
frequencies (where the pulses 'should' overlap
totally)
it skips pulses... so it works over a wider range than
it really should.

Math is bad.  SPICE ~is~ good for my tummy... 
as long as you can tell when it lies.

If your student wants to play guitar into it, tell him
not to bother.

I can send a copy of the PV-1 pitch to voltage
converter docs to you. Its a circuit I did based on 
Bob Moog's Etherwave P/V converter (used by
permission)

I discuss the ramp/hold and tachometer circuits in it.

H^) harry

--- Aaron Lanterman <lanterma at ece.gatech.edu> wrote:

> 
> 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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