[sdiy] Moog ladder & State-variable example lectures up

[Harry Bissell Jr]

The opamp is a differetial amp in this case, so
you amplify the differential (audio) signal and
cancel out the common mode (control) signal.

The "sum with opamp thingy" is the trouble imho :^P

H^) harry

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

> 
> For your watching pleasure, two more mostly
> incoherent lectures:
> 
> users.ece.gatech.edu/~lanterma/ece4803
> 
> 3/15 - state variable VCF examples, Oberheim SEM,
> EML 101 (uses 
> differential integrators, strange circuits), my rant
> about Doepferization, 
> and I also make an ass out of myself at the end of
> the lecture where I try 
> to analyze one of Rene Schmitz's VCAs on the fly and
> get stuck...
> 
> Help! Here's where I got stuck - Check out Rene's
> VCA-2...
> 
> I see the diff pair ladder, which makes me want to
> make the collectors be 
> at opposite voltages, which I then want to sum up
> with an op amp thingy - 
> but looking at the op amp, I apply op amp rules,
> which makes the 
> collectors be at the same voltage.
> 
> So I must be reasoning about that circuit terribly
> wrong...
> 
> 3/27 - Moog ladder! Whoo hoo! Also some handwaving
> about diode ladders and 
> diode rings (Yamaha GX-1, etc)
> 
> The other day I puzzled out the large-signal V/I
> relationship for a GX-1 
> style ring, and came up with
> 
> I = [something with Ic I forget off the top of my
> head] *
>      (sinh(v/vt) / [1 + cosh(v/vt)]
> 
> So it's almost tanh, but it has this extra "1" in
> the denominator...
> I'll write up my derivation when I get time.
> 
> - Aaron
> 
>
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> and Demetrius T. Paris Junior Prof.    Voice: 
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