MS20 ESP Simulation (WOW)

[tomg]

Oh No Harry, this thing is for real... and about those waveforms dancing
around it's really REALLY cool to watch.. anyway here is an old mp3
of the esp in action , it's much better than this now.. I crank up a vco
no filter no nothin' and set it on the bench hooked to the P600 (I think)
then mix the two signals. You know it wasn't that bad even then..

http://www.geocities.com/efm_gc/cbook/pics/esp1.mp3

Tom



> I've simulated part of the MS-20 ESP (TomG / Korg) and got a big surprise.
> I'm only looking at the part I didn't understand (re: the converter). The
> first two comparators form a zero crossing detector which fires a positive
> pulse to the converter.
>
> At low frequencies (below about 1.5-2K) the converter froms a one shot
> multivibrator which gives a pulse every input cycle (as I expected...)
>
> Above that, a strange (and wonderful) thing happens. The pulses begin to
> overlap, and the off time (zero) becomes fixed. So you get one, two,
three,
> four cycles of positive level and then a fixed zero...
>
> Not at all what I expected to see. I don't understand yet how it is
> happening... but it seems to work. This extends the range of the scheme
> above where the "tachometer" circuit should fail.
>
> Above 5K the pulses go to a permanent "high" level and the output voltage
> can't rise any further... But that should have happened two octaves ago...
>
> I don't know why the output filter is linked to the "low cut" input
filter.
> Somebody help me out ???
>
> BTW if you got your ears on, JH.... isn't Korg engineering wonderful...
> I wish they hurry up and put the "Empire" out of business !!!
>