P5 mod, AW: Re: CS-50 !!

[Haible_Juergen#Tel2743]

> Looking at the schems, the way the resistors and capacitors surronding
> the filter chips are connected, I'd almost swear it's two 2-pole
> state variables in cascade.

Yes, I think you are right, checked again last night.

Now this whole CS-50 thing made me think of an easy way to
implement sine shaped PWM on one of my polysynths.
(The JH-4 will have it, but I think it's a long way till this
one is finished!)
Unfortunately, the OB-8 is not the right one, here. :-(
Would have been nice, because on the CS-50 the deep PWM
in combination with rotational voice assignment was real killer.
(repeat the same note, and voices are layered on this note ...)
But now I'd rather go modding the Prophet.

Changing the LFO triangle waveform to sine would be easy:

Replace the 160k resistor between triangle level shift opamp
output and noise/lfo mix ota with a 91k and 12k series combination,
and connect two diodes to gnd (antiparallel) to form a "T"
circuit.
(Only done simulation so far, but should be easy).

Other ideas: When none of the three LFO waveform buttons is
switched on, no LFO output is produced. This is not of much use,
as you can turn off the LFO with the mod wheel anyway.
So I could easily detect this state (all three switches off), and
switch to sine wave. So I could have it as an option.
The same thing would work for the VCO's, btw. Would be nice
to have a sine here, too. Or maybe an inverted saw wave,
which is good to simulate thru-zero-PWM.

Guess I have a lot of things to solder on the weekend!

JH.