mini moog clone

[Tony Allgood]

>The Modulation range is *clipped* (as opposed to "limited") to approx.
10% and 90%. So you can overdrive the PWM without modulating out of
range.

This would indeed have an effect on the PWM sound. But I have always
thought that driving the PWM with a heavily clipped triangle wave sounds
not very nice. Certainly a sine wave sounds better to my ears. But I
wonder if the clipping is actually soft enough to turn the modulating
triangle into a sine. I'm guessing here, I don't know what the CS-xx
uses as a LFO in this case. I'm going to try the clipped input and hear
what happens anyway.

I think part of the problem on some machines is that LFO depth is not
related to initial pulse width. Increasing the modulation depth should
also increase the pulse width so that the PWM causes a 'symmetrical'
phasing sound. If you modulate around an initial PW of 50% it does sound
naff. A pulse width changing from 10% to 90% does not sound so good,
since the first half sounds identical to the second half. A sort of
phasing with a rectified LFO input. IMHO richer PWM can be obtained by
modulating around 70% taking the min to 50% and max to 95%. Obviously
lower vales of modulation will lower the inital PW accordingly. If you
just have one pot to adjust PWM depth then it should automatically
adjust PW too. This can be a simple process of adding the PWM depth CV
to the PW input of the VCO.

Regards,

Tony Allgood  Penrith, Cumbria, England

Modular synth circuits, TB303 clone and Filter Rack
www.techrepairs.freeserve.co.uk/projects.htm
My music: www.mp3.com/taklamakan