[sdiy] Sequencer - "Human Feel"

[Tim Parkhurst]

On 2/6/06, Richard Wentk <richard at skydancer.com> wrote:
> At 21:07 06/02/2006, Tim Parkhurst wrote:
> >Just a quick thought on an old thread (Jan 28th):
> >
> >
> >You should be able to use a triangle wave, a couple of comparators,
> >and a little bit of switching to create a square wave clock where you
> >could vary the position of both the leading edge AND the trailing
> >edge.
> >
> >for the leading edge, another for the trailing edge). If you did this
> >right, you would have pulse position modulation in addition to the
> >familiar pulse width modulation.
> >
> >Any thoughts?
>
> You mean apart from:
>
> >Date: Sat, 28 Jan 2006 20:47:06
> >To: synth-diy <synth-diy at dropmix.xs4all.nl>
> >From: Richard Wentk <richard at skydancer.com>
> >
> >Groove control is pretty easy to do. Master clock is an ascending saw. Use
> >a multiplexed row of pots to drive a comparator. Trigger each step off the
> >rising edge. There's a little bit of extra complexity in making sure the
> >pitch multiplexer switches at the right point, but nothing too frightening.
> >You get full ahead/behind the beat variability with a reasonable hardware
> >count, and no worries about monostables or other messiness.
>
> Richard
>
>

Yeah, that would work too! However, it sounds like the multiplexing
ciruitry could end up being fairly complex. How would that be
implemented? It sounds like you would need to trigger "step" pulses at
varying points along the saw wave, which would involve something like
a 3914 chip (but this wouldn't give control over where the individual
trip points are), or a series of comparators (at least one for each
step). This could end up using several chips, although it would give
you a lot of control over each step, whereas the comparator/triangle
wave clock solution might be better for lead-lag control over longer
periods of time. Simpler circuitry, but a different level of control.
You could also implement pulse position control on a saw wave clock
signal, but doing it with a triangle wave sounds a little easier (you
can use the peak transition on the triangle as the signal to switch
from the 'leading edge' trip level to the 'trailing edge' trip level).


Tim (different level) Servo
--
"Imagination is more important than knowledge." - Albert Einstein