Bi-pulse convertor (ON-topic)

[Colin Fraser]

I wonder what the effect of using separate modulators for the top and bottom
width would be, with different rates.
Should be thick...

You could do this with a couple of comparators driving a PNP and a NPN
transistor - kind of like of a TTL tri-state output. If the top pulse
comparator is on, pull the output high.
If the low pulse comparator is on, pull the output low, otherwise it sits in
the middle (with a potential divider to set the mid point).
Alternatively, use an analogue switch to select variable voltages for the 3
different wave levels, and modulate those too.

It would take so few parts, it's got to be worth trying...

Colin f


----- Original Message -----
From: "KA4HJH" <ka4hjh at gte.net>
To: <synth-diy at node12b53.a2000.nl>
Sent: Thursday, December 28, 2000 9:19 AM
Subject: Bi-pulse convertor (ON-topic)


> Here's a little project for everybody (and I keep thinking I already saw
> this in ElectroNotes or somewhere but...). This evening I got to fool
> around with the software synth Reaktor and I really like the harmonic
sweep
> you get with the "bi-pulse" oscillator. This is basically a pulse wave
> where the positive and negative halves are generated separately and work
in
> opposition. The top varies from 50% to 1% while the bottom varies from 50%
> to 99%, and vice versa.
>
> The waveforms (converting from a ramp) look something like this:
>
> 0% CV
>
> ----------              +5
>           |
>           |
>           |              G
>           |
>           |
>            ----------   -5
>
> 50% CV
>
> -----                   +5
>      |
>      |
>       ---------          G
>                |
>                |
>                 -----   -5
>
> 75% CV
>
> ---                     +5
>    |
>    |
>     -------------        G
>                  |
>                  |
>                   ---   -5
>
> Sounds like PWM but distinctly different. Should also work with a triangle
> input. Obviously this is a simple quantization problem, which has been
> discussed before. Anyone have a schematic?
>
>
> --
> Terry Bowman, KA4HJH
> "The Mac Doctor"