The Magnus phase shifter

[Don Tillman]

   Date: Mon, 18 Sep 2000 02:31:00 +0200
   From: Magnus Danielson <cfmd at swipnet.se>

   http://home.swipnet.se/cfmd/synths/schematics/

Wow, that's a very nice idea.  I like it. 

A couple features I noticed: First, it can do thru-zero frequency PM.
By that I mean if you shift the phase backwards quickly you can
briefly take the frequency negative.

Secondly, you can put a number of these in series to do more than
360-degrees of phase shift.

(Ummm, I'm thinking a couple errors crept into the schematic.  Perhaps
the comparator's input are swapped and the resistor values aren't
quite right.  Also, since the circuit is really dependant on the power
supply voltage it would be a good idea to specify that.  You want the
comparator output transition to exactly compensate for the sawtooth
reset, right?)

This circuit is almost the same as the Chroma sawtooth mix.  

Quick description: The Chroma has a comparator, positive input
grounded, negative input has an equal mix of sawtooth and the PWM
control voltage, and the result is a resistor mix of the comparator
output, the PWM control voltage and the sawtooth.  

But the Chroma mixes in twice as much sawtooth because the goal isn't
a phase shifter but a mix of the original sawtooth and the
phase-shifted sawtooth for a thicker sound.

  -- Don

-- 
Don Tillman
Palo Alto, California, USA
don at till.com
http://www.till.com