Another kind of Phasing

Don Tillman don at till.com
Wed Jan 14 01:25:18 CET 1998


   Date: Tue, 13 Jan 1998 15:46:55 -0800 (PST)
   From: Sean Costello <costello at costello.seanet.com>

   At 03:05 PM 1/13/98 -0800, you wrote:

   >I think what's happening here is that you've got a new implementation
   >of a motorized (ie., Shepard tone, barber pole, continuously
   >ascending) phase shifter.

   "Motorized" phase shifter?  Could you explain this term?  I mean,
   is there a device that produces "barber pole" phasing that actually
   USES some little motor, chugging away?  If so, do you have any more
   details?

Sorry, I was being cute.  By "motorized" I simply meant that instead
of a control voltage controlling the amount phase shift, that a
control voltage would control the rate of change of phase shift, and
that the phase shift could increase continuously, as if there were a
motor in between.  (Except for the fact that there's no actual motor,
I think the term is very descriptive.)

A barber pole phase shifter is where you have two or three parallel
phase shift stages, a multi-phase LFO controlling them and an
electronic fader fading between them all to make a phase shifter that
would appear to go up (or down) forever.  The notches travel up in
pitch, and as they get higher they fade out and new notches fade in at
low pitches.

I don't know if anybody has actually built one of these beasts.  I've
always wanted to, it's been one of my dream projects for a while, but
I've never had the time.

  -- Don
  



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