Motorized Barberpole Phaser (was Re: Another kind of Phasing)

Don Tillman don at
Wed Jan 14 08:20:17 CET 1998

   Date: Tue, 13 Jan 1998 17:36:45 -0800 (PST)
   From: Sean Costello <costello at>

   As far as a barber pole phase shifter, the only way I have heard of is to
   have a Shepard tone generator (a tricky circuit, that) controlling 8 phase
   shifters and 8 VCA's.  

Why 8?

I can see doing a minimal circuit with 2 phase shifters and 2 VCAs
(one PS/VCA has an opportunity to reset in the middle of the other
PS/VCA's cycle).

Or a circuit with 3 phase shifters and 3 VCAs will allow simultaneous
ascending and descending outputs.

   What if you constructed an actual "motorized phase shifter," where the
   amount and speed of the phase shifting is actually constructed by a motor?
   It would be simple enough to do; a very simple implemenation would use 4
   light-dependent resistors and the usual op-amp phase shift stages, where the
   LDR's act as the variable resistors in the circuit.  

Build it with multicolored lights in a translucent box and you've got
yourself one hell of a product!  Then out-there experimental players
will stick their hands inside to hand-modulate the phase shift stages.
Man, it just doesn't get any better than that!  :-)

A "motorized phase shifter" is getting damn close to a Leslie speaker,
isn't it?  :-)

  -- Don

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