Tube phaser

[Don Tillman]

   From: epeasant at telusplanet.net
   Date: Fri, 19 Jan 2001 20:40:34 GMT

   OK, I've checked out the Magnatone circuit, but I was thinking more
   of a multi-stage phaser. 

There are several variations of the Magnatone phase shift circuit for
different amplifier models -- there's a 1-stage unit, a 2-stage unit,
and a dual 2-stage unit where the two pairs are driven 180-degrees out
of phase into stereo power amps.  Pretty cool.

   Now I don't know a lot about these, but would it not be fairly easy
   to implement? I am thinking of a bunch of amplifier stages that
   each invert, or change phase by 180 degrees, and scanning through
   the outputs of each stage sequentially using VCAs driven by
   out-of-phase sine inputs.

   Does this make sense? 

No.  You need some actual phase shifting.  "Inverting" and "changing
phase 180-degrees" are different beasts.  (Ask any sawtooth wave!)

   Is this similar to how the solid-state multistage phasers function?
    Any other thoughts? 

The Magnatone circuit is effectively a tube version of the Univibe
(or to be more historically correct, the Univibe is effectively a
transistor version of the Magnatone circuit).

  -- Don

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