Quadra Phaser clone is working!

Don Tillman don at till.com
Thu Jun 26 17:54:25 CEST 1997

   From: Haible Juergen <Juergen.Haible at nbgm.siemens.de>
   Date: Thu, 26 Jun 1997 13:49:33 +0100

   Started this project long ago, but it didn't work right.
   Yesterday I have pulled the circuit out again, found a stupid
   little component value error, and suddenly it works:

Very cool!  A stereo pair of these in a rack mount unit would be such
a wonderful machine.

   Phaser of the ARP Quadra,
   14-stage symmetric transistor ladder all pass circuit,
   compander system built around a CD4007UBE makes it almost noise free.
   I like it very much. I guess it would win the price for the
   most efficient phaser design: only 2 transistors and 2 capacitors
   for each stage !

Two questions:

How noisy is it without the 4007 circuit?

How noisy would it be without the 4007 but with MAT-02's for the
ladder stages?

   BTW: It uses some "1N34A" diodes for signal limiting at high
   resonance. Didn't find these anywhere. Can anybody
   confirm that this would be germanium types ?

Yes, that's the classic germanium diode.  Here in the US Radio Shack
still carries them.

  -- Don

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