[sdiy] Parts ID request

[John Loffink]

> cascaded 90 degree phase shift network,

...should read all pass phase shift network, but you get the idea.

John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com


> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl [mailto:owner-synth-
> diy at dropmix.xs4all.nl] On Behalf Of John Loffink
> Sent: Monday, February 14, 2005 10:24 PM
> To: 'harrybissell'
> Cc: synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] Parts ID request
> 
> Hmmm...I traced out one op amp stage of the rectangular potted can.  It is
> a
> cascaded 90 degree phase shift network, but the normal connection from +
> op
> amp input to resistor to ground instead connects directly to the
> rectangular
> potted can.  18K feedback and negative input resistors, .002 cap to
> positive
> op amp input.
> 
> The potted can is obviously providing a variable resistive element to
> control the corner frequency of the phase shifter.  This could be done
> through switched capacitor techniques, as well as several others.
>