[sdiy] Parts ID request

[Harry Bissell Jr]

If its switched capacitor it will have a clock.
It would also have anti-alias filters (well it
should :^).

If you suppose its an LED-Photoconductive cell, there
should be an obvious drive for the LED... and you
could meter across it and prove that (might need to
use the voltage drop, depends on your meter...)

I don't think switched capacitor filters became
popular
until the integrated chips. You might switch with FETs
perhaps...  but why pot that kind of module ?

H^) harry


--- John Loffink <jloffink at austin.rr.com> wrote:

> > 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.
> > 
> 
> 
> 
>