[sdiy] schematic

[sbernardi at attbi.com]

A pan circuit it basically two VCA's running off the 
same input signal, but with their control voltages 
inverted and offset so that when one VCA is running at 
maximum the other is at minimum. Using a smooth LFO 
waveform like a triangle will give you a smooth 
transition between left and right; using a square wave 
will give you the "pong" effect.
The circuit at 
http://home.attbi.com/~sbernardi/elec/og2/og3_filterbank_
boost.gif is actually a vc pan circuit. It uses a 
differential pair (Q5 and Q6) to do the current steering 
between the left and right VCA's.
Instead of the DIP switch S1 you would run each OTA 
output into an opamp virtual ground with a 10K resistor 
in the feedback path.
You would still need an LFO. A simple integrator - 
Schmitt trigger type (triangle/square oscillator) would 
work. See 
http://home.attbi.com/~sbernardi/elec/og2/og2_vco_wavesha
per.gif, the PWM section built around U1:C and U4 at the 
bottom.
> 
> 
> Dear experts,
> 
> I am looking for a schematic for stereo ping pong.  What I had in mind is an 
> audio input and then a knob to control the rate of back and forth of the R 
> and L channel.  And then an audio output.  Would this be an easy circuit to 
> design, anyone have any ideas.  Please share.  Thanks.
> 
> -Caleb
> 
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