LM13700 VCAs are used in a configuration identical to that shown in the Nat Semi data sheet that produces minimal distortion. It is not perfect but then VCAs never are. Two VCAs are used in inverse polarity for each of the X and Y multiplier sections to guarantee zero output for zero control current. This ensures that change of control voltage amplitude will only result in increased gain and not an imbalance in the B format signal. (This could happen if one VCA was used as a four quadrant multiplier) The reversible quadrature oscillator from the frequency shifter project is used to provide the sine-cosine control voltages for automatic rotation of the output signal. An X-Y joystick with circular outer restraint is used to provide manual sine-cosine voltages for manual signal rotation.
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Controls and Inputs: Mono to B-format Section
Mono source input 1/4 inch jack unbalanced mono
B format output 5-pin XLR unbalanced
LOG CV input 1/4 inch jack mono
LOG manual control ordinary pot
LIN CV input 1/4 inch jack mono
LIN manual control ordinary pot
Oscillator LOG/LIN switch toggle
Oscillator range switch toggle
Oscillator direction switch toggle
Joystick - oscillator select
Pan-rotate control joystick
Pan-rotate CV input, 1/4 inch jack stereo, shield GND, X control ring, Y control tip, +/- 1V
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