The PAiA 4710 Balanced Modulator can function as a 4 quadrant multiplier with a sum and difference output or as a 2 quadrant multiplier (e.g.  VCA).  The specifications below say the controls are convenient for a VCA or a sine wave doubler.  The banana jacks provide the control input for a VCA but there is nothing to conveniently provide for a frequency doubler.  Normalling the audio to the carrier jack would accomplish this but is not documented in the manual.  This kit was $22.50 in the 1976 catalog.

PAiA 4710 Balanced Modulator User Manual

This particular build used a can style MC1496 IC.

This image shows the PCB traces.

Operation

This scope image shows a frequency doubler.  I used two different frequency sources but tuned them to the same frequency.

This scope image shows a sum and difference with two unequal inputs.

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