NEW PCB REVISION: DIP package LM13700s have been replaced with SMD LM13700s due to the DIP package chip going out of production. All other parts are still through hole. If you'd prefer a PCB for a DIP 13700, let me know when ordering, they're still available.
This module is a specialized VCA that can act as a Four-Quadrant Multiplier (sometimes referred to as a "Ring Mod") or as a panner. The main difference between a 4QM and a standard VCA is how it reacts to negative control voltages. A standard VCA will output zero volts, whiles a 4QM will output an inverted signal with voltage proportional to the input voltages.
The board features PC mounted pots for less wiring, and mounting holes for flexibility in panel layout. There are Eurorack and MOTM power connecters. It's compatible with 12V or 15V synth systems without any parts substitutions.
Here is an mp3 demo showing the showing the panner function. A triangle LFO is modulating the pan and I'm adjusting the Offset and Mod knobs to control how deep the panning is.
For complete descriptions of the way the module is used, and how to build it, including schematics and parts list; download this PDF file.
Boards are available now. Price for 1 PCB is $8.
Unfinished eurorack
panels are available for this project, they are 8HP and cost $8 each.
There is
more information here about panels. If you're interested in drilling your own panel for
this project, feel free to use my
drill guide. That image should be printed at 300dpi for proper
scaling.
