Beat Freqs

From a beat frequency indicator schematic that has floated round the web for years, without the original's CV, pots and XNOR output but with 12 extra gate outputs and many more flashing LEDs. Fed two signals, a ring of four LEDs turns clockwise or anticlockwise depending on which has the higher frequency, faster the further apart they are; at the same frequency a single LED stays lit. In use the gates come in spurts and the rings jerk around: several confident revolutions, then a stutter between two stages, or a shimmer on one spot, at audio and clock rates alike, unpredictable but always putting out useful patterns. The top ring is the main output, the second runs at half its rate, the third jitters across diagonal LEDs, stepping between pairs, and the bottom one runs at a pace like the top's but in bursts. Each ring has its four gate outputs, two on each side; the LEDs shine through the bare board of the panel's four X.

Key features

• IN1 and IN2 in; 16 gate outputs, four beside each ring
• Four rings of four LEDs behind the panel's X
• 8 HP; Nonlinearcircuits publishes no current draw, depth or assembled price (it sells the DIY PCB and panel), and ModularGrid lists none