Low octave switch - extended range with a monoflop

7-42 — elektor july/august 1982 D1 1N4148 1. R1 R3 1N4148 N1 ... N4 = IC1 = 4011 A = from master oscillator B = to top octave generator 82588 bigIT° /1 ow extended range with a monoflop 5 ... 15 V The limited five octave range of many electronic piano"s and organs can be extended by one octave lower with the aid of the circuit here. It is con- nected between the main oscillator (input point A) and the highest octave generator (output point B). A monoflop is constructed with N1, N2, C1, P1 and R4. Its time period is set by P1 so that the monoflop divides the frequency of the main oscillator by two, switch S1 provides the ability to switch between the original tone range and the extra lowered tone range. The diodes D1 and D2 protect the input against high level and negative input signals. The value of C1 depends on the frequency of the main oscillator, but can be found quite easily after some experimenting; the frequency of the piano or organ will suddenly be lowered by one octav...