GB1214146A - Improvements in or relating to frequency doubler and coupler for electronic music generation systems - Google Patents

Abstract

1,214,146. Electronic music generator. CHICAGO MUSICAL INSTRUMENT CO. 4 Dec., 1967, No. 55124/67. Heading G5J. [Also in Division H3] In an electronic music generation system, a square wave of frequency f from a source 11, is inverted at 12, and combined in an adder 13, with a sawtooth wave of equal frequency from a synchronized source 10, to give a sawtooth output wave of frequency 2f. In a frequency doubler embodiment (Fig. 3, not shown) equal frequency square waves (11<SP>1</SP>) and sawtooth waves (10<SP>1</SP>) drive tone colour filters (24, 26, respectively) and in addition the square wave is inverted in a unity gain transistorized inverter (12), its peak amplitude halved in an adder (13) and combined with the sawtooth wave (10<SP>1</SP>) to give a sawtooth output wave of frequency 2f, driving a tone colour filter (25). In an octave coupler embodiment (Fig. 4, not shown), the adder (13) includes a switch (43) to open circuit the inverter, and resistors (28, 30) selected to give a mixture of sawtooth waveforms (13<SP>1</SP>, frequency 2f, 10<SP>1</SP>, frequency f). The gain of the inverter circuit (12a, Fig. 5, not shown) may be controlled by a complex signal at an input (51) and the variable gain inverter connected to the square wave source (Fig. 6, not shown) or a variable control comprising a variable voltage controlled amplifier (74, Fig. 7, not shown) may be coupled to the sawtooth generator.