GB1303867A - - Google Patents

Abstract

1303867 Processing audio frequency signals MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 31 March 1970 [27 March 1969] 15263/70 Heading G5J [Also in Divisions H3 and H4] Audio frequency signals, e.g. tone signals in an electronic musical instrument are separated into frequency bands and the higher frequency bands are phase modulated at a sub-audio frequency before being recombined to provide vibrato without undesirable beats in the bass. Alternatively, amplitude modulation may be used. The separated signals in each of the higher frequency bands on leads 82, 83 are separated by coupling means 120, 121 which may be direct connections and modulated with modulation depth increasing with frequency in modulators 122-125 provided with modulating voltages of different phases and frequencies which increase with the input frequency, possibly stepwise. The signals pass via amplifiers 131-136 to speakers 141-146 and/or to a single amplifier 137 and speaker 147 and their combined effect is to produce a vibrato in frequency and amplitude. The input may be connected to an electronic musical instrument or a tape or disc recording. The modulation depth, or modulation frequency versus input frequency curves may be stepped or continuous, Figs. 2, 3 (not shown). The modulators (122- 123), Fig. 4 (not shown), provide signals modulated in opposite phase which are fed to speakers (148; 149) respectively, the speakers also receiving signals from lead (81). In Fig. 6 (not shown), only one modulator (122) is provided, and its output is mixed with an unmodulated signal of the same frequency both of which are fed to speaker (147). The modulators may be delay lines of variable delay characteristics giving a phase deviation characteristic shown in Fig. 9 (not shown) or a transistor may have equal emitter and collector resistors, connected to an output (330), Fig. 12 (not shown), via a variable resistance, and a variable capacitance, respectively, modulation being obtained by varying either the capacity or resistance at modulating frequency, giving the deviation characteristic shown in Fig. 11 a valve, or FET or transformer may be used instead of a transistor, and a variable inductance may be used to obtain modulation. A number of such circuits may be connected in cascade, Fig. 15 (not shown), to increase either the maximum phase deviation, Fig. 17 (not shown), or increase the frequency range over which the deviation is substantial, Fig. 20 (not shown), by suitable choice of time constant of the variable network in each circuit. Variable resistors R, Fig. 12 (not shown), R 1 , R 2 , R 3 , Fig. 15 (not shown), may utilize the Hall effect, or be light sensitive for example made of CdS or CdSe, and illuminated by a lamp supplied with alternating current at modulation frequency, and variable phase, superposed on a direct current to set the mean value of resistance, Fig. 14 (not shown).