Patent GB-1435015-A (GB)
IPC: G10H1/043
Filed: 1973-07-20
Abstract: 1435015 Electrophonic musical instrument NIPPON GAKKI SEIZO KK 20 July 1973 [20 July 1972 5 Sept 1972 (3) 8 Sept 1972 (3) 27 Oct 1972] 34842/73 Heading G5J To add chorus effect and "moving sound image" to an electric musical instrument, sound signals 11 from the instrument are fed to charge coupled "bucket brigade devices" (BBDs) 12A, 12B, 12C introducing variable millisecond time delay. Each BBD retains a sequence of samples of instantaneous sound signal amplitude and steps these samples from one charge-retaining element to the next, over typically 185 in all, sampling and stepping being under the control of clock pulses at ultrasonic (40-120 kHz) frequency from a voltage controlled oscillator (VCO) 17A, 17B, 17C frequency modulated by a control potential. The control signals comprise a fraction of the output from an oscillator 13 at 0À7 Hz and a lesser - fraction of the equal output from an oscillator 14 at 7 Hz; a separate signal is provided to supply the VCO 17A, 17B, 17C of each BBD 12A, 12B, 12C, these signals being made up of oscillator waves successively phase shifted through the same angle 60 degrees at 0À7 and 7 Hz. The outputs from the BBDs are filtered by three successive low pass (15 kHz cut-off) filters to remove clock pulse components, and are passed to an amplifier 18A, 18B, 18C and loud-speakers 19A, 19B, 19C channels separate for each BBD. In a second embodiment included in Fig. 1, cross coupling is introduced between output channels by resistors R31, R32, R33 or by reactive circuits (Fig. 11, not shown). In a third embodiment (Fig. 15, not shown) a third oscillator at 1À4 Hz is provided, only the 7 Hz oscillator being phase shifted successively to all the BBDs, the other control component being unshifted 1À4 Hz or unshifted 0À7 Hz or shifted 0À7 Hz. In a fourth embodiment (Fig. 16, not shown) the 7 Hz oscillator is replaced by a random white noise generator followed by a low pass filter (10 Hz) feeding all BBDs equally, the 0À7 Hz signal component being phase shifted as normal. In a fifth embodiment (Fig. 17, not shown) stated to enhance the stereophonic effect, the sound signal is divided by filters into three bands, upper and middle being delayed by BBDs feeding loud-speaker channels while a third BBD receives mixed upper and middle input and feeds a third output channel into which the undelayed lower band is mixed. Variants on the system include four BBDs, two controlled by 7 Hz and two by 0À7 Hz oscillators, with 180 degree phase shifts, each BBD receiving either upper or middle band, or alternatively the two oscillators are at 7 and 3 Hz, while a third 0À7 Hz oscillator supplies four phase shifted signals added to the control potential to the VCOs. In the latter case, reactive coupling as in the second embodiment is introduced. In a sixth embodiment (Fig. 22, not shown) the multiple BBD array of Fig. 1, but controlled by only a phase shifted 7 Hz oscillator, is preceded by a single BBD controlled by 0À7 Hz oscillation. Alternatively a multiple BBD array may be followed by a single BBD feeding an extra output channel or adding in to the feed of the normal channels. This embodiment may be combined with the fifth, the upper and middle bands being delayed separately by the first BBDs, recombined and re-divided into multiple delay channels in a second array of BBDs. Control frequencies are 14, 7, 4, 0À7 Hz. In a seventh embodiment (Fig. 26, not shown) two sound sources, e.g. organ keyboards, supply two separate BBD arrays having independent pairs of oscillators, outputs being mixed at loud-speaker channels, with a third undelayed source added into one channel. Loud-speakers should be arranged in cyclic order of phase shift to enhance sound image movement; with some loss of desirable effects, some loud-speaker channels may be combined or omitted. The phase shifters modifying oscillator signals may be replaced by independent oscillators, and the oscillators may be replaced (Fig. 14, not shown) by a low frequency (8À4 Hz) divided down from a suitable tone generator in the organ sound source, with further dividers and a ring of three circuit to supply 0À7 Hz phase shifted signals, for combination with the unshifted 8À4 Hz wave. If oscillators with phase shifters are employed, each may be combined with its phase shifters by providing a positive feedback path across an amplifier comprising an inverter and phase shift RC networks to total 180 degrees, with outlets for each VCO.