| 摘要 |
<p>1406377 Electrophonic musical instrument EMINENT NV 1 March 1973 [3 March 1972] 10085/73 Heading G5J To add chorus effects to an electric organ the audio output 52 is fed to multiple loud-speakers 63, 73, 83 via identical channels 60, 70, 80 with phase modulators 64, 74, 84 supplied from two mixed sinusoidal signals of similar amplitude and having frequencies below 1 Hz and 5-6 Hz. The modulation to each channel is phase shifted through 360 degrees divided by the number of channels, on both modulating frequencies. Modulation is effected via a square ultrasonic pulse train for each channel, frequency modulated via the phase shifting means from the mixed low frequency source. The square waves step MOSFET shift registers, typically of 185 stages, giving 2 ms. delay at 45 kHz stepping frequency. Frequency modulation of this over the range 30-60 kHz varies the delay from 3 to 1À5 ms., giving constant musical interval of modulation on all audio frequencies (i.e. notes). The lowest ultrasonic stepping frequency must exceed twice the maximum audio signal frequency (typically 15 kHz). Outputs from the shift registers are reconverted to musical tones by low pass (20 kHz cut off) filters 61, 71, 81 before amplification 62, 72, 82 and entry to loud-speakers 63, 73, 83 or alternatively to the terminal of a common output channel.</p> |
