Patent GB-682503-A (GB)
Title: Electric organ
IPC: G10H5/02
Filed: 1948-03-19
Abstract: 682,503. Electrophonic organs. MARTIN. C. March 19, 1948, No. 8265/48. Addition to 682,501. Class 88 (ii). The electrophonic organ described in the parent Specification is provided with additional features, (i) the, highest or the lowest note of a chord is doubled at a fixed interval therefrom, Fig. 1 and Fig. 2 (not shown). (ii) operation of a control switch enables the swell pedal to control the timbre as well as the intensity, Fig. 3. (iii) percussive effects are produced by charging and discharging a condenser, Fig. 4. (iv) vibrato effects are produced by periodically opening and closing a link in a resistance capacity network by means of a constant speed induction motor Fig. 5. (v) electric switches are provided in manual and pedal actions Fig. 7, 9. (vi) oscillators are screened to avoid coupling, Fig. 6 (not shown). (vii) oscillators are coupled in known manner to keep them in tune. Doubling the highest and lowest notes of a chord. An oscillator comprising thermionic valves 20a, 20b, Fig. 1 is tuned by means of a condenser 21 and inductances 221, 222-22n. The keys of the manual 27 are coupled to switches 231-23n so that the oscillator is tuned to a frequency determined by the extreme right hand key pressed. The inductance may be constant and the capacity may be controlled by the keys so that the note emitted by the oscillator is determined by the extreme left hand key pressed, Fig. 2 (not shown). Swell organ, timbre. The swell pedal controls the moving contact 29 of a potentiometer 28, Fig. 3 between a harmonic selector b and an amplifier e. When switches 33, 33a are closed to include an inductance and capacity in the circuit, both the timbre and the intensity are controlled by the swell pedal. Percussion. An oscillator I is controlled by a keyboard switch 34 and is connected to a harmonic selector 36 and an amplifier 39 over two paths, one through a transformer T and the other through a switch 38. With the switch in position 1, transients caused by operation of the key switch 34 have access to the harmonic selector 31 and give rise to percussion effects. With the switch in position 2, the resistance 37 and condenser 35 delay the rise of anode potential on the oscillator soften the attack and provide a mellow tone. With the switch in position O, the oscillator behaves normally. Vibrato. A resistance 52, Fig. 5 is periodically. connected across a condenser 53 and a desistance 54 in a voltage dividing network by means of a metallic part 47 mounted on an insulated support 48 which is notched at constant speed by an induction motor. The terminals 541, 543 are connected to the positive and negative poles of the HT source and a varying HT is fed to the oscillator from terminal 542. Manual and pedal action switches. A manual key pivoted at 61, Fig. 7 carries flexible metal needles 68 on an insulating member 67. The needles project through metal eyelets 69 and depression of the key causes the needle to interconnect the eyelets and the metallic strips 72 mounted longitudinally of insulating tubes 71. The strips can be moved out of contact by rotating the tubes 71 under the control of links 73, 74. A pedal board comprises an insulating plate 78 mounted on a spring plate 77. Depression of the pedal board brings conducting elements 80, 82 into contact. The oscillators are screened with sheets of iron interleaved with sheets of copper or aluminium.