US2913947A - Electric organ control circuit - Google Patents

Description

Nov. 24, 1959 R. F. scHNEEBERGER ETAL 2,913,947

ELECTRIC ORGAN CONTROL CIRCUIT Filed' .July 22, 1953 4 sheets-sheet 1 -anh indNI lndlflO FILTER Nov. 24, 1959 R. F. scHNEEBERGER ET AL 2,913,947

ELECTRIC ORGAN CONTROL CIRCUIT 4 Sheets-Sheet 2 Filed July 22. 1953 jara/a5 @s #fm1/g;

NOV 24, 1959 R. F. scHNEr-:BERGER ETAL 2,913,947

i ELECTRIC ORGAN CONTROL CIRCUIT Filed July 22, 195s 4 sheets-sheet s R. F. scHNl-:EBERGER ETAL 2,913,947

Nov. 24, 1959 ELECTRIC ORGAN CONTROL CIRCUIT 4 sheets-sheet 4 Filed July 22. 1953v I u 000000000OQOQQOQQOGCCCCCANL% United States Patent O 2,913,941 ELECTRIC oRGAN CONTROL CIRCUIT l Application July 22, 1953, Serial No. 369,603 i 1 Claim. (Cl. S11-1.08)

This invention is concerned generally with an electronic organ, and more particularly with the general electronic circuits therefor.

The characteristics of the human ear are such that intermediate and high frequencies are heard relatively well while the bass frequencies are relatively discriminated against. In home use electronic organs often are played at relatively low volume levels. Consequently, the bass notes often are practically lost.

A vibrating reed type of tone generator such as disclosed in Hoschke Patent No. 2,015,014 is generally the most satisfactory type yet developed for use in electronic organs. More natural organ tones can be generated by such reeds than by any other known means. However the bass reeds tend to produce electrical oscillations of somewhat lower magnitude than the higher frequency reeds.

It is an object of this invention to provide, in an elec-A tronic organ, an electronic amplifier having separate treble and Kbass inputs thereby allowing the treble and bass tones generated to be treated differently, particularly in their `relative amplications. l f

A further object of this invention is to provide, in an electronic organ, an amplifier having separateibass and treble amplifying channels with a vibrato or tremulant in the treble channel only, thereby avoiding the annoying effects produced when a low vfrequency is varied at a lower frequency. Y

lt has been noted heretofore that this invention is specifically concerned with an electronic organ having vibrating reed tone generators.r Such tone generators can have polarizing voltages applied tothem constantly, and can be vibrated by means of air blasts whenever it is desired for particular notes to play. As another mode of operation the reeds can be vibrated constantly and can be made to play selectively by applying potentials to them. An organ operating in this manner will hereinafter be referred to as a continuous reed organ. A continuous reed organ has certain advantages in that there is nol time lag in operation caused by the inertia of the reeds. However, the attack and decay must be controlled electrically in order to produce realistic organ tones.

lt is an object of this invention to provide an electronic organ having a plurality of vibrating reeds connected in parallel to an amplifier with a filter connected to each pick-up associated with the reeds to control attack and decay.

Another object of this invention is to provide, in a continuous reed organ, a single power source for the various reeds and pick-ups with isolating resistors interposed between the power source and the various stops or banks of reeds and associated pick-ups to prevent interaction between the various banks or stops of tone gen# erators.

In addition to keyboards or manuals, organs are generally provided with pedal claviers. The tones controlled by the pedal clavier of an organ must have somewhat ,different attack and decay characteristics from the re mainder of the organ tones in order to sound properly. More particularly, the pedal notes must decay relatively slowly.

A further -object of this invention is to provide an electronic organ having similar attack and decay controlling iilters individually connected to all of the reeds and pick-ups, and additional filters connected to the reeds and pick-ups associated with the pedal clavierfor further controlling the attack and decay.

Another object of this invention is to'provide an electronic organ amplifier wherein twin amplifying tubes are used in several instances, with the two halves of each twintube being connected in relatively isolated circuits with substantially no chance of interaction.

A further object of this invention is to provide an electronic organ having key switches and stops electrically grouped together, having filters electrically grouped together, having vibrating reed and associated pick-up tone generators electrically -grouped together, and having the various amplifier parts electrically grouped together, all of the foregoing groups being electrically isolated from one another.

In many installations of electronic organs in homes, it is desirable to have all of the sound emanate fromthe vicinity of the organ console. In other installations it is desirable for all of the sound to emanate from a remote location. Por the best possible tonal effects it is desirable to have the sound emanate from the console and a remote location with balancing of the two sound sources'being under the control of the organist.

It is an object of this invention to provide, in an elecl tronic organ, means for balancing the output between a i and console speaker and a remote speaker without disturbing the power loading of the organ amplifier.

Other and further objects and advantages of the present invention willbe apparent from the following description when taken in connection with the accompanying drawings wherein:

Fig. 1 is a fragmentary perspective view of an organ embodying the principles of the invention;

'Fig 2 is a schematic wiring diagram of the organ amplifier;

"Fig 3-is a schematic diagram showing the disposition of the reeds and pick-ups;

Fig. 4 is a schematic diagram-illustrating the disposition of the filters associated with the reeds and pick-ups; Fig. 4u is a schematic diagram of one of the filters;

, Fig. 5. is a schematic diagram of the key switches and organ stops.

`Referring now in greater particularity to the figures, an electronic organ 20 embodying the principles-of the invention is shown in Fig. 1. The organ 20 includes an organ cabinet `22 having a pair of keyboards 24 and a pedal clavier 26. The organ also includes a swell control pedal 28 and a loudspeaker 30. The tone generators,

v as heretofore mentioned, comprise vibratile reeds and associated pick-ups spaced therefrom, these tone generators being of the general type disclosed in Hoschke Patent No. 2,015,014 and not shown herein. The reeds are vibrated continuously by suitable air pressure means (not shown). The manner in which potential is applied to the reeds and Vassociated pick-ups will be disclosed shortly. -The amplifier for amplifying and controlling the oscillations generated by the reeds and pick-ups will be taken up first.

The organ amplifier wire 40 leads Vthrough a resistor 42 to the grid 44 of an amplier tube 46. The Wire 40 is shunted to ground by a high value resistor 48. The tube 46 is self-biased by means of a ygrounded resistor 50 and capacitor 52 connected in parallel to the cathode 54. The plate 56 is connected through a load resistor 58 and a dropping resistor 60 to a B+ bus or supply line 62. The junction between the resistors S8 and 60 is grounded through a capacitor 64.

The tube 46 preferably is of the 6SQ7 type, and the rectifier plates 66 are connected in parallel and are grounded. The amplier plate 56, besides being connected to the load resistor 58, is connected through a coupling capacitor 66 and a resistor 63 to contact No. 2 of a socket 70 connected tothe swell control.

The treble input 34 also includes a jack 72 having an outer Contact grounded at 74. The inner contact is connected by means of awire 76 and resistor 78 to the grid 80 of a vacuum tube 82, Vthe wire 76 being shunted to ground by a resistor S4 of high value; The cathode 86 of the tube 82 is grounded through a parallel connected capacitor 88 and resistor 90 for self-biasing. vThe two rectifier plates 92 are connected together in parallel and are grounded, while the amplifier plate 94 is connected through load resistors 96 and 98 to the resistor 60 and hence to the B-l- Ibus 62.

The junction between the resistors 96 andV 98 is connected by means of a capacitor 100 and a wire 102 to the grid 104 of a phase inverter tube 106. The phase inverter tube 104 is provided with equal resistors in its plate circuit and cathode circuit, namely the resistor 108 connected between the plate 110 and the BJ,- bus 62,

and the grounded resistor 112. The ungrounded end of i this latter resistor is connected to a junction point 114, and this junction point in turn is connected through a relatively small 'biasing resistor 116 to the cathode 118 of the tube 106. A grid resistor 120 connects the grid 104 to the junction point 114.

The plate 110 `further is connected to a pair of substantially parallel, similar phase shifting circuits respectively comprising resistor 122a and capacitor 124a, and resistor 12217 and capacitor 124b. The resistors 122a and 122b are respectively connected to junction points 126 and 128.- The similar circuits vary somewhat in value to produce different phase shift characteristics. As a specific example, each of the resistors 122e and 122b is 62,000 ohms, the capacitor 124a is .00056 microfarad, A

and the capacitor 124b is .0025 microfarad.

The cathode junction point 114 is connected in parallel to a pair of similar tank circuits comprising resistors 130a and 130b and capacitors 13'2a and 132b. The aforementioned similar tank circuits are grounded through a second pair of similar tank circuits comprising capacitors 134a and 134]), and resistors 136s and 136b, the iirst and second tank circuits being connected by wires 138 and 140. The wires 138 and 140 are respectively connected to the junctions 126 and 128 by means of wires 142 and 144.

The junction 128 is connected by means of a capacitor 146 to the grid 148 of one half of a twin triode mixer tube 150. The other junction 126 is connected by means of a capacitor 152 to the other grid 154 of the mixer 150. The two cathodes 156 and 158 are connected in parallel to a cathode resistor 160 which is grounded at 162. The two plates 164 and 166 of the mixer tube 150 are respectively connected through resistors 168 and 170 to a common resistor 172 which is connected through a decoupling resistor 174 and shunting capacitor 176 to the B+.

bus 62.

The amplifier further is provided with an oscillator tube 178 which preferably comprises one half of a twin triode, for example a 6SL7. The cathode 180 of the oscillator tube is grounded through a parallel connected resistor 182 and capacitor 184. The grid 186 is provided witha grid resistor 188 grounded at 190, `and is provided with a 4 t feed-back circuit comprising capacitors 192, 194, and 196, a resistor 198 connected to ground from the junction between the last two named capacitors, and a wire 200 leading from the capacitor 196 to the plate 202.

The plate 202 is connected through resistors 204 and 206, and smoothing capacitors 208 and 210 to a junction 212. The junction 212 is connected through a resistor 214 and wire 216 to a junction 218, this latter junction in turn being connected by means of a wire 220 to a junction 222. The junction 222 is connected through a resistor 224 and a wire 226 to a B-lsupply line 228.

The plate 202 of the oscillator tube also is connected to a resistor 230, and this resistor is connected to a grounded capacitor 232 and also to a capacitor 234, the latter leading to a voltage divider comprising resistors 236, 238, 240, and 242, these resistors being arranged in series and the last one being grounded at 244. Connectors 246, l248, and 250, are respectively connected on the high side of the resistor 236 and between the resistors 236, 238 and 238, 240. These connectors form parts of a common socket mounted on the ampliiier. A wire 252 connects the junction between the resistors 240, 242 to another one of the contacts 254 of this socket. Another contact 256 of the socket is connected by the wire 258 to the junction between the.feedback capacitors 192 and 194, while two of the remaining socket connectors 260 and 262 are grounded through resistors 264 and 266 respectively.

The remaining socket connector 268 is connected through a wire 270 and resistor 272 to a junction 274. This junction is shunted to ground by a capacitor 276 and is connected through another capacitor 278 to the grid 280 of a phase inverter tube 282. The plate 284 of this phase inverter tube is connected through a resistor 286 to the junction 212, and hence to the B+ supplyv line 228. The cathode 288 is connected through a relatively small biasing resistor 290 to a junction 292, and this junction is grounded through a cathode load resistor 294 equal in value to the plate load resistor 286.

The output from the plate 284 is coupled through a capacitor 296 and a wire 298 to a junction 300. This junction is grounded through a resistor 302 and is also connected through a resistor 304 to the grid 148 of the mixer tube 150. The cathode output of vthe phase inverter 282 is taken from the junction 292 and is coupled by means of a capacitor 306 and a wire 308 to a junction 310. The junction 310 is grounded through a resistor 312 and is connected by means of a resistor 314 to the grid 154v of the mixer 150.

The oscillator tube 178 and Aassociated circuits form a low frequency oscillator 316 for effecting a tremulant or vibrato in the` treble circuit. The frequency of the oscillator 316 is on the order of 6 cycles per second, the exact frequency being determined by a vibrato speed control 318. The depth or effect of the tremulant or vibrato is adjusted by means of a vibrato depth control 320. The vibrato depth and speed controls are mounted on the organ cabinet adjacent the keyboards, while the amplifier is mounted in the bottom of the organ cabinet in a location relatively remote to the vibrato depth and speed controls. Connection from ,these controls to the amplifier is made by the individual wires shortly to be described of a cable running to the contact of a plug 322 cooperable lwith the common socket previously discussed and hereinafter identified by the numeral 324.

The vibrato depth control comprises three fixed contactsf326, 328, and 330 respectively connected by the wires 332, 334, and 336 to contacts 338, 340, and 342 lof the plug 322. These contacts are cooperable with the socket contacts 254, 250, and 248 to pick oli progressively greater portions of the output of the oscillator tube 178.

A movable contact 344 is selectively engageable with the fixed contacts 326, 328, and 330 and is connected through a wire 346 to a pair of parallel connected fixed contacts 348. A blind fixed contactp350 is provided adjacent the contacts 348 and is not connected to anything.

A movable contact 352 is selectively engageable with the contacts 348 and 350 and leads through a wire 354 to a contact 356 of the plug 322.

Fixed contacts are positioned opposite to the fixed contacts 348 and 350 and comprise a pair of contacts 358 connected in parallel to a plug contact 360 engageable with the socket contact 260, yand a contact 362 connected to the plug contact 364 cooperable with the socket contact 262..

A movable contact 366 is ganged with the movable contact 352 by an insulating member indicated at 368, and is connected through a wire 370 to the plug contact 372 cooperable with the socket contact 256, the movable contact 366 controlling the vibrato speed.

The operation of the vibrato will be described in greater detail hereinafter. At present, it will be sufficient to state that the phase shifter tube 106 and associated networks provide similar signals on the grids of the mixer tube 150, these signals being 90 apart over a substantial frequency range, specifically from about 500 to 15,000 cycles per second. The low frequency oscillator 316 acts on the phase inverter tube 282 to produce a pair of similar low frequency signals 180 apart. These signals are applied to the grids of the mixer 150 to control the conduction thereof for first emphasizing one and then the other of the two 90 out of phase signals, i.e. the low frequency oscillator modulates the 90 out of phase signals corresponding to the desired organ tones. This causes the resulting phase to swing back and forth, thereby providing a phase shift tremulant or vibrato. When the vibrato speed control 318 is in the position shown, the vibrato is turned off. In this case both of the 90 out of phase signals have an equal effect and produce a slight reverberation in the tonal output of the organ.

The signal -from the mixer tube 150 is taken from a junction 374 between the resistors 172 and 174 and is applied through a capacitor 376 to the grid 378 of a low frequency filter circuit tube 380, this tube specifically being the other half of the 6SN7 comprising the phase shifter tube 106. Since the two triode sections of this tube handle signals that are very similar to one another, there is substantially no chance of unpleasant tonal effects due to interaction. The grid 378 also is connected to a resistor 382 which is grounded through a capacitor 384, and which at the same time is connected to a resistor 386. 'I'he resistor 386 is connected to a capacitor 388, and this capacitor is connected to a line or a wire 390 leading to the plate 392 of the tube 380. The plate 392 also is connected through a resistor 394 to the junction 222, and hence to the B+ bus line 228. The junction 222 .is grounded by a decoupling capacitor 395.

The cathode 396 is grounded through a self-biasing circuit comprising a parallel connected capacitor 398 and resistor 400. The cathode -396 also is connected by a wire 402 to contact No. 4 of a socket 404 cooperable with a plug later to be described for applying a negative feed-back or bucking voltage to the tone generating reeds to reduce background noise.

The wire 390, besides being connected to the plate 394 and the capacitor 388, is connected to a capacitor 406. This capacitor is connected to a capacitor 408 connected in parallel with a resistor 410. The parallel connected resistor and capacitor also are connected to a resistor 412 which is grounded at 414, and to a capacitor 416, the latter being connected to a resistor 418. The resistor 418 is connected to a junction 420 to which the resistor 68 from the bass input circuit also is connected, thereby combining the bass and treble circuits at that point. The junction 420 is connected by a wire 422 to the second contact of the socket 70.

The socket 70 is cooperable with a plug 424 indicated immediately above it in Fig. 2, and the plug 424 is connected by the wires of a cable to a swell control mounted on the organ cabinet adjacent the swell pedal 28. Pin No. 2 of the plug 424 is connected by a wire 426 of the aforementioned cable to the high side of a potentiometer resistor 428, the low side of this resistor being connected by a wire 430 to pin No. 5 of the plug 424. Contact No. 5 of the socket 70 is grounded as indicated at 432. A part of the lower end of the potentiometer resistor 428 is paralleled or by-passed by a series connected capacitor 434 and resistor 435 for tone compensation. The sliding tap 436 on the potentiometer resistor is connected by means of a wire 438 of :the aforesaid cable to pin No. l of the plug 424.

Contact No. 1 of the socket 70 is connected through a shielded lead 440 to a coupling capacitor 442, and from this capacitor a resistor 444 and wire 446 lead to the grid 448 of a gate tube 450. The gate tube 450 is normally biased substantially to cut olf with no musical tones being generated, thereby preventing the transmission of background noises to the output circuit of the organ. Each time a key or pedal is depressed to play a note, a suitable contact is closed to change the biasing on the tubeA for effecting a relatively high amplification by the tube. It will be understood that substantially greater background noise can be tolerated when one or more tones are being generated as such tones serve to mask or cover background noises.

More specifically, the tube 450 normally is biased for unitary amplification to avoid the key clicks that would be caused if the tube were completely cut off with no tones playing. This is accompanied by cathode biasing of the tube 450. The cathode 452 is grounded through a pair of series connected resistors 454 and 456. These resistors act as .a voltage divider with a resistor 458 which also is connected to the cathode 452 and which is connected to the junction point 218, and thence to the B+ bus 228. v

The grid 448 is grounded through a resistor 460 and is connected through a resistor 462 to an output terminal 464 of a filter circuit 466. The input terminal 468 of the lter is connected to a grounded capacitor 470, and is connected by means of a wire 472 to the sixth terminal of the socket 404. When a key is depressed to play a note, a connection is established between contact No. 6 and contact No. 2 by means later to be described. Contact No. 2 is connected to a wire 474 which leads to a junction 476 and then to a junction 478. The junction 478 is grounded through a resistor 480 and further is connected through a resistor 482 to a wire 484 which leads to a junction 486, the latter being shunted to ground through a capacitor 488 and connected by a resistor 490 to the B-lbus 228. Thus, whenever a key is depressed a positive voltage is applied to the input terminal of the filter and thence to the grid 448 of the gate tube 450 to raise the amplification thereof substantially, specifically to an amplification ratio of 10.

The construction of the filter 466 is such that the input terminal 468 is connected to resistors 492 and 494, the former being connected to the third terminal 496 which is grounded at 498. The resistor 494 is connected to an intermediate junction point 500. A capacitor 502- is connected between the junction 500 and the grounded terminal 496. The point 500 further is connected to the output terminal 464 by means of a resistor 504, and the output terminal 464 is grounded through a capacitor 506. The design of the filter and the circuit constants therein are such as to control the build up and decay of potential on the grid of the gate tube in accordance with the build up and decay of the electrical oscillations generated by the vibrating reeds, thus to insure uniform amplification of the tone oscillations without passing any background noise during silent periods of the organ,

The plate '508 is connected'by a wire 510 to a junction 512. This junction Vis connected to a resistor 514 paralleled by a capacitor 516 'leading tothe wire 484 and hence 'to the B-lbus 288. The wire 484 also leads through a dropping resistor 518 to the first mentioned B-jline 62, the line 62 being at a lower potential than the B-lbus 228.

The plate 508 of the gate tube is coupled through a 4capacitor 520 connected to the junction 512 to the grid 522.l of a phase inverter tube 524. This tube specifically comprises the other half of ythe 6SN7 tube serving as the ,phase inverter tube 282. The plate 526 of the phase inverter ltube 524 is connected through a resistor 528 to the junction 486 and hence to the B-I- bus 228. A resistor 530 equal in size to the resistor 528 is incorporated inthe cathode circuit of Vthe tube 524 and is connected between Va junction 532 and ground as at 534. A small biasing Yresistor 536 is connected between the junction .53,2 and the cathode 538. A grid resistor 540 is connected between the grid 522 and the junction 532. The `equal plate and cathode resistors 528 and 530 afford output signals 180 out of phase with one another at the plate 526 Vand at the junction 532. The plate 526 and junction 532 are respectively coupled through capacitors 541 and 542 to the control grids 544 and 546 of a pair of push- pull output tubes 548 and 550. The suppressor grids 552 and 554 are directly connected to the cathodes 556 and 558, as is conventional, and the cathodes are connected together at a junction 560. This junction is connected through a self-biasing resistor 562 and 564 to ground, this resistor and capacitor being connected in parallel according to conventional practice. The control grids` 544 and 546 are grounded through grid resistors 566 and 568.

The plates 570 and 572 of the push-pull output tubes Aare connected to vthe opposite ends of the primary coil 574 of an output transformer 576. The primary is center tapped at 578, and the center tap is connected by a wire 530 having a junction 582 to the output terminal 584 of a power supply 586. The junction 582 is connected through a dropping resistor 588 and a smoothing shunt capacitor'590 to the aforementioned B+ bus 228 to supply B+ potential to this bus.

The power supply 586 comprises a full wave rectifier tube 592, a specific example of a satisfactory tube being a U4. The two plates 594 of the tube are connected to the opposite ends of the high voltage winding 556- of a power transformer 598. The coil 596 is center tapped at 600, and a wire 602 leads from the center tap to pin No. 2 of the speaker socket 604. A speaker plug 606 cooperates with the socket 604, and pin No. 2 of this plug is directly connected to pin No. 1. Connector No. 1 of the socket 604 is grounded as at 608, the center tap 600 of the high voltage coil thereby being grounded.

The transformer 598 also is provided with a filament winding 610 connected to the filament 612 of the tube 592. The filament also is connected to a wire 614 leading to the previously mentioned junction 584. The juncture 584 is grounded through a smoothing capacitor 616 of high value, and is connected through a resistor 618 to connector No. 5 of the control socket 604, and also through a power supply capacitor 620 to ground. lunction 584 supplies high potential B+ voltage through the wire 580, While .connector No. 5 of the control socket supplies better filtered, and slightly lower potential B-lvoltage to the reeds as hereinafter will be set forth in greater detail. The transformer 598 further is provided with a filament winding 622 parallel connected to all of the filaments 624 heretofore enumerated. The filaments have connected to them in parallel a pair of series resistors 626 and 628 with their junction 630 grounded. The resistors 626 and 628 are of different values, the resistor 626 specifically lbeing 82 ohms and the resistor 8 628 being 180 ohms. The transformer 598 is ,completed by a primary or input winding 632 which is connected through a switch and fuse 634 to a line plug 636. The line plug 636 is plugged into any conventional 110-120 volt outlet when it is desired to play the organ.

The speaker 30 as indicated in Fig. 2 includes a speaker cone 638 and a voice coil 640 connected between pins 1 and 3 of the speaker plug 606. Contact No. 1 of the socket 604 is grounded as previously indicated, and this forms one terminal for the voice coil. The other pin, No. 3, connected to the voice coil cooperates with contact No. 3 of the socket 604. Contact No. 3 is directly connected to contact No. 4, and both of these contacts are connected by means of a wire 642 to the secondary coil 644 of the output transformer 576 as will be set forth hereinafter in greater particularity.

The speaker 30 also includes afield coil 646 having one end connected to the aforementioned grounded pin No. 1 of the plug`606. The field coil 646 also is connected to pin No. 5 of plug 606, and hence to contact No. 5 of the socket 604. Contact No. 5 of the socket 604 is connected through a resistor 648 to the junction 582 on the B+ line 580.

The secondary coil 644 of the output -transformer `576 is grounded at one end as indicated at 648. The other end is connected to a feed-back circuit at 656 comp-rising a wire 652 and a resistor `654 leading to the junction between the resistors 454 and 456 in the cathode circuit of the gate tube 450. The secondary coil 644 also is connected at 650 to a wire 656. The wire 656 is connected to contacts 1 and 2 of a main speaker switch 658, and to contacts 4 and 5 of an auxiliary speaker switch 660. Contact No. 3 of the main speaker switch 658 is connected in parallel with contact No. 3 of the auxiliary speaker switch 660 to a tap 662 on the secondary coil 644 relatively toward the ungrounded end there of. Contact No. 4 ofthe main speaker switch, and contact No. 2 of the auxiliary speaker switch are connected in parallel toa tap 664 substantially at the center of the output coil 644. Contact No. 5 of the main speaker switch and contact No. 1 of the auxiliary speaker switch are open contacts, i.e. they are not connected to anything. A movable switch arm 666 on the main speaker switch is cooperable with the contacts numbered 1 through 5 and is connected to the wire 642. A mov able switch arm 668 of the auxiliary speaker switch is engageable with the live numbered contacts of the auxiliary switch and is ganged for movement with the arm 666 as indicated by the dashed line at 670. The movable arm 668 is connected to one contact 672 of an auxiliary speaker jack 674. The other contact 676 of this jack is grounded. An auxiliary speaker of suitable construction, preferably a permanent magnet speaker, can be connected by a suitable cable and plug to the jack 674 for operation in conjunction rwith the main speaker 30. v

The speaker 30 has an 8 ohm voice coil, and an external or auxiliary speaker tube used with the organ likewise should have an 8 ohm voice coil. The percentage of total output power going to each speaker, and hence the effect of each speaker when an auxiliary speaker is used, is controlled by the main speaker switch 658 and auxiliary speaker switch 660. The two switches are operable together by a screw driver adjustment, and the switches preferably are set at a desired position at the time the organ is installed. However, the switches could be provided with ya control knob readily operable by the organist to control the effect of the speakers as desired. When the two switches are in switch position No. 1, that is the two switch arms y666 and 668 are on the respective fixed contacts numbered l, 100% of the output power goes to the main or console speaker, while none of the output power goes to the auxiliary or external speaker. With the switches in position No. .2,

of the output power 'is allocated to the main speaker,

agisse and 25% to the auxiliary speaker. With the switches in third position the power is divided evenly, 50% going to the main speaker, and 50% to the auxiliary speaker. When the switches are placed in fourth position, 25% of the power goes to the main speaker and 75% to the external speaker. With the switches in position No. all of the output power goes to the auxiliary speaker, and none goes to the main speaker.

The reeds and pick-ups The tone generators of the organ `disclosed herein are, as heretofore mentioned, of the variable capacitor type comprising vibratile reeds and associated pick-up elements. From one to three or more pick-up elements may be associated with each reed, land. these pick-up elements are spaced along the associated or corresponding reed. It will be understood that the reeds are twisted and are bent longitudinally to impart predetermined vibratile characteristics to the reeds. Different parts of a reed shaped in this manner have different modes of vibration, and the pick-up elements associated with each reed are spaced apart so as to cooperate with the parts of the reed vibrating in diferent modes. This allows a single reed to generate tones corresponding to a plurality of organ stops or banks without the necessity of complicated tone shaping circuits.

The reeds are arranged in six different compartments, boxes, or pans as indicated by the dot-dash lines at 678, 680, 682, 684, 686, and 688. The tone of the musical scale to which each reed corresponds is indicated in the boxes beneath the labels Reeds in Fig. 3 along with numbers indicating the order in which the corresponding pedals and keys are laid out in the organ. It will be noted that the lowest octave of reeds is housed in the top center pan, and that musically adjacent reeds are physically spaced apart to prevent interaction among the reeds. All of the reeds of the lowest octave are connected in parallel as indicated by the wire 690, and the reed corresponding to the next lowest tone, indicated as reed C-13 in the bottom center box, is connected to this octave of reeds by a wire 692. A bass reed output wire 694 leads from these 13 parallel connected reeds,

`all of which are controlled by an equal number of foot pedals in the pedal clavier.

The remaining octaves of reeds, five in number, are mounted in the five remaining pans, one octave to a pan. The musically adjacent octaves are, in general, physically spaced apart Ifurther to preclude any interaction among the reeds. The reeds in the pan 678 are connected to the reeds in the pan 684 by a wire 694, and the reeds of the bottom pans 684-688 are connected in parallel by a Wire 696. The reeds of the two right pans 682 and 688 are connected together in parallel by a wire 698, and the wire 698 is connected to a treble output wire 700. In short, the thirteen bass reeds generating tones from 65 to 130 cycles are connected in parallel to the bass output wire 694, while all of the remaining reeds are connected in parallel to the treble output Wire 700. The bass output wire is connected from a junction 702 through a capacitor 704 to a shielded lead 706 having a grounded outer shield 708. This lead is provided with a plug adapted to be inserted in the bass jack 36. The treble output wire 700 is connected from a junction 710 through a capacitor 712 to a shielded lead 714 having a grounded outer shield 716. The lead 714 is provided with -a plug adapted to be inserted in the treble input jack 72. u

The junction 702 on the bass output line 694 is connected through a resistor 718 to a junction 720betvveen a pair of resistors 722 and 724, the latter being grounded at 726. The junction '710 on the treble output line 700 also is connected to the junction 720 by means of a .resistor 728.

The top of the resistor 722 is connected to a sliding tap 730 on a potentiometer '732, one side of which is 75 10 grounded at 734. The other side of the potentiometer is connected to a shielded lead 736 having an external, grounded shield 738. The shielded lead 736 leads to pin No. 4 of a control plug 740 which is adapted to be inserted in the control socket 404 shown in Fig. 2. Contact No. 4 of the control socket is connected to the feedback line 402 leading to the cathode of the low frequency filter stage. A bucking voltage thus is applied via the wire 402, socket 404, plug 740, shielded lead 736, potentiometer 732, 730, resistors 722 and 724, and resistors 718 and 728 to the bass and treble reeds. This bucking voltage, which is adjustable by moving the sliding tap 730, is utilized to balance out background noise.

Pin No. 1 of the plug 740 is connected by means of a wire 742 to the external shield 744 of a shielded lead 746. The external shield 744 is grounded at 748, and since contact No. l of the control socket 404 is grounded, the chassis on which the amplifier is mounted and on which the reeds and pick-up are mounted have a common ground. The shielded lead 746 is connected by means of pin No. 5 of the plug 740 and contact No. 5 of the socket 404 to the power supply for supplying 310 volts B-lpotential to the reeds as will be set forth hereinafter.

Pin No. 2 is connected by a wire 750 to a wire 752, thereby to maintain the wire 752 at a substantially lower positive potential, specifically 60 volts from contact No. 2 of the socket 404. Pin No. 3 of the plug 740 is an open pin, i.e. it is not connected to anything.

Pin No. 6 of the plug 740 is connected by a wire 754 to a wire 756 which is connected to the gate switches associated with the keys. Cooperating contact No. 6 of the socket 404 is connected to the gate tube 450 for changing the bias thereof when one of the gate switches is closed to increase the amplification of the gate tube.

A cable 758 and branch cables 760 and 762 lead, by means of subcables 764, 766, 768, 770, 772, and 774 to the various pick-ups associated with the several reeds. There are 165 output connections in all from the pickups to the filters shortly to be set forth. These connections are numbered the same as the pick-ups which are numbered in Fig. 3. The pick-ups also are coded according to stops to which they correspond. More specilically, pick-ups numbered 1 73 are iiute pick-ups and are identified by the symbol A. The accompaniment pick-ups comprise those numbered 74-109 identified by the symbol l. Pick-ups -152 comprise the trumpet pick-ups and are identified by the symbol n. The remaining pick-ups are the pedal pick-ups numbered 153-165 and identified by the symbol t.

The filter The cable 758 leads to a plurality of filters 776 arranged in four banks as shown in Fig. 4. Each of the filters, las shown in Fig. 4a, comprises a printed circuit having an input at 778, an output at 730, and a grounded connection at 782. A resistor 784 interconnects the input and grounded connection, and a capacitor 786 connects the output and grounded connection. A resistor 788 leads from the input to an intermediate junction 790, and a resistor 792 leads from this junction to the output. The intermediate junction 790 is connected by a capacitor 794 to the grounded connection 782.

One of the filters 776 is shown in dashed lines at the left end of each of the four banks. The input and output connections of all of the filters are indicated by circles containing the numbers corresponding to the filters. For example, the four filters shown in dashed lines have their input and output connections respectively indicated at 1 1, I3- 43, 88-88, and 127-127.

The output connections of the filters are connected individually to the wires of four subcables 796, 798, 800 and 802, thus to connect the filters to the pick-ups. The input connections of the filters 776 are connected to three subcables 804, 806, and 808 leading to a cable 810 which is shielded and grounded at both ends. The wires of this cable lead to the key contacts and are split up into three-branches indicated at SlZ, 814, and 816 in Fig. 4.

The center grounded contacts of the filters are connected kto wires S18, 820, 822, and S24, all of which are connected to a grounded wire 826. The iilters are coded with symbols similar to those used on the pick-ups, but having somewhat diterent signicance as will be set forth more fully with regard to the key switches.

The key switches and organ stops The key switches and organ stops are shown in Fig. 5. The contacts associated with the individual'switches are indicated by circles with numerals in them in accordance with the order of the notes starting with the lowest note and working up to the highest note` lt will be noted that some of the numerals are duplicated, and it will be understood that these key contacts are jumpered from one to another. The key contacts are arranged in organ stops and comprise movable contact members engageable with stop contacts. The stop contacts are indicated at 828 in the upper manual, at 830 in the lower manual, and at 832 in the pedal clavier. All of the upper manual and lower manual stop contacts 823 and S30 are of similar construction and comprise insulating rods S34. These rods, by way of example, may be made of the phenolic composition known as Bakelite The rods 334 extend, in general, completely across the keyboard, although it will be observed that the sixteen foot bassoon stop rod in the upper manual and the eight foot tenor trumpet stop rod in the lower manual are made in two sections. Each o the rods is provided with a longitudinally extending conductive insert 836 in its surface. The rods 834 are rotatably mounted and are rotatable by means of suitable stop controls (not shown) mounted adjacent the keyboards 2d from active position as shown by the tone coloring l3/s foot stop in the upper manual and by the tone coloring 11/3 foot stop in the lower manual to inactive position as shown by the remaining stop rods. When the stop rods are in active or playing position, the conductive inserts 336 are positioned for engagement by the key switches, whereas when they are in inactive or non-playing position, the conductive inserts are'positioned where they will not be engaged by the movable key switches.

All of the vertically aligned movable key switch contacts in the upper manual are actuated by a key corresponding to the note indicated along the top of the upper manual. Similarly, the vertically aligned movable switch contacts in the lower manual are simultaneously actuated by the corresponding keys in the lower manual as indicated along the top of the lower manual. Whether or not a given key switch is operable to cause a tone to 'be produced depends upon whether the associated stop control is in open, playing position or in closed, nonplaying position.

In the pedal clavier indicated at the bottom of Fig. 5 there is only one contact per pedal, and the stop rod 832 consequently is a conductive member which at all times is positioned for engagement by the associated pedal switch when the pedal is depressed.

The previously mentioned high potential or B-lwire 7&6 (Fig. 3) leads to a bus or conductor 83S (Fig. 5) extending adjacent corresponding ends of the stop rods S28, S30, and S32. The bus or conductor supplies potential to all of the stop rod conductors 836 through isolating resistors S40 and chokes 842. The right-hand ends (as shown in Fig. 5) of the sixteen foot bassoon stop rod in the upper manual and the eight foot tenor trumpet stop rod in the lower manual are diderently connected. A voltage divider S44 is connected to the line or conductor 838 at 856 and comprises resistors 848 and S59, the .latter being grounded as at 852. A line 854 :leads from the junction 856 between these two resistors through a resistor 858 and a choke 869 to the l2 sixteen foot bassoon. A similar wire 862 leads from the junction 856 through a resistor S64 and a choke 866 to the eight foot tenor trumpet.

The pedal contact or rod 832 is supplied with voltage from a voltage divider 86S connected to the wire 838 and grounded at 87d. The voltage divider comprises resistors 872, 874, and 876. Taps or contacts 878, 880, and 882 are provided at the high end of each of the resistors of the Voltage divider, and a movable contact 3Std is selectively engageable with these taps and is connected through a wire 886 and resistor 88S to the pedal bar or contact 832. The pedal balance or emphasis of the pedal notes relative to the keyboard notes is controlled according to which of the taps S73, S30 and V382 is engaged by the movable contact 884.

At tie bottom of each vertical row of key switches in the upper manual there is provided a gate switch contact 838 each of which is movable by its associated key into contact with a xed gate contact S9@ extending beneath all of the movable contacts ddd. All of the contacts 888 are connected to a wire 392 (Figs. 5 and 3) leading to the wire 752 (Fig. 3). The fixed contact 890 is connected by a wire 394 (Figs. 5 and 3) to the wire 756 (Fig. 3). Similar movable gate contacts 896 are provided in the lower manual and are connected to the wire 752 by a wire 89S. A iixed gate switch contact 9d@ associated with the lower manual is connected by means of a wire 902 to the wire 756.

The pedals also are provided with gate switch contacts 904, one per pedal, and with a xed gate contact 966 engageable by the movable contacts 934. A wire 903 connects all of the movable pedal gate contacts to the wire 756, while the wire 9i@ connects the fixed pedal gate contact 906 to the wire 752.

Thus, whenever any key or pedal is depressed, the wire S92 is connected to the wire 394 through a corresponding pair of the contacts Sd, 399, or S96, 9%, or 9M., 906. This connection o the wires 392 and 394 connects pins 2 and 6 of the control plug 71A) together, and hence connects contacts 2 and 6 of the control socket 404 together, thereby raising the potential of the control grid 448 of the gate tube 45d to raise the amplication of this tube and thereby to pass oscillations from the tone generators.

The pedal contacts are provided with shaping circuits 912 for controlling the attack and decay of the pedal notes somewhat differently from the remainder of the musical tones. There is one of these circuits Ifor each pedal, and each of the circuits 912 is mounted adjacent one of the movable pedal contacts 914. Each circuit 912 comprises a series connected capacitor 916 and resistor 913 shunting the adjacent contact 914 to ground. The tones to which the respective movable pedal contacts correspond are indicated in Fig. 5.

The movable contacts of the upper manual are connected to the wires of the cable 812, while those of the lower manual are connected to the cable 814, and those of the pedal clavier are connected to the wires of the cable 816. In the lower manual, there are 152 wires from the movable key contacts to the input of the printed circuit lters. These wires are soldered to one Contact on a key Contact block and are arranged in the cable as aforesaid. The other ends of these 152 circuit wires are connected to the input side ofthe printed circuit filters with corresponding numerals and symbols identifying the opposite ends of the same wire.

The 152 wires coming from the key contact blocks are as follows:

In all other rows containing the above numbers and symbols, jumper wires are used between rows. For exam- 13 ple, No. (6) A contact of the horn S row is jumped to No. (6) A of the bass 16 row; In reading the circuits from any row, always matchthe same number and the same symbol to follow the circuit to the input of the printed circuit filter.

In the upper manual, there are 142 wires from the key contacts to the input of the printed circuit filters. These wires are soldered to one end of a key contact block and are neatly arranged in the cable as aforesaid. The other ends of these 142 circuits are wired to the input side of the printed circuit lters. These filters are shown in the upper lleft of the schematic.

The 142 Wires coming from the key'contact blocks are as follows:

Bass 16-ro w 6 to 48 symbol A-total 43 Orch. flute 4-row 49 to 73 symbol A-total 25 Soft flute 8row 79 to 109 symbol total 31 A Bassoon 16-row 110 to 152 symbol -total 43 1-73--symbol A-Flute-total 73 74109-symbol l-Accomp.-total 36 110-152-symbol m-Trumpet-total 43 153-165-symbol Pedal-total 13 Operation Once the organ herein shown and described has been installed, all that is necessary to operate it is to turn on the power switch by a conveniently positioned external switch operator, lever, or knob (not shown) and wait for a short time for the organ to warm up. Suitable organ stop controls (not shown) at the left end of the keyboards 24 are operated by the organist in accordance with the Stops to be played to position the conductive inserts 336 in the stop rods 834 for engagement by the key switches. The key switches preferably comprise hard Nichrome wires while the conductive inserts 836 comprise soft Nichrome wires.

Whenever any key or pedal is depressed, the switches associated therewith contact the stop rods in open position to apply potential to the associated filters 776. These lters control the build up and decay of potential applied to the piek-ups associated with the reeds thereby to control the build up and decay of oscillations so that the resulting organ tones will be substantially indistinguishable from the tones of a pipe organ. All tones are controlled by the filters 776, and the pedal tones additionally are controlled by the filters 912. The build up of potential and of oscillations of the pedal tones is substantially the same as those of the upper and lower manual, but the decay time is Substantially increased to give a strong effect to the pedal tones.

The bass tones from 65 to 130 cycles are applied via the bass output wire 694 (Fig. 3) and the shielded lead 706 to the -bass input 32 (Fig. 2). The treble tones are applied via the treble output wires 700 (Fig. 3) and the shielded lead 714 to the treble input 34. The bass input has a higher amplification than the treble input in order to compensate for the frequency characteristics of the human ear and of the vibrating reed tone generators.

The treble input is converted into two signals 180 apart by the phase shifting tube 106 and associated plate and cathode resistors 108 and 112. These out of phase signals are converted into signals which are substantially '14 A apart and which are applied to the grids 148 and 154 ofthe mixer tube 150.

The manner in which the 90 out of phase signals are developed has been worked out mathematically and can be explained in this manner. However, the operation can be set forth generally in simpler terms which are readily understood. Referring first to the phase shifting network having the a suffixes, the capacitors 12411 and 132:1 have practically infinite impedance at the lowest frequencies and the oscillations are transmitted ene tirely by the resistance e. At higher frequencies, capacitor 124s passes the oscillations more freely than the resistance 130e, and a phase shift progressively increasing in frequency to 180 takes place in the voltage between the terminal and junction 126 and ground. On a further increase in frequency the impedance of capacitor 124:1 becomes low relative to that of resistance 122:1 and the latter controls the transmission through this branch. At still higher frequencies the impedance of capacitor 132e gradually reduces and this condenser nally passes oscillations more freely than resistance 122a, thereby producing a further 180 phase shift. Thus as the frequency varies from the low end of the range to the high end a complete 360 phase shift takes place in the voltage between the output terminal or junction 126 and ground.

The operation of the phase shifting network having the b suffixes is similar, except that the circuit values are somewhat different so that the signal appearing at the terminal 128 will be 90 out of phase with the signal appearing at the terminal 126 throughout the range, the components being chosen so that this range extends from 500 to 15,000 cycles.

In the range above 15,000 cycles per second the phase difference becomes less than 90, but this is of relatively little importance as the percentage change is very small and few people can detect much sound above 16,000 cycles per second. Below 500 cycles per second the phase shift also is less than 90, varying substantially in proportion to the frequency of the tone generator. This is important as in this low frequency range the phase shift must be substantially proportional to frequency to produce a satisfactory impression on the ear.

The output of the mixer is combined in the common load resistor 172. When the vibrato or tremulant is turned off, the two 90 out of phase signals determine the output equally. This results in a slight reverberation in the tonal output closely resembing the reverberation associated with a pipe organ installation.

When the oscillator 316 is turned on by moving a suitable control (not shown) to the left of the keyboards 24 to move the movable contact 352 from the open contact 350 to one of the fixed contacts 348, the oscillator oscillates at a frequency determined in accordance with which of the fixed contacts 358, 362 is engaged by the movable tap 366. In position No. 1 of the switch with the movable contact 366 engaging the right-hand one of -the contacts 358, the frequency of the oscillator is approximately 5.7 c.p.s. With this movable contact in engagement with fixed contact 362 the frequency of oscillation is approximately 6.7 c.p.s.

The oscillation signal is applied to the phase inverter 282 at a magnitude determined by which one of the fixed switch contacts 326, 328, or 330 is engaged by the movable contact 344 of -the vibration depth control, this control (not shown) being mounted on the organ cabinet to the left of the keyboards 24. The two outputs of the phase inverter tube 232 are connected to the grids 148 and 154 and control the relative conduction of the two halves of the tube, first relatively emphasizing one of the 90 out of phase signals, and then the other. This results in a shifting back and forth of the phase and produces a phase shift vibrato or tremulant which is most pleasing to the human ear.

The output of the mixer is fed to the low frequency filter 'feed-back `tube 380, which in conjunction with the circuits to which it is connected cuts cti in response sharply below 130 c.p.s. This yprevents the low frequency oscillations of the yoscillator from appearing in the out-put of the organ. The wire 402 leading from the cathode of the tube 380 also applies Va backing voltage to the reeds as aforesaid to reduce background noise.

The -t-reble and bass outputs areicombined at the junction 420 and are applied via the socket 70 and the plug 424 to the swell control which returns the signal via the same plug and socket to the grid of the gate tube 45t?. This tube normally is biased to have a unitary amplification so as to prevent the passage of background noises when -no tones are being generated, but the organ is turned on. When any of the keys or pedals is depressed, one of the parallel connected gate switches is closed as heretofore discussed to raise the potential of the grid 448 and thereby to increase the amplification substantially, for instance to 10.

The output from the gate tube is applied to the phase shifter tube 424 to produce, in conjunction with the plate resistor 528 and cathode resistor 530, two signals 180 out of phase for `driving the push- pull output tubes 548 and 550.

The output of the push-pull tubes is applied to the output transformer 576 in accordance With conventional practice. Conventional practice leaves off with the transformer, however. The output of the transformer is connected via the main speaker switch 658 to the main speaker and via the auxiliary speaker switch 660 to the auxiliary speaker jack 674 for distributing the output of the organ between the main speaker and an auxiliary speaker without reacting upon the organ amplier.

It now will be apparent that a new and improved electronic organ has been disclosed, and that the objects of the invention have been met. Various changes in structure can be made without departing from the spirit and scope ofthe invention as expressed in the following claim.

The invention is hereby claimed as follows:

An electronic musical instrument comprising bass ampliiier means, treble amplifier means, combining amplifier means, means operatively connecting said bass amplilier means and said treble amplilier means to said combining ampliiier means, electro-acoustic transducing means connected to said combining amplier means for converting electrical oscillations to audible tones, a plu rality of continuously wind-blown vibratile reeds including a plurality of bass reeds and a plurality of treble reeds, said plurality of bass reeds being electrically connected in parallel with one another to said bass amplifier means, said plurality of treble reeds being electrically connected inl parallel with one another to said treble ampliiier means, a plurality of pick-up elements capacitively associated respectively with said reeds, electric potential supplying means, a plurality of key switch means respectively connected to said potential supplying 16 means, a plurality of filters respectively connected bei tween said -key switch means and-said pickup elements for controlling the build up and decay of potential -on said elements 'for controlling the attack and deca-y yof musical tones produced by said instrument, means connected vto said .treble amplier means and to said reeds for applying a negative feedback bucking voltage :from

onlysaid treble 'amplifier means to .all of said reeds for reducing background noise caused by wind-developed static charges on said reeds and pickup elements, Va subaudio low frequency oscillator, said treble amplier means including a phase shifting electronic valve and` phase shifting network to which said low frequency oscillator is connected to produce a phase shift vibrato in the electrical oscillations generated by the treble reeds and associated pickups, said treble amplifier means having a low frequency cut off filter preventing passage of the oscillations of the low frequency oscillator, a gate circuit in'said combining amplifier means including electronic valve means normally substantially cut olf when no potential is applied to said pickup elements by said key switch means, and means connected to said key switch means for increasing the amplication of said last mentioned electronic valve means when any of said key switch means is operated to apply potential to any of said pickup elements.

References Cited in the iile of this patent UNTTED STATES PATENTS Re. 22,321 Fisher May 25, 1943 1,295,691 Cahill Feb. 25, 1919 1,877,317 Hitchcock Sept. 13, 1932 1,901,985 Ranger Mar. 21, 1933 2,048,900 Usselman July 28, 1936 2,187,611 Miessner Jan. 16, 1940 2,246,855 Miessner lune 24, 1941 2,276,390 Hanert Mar. 17, 1942 2,382,413 Hanert Aug. 14, 1945 2,403,090 Larsen July 2, 1946 2,463,597 Cahill Mar. 8, 1949 2,471,534 Muth et al May 31, 1949 2,485,538 Rowe Oct. 18, .1949 2,534,342 Daniel Dec. 19, 1950 2,542,065 Wye Feb. 20, 1951 2,579,358 Boum Dec. 18, 1951 2,583,566 Hanert Jan. 29, 1952 2,601,218 Zuck June 17, 1952 2,623,996 Gray Dec. 30, 1952 2,639,639 Schmidt May 26, 1953 FOREIGN PATENTS 613,416 Great Britain Nov. 29, 1948 1,000,922 France Oct. 17, 1951 OTHER REFERENCES Publication: Radio Engineering, by Terman, 3rd ed., page 313. t

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