US3443017A

US3443017A - Electronic organ system

Info

Publication number: US3443017A
Application number: US511037A
Authority: US
Inventors: Edward M Jones
Original assignee: DH Baldwin Co
Current assignee: BPO ACQUISITION CORP; Baldwin Piano and Organ Co; DH Baldwin Co
Priority date: 1965-12-02
Filing date: 1965-12-02
Publication date: 1969-05-06
Anticipated expiration: 1986-05-06

Description

MASTER 056.

y 1969 E. M. JONES 3,443,017

I ELECTRONIC ORGAN SYSTEM Filed Dec. 2, 1965 7 Sheet I of s ll6 Sl4|5|2H 119 118 INVENTOR EDuJARD M. JONES BY d [2071.

ATTORNEYS y 1969 E. M. JONES 3,443,017

ELECTRONIC ORGAN SYSTEM Filed Dec. 2, 1965 Sheet 2 of 3 SQUARE UJAVE I 65 e f? BL 4 SQUARE OUTPUT op q R R2 "c LUAVE PREVIOUS STAGE 20o OUTPUT D.C. 201- AMPLH IER LLHTH $16.2 VOLTAGE 2 CURRENT 2 emu i DIQZ' SALUTOOTH OUTPUT a & oEo

REFERENCE POTENTIAL 145V F1 fiv 4.1K

M J 311 cge lmo I f (SK 2 310 e4 SQUARE U A ma, 5 321 9M, 3i4 OUT PUT smee 301 202 c 'sv L 306 9 WWUT INVENTOR EDLUARDMJONES ATTORNEYS ay 6, 1969 E. M. JONES 3,443,017

ELECTRONI C ORGAN SYSTEM Filed Dec. 2, 1965 I Sheet 3 of 3 G, +J6v 404 Q AOOu-wf 3 H 0 we? SQUARE OUTPQT wAvE OUTPUT OP PREV. STAGE OUTPUT a 5 r 1 2 5 4 s *7 7 TV 346 t? V-A W INVENTOR I EDLUARD MJoNEs I ATTORNEYS United States Patent 3,443,017 ELECTRONIC ORGAN SYSTEM Edward M. Jones, Cincinnati, Ohio, assignor to D. H. Baldwin Company, Cincinnati, Ohio, a corporation of Ohio Filed Dec. 2, 1965, Ser. No. 511,037 Int. Cl. Gl0h 1/00 US. Cl. 84--1.01 12 Claims ABSTRACT OF THE DISCLOSURE An electronic organ employing an array of nineteen master oscillators from each of which are derived tone signals by means of divide-*by-three circuits arranged to provide both square and sawtooth waves.

It has heretofore been the usual practice to generate organ tones from an array of twelve master oscillators, by divide-by-two divider chains, so that twelve divider chains are available, each of which provides tones of one nomenclature. The tones provided by a divider chain are then precisely octavely related, and are locked to each other in phase. In order to provide celeste effects, two or more sets of tone generators, mutually detuned, are usually utilized.

Where tones are generated by divide-by-three circuits, each chain provides an array of tones which are of different nomenclature, and the total array of tones is such that octavely related tones are not precisely related in frequency, nor are they locked in phase. Octaves are stretched in frequency, as in a piano. Fifths are out of tune, but not quite as much as in the tempered state. Twelfths are tuned to zero beat. By throwing some of the master oscillators sharp and some fiat all the octaves can be thrown out of tune to desired extents, and rapid beats can be obtained when various footages are played together, giving a celeste-type effect. This is not a true celeste, as usually understood, because in the true celeste stops of the same footage are out of tune.

In an organ of the type above described, square waves cannot be obtained from outphased addition of sawtooth waves, nor can sawtooth waves be synchronized by addition of square waves, because all octaves are out of tune. Yet both square wave and sawtooth waveforms are required, to provide a full complement of tone colors. It is a feature of the present invention to provide a divide-bythree organ in which the divide-by-three circuitry generates both sawtooth and square waveforms, on separate terminals, so that these can be collected by separate key switches, for application to separate tone color circuits.

It is a further object of the invention to provide a novel divide-by-three circuit, directly capable of producing square waves in response to square waves, and also capable of providing sawtooth waves.

It is another object of the invention to provide a divideby-three circuit capable of providing square wave output in response to square wave input, and which shall utilize a minimum of circuitry composed of conventional low cost components, in order to minimize cost per divider.

It is a further object of the invention to provide a divide-bythree circuit responsive to square wave input and providing both square wave and ramp wave output.

Another object of the invention resides in the provision of a square wave to square wave divide-by-three circuit capable of being tuned by a single condenser.

While divide-by-three circuits of wide variety can be devised, it is undesirable from a cost viewpoint, that diodes be utilized in producing sawtooth voltages from square wave voltages. It is one feature of the invention to avoid inclusion of diodes by utilizing the rectifying effect available at emitters of semiconductor amplifiers.

A more important feature of the invention involves the provision of a divide-by-three which requires only one tuning capacitor per stage, with positive lock on of both halves of the divided wave from the input wave, so that dividers operative over the entire gamut of tones can be nearly identical, while operation from stage to stage is positively locked.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a block diagram of a divide-by-three organ according to the invention;

FIGURE 2 is a generalized circuit diagram of a divide by-three circuit according to the invention, including a high gain amplifier illustrated in block form;

FIGURES 3, 4, 5 are circuit diagrams of amplifiers suitable for inclusion in the circuit of FIGURE 2;

FIGURE 6 is a schematic circuit diagram of a frequency divider according to the invention, utilizing two transistors of opposite type;

FIGURE 7 is a schematic circuit diagram of a frequency divider according to the invention, utilizing two transistors of the same type; and

FIGURE 8 is a series of plots of waveforms occurring in each divide-by-three stage of the invention, and pertaining to FIGURES 2-7, inclusive.

Referring now to FIGURE 1 of the drawings, ninetyseven (97) tone sources are illustrated, each in block form, #1 being the source of lowest frequency and #97 the source of highest frequency. Source #1 is C and source #97 is C Sources 9779, inclusive, are master oscillators, representing notes C9 to F#7, and provide square wave outputs. Some of the sources 97-79, inclusive, are frequently controlled by voltages, +E and E, supplied at

terminals

100, 101. Potentiometers 102, 103 extend from

terminals

100, 101 to ground, and

sliders

104, 105 are connected to celeste control knobs 106. 106 may be a single knob for joint control. Lead 107 extends from slider 104 to

sources

80, 83, 88, 91, 94, 97. Lead 108 extends from slider 105 to

sources

81, 84, 86, 89, 92, 95, as exemplary connections.

What can then be accomplished by knob 106 is to throw some of the sources sharp and some fiat, while some are unaffected, if desired, so that all the octaves can be thrown selectively or adjustably out of tune. Thereby rapid beats can be obtained when various footages are played together, giving a celeste-type effect.

Master oscillator 97 controls a divide-by-three

chain including sources

78, 59, 40, 21, 2. It will be noted that this chain includes no sources of the same nomenclature. Additional divider chains proceed from each of the master oscillators, so as to produce the required gamut of tones, from #1 to #97. Obviously, the total number of notes in a given organ involves a matter of choice. Master oscillators 97-79, inclusive, are provided only with square wave outputs. Master oscillators 85-79 are provided with key switches, 110, 111 operated by one key. Key switch 111 leads to bus 112, which supplies four-foot sawtooth tone color circuits, while key switch 110 leads to bus 113, which supplies four-foot square wave tone color circuits. In general, sawtooth tone color filters are supplied only with sawtooth waves, but in the case of master oscillator notes, this is not necessary. A third switch not shown would provide two-foot tones from oscillator 85 from a key an octave below.

Each of the sources #7 8-#1 is provided with two outputs, as 501, 502. Output 501 is a sawtooth signal, which, passing through key switches, as 115, leads to sawtooth tone color circuits, as 118, and output 502 is a square wave signal which, passing through key switches such as 116, leads to square wave tone color circuits, as 119. A typical organ may include 2 square wave, 4 square wave, 8' square wave, 16' square wave, 4' sawtooth, 8' sawtooth and 16' sawtooth tone color circuits on two or more manuals and pedals, so there are many more key switches than are illustrated in FIGURE 1, which only shows key switches for the lowest and highest notes on one manual.

Referring now to FIGURES 2 and 8 of the accom panying drawings, there is illustrated generally a divideby-three circuit which accepts square wave inputs and provides square wave outputs, but which also produces sawtooth outputs. The circuit of FIGURE 2 utilizes a DC amplifier A having voltage and current gain very much greater than plus 1, and preferably of about 100. Such amplifiers, when provided with feedback, can be bistable, i.e., if an input signal is inserted, of sufficient amplitude, feedback drives the amplifier to saturation and holds the amplifier in the condition demanded by the signal. A signal in the opposite sense, then, can overcome the feedback signal and reduce the amplifier to a zero output. The amplifier accordingly has two stable states, which may be denominated and 1.

Input to the amplifier is supplied from circuit input terminal 200 to amplifier input 201 via differentiating circuit composed of capacitor C and resistance R The output terminal 202 of the amplifier is then connected back to the input terminal via a capacitor C and a resistance R in series, so that feedback derives from the junction of R and R A resistance R, is connected directly between input and output. R is not essential, but provides a primary advantage in that it improves tolerances of operation, prevents transfer of state without triggering action, and provides stable triggering points. The amplifier may need a bias current at its input, assuming transistor amplifier elements, which is midway between the two currents in R representing the two states of the amplifier, and such that the amplifier has a low impedance for one polarity of signal. A diode D connected between input 201 and a reference point provides a low impedance for the other polarity of input current.

In response to a square wave e triggers are derived by differentiation by C to provide the waveform e As suming that at a given time t the feedback via C is low, the output of the amplifier will assume the positive or 1 state, as at t waveform e The amplifier is then maintained in its 1 state both by feedback via R and via C The next negative trigger at 1' cannot overcome the two feedbacks, so that the amplifier remains in its 1 state. The trigger e at time t has no effect because it is of the wrong polarity. The current through C has been subsiding, but R holds the amplifier in its 1 state. The next trigger at time 12,, is sufficient to overcome the amplifier bias, which now derives primarily from R and the amplifier will transfer to its zero state. Again, feedback via C prevents the next positive trigger, at t from transferring state, but at t that feedback has decreased sufiiciently to permit transfer. The result is the generation of waveform e Feedback from the output of the amplifier is differentiated by C to produce a voltage e across R During the negative portion of the cycle the voltage divider R R produces a voltage e across R in series with D, 2;, approximating a sawtooth of the same frequency as pertains to 6 On the assumption that the amplifier A is transistorized, and for the diode D polarity illustrated, it should have low input impedance for negative signals. If low input exists, instead, for positive signals, diode D should be reversed.

Suitable component values for the circuit of FIGURE 2 are, for operation at c.p.s.,

R 1K E volt -.4 R 10K R 22K R 22K C .001 C .12

Suitable configurations of transistors for use in amplifiers A are illustrated in FIGURES 3, 4, 5.

In FIGURE 3, use is made of an NPNP type transistor 220, the [i of the PNP section of the transistor 220 being at least 100. Operation is according to the description of FIGURE 2. Positive supply voltage, at terminal 221 is applied via a 1K load resistance 222 for the output collector. The input supply voltage is 15 v. applied ".0 terminal 223 and resistance 224 of 47K separates the terminal 223 from the input terminal 225. Waveform e appears at terminal 225 and waveform e.; at terminal 226.

In FIGURE 4 is illustrated an amplifier utilizing an NPN transistor 230 connected to drive a PNP transistor 231. The system of FIGURES 2 and 3 are therefore analogous. Signal input e is applied to terminal 225, and output e derived from terminal 226. Terminal 225 is supplied with negative bias voltage 15 v. from supply terminal 230 via a resistance 224 (47K). Terminal 225 is directly connected to the emitter of transistor 230, while the base of that transmitter is directly connected to a reference potential source E which may be slightly below ground, if desired. The reference source E is directly connected to the collector of transistor 231, while the base of transistor 231 is directly connected to the collector of transistor 230, output deriving from the emitter of transistor 231. Transistor 231 is thus emitter loaded, and. is provided with a drive signal from transistor 230.

In FIGURE 3, two

PNP transistors

240, 241 are employed, each having a 13 20. Both

transistors

240 and 241 have emitters connected directly to reference voltage E Input signal is applied to the base of transistor 240, which has a collector load 242 (10K) connected to a negative terminal 244 (-15 v.). The collector of transistor 240 is directly connected to the base of transistor 241 and the collector of 241 is loaded by resistance 24S (1K). The output terminal 226- derives from the collector of transistor 241.

The systems of FIGURES 2, 3, 4, 5 employ diodes in order to derive sawtooth waveforms. Instead, the systems of FIGURES 6 and 7 rely on the rectifying effect of the emitter of the first transistor of the amplifier A to provide the required sawtooth waveform. The emitter resistor makes the input impedance of this first transistor become sufliciently high in value not to seriously shunt its base resistor and as a result, the generated sawtooth is, at the base of the transistor, symmetrical. The rectifying action then produces a sawtooth of the proper period, i.e., coextensive with the accompanying square wave from the symmetrical sawtooth wave at the base. Further, the system of FIGURE 7 has the advantage of utilizing only one type of transistor, although special biasing is required to keep the first transistor, of the pair of transistors included in the amplifier, from saturating and having a low impedance, and also to provide symmetrical triggering conditions.

The system of FIGURE 6, on the other hand, requires a minimum of supply and bias voltages, essentially one.

In FIGURE 6, a square wave e may be applied to input terminal 200. A capacitor 300 (100 /.L/l.f.) and a resistance 301 (47K) are connected in series with each other and between terminal 300 and the base 302 of the NPN transistor 303, having an emitter 304 and a collector 305. A reference voltage bus 306 is provided, at 0.9 v. although this bus may, in principle, be grounded. A bias resistance 307 (4.7K) is connected between base 302 and bus 306, and a load resistance 308 (4700) is connected between emitter 304 and bus 306.

The collector 305 is directly connected to the base 310 of a PNP transistor 311. The emitter 312 of transistor 311 is directly connected to a positive supply terminal 313, and the collector 314 is connected directly to output terminal 202, a load resistance 315 (1K) being connected between output terminal 202 and reference bus 306.

An AC feedback path composed of series capacitor 320 and resistance 321 extends between output terminal 202 and base 303. A DC feedback path composed of resistance 322 parallels the AC path, and corresponds in function and modes of operation to R FIGURE 2, its value being selected according to the principles of the invention explained in describing the circuit of FIGURE 2.

The operation of the system of FIGURE 6 corresponds with the operation of the system of FIGURE 2, generally, the primary distinction residing in that sawtooth waveform can be derived from emitter 304, i.e., across load resistance 308, relying on the rectifying properties of the emitter 304. The system'can be tuned by variation of capacitor 320 alone, which greatly reduces problems of mass production and tuning of the divider chains of electric organs.

In FIGURE 6, the impedance of the base-emitter circuit becomes sufiiciently high that the resistance 307 is not seriously shunted. Thereby, the input impedance of the system, as seen at input terminal 200, and the input impedance, also, as seen by the feedback loops, are essentially the same in both half cycles of the output waveform. This implies that the time constant of the sawtooth wave a (see FIGURE 9) at base 302, is nearly the same for both half cycles. The pips 340 on each of waveforms 2 and e derive from differentiation of the input waves.

The bus 306 is maintained at .9 v. to provide a zero DC component for the sawtooth output, and its value therefore is selected according to the average value of the DC component. Apart from this consideration, bus 306 could be grounded.

The system of FIGURE 7 corresponds with the system of FIGURE 5, in principle, except in that two

NPN transistors

400, 401 are employed, and that sawtooth waveform e;, is derived directly from the emitter of transistor 400, as in FIGURE 6. Separate

bias voltage sources

403, 404 are required for the

transistors

400, 401, and a considerable number of distinct bias sources, to keep transistor 400 operating out of saturation, in a high impedance region and to provide symmetrical triggering conditions for the two half cycles of the signals e Clearly, a wide variety of specific transistor amplifiers can be employed, within the broad principles of the invention as indicated in FIGURE 2, which are defined by the appended claims.

What I claim is:

1. A tone generator for an electric organ,

said tone generator including an array of master oscillators arranged to have frequencies in accordance with notes of the musical scale and encompassing at least one octave of such notes and having square wave output waveforms,

a plurality of divide by three divider chains arranged to provide square wave output waveforms in response to square wave input waveforms,

each of said divider chains having an input circuit and a plurality of frequency dividers,

means connecting each of said input circuits to one of said master oscillators,

a plurality of tone forming filters,

key operated means connecting the square wave output waveforms of said master oscillators and of said frequency dividers to selected ones of said tone forming means at will,

an amplifier connected in cascade with said tone forming filters, and

an acoustic radiator driven by said amplifier.

2. The combination according to claim 1 wherein each of said frequency dividers includes means for generating a sawtooth wave ha ving the same period as the square waveform provided by that frequency divider.

3. A divider system, for dividing by an odd integer, including a source of square waves, a differentiating circuit responsive to said square waves to provide sequential positive and negative pulses,

an amplifier having a large positive amplification factor,

said amplifier having an input terminal connected in series with said differentiating circuit,

said amplifier having an output terminal,

a first feedback circuit extending from said output terminal to said input terminal,

a second feedback circuit extending from said output terminal to said input terminal,

said first feedback circuit being a feedback circuit capable of transferring only AC current,

said second feedback circuit being a DC feedback circuit,

said second feedback circuit providing maximum feedback current of substantially smaller value than the maximum current provided by said first feedback circuit in response to said input square wave, said first feedback circuit having a time constant appropriate to provide an output square wave having a period equal to an odd integer multiplied by the period of said input square waves.

4. The combination according to claim 3, wherein said second feedback circuit is arranged to provide approximately one half the current that is provided by said first feedback circuit in response to said input square waves.

5. The combination according to claim 3, wherein said first feedback circuit includes a capacitor and a resistance in series, the time constant of said capacitor and resistance being selected to be approximately equal to half the period of said output square wave.

6. The combination according to claim 3, wherein said odd integer is three.

7. The combination according to claim 3, wherein is further provided a point of reference potential, a diode, a load resistance in series between said input circuit and said point of reference potential, and an output terminal connected to the junction of said diode and said load resistance.

8. The combination according to claim 3, wherein said amplifier includes a first transistor having a base, an emitter and a collector,

means connecting said input circuit to said base,

a point of reference potential,

a load resistance connected between said emitter and said point of reference potential,

a second transistor,

means connecting said second transistor in driven relation to said first transistor, and

means applying operating potentials to said first transistor such that said emitter provides rectification of pulse current tfiow to said load resistance from said output terminal via said first feedback circuit to said base.

9. The combination according to claim 81 wherein said first and second transistors are of opposite conductivity types, and wherein a single supply voltage is provided for energizing and biasing said transistors.

10. The combination according to claim 8 wherein said transistors are of the same conductivity type and are connected in cascade.

11. A divide by three circuit comprising an amplifier having a large positive gain,

a source of square waves of frequency f,

means differentiating said square waves to provide successive pulse of alternate polarity,

said amplifier having an input terminal and an output terminal,

means connecting said pulses to said input terminal,

a capactive-resistive feedback circuit between said output terminal and said input terminal,

said amplifier and feedback circuit having parameters selected to cause transfer of said amplifier between a first and a second stable state only in response to a first of said pulses and thereafter in response to every third one of said pulses, positive ones of said pulses tending to drive said amplifier into one of said states and negative ones of said pulses tending to drive said amplifier into the other of said states.

12. The combination according to claim 11 wherein is References Cited UNITED STATES PATENTS 6/1951 Mork 841.19 X 8/1964 Peterson 841.01 X

ARTHUR GAUSS, Primary Examiner.

B. P. DAVIS, Assistant Examiner.

US. Cl. X.R.