US3502782A - Electronic musical effect apparatus - Google Patents

Description

March 24, 1970 R. B..SCHRECONGOST 3,502,782

ELECTRONIC MUSICAL EFFECT APPARATUS 3 Sheets-Sheet 2 Filed Oct. 9. 1967 l I I l I l J INVENTOR TMW m f AWQH 2 Y @M March 24, 1970 R. B. SCHRECONGOST 3,502,782

ELECTRONIC MUSICAL EFFECT APPARATUS 3 Sheets-Sheet 5 Filed Oct. 9. 1967 m 6Q um. um. Om.

FDA F30 ATTORNEYS United States Patent 3,502,782 ELECTRONIC MUSICAL EFFECT APPARATUS Ray B. Schrecongost, Park Ridge, 11]., assignor to Hammond Corporation, Chicago, Ill., a corporation of Delaware Filed Oct. 9, 1967, Ser. No. 673,559 Int. Cl. Gh 1/02, 1/04 US. Cl. 84-134 3 Claims ABSTRACT OF THE DISCLOSURE Disclosed is an electronic musical effect apparatus for producing celeste and/or vibrato effects. The apparatus includes an artificial delay line comprising a plurality of cascaded stages, each stage including a transistor which drives a resistive-capacitive network from which outputs for the succession stage and for a scanner are taken; The delay line is fed from a source of electrical tone signals and progressively alters the signals fed to the scanner.

The scanner sequentially samples the outputs of the delay line in a selected predetermined manner to produce a composite signal having the desired musical effect.

FIELD OF THE INVENTION output signal with a preselected effect, such as the vibrato or the celeste effect.

DESCRIPTION OF THE PRIOR ART Apparatus of the general type as that of the present invention is disclosed in United States Letters Patent No. 2,905,040, entitled, Method and Apparatus for Producing Chorus Effects in Music, which issued on Sept. 22, 1959, to J. M. Hanert; United States Letters Patent No. 3,258,519, entitled Method and Apparatus for Securing Vibrato Effects, which issued on June 28, 1966, to A. C. Young; and in the application for United States Letters Patent, Ser. No. 482,848, entitled Apparatus and Method for Producing Celeste Animation in Music which was filed on Aug. 26, 1965, in the name of the present inventor. These Letters Patents and application for Letters Patent are assigned to the assignee of the present application, Hammond Organ Company, a corporation of the State of Delaware.

In general, the apparatus of the above cited patents and application employ an artificial delay line comprising sections of inductive and capacitive elements for progressively altering the phase of a musical tone signal impressed at one end thereof. At each successive section, an output signal related to the input signal but altered therefrom is taken and sampled or scanned in a scanner. That is, the output signals are successively sampled and combined in accordance with a preselected and predeter mined rule into an electronic musical tone output signal exhibiting the musical effect desired.

Artificial delay lines employed in celeste or vibrato musical effect apparatus including electronic organs have used air-core inductors which were lossy and bulky in size and required special design precautions to avoid mutual coupling and cross-talk between inductors. Although these problems have been somewhat lessened by the use of ferrite magnetic materials for the core of in- 3,502,782 Patented Mar. 24, 1970 ductors, this has been achieved only at the added expense of the ferrite magnetic cores. The present invention eliminates the need for these special cores and obviates the problems of mutual inductance by providing an artificial delay line for such apparatus which completely eliminates the need for inductive elements.

These apparatus employing an inductive-capacitive delay line while adequate for many applications and in successful commercial use had the twin disadvantages of passing only a limited range of frequencies because of the filtering effects of a capacitive-inductive artificial delay line and of being relatively expensive. The frequency band passed by the delay line could be extended to accommodate a greater range of frequencies only with even more expensive components. Furthermore, the inherent losses of the inductors and capacitors used in these lines tended to attenuate the impressed signals and standing and reflected waves were generated in these lines all resulting in outputs of uneven amplitude.

The present invention provides a musical tone apparatus that provides a full audio range, greatly reduces or eliminates entirely the effects of attenuation, standing and reflected waves, while at the same time greatly reducing the cost of the apparatus relative to those of the prior art.

SUMMARY OF THE INVENTION An electronic musical effect apparatus constructed in accordance with the present invention includes a source of electrical tone signals, and a scanning device for sequentially sampling a plurality of altered output signals in a preselective manner so as to produce the musical effect therefrom. The output signals are derived from the source by means of cascaded stages the first of which is coupled to the source and each of which comprises an amplifier device and at least one resistive-capacitive circuit. The output is taken from the resistance capactive circuit which also serves to drive the next stage.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings in which similar reference characters refer to similar parts throughout the several views:

FIG. 1 is a diagrammatic representation of a general arrangement of an electronic musical effect apparatus embodying the present invention;

FIG. 2 is a circuit diagram of a portion of the apparatus of FIG. 1; and

FIGS. 3A and 3B are graphical representations comparing the relative phase delay at various frequency and of the relative amplitudes of the outputs of a typical capacitor-inductor artificial delay line, with a specific embodiment of the invention such as the circuit of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the illustrated embodiment the invention is described in the environment of an electronic organ. It will be understood that the invention may be applied in other electronic musical instruments and toward a section of an electronic organ, and the application to the various sections may be the same, or minor changes which Will suggest themselves and will reflect individual preference may be made at different organ sections.

Referring now to FIG. 1, an electronic musical effect apparatus is depicted and is generally designated by the numeral 10. The apparatus 10 is driven by a musical tone signal source 12 which may be the electronic musical output signal of an electronic organ. The source 12 feeds a signal altering unit 14 from which a plurality of outputs of altered signals as indicated by the lines 15 are provided. The unit 14 functions in its overall operation in a manner similar to the artificial delay lines employed in the above cited patents, that is, it produces a series of output signals which are related to the input signal from source 12 by being, at least, progressively delayed. The outputs 15 are fed to a mode selector 16 which performs a function of selectively applying the outputs of the unit 14 to ultimately derive either celeste or vibrato elfects. The outputs from the mode selector 16, which are generally indicated by 17, are fed to a scanner 18. The scanner 18 may be one of the types shown in the above mentioned patents or may be any other means for successively sampling the outputs 17. The scanner 18 functions to deliver on output lines 19 and 20 musically altered signals. The lines 19 and 20 are coupled, respectively, to one of a pair of audio amplifiers 21 and 22 which respectively drive separate speakers 23 and 24 for producing the musical tones, including the selected effect, therefrom.

For some musical effects and in some applications. it is desirable to use only one of the outputs from'the scanner 18. This situation is symbolized by the switch 25 and the connecting line 26. When this switch is thrown, it disconnects the line 19 from the amplifier 21 and couples that amplifier via line 26 to the output line 20. In this case the output on line 20 is fed to both amplifiers 21 and 22 to be fed to both speakers 23 and 24.

The signal altering unit 14 comprises, in accordance with the present invention, a plurality of stages A, 30B 30N. There may be any number of stages 30, the letter N symbolizing the Nth stage or any number desired. For example, a six stage unit, each stage with three outputs to yield a total of eighteen outputs, has been constructed and tested and found entirely satisfactory. However, a greater or lesser number of stages and outputs per stage may be employed.

Each of the stages 30' produces a number of differing output signals on a number of output lines 15. One of these outputs is coupled to the next stage, as symbolized by the lines 27A, 27B 27(N-1), to serve as the input to that stage. The first stage 30A is driven directly from the musical tone signal source 12 while the last stage 30N does not have any connection such as lines 27A-27(N-1).

Referring to FIG. 2 the stages 30 are there depicted in greater detail. Each stage 30 is identical to the others and thus only one stage will be here described, it being understood that each of the stages 30 may be constructed in the same manner. Each stage 30 includes an amplifier device such as a transistor 31. The transistor 31 is of the NPN type and has an input line 32 connected to its base. In the case of particular stage 30A the output from the signal source 12 is coupled to line 32, and in the case of the succeeding stages 30B30N the lines 32 are coupled to an output of the preceding stage. The base of the transistor .31 is also connected to a source of positive potential B+ through a linkage resistor 33. The collector of the transistor 31 is connected to the same source of positive potential B-lthrough a resistor 34. The emitter of the transistor 31 is connected through a resistor to a plane of reference potential or ground.

The resistors 33, 34 and 35 together with the source of positive potential B+ determine the direct current operating conditions of the transistor 31 and determine those conditions so that the transistor 31 is operating in substantially class A amplification. That is, the transistor 31 should be so biased as to substantially reproduce the alternating current signal impressed on line 32.

The transistor 31 serves as a phase splitter in that the output signal developed at its collector is the inverse, i.e., 180 out of phase, of the signal impressed upon its base relative to ground while that developed at its emitter is in phase with the impressed signal.

Connected across the emitter and collector of the transistor is a capacitive-resistive circuit, generally designated by 29. The circuit 29 is coupled to the collector of transistor 31 via a line 39- and to its emitter via a line 40. The circuit 29 comprises three capacitive-resistive parallel branches 36, 37 and 38. The branch 36 comprises a capacitor 36C one end of which is connected to the line 39 and the other end of which is connected to one end of a resistor 36R. The other end of the resistor 36R is connected to line 40. The branch 37 has a capacitor 370 and a resistor 37R connected in series with each other.

The series connected capacitor-resistor branch 37 is also connected in parallel with the capacitor-resistor branch 36 by having one side of the capacitor 37C connected to line 39 and one side of the resistor 37R con nected to line 40.

The third branch 38 likewise comprises a series connected capacitor 38C and resistor 38R which series connected circuit is also connected in parallel across line 39 and 40 in the manner of branches 36 and 37.

The outputs of each stage are taken from the junctions of the series connected capacitors and resistors of the branches 36, 37 and 38. The junction between each of the capacitors and resistors of each branch 36, 37 and 38 has an output line 15 connected thereto. Successive output lines 15 of successive stages are individually designated by an individual afterscript as the output from each of the lines 15 is different from the output of any other line 15. Thus, the output line of branch 36 is designated 15A, the line from branch 37 is designated 15B and the line from branch 38 is designated 15C.

One of the outputs 15 from each of the stages 30 except for the last stage 30N, functions as the input of the next stage 30. Thus in the case of stage 30B its input line 32 is connected to the output line 15C of stage 30A. Similarly, the output line 15F of stage 30B is connected to the next stage, and so on until the last stage 30N.

In the operation of each stage 30 thetransistor 31 functions to phase split the signal received on its input line 32 and to apply the two out of phase signals to the capacitive-resistive circuit 29. These signals are applied via lines 39 and 40 to each branch 36, 37 and 38. The capacitive resistance branches 36, 37, and 38 have components so chosen as to achieve progressively greater phase delay or alteration of the signal impressed thereon between the lines 39 and 40. Thus, the signal on output line 15A may be, for example, shifted by approximately 10 from that of a specific input signal from source 32. The signal on output line 15B may be shifted 20 from the source signal, and the signal on output line 15C may be shifted by 30. As the signal shifted by 30 also serves as an input to the next stage 30B which is identical to the stage 30A, the outputs of the corresponding output lines 15D, 15B and 15F from stage 30B are likewise progressively shifted by 10. Additional stages 30 result in progressively greater phase shift for the output line 15. Continuing the above examples, the output from line ISD is shifted by 40 from the initial input from the signal source while the signal on the output line 15E is shifted 50 and that on the output line 15F is shifted 60 from the input signal from source 12. Since the output on line 15F also serves to feed the next stage it can be seen that progressive phase shifts may be obtained for any desired range depending on the number of stages 30 employed.

A theoretical circuit analysis and derivation has been carried out with respect to the generalized branch 36, 37 or 38 of the circuit 29 by Mr. A. J. Borrevik of the Hammond Organ Company Engineering Department. The phase shift 1 of the output of such a branch was found to be expressed by the formula:

4 arctan Where in Formula 1, R is the resistance in ohms of the of the capacitor 36C, 37C or 38C and w is the angular frequency of the impressed signal.

The derived output voltage e expressed in the convention or square root of minus one notation, is the following:

where e is the input voltage in relation to ground developed on line 39 by the transistor 31, which, of course, is the negative of the input voltage developed on line 40.

The magnitude of the output voltage has been derived from Formula 2 and shown to be:

That is, the magnitude of output voltage is always equal to the magnitude of the input voltage developed on lines 39 and 40 despite variations in frequency of the impressed signals or in the resistance or capacitance of the various branches.

A particular embodiment of the artificial line unit 14 of FIGS. 1 and 2 was constructed and tested. This delay line unit 14 employed six stages with three outputs each.

Referring now to FIG. 3A, there is depicted a graphical comparison of the phases of the progressive signal alternating unit 14 of this specific construction and a generally corresponding capacitive-inductive multiple take-0E point artificial delay line such as has been used in the prior art.

In FIG. 3A the progressive phase shifts at the eighteen outputs of the unit 14, (labeled 15A, 15B 15M, 15N, 150 15R and 15$), for various frequencies impressed are depicted in solid lines While that of a typical prior art capacitive-inductive artificial delay line are shown in dashed lines.

From FIG. 3A it can be seen that the phase shift of the unit 14, at 200 cycles per second, as represented by line 40 is greater for all outputs than the phase shift represented by line 41 of the typical prior art capacitiveinductive artificial delay line. At one kilocycle, as indicated by the line 42, the phase shift of the unit 14 is still greater than that of the typical prior art delay line, as indicated by line 43. However, at two kilocycles, as indicated by line 44 and line 45, the unit 14 produces a phase shift that is somewhat smaller at all outputs than that of the compared capacitive-inductive line, At five kilocycles the difference is quite large as indicated by the lines 46 and 47. At ten kilocycles the shifts of outputs of the unit 14 are only slightly greater than that of five kilocycles. This lack of proportionality can be adjusted somewhat to optimize the musical effect.

This means that the unit 14 passes a wide frequency range signal with much less average distortion than that of the prior art electronic tone effect apparatus using capacitive-inductive artificial delay lines. In many such prior apparatus it has been conventional to employ high pass filters for passing the high end of the composite musical tone signals from a source such as 12 around the musical effect apparatus and to recombine this portion of the signal at speaking amplifiers such as the amplifiers 21 and 22. The elimination of the need for this constitutes a major advantage of the present invention over the prior art.

In FIG. 3B the relative amplitudes of a typical capacitive-inductive delay line and the particular tested six stage, 18 output unit constructed in accordance with the present invention are compared. As can be seen by comparing line 50, representing the voltage at various output lines of a unit such as the unit 14 of FIGS. 1 and 2, with the line 51, representing the output voltage of a conventional artificial delay line, the amplitude of the output on the output lines ISA-15S is relatively constant while that of the prior art varies. The variations in output voltage represented by the line 51 in FIG. 3B resulted 6 in large part because of standing Waves generated in the line.

The results of FIGS. 3A and 3B represent experimental data from a specific embodiment of the invention. The circuit parameters of this specific embodiment are set out below. These values are for illustration purposes only. Many other values as well as other variations may be made by those skilled in the art without departing from the spirit of the present invention.

Transistor 31-2N2926 Resistor 33-470K ohm Resistors 34 and 3510K ohm Capacitor 36C- 270 mf.

Capacitor 37C680 mf.

Capacitor 38C5,600 mf.

Resistors 36R and 37Rl00K ohm Resistor 38R-22K ohm A thirty volt direct current source of positive voltage B-I- was employed with the input signal source 12 generating an alternating electrical tone signal of ten volts, peak to peak.

In overall operation, the apparatus of FIGS. 1 and 2 generates from the electrical tone signal of source 12 a musical tone at the speakers 23 and 24 which has a preselected musical tone efiect, such as the celeste effect or the vibrato effect. It accomplishes this by producing progressively delayed output signals 15 from the source signal in the unit 14. These continuous signals are fed through a mode selector 16 to a scanner 18 from which a composite continuous signal is derived on lines 19 and 20 composed of sequential time samples of the various altered signals of lines 15. These composite signals are then fed through and amplified by the pair of amplifiers 21 and 22 to drive the speakers 23 and 24.

The mode selector 16 functions to switch the different output signals on the lines 15 to difierent portions of the scanner 18 so that the same scanner 18 may generate different composite signals. The depicted scanner is of the capacitor pick-up type in which a rotating arm having a capacitor plate at at least one end is caused to move past a plurality of capacitor plates upon which the output signals are impressed. The pickup arm is rotatable at two speeds, one for the celeste effect and another for the vibrato effect.

The described apparatus has been found to exhibit less objectional rotational effects than those experienced in conventional apparatus and to be better adaptable to a variety of electronic musical instruments of the organ type as well as to other electrical musical instruments.

As is now obvious, a new and improved electronic musical effect apparatus which provides a wide pass band without substantial variation in output amplitude, is easily and economically made, assembled and operated and isadaptable to many applications has been described.

While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

I claim as my invention: 1. An electronic musical effect apparatus comprising: a source of electronic tone signals; an artificial delay line coupled to said source and having a plurality of outputs, said artificial delay line including:

a biasing source of positive direct current potential; a first transistor having a base coupled to said source, an emitter and a collector; a first leakage resistor connected to the base of said first transistor and to said biasing source; a first current limiting resistor connected between the collector of said 'first transistor and said biasing source;

first biasing resistor connected between an emitter of said first transistor and a plane of reference potential;

first branch of a series connected first resistor and first capacitor connected between the emitter and collector of said first transistor;

first output conductor connected to the junction of the series connected first resistor and first capacitor of said first branch;

second branch of a series connected second resistor and second capacitor connected between the emitter and collector of said first transistor;

second output conductor connected to the junction of the resistor and the capacitor of said second branch;

third branch of a series connected third capacitor and third resistor connected between the emitter and the collector of said first transistor; third output conductor connected to the junction of the resistor and the capacitor of said third branch;

second transistor having a base coupled to said third output conductor, an emitter and a collector;

second leakage resistor connected between the base of said second transistor and to said biasing source of direct current potential;

second current limiting resistor connected between the collector of said second transistor and said biasing source;

second biasing resistor connected between the emitter of said second transistor and the plane of reference potential;

fourth branch of a series connected fourth resistor and fourth capacitor connected between the emitter and collector of said second transistor;

fourth output conductor connected to the junction of the resistor and the capacitor of said fourth branch;

fifth branch of a series connected fifth resistor and fifth capacitor connected between the emitter and collector of said second transistor; fifth output conductor connected to the junction of the resistor and the capacitor of said fifth branch;

sixth branch of a series connected sixth capacitor and sixth resistor connected between the emitter and the collector of said second transistor;

sixth output conductor connected to the junction of the registor and the capacitor of said sixth branch;

nth transistor having a base coupled to the output of said 3(nl) branch, an emitter and a collector;

nth leakage resistor connected between the base of said nth transistor and to said biasing source of direct current potential;

nth current limiting resistor connected between the collector of said nth transistor and said biasing source;

nth biasing resistor connected between the emitter of said nth transistor and the plane of reference potential;

3n-2 branch of a series connected 3n-2 resistor and 3n-2 capacitor connected between the emitter and collector of said nth transistor; 3n-2 output conductor connected to the juntion of the resistor and the capacitor of said 3n-2 branch;

3n-1 branch of a series connected 3nl capacitor and 311-1 resistor connected between the emitter and the collector of said nth transistor;

a 3n1 output'conductor connected to the junction' of the resistor and the capacitor of said 3n-1 branch;

a 3n branch of a series connected 3n capacitor and 3n resistor connected between the emitter and collector of said nth transistor;

a 3n output conductor connected to the junction of the resistor and the capacitor of said 3n branch;

a mode switching unit connected to said first, secnd, third, fourth, fifth, sixth, 3n-2, 3n-1 and 3n output conductors for selectively switching the signals on'said conductors on to ones ofa plurality of lines;

a scanner including a plurality of capacitor plates each of which is coupled to one of the plurality of lines of said mode selector switch, and a rotating pick up capacitor plate mounted for rotation adjacent to said plurality of capacitor plates for sampling in time sequence the'signals thereon, to produce a composite output signal;

an amplifier coupled to the pick up capacitor plate of said scanner for amplifying the composite output signal; and

at least one speaker coupled to said amplifier for reproducing in sound the amplified output signal.

.2. In an electrical musical instrument a phase shifting for providinga multiplicity of progressively phase shifted outputs for a complex music signal which comprises a plurality of solid state phase splitter amplifiers connected in cascade with an input for the first in the cascade connected to receive the complex music signal, all of said phase splitter amplifiers being substantially identical and each having two outputs providing signals of substantially identical composition but phase displaced 180 with respect to each other, a plurality of signal output circuits connected in parallel across each of said amplifier outputs, each of said signal output circuits comprising a capacitor 40 and resistor in series, signal output terminals connected individually to the junctions between said resistors and capacitors, the values of the capacitors and resistors in said signal output circuits being different and chosen so as to shift the phase a different amount at different ones of said terminals, the one of said signal output terminals of a particular stage having the greatest phase shift being connected tothe input of the next amplifier in the cascade, all of the phase shift amplifier stages in the cascade hav ing substantially identical signal output circuits, the progressive phase difference for each successive signal output terminal of each stage being substantially identical and substantially identical to the phase difference in the same direction between the terminal of greatest phase shift of one stage and the terminal of least phase shift of the next stage.

3. The phase shift system called for in claim 2 in which there are at least three signal output circuits with different degrees of phase shift for each stage and at least two stages. References Cited UNITED STATES PATENTS 2,509,923 5/1950 Hanert 841. 24 X 2,905,040 9/1959 Hanert 84-124 3,256,380 6/1966 Meinema et a1 84-125 3,258,519 6/1966 Young 84-124 X 3,413,403 11/1968 JOCOb 841.25 3,418,418 12/1968 Wilder 841.1Z5

HERMAN KARL SAALBACH, Primary Examiner SAXFIELD CHATMON, JR., Assistant Examiner

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