Neubauer, Fred H. (Pacific Palisades, CA)
Jacobson, Sava W. (Northridge, CA)

04/631008

07/06/1971

04/14/1967

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Warwick Electronics Inc. (Chicago, IL)

84/684

84/733, 84/DIG.009, 84/DIG.007, 984/327, 84/721

G10H1/12; G10H1/06; G10H1/02

84/1.24,1.25,1.16,1.01,1.11,1.14,1.19,1.21,1.27

2698360	Means for controlling the tone quality and tone volume of electrical musical instruments	December 1954	Seybold
3045522	Light responsive variable resistance control devices for electronic musical instruments	July 1962	Markowitz et al.
3240859	Electronic tremolo unit	March 1966	Rowe
3278672	Noise limiter and signal level control for electronic amplifiers	October 1966	Grodinsky et al.

ALTERNATING-CURRENT CIRCUITS, by Russell M. Kerchner and George F. Corcoran, (1958) pp. 468, 469.

Hirshfield, Milton O.

Witkowski, Stanley J.

What we claim is

1. Tone control circuit for a hand-held musical instrument amplifier, comprising:

2. Tone control circuit for a hand-held musical instrument amplifier, comprising:

3. Tone control circuit for a hand-held musical instrument amplifier comprising:

4. Tone control circuit for a hand-held musical instrument amplifier, comprising:

5. Tone control circuit for a hand-held musical instrument amplifier, comprising:

6. Tone control circuit for a hand-held musical instrument amplifier, comprising:

7. Tone control circuit for a hand-held musical instrument amplifier, comprising:

8. Tone control circuit for a hand-held musical instrument amplifier, comprising:

9. Tone control circuit for a hand-held musical instrument amplifier, comprising:

BACKGROUND OF THE INVENTION

Tone control circuits are well known in the field of musical amplifiers. Refined versions of said circuits are to be found, for example, in the formant circuits of electronic organs. By actuating appropriate formant tabs, the organist is able to devise a wide variety of tonal effects, by selecting those circuits which give desired timbre to the tone sounded. Such tabs, although located within easy access of the organist, are not playing keys, in that the organist does not constantly rest his hands upon and continually run back and forth over the tabs in the manner of the playing manual of the organ. The tabs are left in actuated position for several and usually many bars of the music.

With the advent of electronic amplification to many forms of musical instruments which were previously purely acoustic, the manner of placement of tone controls became of serious concern, because the amplifier and control panel for the instrument, unlike the case of an organ, is usually spaced some distance from the instrument and the performer.

SUMMARY OF THE INVENTION

A tone control circuit is incorporated into the amplifier of a hand-held musical instrument. This circuit discriminates significantly in favor of a given narrow band of frequencies. It is selectively enabled or disabled, i.e., placed in operative association with the amplifier or otherwise, by means of a control member which is under the ready and constant manipulation of the instrument player, for example, a foot pedal on which a guitar player may at will operate the control member with his foot. In this way the guitarist may quickly and with great rapidity enable and disable the frequency selective circuit. If desired, this may be done in tempo with the playing of the music, to create strikingly novel musical effects.

Another control, which is preferably placed on the panel of the amplifier itself, enables the performer to select one of a number of different frequency bands which are to be preferred by the foot-controlled circuit.

The present invention also involves the incorporation of the frequency selective circuit into the conventional treble and bass controls to make multiple use of circuit components and create a desirable frequency response in the amplifier.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a complete amplifier for a hand-held musical instrument, such as a guitar;

FIG. 2 is a circuit diagram of that portion of the amplifier involving the circuit of the present invention;

FIG. 3 are frequency response curves illustrating operation of the invention;

FIG. 4 is a drawing of an alternative form of control for the circuit of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 is a block diagram of an amplifier, specifically an amplifier for hand-held musical instruments, such as a guitar. Blocks 12, 2, and 16 represent, respectively, different input channels to which the musical instruments represented by the tone generator symbols 18 may be plugged into. Block 12, for example, represents a normal channel; block 2 a brilliant channel, i.e., one tending to favor somewhat the higher frequency components of the tone; and block 16 represents a bass channel.

Channels 12 and 2 may be fed to a reverberation circuit 20, thence through a tremolo circuit 22, and thence through a peak limiter 24 and amplifier 26 to a loudspeaker 28. The bass channel output is sent direct to the amplifier 26 through peak limiter 24.

The circuit of the present invention is incorporated in the brilliant channel 2, as will now be described with reference to FIG. 2.

In FIG. 2, 30 represents parallel input jacks by means of which two hand-held instruments, such as guitars, may be simultaneously fed into the amplifier. Tone signal applied at 30 is first amplified in a two-stage amplifier represented by transistors 34 and 36. The tone is then applied across a treble potentiometer 38 and a bass potentiometer 40, connected in series through a resistor 42. FIG. 2 being the brilliant channel of the amplifier, the capacitor 44 tends to give some preference to the higher harmonics in the tone.

The slider 46 of the treble potentiometer 38 is connected to capacitors 48, 50, and 52, any one of which may be selectively placed in series with the slider 46 by the triple-throw switch 54. In the position shown, switch 54 places the capacitor 48 in the circuit.

Tone signal passing through capacitor 48 is applied through capacitors 56 and 58 across a volume control potentiometer 60 and back to the ground connection 62. Output from the brilliant channel FIG. 2 is taken from the volume control slider 64 and applied to the next stage. In the example of FIG. 1 this would be the block 20.

An intermediate tone path is taken from the junction point 66 between the resistors 42 and 40, through an inductor 68 and resistor 70, to the junction point 71 between the capacitors 56 and 58. A manually operable switch 72 is connected between the points 74 and 76. This switch is preferably located on the panel of the amplifier. Switch 72 is paralleled by switch contacts 78 controlled by a relay 80, energized from a pedal-controlled switch 82, which completes the circuit to ground from the voltage source 90 through a resistor 92 and the relay coil 80. Either or both the switches 72 and 78 may be replaced by a light-dependent resistor (LDR) with an associated light source under the control of the performer. When the performer illuminates the LDR, the circuit is closed; when he darkens the LDR, the circuit is open. In FIG. 4 the performer or guitarist 101 controls with his foot a light source 102 whose beam 103 is directed onto a LDR 72A. FIG. 4 thus illustrates the replacement of the switch 72 of FIG. 2 with a LDR 72A as explained above. By suitable foot control of the light source 102, the performer 101 may either turn the light beam completely off or completely on, or may modulate this intensity with consequent modulation of the resistance of the LDR 72A.

A series-connected capacitor 84 and resistor 86 are connected in shunt across the bass potentiometer 40, and the junction point between these two is connected to the bass slider 88 of the potentiometer 40.

OPERATION

The switch 78 is normally biased to open condition and must be held in closed condition by the performer. In the case of the switch 78, this involves keeping the coil 80 energized, which is done by keeping depressed the pedal that closes the switch 82. When the pedal is released, the switch 82 opens, deenergizing the relay and opening the contact 78.

With both switches 72/78 open, the frequency response is as shown at curve 100 in FIG. 3, which represents output amplitude as ordinate and frequency as abscissa, for a given setting of tone controls 46 and 88. In the low and middle frequency ranges, the response, as shown at 100, is that of a typical audioamplifier. Several of the components, primarily 44, 68, 70 and 56 contribute to produce a rising high frequency response, as shown.

With either of the switches 72/78 closed, the pass circuit represents essentially an L-section capacitance/inductance, high pass filter network, operating above critical damping, and the response is as shown in curve 102. This curve has a rather round frequency peak at 104, due essentially to the resonance between capacitor 48 and inductor 68. With the switch 78 (or 72) closed, 70 and 56 represent simply a parallel connected RC circuit, taking the output from point 76 and applying it through the coupling capacitor 58 to the output volume resistor 60. As the frequency increases, the resonance peak 104 is passed and the amplitude drops off, as shown at 106. It then begins to rise steadily as the inductor 68 increases in impedance and the capacitor 56 decreases in impedance.

When the switch 54 is actuated to insert the capacitor 50 in lieu of 48, the resonant frequency is lower, and, hence, the peak 108 moves down the frequency scale. Similarly, when capacitor 52 is switched into the circuit, the resonant peak appears at 110.

With normal playing, the amplifier of FIG. 2 responds along the curve 100. By depressing the pedal 82, on which his foot continually rests, the performer can instantly cause the response to peak as shown, for example, at 104. Then by simply lifting his foot, or releasing the pedal, the response reverts to the curve 100. This instant switching between response curves can be done in tempo with the rhythm of the music to produce many varied effects.

Capacitors 48, 50, 52 may be replaced by a single, variable capacitor controllable by the performer. The resonant peak 104 (108,110) then becomes continuously adjustable across the frequency spectrum. Such adjustment may also be by pedal control, if desired.

The treble control 46 and the bass control 88 also make use of some of the same components as are employed in the selective frequency control heretofore described. Consider first the reaction of the circuit with the switches 72/78 open. When the slider 88 is in its lowermost position, the resistor 86 is short circuited and in effect replaced by the capacitor 84. The capacitor 84 is of such value as to represent a considerable impedance for lower frequencies, but a much less impedance for the higher frequencies of the tone. Thus there is considerable bass tone developed across capacitor 84, which is fed from the point 66 through the components 68, 70, and 58 to the output resistor 60. This is the maximum bass position.

When the slider 88 is in its uppermost position, there is a short circuit across capacitor 84. Since resistor 86 is very small, very little signal is developed at point 66. Thus the principal path is through 48 and 56, which represent high impedance to bass tones. This is the position of minimum bass amplification or tone.

Considering the treble control, the capacitors 48, 50, 52 and 58 are relatively large compared to capacitor 56. Therefore, as a first approximation, they have little effect on treble tones. When the slider 46 is uppermost, there is maximum transmission of the treble tones, which pass through the capacitors 48, 56, and 58 to the output. As noted, the capacitor 56 is relatively small and, therefore, gives significantly greater pass preference to the treble tone signals.

When the slider 46 is in its lower position, the tone signals developed across the resistor 38 are no longer applied to the output and, hence, the only signals that are applied are those developed across the resistors 40, 42, which are applied to the capacitors 48, 56, and 58.

The inductor 68 has the function of tending to block the treble tone signals, even those developed across the network 40, 84, and 86, so that the significant treble tones which reach the output do so from the slider 46. The preference of the path 48, 56 for high frequency or treble tone signals is further accentuated by the function of the inductor 68, serving as a relatively high impedance load connected from the point 71 to ground through the bass circuit components 40, 84 and 86. The inductor 68 thus has the double function of presenting a load at point 71 which favors the passage of treble tones through the circuit 48, 56, and of representing a series blocking impedance which blocks the passage of treble tones from the point 66 to the output point 71.

With either of the switches 72, 78 closed, the components 70, 56 represent, as noted hereinbefore, simply a parallel connected RC circuit coupling the output point 76 to the output volume control resistor 60. The function of the components discussed immediately above in connection with the treble potentiometer 38 and the bass potentiometer 40, is substantially the same as described hereinbefore. The significant output point in this case is simply the point 76 rather than the point 71, because of the closing of the switch 72 (or 78).

A satisfactory circuit constructed according to FIG. 2 has the following parameters.

Transistors 34 and 36 2N900A Capacitor 44 2 2 microfarads

Resistance 38 1000 ohms

Resistor 42 100 ohms

Resistance 40 10,000 ohms

Capacitor 48 0.047 microfarads

Capacitor 50 0.1 microfarad

Capacitor 52 0.22 microfarad

Capacitor 84 1 microfarad

Resistor 86 100 ohms

Inductor 68 0.5 henrys

Capacitor 56 0.0047 microfarad

Capacitor 58 0.033 microfarad

Resistor 70 10,000 ohms

Resistance 60 10,000 ohms

Whereas the present invention has been shown and described herein in what is conceived to be the best mode contemplated, it is recognized that departures may be made therefrom within the scope of the invention, which is, therefore, not to be limited to the details disclosed herein, but is to be afforded the full scope of the invention as hereinafter claimed.