US3816661A - Tone control utilizing an operational amplifier with differential inputs - Google Patents

Tone control utilizing an operational amplifier with differential inputs Download PDF

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Publication number
US3816661A
US3816661A US00286680A US28668072A US3816661A US 3816661 A US3816661 A US 3816661A US 00286680 A US00286680 A US 00286680A US 28668072 A US28668072 A US 28668072A US 3816661 A US3816661 A US 3816661A
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United States
Prior art keywords
point
inverting
ohmic resistance
operational amplifier
potentiometer
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Expired - Lifetime
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US00286680A
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English (en)
Inventor
D Huszty
K Szabados
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Elektroakusztikai Gyar
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Elektroakusztikai Gyar
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G5/00—Tone control or bandwidth control in amplifiers
    • H03G5/02—Manually-operated control
    • H03G5/025—Equalizers; Volume or gain control in limited frequency bands
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G5/00—Tone control or bandwidth control in amplifiers
    • H03G5/02—Manually-operated control
    • H03G5/04—Manually-operated control in untuned amplifiers
    • H03G5/10—Manually-operated control in untuned amplifiers having semiconductor devices

Definitions

  • ABSTRACT A tone control circuit of a design simpler and more effective than that of those hitherto known, built up of an operational amplifier with differential input, which at the low and/or high tones and/or over a single section, or several, of the audio frequency band permits a transmission characteristic departing from the straight line which in a manner differing from similar known methods guarantees the monotonous decay of the transmission characteristic on the edges of the audio frequency band.
  • monotonous decay is achieved by inserting in series with a reactance connected between the slide and the earth point of the potentiometer connected between the inverting and non-inverting points of the operational amplifier an ohmic resistance, whereas according to need adifferentiatingor integrating RC circuit is connected between the controlling signal source and the non-inverting point, as the case may be.
  • the subject-matter of the invention is a tone control circuit of a design simpler and more effective than that of those hitherto known, built up of an operational amplifier with differential input, which circuit at the low and/or high tones, and/or over any section or sections of the audio frequency band permits a transmission characteristic departing from the straight line in a manner such that on the edges of the audio frequency band the transmission characteristic is decaying monotonously.
  • the tone control circuit has important functions to perform in the electroacoustic transmission chain.
  • the transmission characteristic of the complete transmission chain may be compensated in a manner such that in a definite frequency band dependent on the frequency this characteristic takes on a definite, e.g. straight-line character.
  • the transmission characteristic of the electroacoustic chain is in all cases uneven (l).
  • the unevennesses are partly in the nature of resonance, i.e., within the region of a narrow frequency band the characteristic presents an acute peak or decay, partly presenting a rise or decay, as the case may be, extending over a relatively wide frequency band.
  • the unevennesses of the transmission characteristic extending over a wide band are normally compensated by tone control circuits including passive (2) or active elements (3).
  • a network built up of passive elements, consisting of parallel oscillating circuits in series is recommended (4).
  • Each of the known methods presuppoeses the use of a large number of components, and also the adjustment of the circuits is of extreme complexity.
  • a critical deficiency of a low tone control circuit of this design is that below the lower limit of the useful audio frequency band, i.e., below about 40 Hz, the amplifier is devoid of band limitation, and therefore transmits signals of very low frequencies, even direct current, with the same gain, i.e., a gain of unity. ln this way the amplifier transmits the noise output of the signal sources connected before the circuit of below the lower limit of the audio frequency band with a gain of unity and consequently disturbs the gain of the useful signals.
  • a drawback of the high-tone control circuit here referred to is that at the upper limit of the useful audio frequency band, i.e., for signals of a frequency in excess of l6 kHz the gain or loss of the circuit varies with a slope of respectively +6 dB/octave and -6 dB/octave, whereas with the slide of the potentiometer in midposition, in a wide band this value will be constant for frequencies higher than the upper cut-off frequency of the audio frequency band.
  • the present invention eliminates the deficiencies and drawbacks of both the low-tone and high-tone control circuits.
  • the tone control circuit which contains at least one operational amplifier of a differential input, controlled at its non-inverting point, with an ohmic resistance inserted between the inverting and earth points and also between the noninverting and earth points, further with another ohmic resistance connected between the inverting point and the output point of the operational amplifier, while there is a potentiometer connected between the inverting and non-inverting points, with a slide via a reactance connected to the earth point, while there'is an ohmic resistance connected between the controlling signal source of theoperational amplifier and its noninverting point, this is achieved in a way such that an ohmic resistance is connected in series together, with an inductance or condenser, with the reactance inserted between the slide of the potentiometer and the earth point, whereas differentiating and integrating RC circuits are inserted between the controlling signal source and the non-inverting point.
  • FIG. 1 presents the circuit diagram of a known lowtone control circuit.
  • FIG. 2 displays the transmission characteristic associated with the previous tone control circuit.
  • FIG. 3 shows the circuitry of a low-tone control circuit according to the invention.
  • FIG. 5 shows the circuitry of a known high-tone control circuit.
  • FIG. 6 displays the characteristic of the set-up according to FIG. 5.
  • FIG. 8 presents an embodiment of the high-tone control set-up according to the invention.
  • FIG. 9 displays the transmission characteristic of the set-up according to FIG. 8.
  • FIGS. 10 and 11 present each a variant of the set-up according to FIG. 8.
  • FIG. 12 present a possible embodiment of the circuitry of the combined lowand high-tone control circuit according to the invention.
  • FIG. 13 displays the transmission characteristic of the set-up according to FIG. 12.
  • FIG. 14 a set-up has been presented where in addition to general lowand high-tone control local peak or hole control may be performed.
  • FIGS. 18 and 19 an embodiment of an improved variant of the tone control circuit according to the invention has been displayed.
  • FIG. 1 shows a tone-control circuit of known design built up of an operational amplifier, controlled at its non-inverting input point (5).
  • the operation of the circuit relies on the understanding that if potentiometer P is turned to its non-inverting input point 2, the oscillating circuit in series consisting of L elements will at the resonance frequency present a low impedance and consequently shunt the resistance R inserted between the non-inverting input point 2 and the earth. As a result of this shunting process the transmission characteristic will present a minimum at the resonance frequency.
  • potentiometer P If potentiometer P is turned to mid-position, owing to the bridge type circuitry the oscillating circuit in series will be ineffective, i.e., the transmission characteristic will become a straight line.
  • potentiometer P is turned towards inverting point 1, the minimum resistance of the oscillating circuit in series at the resonance frequency will shunt resistance R, connected between the inverting input point 1 and the earth and consequently owing to the known properties of the operation amplifier a maximum gain will be indicated.
  • R R R R R l kohm, P l kOhm, L O,l H and C I00 F the transmission characteristic of the low-tone control circuit has been plotted in the diagram in FIG. 2.
  • Curve I will manifest itself with the slide of potentiometer P at the inverting input point 1, curve II has been plotted for the slide in mid-position, curve III is associated with the slide at the non-inverting point 2.
  • FIG. 5 a known design is shown of a high-tone control circuit built up with an operational amplifier and controlled at its non-inverting point (5). If potentiometer P is in mid-position, condenser C will be ineffective, so that the characteristic will be a straight line (curve II in FIG. 6). On the other hand if by turning the potentiometer condenser C will become connected between the inverting input point 1 and the earth and above a definite frequency a characteristic rising with a slopeof 6 dB/octave will be obtained (curve I, in FIG.
  • band limitation will in each case take place above the upper cut-off frequency of the audio frequency band irrespective of the position of the slide of potentiometer P
  • the same result may also be guaranteed if instead of a condenser of capacity C another of a capacity C is connected parallel to resistance R (FIG. 10).
  • the circuitry shown in FIG. 11 may be extended by connecting a chain formed of ohmic resistances between the inverting and non-inverting input points.
  • the interconnected points of the resistances are terminated upon contact with a section switch and by connecting a network formed of a resistance R and condenser C to the contacts of the section switch a precision tone control circuit will be obtained.
  • a lowand high-tone control circuit may also be obtained by connecting the circuits described above, one after the other.
  • the circuitry may be used for the compensation of the local unevennesses, peaks and depths, of the transmission characteristic.
  • a circuitry suited for this purpose is shown in FIG. 14, where by means of the loss-type oscillating circuits in series, L C R further L C R and the potentiometers, respectively P and P attached to them at two optionally selected frequencies in a manner controlled independently of each other peak and/or hole type unevennesses may be brought about.
  • the bandwidths of the unevennesses may be controlled one by one by the choice of the resistances R and R
  • five local unevennesses (peak and/or hole) controlled separately from one another may be brought about on the transmission characteristic.
  • FIG. 19 An improved variant of the method of FIG. 18 is shown in FIG. 19.
  • the inputs of the tone control circuits are again connected in parallel, whereas their outputs are through the intermediary of resistances in series terminated on the inverting point of another operational amplifier of differential input.
  • a tone control circuit for high and/or low tone control containing at least one operational amplifier of differential input controlled at its non-inverting point, with an ohmic resistance connected between the inverting point and earth point and also between the noninverting point and earth point of the amplifier, further with an ohmic resistance connected between the inverting point and the output point of the operational amplifier, a potentiometer connected between the inverting and non-inverting points, the slide of said potentiometer being connected through a reactance to the earth point, and an ohmic resistance connected between the controlling signal source of the operational amplifier and the non-inverting point
  • the improvement comprising an ohmic resistance connected in series with the reactance. inductance and condenser connected between the slide of the potentiometer and the earth point, and an RC circuit connected between the controlling signal source and the non-inverting point.
  • a tone control circuit characterized in that the resistance in series with the inductance is formed by the ohmic resistance of its own of the winding constituting the inductance.
  • a tone control circuit characterized in that between the inverting and noninverting points of the operational amplifier at least two potentiometers are connected in parallel, between the slide of the one and the earth point the connection in series of an inductance and an ohmic resistance, between the slide of the other and the earth point the connection in series of a condenser and an ohmic resistance being connected, and a differentiating and integrating RC circuit connected between the controlling signal source and the non-inverting point.
  • a tone control circuit and a further potentiometer connected in parallel between the inverting and non-inverting points, between the slide of which potentiometer and the earth point at least one network comprised of a resistance, condenser and inductance in series is connected.
  • a tone control circuit which includes at least two operational amplifiers, together with the associated circuit, which are connected in parallel between the controlling signal source and the output of the circuit in a manner such that the outputs of the operational amplifiers are terminated on the common output by inserting an ohmic resistance, while an ohmic resistance is connected between the common output point and the earth point.
  • a tone control circuit in which instead of the ohmic resistance connected between the commoned output point of the operational amplifiers and the earth point the inverting input of a further operational amplifier with a differential input is terminated on the common output point, an ohmic resistance connected between the non-inverting input and the earth point, and an ohmic resistance connected between the inverting input and the output of the operational amplifier, at the same time constituting the output of the circuit as a whole.
  • a tone control circuit in which at least one potentiometer connected between the inverting and non-inverting points of the operational amplifier is replaced by two resistances of different values in series and on the common point of these resistances a circuit consisting of a reactance and ohmic resistance, with its other end connected to the earth.
  • a tone control circuit for high and/or low tonecontrol containing at least one operational amplifier of differential input controlled at its non-inverting point, with an ohmic resistance connected between the inverting point and earth point and also between the noninverting point and earth point of the amplifier, further with an ohmic resistance connected between the inverting point and the output point of the operational amplifier, a potentiometer connected between the inverting and non-inverting points, the slide of said potentiometer being connected through a reactance to the earth point, and an ohmic resistance connected between the controlling signal source of the operational amplifier and the non-inverting point
  • the improvement comprising an ohmic resistance connected in series with the reactance, inductance and condenser connected between the slide of the potentiometer and the earth point, an ohmic resistance connected between the signal source and the non-inverting point, and a condenser connected in parallel to the last-named ohmic resistance and connected between the inverting point and the output of the operational amplifier
  • a tone control circuit for high and/or low tone control containing at least one operational amplifier of differential input controlled at its non-inverting point, with an ohmic resistance connected between the inverting point and earth point and also between the noninverting point and earth point of the amplifier, further with an ohmic resistance connected between the inverting point and the output point of the operational amplifier, a potentiometer connected between the inverting and non-inverting points, the slide of said potentiometer being connected through a reactance to being connected to the controlling signal source.

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  • Networks Using Active Elements (AREA)
  • Tone Control, Compression And Expansion, Limiting Amplitude (AREA)
US00286680A 1972-02-15 1972-09-06 Tone control utilizing an operational amplifier with differential inputs Expired - Lifetime US3816661A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
HUEE2004A HU163256B (hu) 1972-02-15 1972-02-15

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US3816661A true US3816661A (en) 1974-06-11

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US (1) US3816661A (hu)
AT (1) AT341581B (hu)
BG (1) BG20834A3 (hu)
CA (1) CA983402A (hu)
CS (1) CS188885B2 (hu)
DD (1) DD98404A5 (hu)
DE (1) DE2243608A1 (hu)
FR (1) FR2172639A5 (hu)
GB (1) GB1410380A (hu)
HU (1) HU163256B (hu)
PL (1) PL84703B1 (hu)
SE (1) SE375420B (hu)
SU (3) SU635903A3 (hu)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3980965A (en) * 1975-05-16 1976-09-14 Rockwell International Corporation Frequency response control circuit apparatus
EP0050067A1 (en) * 1980-10-03 1982-04-21 Tommyca Freadman Audio system
US4382158A (en) * 1980-03-22 1983-05-03 Sharp Kabushiki Kaisha Tone control of the operational type
US4538298A (en) * 1982-09-29 1985-08-27 Bose Corporation Fixed bandpass tone controlling
US4633189A (en) * 1984-10-15 1986-12-30 Pioneer Electronic Corporation NF tone control circuit
US4994770A (en) * 1988-10-21 1991-02-19 Mitsubishi Denki Kabushiki Kaisha Tone control device
US5994956A (en) * 1998-05-06 1999-11-30 Concorso; James A. Inductive-capacitive feedback compensation for amplifier systems
US6078215A (en) * 1998-07-20 2000-06-20 Fiori, Jr.; David Impedance altering apparatus
US20080111607A1 (en) * 2006-11-10 2008-05-15 Hart Robert T Amplitude-linear differential phase shift circuit

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2511098C2 (de) * 1975-03-13 1983-01-05 Siemens AG, 1000 Berlin und 8000 München Schaltungsanordnung zur Decodierung eines frequenzmodulierten Stereo-Rundfunksignals
JPS5340257A (en) * 1976-09-25 1978-04-12 Nippon Gakki Seizo Kk Tone control circuit
DE2739194C2 (de) * 1977-08-31 1982-10-21 Standard Elektrik Lorenz Ag, 7000 Stuttgart Schaltungsanordnung mit einem NF- Verstärker und einer an dessen NF-Eingang angeschlossenen Klangfarbeneinstellungsanordnung für die hohen Töne

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3980965A (en) * 1975-05-16 1976-09-14 Rockwell International Corporation Frequency response control circuit apparatus
US4382158A (en) * 1980-03-22 1983-05-03 Sharp Kabushiki Kaisha Tone control of the operational type
EP0050067A1 (en) * 1980-10-03 1982-04-21 Tommyca Freadman Audio system
US4538298A (en) * 1982-09-29 1985-08-27 Bose Corporation Fixed bandpass tone controlling
US4633189A (en) * 1984-10-15 1986-12-30 Pioneer Electronic Corporation NF tone control circuit
US4994770A (en) * 1988-10-21 1991-02-19 Mitsubishi Denki Kabushiki Kaisha Tone control device
US5994956A (en) * 1998-05-06 1999-11-30 Concorso; James A. Inductive-capacitive feedback compensation for amplifier systems
US6078215A (en) * 1998-07-20 2000-06-20 Fiori, Jr.; David Impedance altering apparatus
US6211731B1 (en) * 1998-07-20 2001-04-03 David Fiori, Jr. Impedance altering apparatus
US20080111607A1 (en) * 2006-11-10 2008-05-15 Hart Robert T Amplitude-linear differential phase shift circuit

Also Published As

Publication number Publication date
ATA750972A (de) 1977-06-15
PL84703B1 (en) 1976-04-30
SU635903A3 (ru) 1978-11-30
CS188885B2 (en) 1979-03-30
FR2172639A5 (hu) 1973-09-28
SE375420B (hu) 1975-04-14
BG20834A3 (hu) 1975-12-20
CA983402A (en) 1976-02-10
SU580854A3 (ru) 1977-11-15
SU593678A3 (ru) 1978-02-15
AT341581B (de) 1978-02-10
HU163256B (hu) 1973-07-28
DD98404A5 (hu) 1973-06-12
GB1410380A (en) 1975-10-15
DE2243608A1 (de) 1973-10-11

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