US 5,398,005 A · Voss tone control circuit with reduced distortion and reduced DC offset

Abstract

A Voss-type electronic tone control circuit in which the output of an amplifier is connected to the circuit output. An input resistor interconnects the circuit input and the amplifier inverting input and a feedback resistor interconnects the amplifier output and inverting input. One end of a first resistor is switched between the circuit input and the amplifier output. A first capacitor is connected between the other end of the first resistor and ground. A second capacitor is connected between the other end of the first resistor and one end of a potentiometer, the other end of which is grounded. The potentiometer slider feeds the amplifier non-inverting input. The capacitance of the second capacitor is different from that of the first capacitor, which enables the resistance of the first resistor to be increased, and the resistance of the potentiometer to be reduced compared with a conventional circuit. Increasing the first resistor resistance reduces loading on the boost/cut switch. Decreasing potentiometer resistance reduces the average source resistance presented to the amplifier non-inverting input, and, hence, the source resistance imbalance between the inverting and non-inverting inputs. The effects of the remaining source resistance imbalance are mitigated by unbalancing the input currents of the amplifier. The base of an auxiliary input transistor is connected to the amplifier inverting input. The emitter of the auxiliary transistor is connected to the second current generator to increase the current drawn by the inverting input.

Claims14

Dependent claims

An electronically-controlled tone control circuit having a circuit input and a circuit output, the circuit comprising:

an amplifier having a non-inverting input, an inverting input, and an amplifier output, the amplifier output being connected to the circuit output;
an input resistor connected between the circuit input and the inverting input;
a feedback resistor connected between the amplifier output and the inverting input;
and
a frequency-selective network comprising:
a first resistor having a first terminal switchably connected to one of the circuit input and the amplifier output, and a second terminal,
a first capacitor having a first terminal connected to the second terminal of the first resistor and a second terminal connected to signal ground, the first capacitor having a first capacitance,
a second capacitor having a first terminal connected to the second terminal of the first resistor, and a second terminal, the second capacitor having a second capacitance different from the first capacitance, and
a potentiometer having a first terminal connected to the second terminal of the second capacitor, a second terminal connected to signal ground, and a slider terminal connected to the non-inverting input.

6 more elements

An electronically-controlled tone control circuit having a circuit input and a circuit output, the circuit comprising:

an amplifier having a non-inverting input, an inverting input, and an amplifier output, the amplifier output being connected to the circuit output, the amplifier comprising:
a first input transistor connected in a balanced long-tail pair configuration fed by a first current generator, each input transistor having a collector, the first input transistor having a base connected to the non-inverting input, the second input transistor having a base connected to the inverting input;
means for deriving an output voltage from the collectors of the first input transistor and the second input transistor and for feeding the output voltage to the amplifier output;
a second current generator;
and
a third transistor, including:
a base connected to the inverting input, and
an emitter connected to the second current generator;
an input resistor connected between the circuit input and the inverting input;
a feedback resistor connected between the amplifier output and the inverting input;
and
a frequency-selective network comprising:
a first resistor having a first terminal switchably connected to one of the circuit input and the amplifier output, and a second terminal,
a first capacitor having a first terminal connected to the second terminal of the first resistor and a second terminal connected to signal ground, the first capacitor having a first capacitance,
a second capacitor having a first terminal connected to the second terminal of the first resistor, and a second terminal, the second capacitor having a second capacitance different from the first capacitance, and
a potentiometer having a first terminal connected to the second terminal of the second capacitor, a second terminal connected to signal ground, and a slider terminal connected to the non-inverting input.

13 more elements

Dependencies are inferred from the claim text.

Voss tone control circuit with reduced distortion and reduced DC offset

Life of this patent

Voss tone control circuit with reduced distortion and reduced DC offset

Life of this patent

Abstract

Claims14