US 5,736,897 A · Low input signal bandwidth compressor and amplifier control circuit with a state variable pre-amplifier

Abstract

A state-variable pre-amplifier responsive to a program input signal drives a filter circuit, and an absolute value circuit. The state-variable pre-amplifier uses a state-variable filter to provide a compensated signal at an output. The compensated signal has compensated high, low and mid-range frequency signal components. The pre-amplifier has a first amplifier stage for providing a high frequency compensated signal. A second amplifier stage provides a mid-range frequency compensated signal. A third amplifier stage provides a low range frequency compensated signal. An adjusting means adjusts the balance between at least two of the three frequency compensated signals. A summing circuit adds the three compensated signals to form the compensated signal. A balance means adjusts the balance between the high frequency, the mid-range and the low frequency compensated signals to provide a compensated signal. The filter circuit is coupled to receive and automatically filter the compensated signal to provide an output signal and a modified compensated signal. The filter circuit has an adjustable bandwidth that is automatically adjusted in response to the control signal for automatically reducing the bandwidth of the filter circuit in response to lower values of the control signal to obtain the output signal. The filter circuit uses a voltage controlled amplifier or a photo cell in combination with an integrator. An absolute value circuit senses the modified compensated signal and provides a control signal proportional to the average peak value of the amplitude of the modified compensated signal.

Claims19

Dependent claims

An amplifier circuit comprising:

a state-variable pre-amplifier responsive to a program input signal having high, low and mid-range frequency signal components for providing a compensated signal, the pre-amplifier having gain control circuitry for balancing and summing the high, low and mid-range signal components;
a filter circuit coupled to receive the compensated signal, and a control signal and to provide an output signal, the filter circuit having an adjustable bandwidth, the filter circuit being responsive to the control signal for automatically adjusting the bandwidth of the filter circuit to reduce the bandwidth of the filter circuit in response to reduced amplitude values of the control signal;
and
an absolute value circuit for providing the control signal proportional to the amplitude of the compensated signal.

1 more element

An amplifier circuit comprising:

a state-variable pre-amplifier responsive to a program input signal having high, low and mid-range frequency signal components, the state-variable pre-amplifier having
a state-variable filter circuit and a summing amplifier for providing a compensated signal comprising high, low and mid-range frequency signal components, the state-variable pre-amplifier having means for balancing and summing the high, low and mid-range signal components;
a filter circuit coupled to receive and automatically filter the compensated signal to provide an output signal and a modified compensated signal, the filter circuit having an automatically adjustable bandwidth, the filter circuit being responsive to a control signal for automatically reducing the bandwidth of the filter circuit in response to reduced values of the control signal to obtain the output signal;
the filter circuit comprising:
an input amplifier for summing the compensated signal and an integrator output signal to provide a modified compensated signal;
a photocell having
a photosensitive resistor and a light emitting diode, the photosensitive resistor being responsive to the light from the light emitting diode for modifying the modified compensated signal to be an integrator input signal and for coupling the integrator input signal to an integrator input;
and
the light emitting diode being responsive to the control signal for illuminating the light sensitive resistor, the resistance of the light sensitive resistor being increased in response to lower values of the control signal;
and,
an absolute value circuit responsive to the modified compensated signal for providing the control signal proportional to the amplitude of the modified compensated signal.

8 more elements

An amplifier circuit comprising:

a state-variable pre-amplifier responsive to a program input signal having high, low and mid-range frequency signal components, the state-variable pre-amplifier having
a state-variable filter for providing a high frequency compensated signal, a low range compensated signal and a mid-range compensated signal, the state-variable filter having;
a first amplifier stage responsive to the program input signal for providing the high frequency compensated signal;
a second amplifier stage responsive to the high frequency compensated signal, for providing the mid-range compensated signal;
and,
a third amplifier stage responsive to the mid-range compensated signal for providing the low range compensated signal;
an adjusting means for adjusting the balance between the high frequency compensated signal, the mid-range compensated signal, and the low range compensated signal;
and
a summing amplifier for adding the high frequency compensated signal, the low range compensated signal and the mid-range compensated signal to provide a compensated signal;
and
speaker and amplifier means responsive to the compensated signal for producing an audible sound in response to the compensated signal.

8 more elements

Dependencies are inferred from the claim text.

Low input signal bandwidth compressor and amplifier control circuit with a state variable pre-amplifier

Life of this patent

Low input signal bandwidth compressor and amplifier control circuit with a state variable pre-amplifier

Life of this patent

Abstract

Claims19