Abstract: A device is disclosed for converting an input signal to a digital output signal at a preselected sampling rate with an increase in dynamic range without aliasing. The preferred embodiment utilizes a converter for producing a low resolution digital signal at a higher frequency and an averaging digital filter arrangement for increasing the resolution at the preselected sampling rate. The device is easily capable of producing digital output signals of at least 17 bits at any frequency such as 48 KHz.

Abstract: An adaptive signal weighting system is disclosed for use in transmitting an electrical information signal of a predetermined bandwidth along a signal path. The system can be used to encode or decode the signal. The system comprises filter means disposed in the signal path for varying the gain impressed on the portion of the information signal within a first select spectral region within the preselected bandwidth. The gain is varied in response to and as a function of a first control signal. Means are provided means for generating the first control signal in response to and in accordance with the signal energy of the information signal substantially within at least a part of the first select spectral region.

Abstract: The disclosure relates to an audio signal reproduction system having one or more of the following features: (1) a loudspeaker having (a) a flat frequency response and (b) a predetermined power response; (2) two loudspeakers adapted to be positioned relative to one another so that they reproduce a stereophonic image substantially independent of the listener's position along a listening line spaced from the loudspeakers and nonintersecting a line extending between the two speakers; (3) an improved cross-over network having a substantially constant input impedance as a function of frequency; (4) a power sensor for sensing the power applied to a transducer so that audio signals are transmitted over a first signal path through the system when the sensed power is above a predetermined minimum level, and over a second path when the sensed power falls below the minimum level; (5) a power monitoring circuit to prevent a loudspeaker driver from being overdriven; and (6) a circuit for substantially balancing the signal

Abstract: The disclosure relates to an audio signal reproduction system having one or more of the following features: (1) a loudspeaker having (a) a flat frequency response and (b) a predetermined power response; (2) two loudspeakers adapted to be positioned relative to one another so that they reproduce a stereophonic image substantially independent of the listener's position along a listening line spaced from the loudspeakers and nonintersecting a line extending between the two speakers; (3) an improved cross-over network having a substantially constant input impedance as a function of frequency; (4) a power sensor for sensing the power applied to a transducer so that audio signals are transmitted over a first signal path through the system when the sensed power is above a predetermined minimum level, and over a second path when the sensed power falls below the minimum level; (5) a power monitoring circuit to prevent a loudspeaker driver from being overdriven; and (6) a circuit for substantially balancing the signal

Abstract: An improved bias generator provides a bias voltage output which is a function of an input current Iprog and provides a bias current to a preselected load which tracks the input signal independently of temperature. The amount the bias voltage output changes with temperature is determined by (1) V(T, Iprog), a voltage-current temperature dependent function of the base-emitter voltage drop of at least one transistor and (2) X, a scalar which is easily provided by setting the ratio of two resistors. The generator can therefore be easily constructed for particular circuit loads which include at least one semiconductive junction such that the biasing current through the load will be substantially independent of temperature.

Abstract: A signal gain controlled system comprises an operational amplifier including a feedback path between the input and output terminals of the amplifier. The system includes first variable impedance means for varying the output voltage at the output terminal of the amplifier in response to and as a function of the input current signal applied to the input terminal and a first control signal. A signal path coupled between the output terminal of the operational amplifier and the output terminal of the system includes second variable impedance means for varying the output current of the system in response to and as a function of (a) the output voltage at the output of the amplifier and (b) a second control signal. The signal gain of the system is a function of the ratio of the second and first control signals.The preferred amplifier is the type having an input resistance and a feedback resistance, wherein at least one of the resistances includes a transistor which is biased to operate in its saturated region.

Abstract: A signal conditioning system is disclosed for modifying the dynamic range of an electrical input signal. The system comprises gain control means for controlling the gain of the input signal as a function of a gain control signal, and control signal generating means for generating the gain control signal. In accordance with one aspect of the present invention the control signal generating means comprises (1) means for generating a first signal as a function of the amplitude of the input signal, and (2) means responsive to the first signal for generating the gain control signal as a function of only those portions of one polarity of the time derivative of the first signal. In accordance with another aspect of the present invention means are provided for substantially lengthening and/or linearizing the release behavior of the control signal waveform applied as the control signal input signal to the gain control means.

Abstract: The invention relates to an improved voltage control amplifier of the type comprising a gain cell. The gain cell is of the type that includes at least one log transistor for each polarity of input signal and at least one antilog transistor for each log transistor, means for algebraically summing a control signal with the log signal provided by each log transistor and means for providing a symmetry adjust signal to the base of a selected transistor of the cell so that the cell provides substantially the same gain for each polarity of input signal when the control signal level is set for zero. The improvement comprises means for generating a correction signal as a function of the control signal level so as to substantially correct for differences between the early effects exhibited by said transistors as said control signal varies and means for applying the correction signal to the base of one the transistors.

Abstract: A device is described for modifying the charging behavior of a charge storage device, such as a capacitor, so that the device charges substantially in accordance with a square law function responsively to a linear charging input current. The device has particular utility in a signal-conditioning system of the type including an averaging detector, a gain stage and a charge storage device coupled between the output of said detector and the input of said gain stage so that the input to said gain stage behaves in a similar manner to the output of an RMS detector.

Abstract: An improved multiplier circuit of the type including an input operational amplifier and a gain cell is disclosed. The gain cell is connected to the amplifier such that a first signal can be generated in response to and as a logarithmic function of an input signal, a control signal can be added to the first signal and a second signal can be algebraically generated as an antilogarithmic function of the algebraic sum of the first and control signals. The improvement includes means for providing a correcting signal as a function of the control signal at the output of the input amplifier substantially equal and opposite to signals produced at the output of the input amplifier by changes in the control signal.

Abstract: A network operates in the log domain so as to filter logarithmic signals and has a signal-controlled variable system frequency response. A method is also described for constructing such networks so that they function substantially identical to equivalent RC networks.

Abstract: An improved amplifier of the type comprising bipolar transistor means coupled between the input terminal of the amplifier and a differential pair of transistors. Compensation means is provided for generating a compensating signal through the bipolar transistor means such that the bipolar transistor means and compensation means reduce the amount of bias current drawn from the input signal to the amplifier. Other aspects of the present invention include the provision of reducing DC offset voltages between each side of the differential amplifier due to the operation of the device with its input terminals at different voltage levels, and the provision of a zero in the transfer characteristics of the amplifier to mitigate the effects of poles provided in the transfer characteristics.

Abstract: An improved current mode operational rectifier having loop transmissions through both feedback paths of an operational amplifier stage which limit at unity gain. An improved bias generator which can be used to bias the operational rectifier is also disclosed.

Abstract: An improved gain control circuit of the "eight transistor gain cell" type is disclosed. The improvements comprise (1) means for operating the circuit as a Class AB amplifier and (2) means for reducing the distortion component in the output signal due to the inherent parasitic base and emitter resistances of the transistors of the gain cell of the gain control circuit.

Abstract: A signal conditioning system comprises an improved gain control module 10 and an improved detector 12 which are adapted to be manufactured in integrated circuit form.

Abstract: An improved system for and method of testing a transistor for its V.sub.be -I.sub.c characteristics independent of temperature is disclosed. The system for carrying out the method comprises means for generating a first signal which varies with temperature in accordance with the base-to-emitter voltage of the transistor as a function of temperature and means for generating a second signal which varies with temperature in accordance with the transconductance gain of the transistor as a function of temperature. Means are provided for modifying at least one of the first and second signals so that as modified the two signals vary with temperature in an equal and opposite manner to one another. The system also includes means for adding the two signals as modified so as to provide an output signal representative of the V.sub.be -I.sub.c characteristics of the transistor independent of temperature.

Abstract: Amplification means responsive to an input signal of a gain control circuit is utilized in each log-antilog transmission path of the gain control circuit so as to provide in each path signal gain as a function of said input signal.

Abstract: An improved bias generator provides a bias voltage output which varies with temperature in accordance with a predetermined voltage-temperature function.

Abstract: An improved equalizing system for modifying an input electrical signal representative of original sound so as to correct for the inherent nonflat frequency response of an audio signal processing apparatus and the acoustic effects of listening environment in which the loudspeaker system of the audio signal processing apparatus may be disposed. The improved equalizing system includes a comparator for comparing the signal energy in each of a plurality of select frequency bands of a predetermined frequency range of the input signal with that of the corresponding signal energy in a like plurality of bands of a like range of a second signal representative of the acoustic output of the loudspeaker system and as a function of the nonflat frequency response and the acoustic effects of the environment. A correction signal representative of the comparison is used to modify the energy within each band of the input signal so as to substantially correct for the nonflat response and the acoustic effects of the environment.

Abstract: A multiplier circuit for controlling gain amplification of an electrical input signal responsively to a control signal comprises log conversion means for producing a log signal as a logarithmic function of the input signal, means for producing a multiplier signal as a function of the sum of the log signal and the control signal and antilog-conversion means for producing an antilog signal as an antilogarithmic function of the multiplied signal. The improvement is characterized by the log conversion means and antilog conversion means each including passive elements capable of exhibiting log-linear and antilog-linear transfer characteristics. The passive elements are preferably in the form of diode elements connected in a diode bridge.