Abstract: In general, according to one embodiment, an ultrasonic diagnostic apparatus includes an ultrasonic probe, a plurality of power supplies implemented by circuitry, at least one pulser, and a controller implemented by circuitry. The ultrasonic probe includes a plurality of piezoelectric transducers which generate ultrasonic waves in response to supplied driving signals. The pulser outputs the driving signal based on an applied voltage applied from any one of the plurality of power supplies. The controller switches the plurality of power supplies in accordance with the at least one pulser used for generation of the driving signal in one transmission mode period.

Abstract: A circuit for biasing a transducer including a first plate and a second plate includes a front-end buffer and a charge pump. The front-end buffer generates an internal signal at an internal node in response to a voltage signal of the second plate. The transducer receives the incident sound wave at the first plate to generate the voltage signal at the second plate. The charge pump boosts the internal signal into a boost voltage at the first plate according to a first clock signal.

Abstract: An amplifier circuit includes an amplifier and a voltage boost circuit configured to provide a variable supply voltage to the amplifier, the variable supply voltage continuously proportional to an audio input signal, the variable supply voltage configured to follow an output of the amplifier.

Abstract: In general, the subject matter described in this disclosure can be embodied in methods, systems, and program products for analyzing, by a computing system, one or more signals transmitted to an audio transducer. The computing system determines, based on the analyzing the one or more signals, an inductance of electronic components affecting the one or more signals. The computing system modifies, based on using the determined inductance to determine that atypical displacement of the membrane of the audio transducer has occurred, the one or more signals to compensate for the atypical displacement of the membrane of the audio transducer.

Abstract: An embodiment amplifier circuit includes a pair of subcircuits that includes a first subcircuit and a second subcircuit, each of which includes a buffer amplifier and a feedback circuit that includes a feedback capacitor. The amplifier circuit also includes a pair of output terminals. The first subcircuit and the second subcircuit each generate a different output signal of a pair of output signals that includes a first output signal and a second output signal. The amplifier circuit is configured for receiving a positive differential input signal at the first subcircuit, receiving a negative differential input signal at the second subcircuit, and receiving the pair of output signals at the pair of output terminals. The amplifier circuit is also configured for transmitting the first output signal to the feedback circuit of the first subcircuit, and transmitting the second output signal to the feedback circuit of the second subcircuit.

Abstract: A computer-implemented method to generate an audio output signal is disclosed. The method may include receiving an audio input signal at an automatic gain control (AGC) unit. The method may further include receiving a volume setting indicator signal at the AGC unit. Further, the method may include setting one or more operational parameters for the AGC unit based on the volume setting indicator signal. In addition, the method may include applying a gain to the audio input signal based on the one or more operational parameters to generate an audio output signal at a desired output level.

Abstract: A flat panel speaker system is provided. The system includes, a modified panel having a front surface and a rear surface, wherein the modified panel acts as a diaphragm for the flat panel speaker system; a supporting member coupled to the rear surface of the modified panel; and a detachable driver operationally coupled to the supporting member.

Abstract: An audio system includes a reference voltage generation circuit to generate a digital encoding signal and generate an analog reference voltage according to the digital encoding signal, wherein, during a booting procedure and/or a shutdown procedure, the analog reference voltage is smoothly increased and/or decreased at a smooth rate related to a bit number of the digital encoding signal; a first analog operational amplifier for receiving the analog reference voltage to generate a common voltage, which is smoothly increased and/or decreased during the booting procedure and/or the shutdown procedure; and a differential analog operational amplifier pair, coupled to the first analog operational amplifier, for receiving a differential audio input signal pair and outputting a differential output voltage pair to drive a load, wherein, during the booting procedure and/or the shutdown procedure, the differential audio output signal pair is smoothly increased and/or decreased.

Abstract: Described herein is a head-mounted device including an audio system configured to provide a surround sound audio effect. The device may include one or more of a forehead assembly, a rear-head assembly, a set of speakers, a set of straps connecting the forehead assembly to the read-head assembly, and/or other components. The forehead assembly may include one or more speakers. Individual ones of the straps may include one or more speakers.

Abstract: This application relates to an integrated circuit die (200) comprising a MEMS transducer structure (101) integrated with associated electronic circuitry (102). The electronic circuitry comprises a plurality of transistors and associated interconnections and is formed in a first area (103) of the die from a first plurality (104) of layers, e.g. formed by CMOS metal (107) and dielectric (108) layers and possibly doped areas (106) of substrate (105). The MEMS transducer structure is formed in a second area (111) of the die and is formed, at least partly, from a second plurality (112) of layers which are separate to the first plurality of layers. At least one filter circuit (201) is formed from said second plurality of layers overlying the plurality of transistors of the electronic circuitry (102).

Abstract: A powered speaker system comprising a cabinet and an input to receive an audio signal from an external amplifier. An audio splitter receives and splits the audio signal into first and second portions. At least one first speaker driver receives the first portion of the split audio signal, and an effects output jack receives the second portion. An effects input jack that is connectable to the external effects device, receives the second portion of signal that is modified by the external effects device. An internal amplifier is coupled to the effects input jack and receives and amplifies the modified second portion of the signal. At least one second speaker driver receives from the internal amplifier, the amplified modified second portion. The first speaker driver outputs the first portion simultaneously while the second speaker driver outputs the amplified modified second portion of the split audio signal.

Abstract: A sound detection system of a musical instrument with vibrating parts includes at least a pair of sensors and a preamplification unit for processing the signal output from the two sensors along respective channels. At least one of the pair of sensors is a piezoelectric transducer and the other one of the pair of sensors is a different-type transducer. The preamplification unit includes, for each channel, an input stage, including an amplifier circuit and an equalization circuit, and an output stage including at least a weighted adder circuit and at least two volume controls with arbitrary logarithmic response curve. At least the input stage for the channel of the piezoelectric transducer is a charge amplifier circuit and at least one of the other input stages can be configured both as a charge amplifier and as non-inverting amplifier with high input impedance. The equalization circuit includes an RC circuit.

Abstract: An audio amplifier has an input for an audio signal being amplified and an output powering a load on the basis of the amplified audio signal; a generator of reference voltage of very high linearity and low output impedance, able to receive, as input, the audio signal to be amplified; a power current generator including a power voltage generator whose output is connected to the output of the reference voltage generator through a coupling inductance; and a signal adder introducing, for its control, as input to the power current generator, a signal representative of the current provided as output by the reference voltage generator. The signal adder is able to introduce a signal ( L ? di LOAD dt ) representative of the product of the value of the coupling inductance and the drift with respect to time of the current ( di LOAD dt ) provided to the load.

Abstract: Aspects of the disclosure provide an apparatus having a first connector and a signal processing circuit. The first connector is configured to receive a second connector so that connecting terminals at respective portions of the first and second connectors are coupled together. The signal processing circuit is configured to generate a first output signal at a first amplification gain, determine a first load resistance value at a first connecting terminal of the second connector that is configured to receive the first output signal when coupled to the first connector, and set the first amplification gain based on the first load resistance value.

Abstract: An electronic device having a speaker device. The electronic device may include a housing, a speaker device disposed inside the housing, and a sound generation circuit electrically connected to the speaker device. The speaker device may include a sound generation plate movable in a first direction, and a sound reflection construction facing the sound generation plate to form a space between the sound generation plate and the sound reflection construction. The sound generation plate includes a first surface disposed substantially at a center of the sound generation plate, the first surface having a convex shape when viewed from inside the space, and the sound reflection construction includes a second surface substantially aligned with the first surface along an axis of the housing, the second surface having a concave shape when viewed from inside the space.

Abstract: The DC detection circuit includes: a OR circuit configured to generate a logical OR flag on the basis of logical OR of values of X bits from a (MSB-1)th bit to a (MSB-X)th bit of input data; a NAND circuit configured to generate a NAND flag on the basis of a NAND of values of X bits from the (MSB-1)th bit to the (MSB-X)th bit of the input data; a counter configured to count up and a counter value which outputs a DC detection flag if a counter value is exceeds predetermined set value on the basis of the MSB and any one of the logical OR flags of NAND flags. Accordingly, safety can be secured by detecting whether the DC data is included in the input PCM data, and thereby preventing degradation and breakage of the loudspeaker etc. due to the DC data.

Abstract: A microphone biasing circuit comprises a microphone connected between a first node and a first DC bias voltage, the microphone configured to provide a sensed voltage at the first node in response to sound; a first diode and a second diode, the first diode and the second diode connected antiparallel with one another between the first node and a second node, the second node having a second DC bias voltage; an amplifier having an input connected to the first node and an output connected to a third node, the amplifier configured to provide an output voltage to the third node based on the sensed voltage at the first node; and a feedback path connected from the third node to the second node. The feedback path comprises at least one element configured to couple alternating components of the output voltage at the third node to the second node.

Abstract: A driving circuit for driving a capacitive load includes a signal modulation section that causes an original drive signal to be pulse-modulated to generate a modulation signal, a signal amplification section that amplifies the modulation signal to generate an amplification modulation signal, and a coil that smooths the amplification modulation signal to generate a drive signal.

Abstract: Techniques for providing multiple power supplies in electronic devices are disclosed. According to one aspect of the present invention, an appropriate power supply is provided only to accommodate a volume setting. In other words, there are at least two power supplies, one with a low voltage and the other with a high voltage. The high voltage power supply is only applied when there is a need to accommodate a volume setting. Thus the power consumption of the amplifiers is well controlled. As a result, the designs of the device and heat dissipation therein can be simplified and lowered in cost.

Abstract: A novel ribbon microphone incorporates rounded-edge magnet motor assembly, a backwave chamber, and a phantom-powered JFET circuit. In one embodiment of the invention, one or more novel rounded-edge magnets may be placed close to a ribbon of the ribbon microphone, wherein the one or more novel rounded-edge magnets reduce or minimize reflected sound wave interferences with the vibration of the ribbon during an operation of the ribbon microphone. Furthermore, in one embodiment of the invention, a novel backwave chamber operatively connected to a backside of the ribbon can minimize acoustic pressure, anomalies in frequency responses, and undesirable phase cancellation and doubling effects. Moreover, in one embodiment of the invention, a novel phantom-powered JFET preamplifier gain circuit can minimize undesirable sound distortions and reduce the cost of producing a conventional preamplifier gain circuit.

Abstract: A JFET structure may be formed such that the channel region is isolated from the substrate to reduce parasitic capacitance. For example, instead of using a deep well as part of a gate structure for the JFET, the deep well may be used as an isolation region from the surrounding substrate. As a result, the channel in the JFET may be pinched laterally between doped regions located between the source and the drain of the JFET. In other example embodiments, the channel may be pinched vertically and the isolation between the JFET structure and the substrate is maintained. A JFET structure with improved isolation from the substrate may be employed in some embodiments as a low-noise amplifier. In particular, the low-noise amplifier may be coupled to small signal devices, such as microelectromechanical systems (MEMS)-based microphones.

Abstract: For use in professional audio amplifier applications, high current charge pump circuits including charge circuits and dynamic release circuits are connected between respective storage capacitors and the audio power amplifier output. The charge circuits charge their storage capacitors when an output signal swing of the power amplifier is below a corresponding predetermined positive and negative threshold. The dynamic release circuits release power from their charged storage capacitors to dynamically vary the voltage levels of their positive and negative power supply rails in direct relation to the output signal swing of the power amplifier, preferably at unity gain. Multiple positive and negative power supply rails at different voltage levels can be used with cascaded multi-stage dynamic release circuits to maximize system efficiency. The charge and dynamic release circuits can be connected between their storage capacitors and a buffer amplifier which also receives the power amplifier audio input.

Abstract: A method may be provided for powering up or down a playback path comprising a digital-to-analog converter (DAC) for generating a non-ground-centered analog intermediate voltage centered at a common-mode voltage and coupled to a driver for generating a ground-centered playback path output voltage at an output of the driver wherein the output of the driver is clamped via a finite impedance to a ground voltage. The method may include transitioning continuously or in a plurality of discrete steps the analog intermediate voltage from an initial voltage to the common-mode voltage such that the transitioning is substantially inaudible at the output of the driver. A method for operating an output clamp of an output driver stage of a playback path may include transitioning continuously or in a plurality of discrete steps an impedance of the output clamp in order to match an output offset of the output driver stage in order to minimize audio artifacts appearing at an output of the output driver stage.

Abstract: An audio playback path of an audio apparatus includes a digital modulator, a digital-to-analog converter (DAC), and a power amplifier. The digital modulator receives a playback signal corresponding to playback audio content and generates a digital input signal in accordance with the playback signal. The DAC receives the audio input signal and generates an analog preamplifier signal. The power amplifier generates an audio output signal in accordance with the preamplifier signal and an analog attenuation determined by the analog attenuation signal.

Abstract: Novel active phantom-powered ribbon microphones that provide switchable proximity effect response filtering for voice and music applications are disclosed with unique adjustable interfaces. In one embodiment of the invention, a slider-based full frequency response vs. low frequency response and high pass filtering adjustment interface on a surface of a microphone casing provides a convenient switching between a “Music” mode and a “Voice” mode, wherein the “Voice” mode reduces the undesirable proximity effect in an active phantom-powered ribbon microphone, when a sound source is situated overly close to the active phantom-powered ribbon microphone. Furthermore, in one embodiment of the invention, a slider-based or a knob-based variable voice mode adjustment interface can also be integrated on a surface of a microphone casing to provide various preset levels of low frequency reduction and/or proximity effect response filtering when the “Voice” mode is enabled.

Abstract: Provided is a method of removing an earphone noise of a portable terminal includes: recognizing a connection of an earphone through an interface unit; applying power to a mike bias port in case the earphone is recognized; sensing a signal which indicating a detachment of the earphone from the interface unit during applying power to the mike bias port; and discharging the power of the mike bias port when the detachment occurs.

Abstract: An electronic device having a touchless user interface for providing at least one input to the device, said touchless user interface comprising at least one ultrasound transmitter arrangement arranged to transmit ultrasonic signals and at least one ultrasound receiver arrangement arranged to receive reflections of said ultrasonic signals from an input object, wherein the device further comprises a substantially continuous outer surface portion, wherein said outer surface portion comprises at least one localised zone 30? having a greater compliance for moving in response to impingement by said ultrasonic signals or reflections such that said localised zone 30? forms part of said transmitter arrangement and/or said receiver arrangement.

Abstract: Techniques are described for controlling operation of both a host device and a wearable display device connected to the host device based on a use status of the wearable display device. The techniques include automatically determining a use status of a wearable display device based on feedback from one or more touch sensors within the wearable display device that indicates whether the wearable display device is worn by a user. Based on the determined use status, the wearable display device controls its own operation (e.g., controls operation of display screens of the wearable display device, a communication session with the host device, and display processing of data received from the host device). The wearable display device also sends an indication of the use status to the host device. The host device then controls its own data processing for the wearable display device based on the indicated use status.

Abstract: This application relates to amplifier circuitry for amplifying a signal from a MEMS transducer. A super source follower circuit (40) is provided which includes a feedback path from its output node (Nout) to a control bias node (BC) in order to provide a preamplifier signal gain that may be greater than unity. A first transistor (M1) is configured to have its gate node connected to an input node (NIN) for receiving the input signal (VIN) and its drain node connected to an input node (X) of an output stage (A). The source node of the first transistor is connected to the output node (NOUT). A current source (I2) is configured to deliver a current to the drain node of the first transistor (M1), wherein the current source (I2) is controlled by a bias control voltage (VBC) at the bias control node (BC). A feedback impedance network (Z1) comprising a first port connected to the output node (NOUT) and a second port connected to the bias control node (BC) is provided.

Abstract: An electronic device includes a circuit electrically connected to first and second contacts and a processor electrically connected to the circuit, wherein the circuit compares a first signal occurring by an electrical contact of the first contact and the external material with a first threshold value to generate a first comparison signal, compares a second signal occurring by an electrical contact of the second contact and the external material with a second threshold value to generate a second comparison signal, and generates a third signal based on a portion of the first and second comparison signals and provides the third signal to the processor, wherein the external material includes one of moisture and a foreign substance or the external connector, and the processor prevents recognizing a contact of the moisture or the foreign substance as a contact of the external connector based on a portion of the third signal.

Abstract: Otherwise incompatible digital predistortion and uptilt can be used together, such as in a cable television or other cable communications system having a frequency-dependent signal loss at high frequencies. The predistortion can be used to compensate for a nonlinear gain compression of a power amplifier at higher frequencies. Additional uptilt and equalizer circuits can be included to address deleterious distortion effects that may otherwise arise by using predistortion and uptilt together. Training and adaptation of various components are described. Fine and coarse uptilt adjustments can be provided.

Abstract: A communication device is configured to receive signals using at least one acoustic microphone and at least one structural microphone. The communication device calculates one of first a signal-to-noise (SNR) ratio and a speech-to-noise ratio for the at least one acoustic microphone from received signals and calculates a SNR for the at least one structural microphone from received signals. The communication device compares one of the first SNR and the speech-to-noise ratio for the at least one acoustic microphone with the SNR for the at least one structural microphone. The communication device selects one of the at least one acoustic microphone and at least one structural microphone to receive speech responsive to the comparing and places a selected one of the at least one acoustic microphone and at least one structural microphone in a standby mode.

Abstract: An electric amplifier circuit for amplifying an output signal of a microphone comprises a supply input terminal (V10) to apply a supply potential (VDDA) for operating the electric amplifier circuit and a differential amplifier (110) having a first input terminal (E110a) for applying the output signal of the microphone (20), a second input terminal (E110b) and an output terminal (A110) for outputting an amplified output signal (OUT) of the microphone (20). A feedback path (FP) is provided between the output terminal (A110) of the differential amplifier (110) and the second input terminal (E110b) of the differential amplifier (110). A charge supplying circuit (120) is coupled to the feedback path (FP) to supply an amount of the charge to the feedback path (FP) in dependence on the supply potential (VDDA). The amount of charge supplied to the feedback path may be dependent on a change of the supply potential (VDDA).

Abstract: A method may include providing a power supply voltage to a power supply input of a power amplifier by a charge pump power supply having a select input for selecting an operating mode of the charge pump power supply, such that in a first operating mode, the power supply voltage is equal to a first voltage, and such that in a second operating mode the power supply voltage is equal to a fraction of the first voltage; wherein the power amplifier has an audio input for receiving an audio input signal, and an audio output for providing the output signal, and generates the output signal based on the audio input signal.

Abstract: Amplifier circuitry that is operative to provide selective control of the amplitude of a musical signal as the signal transitions from the pre-amplifier to power amplifier components of an electric guitar amplifier. According to a preferred embodiment, at least one low variable power amplifier is integrated into the signal path from the pre-amplifier to the power amplifier components of the guitar amplifier. The low power amplifier allows for selective control of the amplitude of the musical signal such that the signal ranges from ‘zero volts’ to more than 100 DB. Such low power amplifiers may be selectively deployed in guitar amplifiers utilizing either Class A or Class A/B circuitry and enables a musician to have full control of the power amplifier from 0% gain to 100% gain at any tone selection and any power amp wattage, as may be desired.

Abstract: An audio amplifier circuit may include a power amplifier, a charge pump power supply, and a control circuit. The power amplifier may have an audio input for receiving an audio input signal, an audio output for providing the output signal, and a power supply input. The charge pump power supply may provide a power supply voltage to the power supply input. The charge pump power supply may have a select input for selecting an operating mode of the power supply. In a first operating mode, the power supply voltage may equal to a first voltage, and in a second operating mode, the power supply voltage may be substantially equal to a second voltage which is a rational fraction of the first voltage. The control circuit may generate the select input based on a magnitude of anti-noise generated by an adaptive noise cancellation system associated with the audio transducer.

Abstract: A power cable having improved durability and associated methods of assembly and use are described herein. In one aspect, the power cable is adapted for use in powering an implantable circulatory pump system. The cable includes one or more conductors of uninsulated wire strands that are loosely packed so as to move relative one another during cable flexure. The driveline cable may include a plurality of conductors, each comprised of multiple uninsulated bundles of uninsulated, loosely packed wire strands of a conductive material, that are wrapped about a central core. The cable may include at least six conductors, each conductor having at least 200 wire strands of a 30 gauge or higher. The cable may include the plurality of wire strands wound in a Litz style configuration to provide improved durability over many cycles of use at reduced cost, improved integrity of the electrical connection and reduced diameter.

Abstract: A dynamic multiple input rail switching unit includes a plurality of DC input voltage rails and a rail switching section coupled to the plurality of DC input voltage rails that is configured to individually connect selected ones of the plurality of DC input voltage rails to a switched rail output. The dynamic multiple input rail switching unit also includes a rail selection section that is coupled to the rail switching section and configured to dynamically choose the selected ones by balancing rail supply currents from the plurality of DC input voltage rails based on rail supply current capacity margins and a switched rail output current. A dynamic multiple input rail switching unit operating method, and a dynamic multiple input rail power converter are also provided.

Abstract: A microphone preamplifier circuit is adapted to be connected to a microphone circuit, the microphone circuit including a microphone and at least one output node. The microphone preamplifier circuit includes a preamplifier including: an operational amplifier having at least one input and at least one output; at least one input DC decoupling capacitor connected to the at least one input of the operational amplifier; at least one feedback capacitor connected between the input and the output of the operational amplifier in order to set together with the at least one input DC decoupling capacitor a gain value of the preamplifier circuit; and first and second feed nodes adapted to be fed by first and second bias voltages respectively. The preamplifier further includes at least one switched capacitor adapted to be selectively and alternatively connected in response to a clock signal: between the at least one input and the at least one output of the operational amplifier; and between the first and second feed nodes.

Abstract: Example implementations described herein may involve activating an amplifier in a playback device based on an anticipated command. An example implementation involves a first playback device determining that a command associated with the first playback device is anticipated. Based on the determination that that the command is anticipated, the first playback device identifies one or more second playback devices of a zone group that is associated with the playback device and causes the one or more second playback devices of the zone group to activate respective amplifiers.

Abstract: An amplifier circuit comprises an input, for receiving an input signal to be amplified; a preamplifier, for amplifying the input signal based on a variable gain; a power amplifier for amplifying the signal output from the preamplifier; and a variable voltage power supply for supplying one or more supply voltages to the power amplifier. The supply voltages are adjusted based on the variable gain or the input digital signal. According to other aspects of the invention, a power supply of an amplifier circuit is clocked using a clock signal, whereby the clock signal has a frequency that varies in accordance with a volume signal or an input signal.

Abstract: A priming signal processing technique modifies digital audio recordings to reduce the stress experienced by a listener's auditory system. A priming signal may reduce the instantaneous stress experienced by the auditory system during sudden changes in signal energy. The priming signal may leverage the temporal auditory masking, such that pre-signal priming additions may not result in obvious differences in perceived sounds.

Abstract: An audio and video signal transmission interface apparatus includes a left sound channel interface, a right sound channel interface, a multimedia terminal interface, and a ground interface; where a first power supply and a first resistor are connected in series in the multimedia terminal interface; and the apparatus further includes a voltage detecting module, a determining module, a control module, and a second resistor connected in series in the multimedia terminal interface, where a resistance value of the second resistor is greater than an internal resistance value of an audio and video terminal and smaller than an internal resistance value of a microphone terminal in reverse connection; the determining module identifies different types of transmission lines by using a voltage value measured by the voltage detecting module; and the control module is configured to implement adaptation of different transmission lines.

Abstract: A signal path may operate in one of a plurality of gain modes such that for each gain mode, the product of a digital gain and an analog signal gain of the signal path associated with the particular gain mode are approximately equal to a fixed path gain. During each of one or more calibration phases, a calibration system may measure analog signals at a plurality of nodes of the first path portion, calculate an actual analog gain associated with the gain mode based on the analog signals measured at the plurality of nodes, calculate an error between the fixed path gain and a mathematical product of the actual analog gain associated with the gain mode and the digital gain associated with the gain mode, and modify at least one of the digital gain and the analog gain associated with the gain mode in conformity with the error.

Abstract: In accordance with an embodiment, an interface circuit includes an amplifier configured to be coupled to a transducer, a first bypass circuit coupled to a first voltage reference and the amplifier, a second bypass circuit coupled to the first voltage reference and the amplifier, and a control circuit coupled to the second bypass circuit. The first bypass circuit conducts a current when an input signal amplitude greater than a first threshold is applied to the transducer and the control circuit causes the second bypass circuit to conduct a current for a first time period after the first bypass circuit conducts a current.

Abstract: A power amplifier containing a DC-DC converter, a linear amplifier and a control block. The DC-DC converter receives power from a power source and generates a regulated power supply voltage whose magnitude is controlled by the magnitude of a control signal provided to the DC-DC converter. The linear amplifier receives an input signal and generates a power-amplified output signal, and receives the regulated power supply voltage for operation. The control block is coupled to receive the input signal, and generates the control signal with a magnitude based on the amplitude of the input signal. The regulated power supply voltage is modulated based on the amplitude of the input signal, for peak-to-peak amplitudes of the power-amplified output greater than or less than or equal to the magnitude of the power source. High efficiency for the power amplifier is thereby obtained.

Abstract: An audio amplifier apparatus and method which has a preamp, active 2-way crossover, solid-state power amplifier, and tube power amplifier. Audio input from a musical instrument enters the preamp where pre-amplification, equalization, and other processes such as limiting or compression take place. Audio leaves the preamp and goes to a crossover, wherein frequencies below a crossover point are sent to a solid-state power amp via a first signal path, and wherein audio frequencies above the crossover point are sent to a tube power amp via a second signal path. Outputs from the solid-state power amp and tube power amp are sent to external or internal loudspeakers.

Abstract: Embodiments are provided for intelligently activating an amplifier in a playback device based on proximity detection. The playback device may be in a quasi-idle state when the playback device is not rendering media content. The quasi-idle state of the playback device may involve an amplifier in the playback device being inactive, while some other components or modules of the playback devices remain active. The playback device may include a proximity sensor configured to detect movement relative to the playback device. If movement is detected indicating that a user input to cause the playback device to render media content is anticipated, the amplifier may be pre-emptively activated such that the playback device enters an active state from the quasi-idle state. In some cases, the playback device may send a message to one or more other playback devices to cause the other playback devices to enter an active state.

Abstract: An interface circuit is provided that is adapted to connect a microphone circuit to a preamplifier. The microphone circuit has a microphone and at least an output node and the preamplifier has at least an input node connected to the output node by the interface circuit. The interface circuit has at least a decoupling capacitor for DC decoupling the input node from the output node. The decoupling is connected between the input node and the output node. The interface circuit has at least one active circuit, comprising a resistor connected the decoupling capacitor. The resistor acts as part of a resistance multiplier and has an equivalent resistance that together with the decoupling capacitor defines a high-pass filter connected between the microphone and the preamplifier. The interface circuit may also have a biasing circuit connected to the resistor.

Abstract: A sink circuit for protecting connectivity of a digital multimedia interface, the sink circuit is connected in a sink multimedia device. The sink circuit comprises a sink port configured to provide a connection to a source multimedia device; a termination coupled to the sink port; and a protection component coupled in series between the termination and a power source of the sink multimedia device, the protection component blocks any direct current path through the sink port when the sink multimedia device is off and the power source of the source multimedia device is on.