Abstract: A digital audio-signal output circuit is provided, which is capable of outputting an audio signal without generating pop noise. In suppressing pop noise, the audio signal output circuit requires no analog circuit nor mute control signal for external peripheral devices. Upon receipt of a digital input audio signal having an AC component superposed on a reference voltage VREF, the circuit selects one of a pulse-density-modulated audio signal derived from the input audio signal and a transition signal that smoothly varies between zero volt and the reference voltage, and provides the selected signal to speakers.

Abstract: A surge protection circuit acquires a surge signal of a left channel (LC) signal line and a right channel (RC) signal line. After the surge signal transmitting on the LC signal line and the RC signal line are removed, an audio signal outputted from a signal input device are transmitted to an audio output device via the LC signal line and the RC signal line.

Abstract: A signal output device includes: a control circuit for receiving at least a first input control signal and outputting an output control signal according to at least the first input control signal, wherein the first input control signal comprises a first signal segment followed by a second signal segment; and a driver circuit, operated according to a supply power, for receiving the output control signal from the control circuit and selectively generating an output signal according to the output control signal; wherein the supply power is turned on before the second signal segment of the first input control signal is received by the control circuit; when the supply power is turned on, the driver circuit operates under a specific power state; and when the second signal segment of the first input control signal is received by the control circuit, the driver circuit keeps operating under the specific power state.

Abstract: An amplifier is disclosed, wherein the output stage is split between a primary output stage and a secondary stage. To minimise or eliminate any audible plop when the amplifier is switched on, the primary stage is connected, and the second stage is gradually connected using a switch. The gradual connection can be by means of varying the pulse-density of a pulse wave modulation on the switch, from fully open (0% pulse-density) to fully closed (100%). The inverse process can minimise or eliminate plop during switch-off. Separate feedback loops are switchable, from the primary and secondary stages; in a DC-coupled embodiment, the feedback loop from the secondary stage may include DC-offset cancelling circuitry, to both reduce or eliminate the plop and avoid and DC-offset current through the speaker.

Abstract: A muting circuit of the present invention includes: an input terminal that receives a control signal for allowing switching between ON and OFF of a mute operation; and a muting transistor connected to the input terminal and an output terminal of the amplifier. The muting transistor is a MOS transistor, and a gate is connected to the input terminal, a drain is connected to the output terminal of the amplifier, and a source is grounded. Consequently, a shot noise due to a DC difference caused when a mute state is switched between ON and OFF can be suppressed.

Abstract: A codec includes an output module for converting a digital input signal into an analog output signal. A controller module monitors a plurality of status conditions and asserts a mute signal for engaging an output mute switch based on a plurality of disconnect rules.

Abstract: A switching transistor has its drain and source respectively connected to a gate and a source of an output transistor for supplying output current to a load, and its gate connected to an internal grounding wire GW to be connected to a grounding terminal GND. A resistance element R1 connects the gate to the source of the switching transistor. When a voltage not smaller than a predetermined value is generated across the resistance element R1 at turn-on, due to a parasitic capacitance existing between a power supply terminal. Vcc and the internal grounding wire GW, the switching transistor can be turned on to turn off the output transistor.

Abstract: A method and an apparatus for squelch gating a receiving signal depending on the level of phase noise in said receiving signal determines sampled amplitudes and sampled phases of said receiving signal, determines sampled phase noise by differentiating subsequent sampled phases, determines a squelch signal by rectifying and averaging said sampled phase noise, determines a start point of gating after a rising of said squelch signal above a higher threshold delayed by a first delay time, determines a end point of gating after a dropping of said squelch signal below a lower threshold delayed by a second delay time and gates said sampled amplitudes from said start point of gating until said end point of gating.

Abstract: A method is provided to remove an unexpected pop-up noise that occurs while audio data such as a key tone is output in an electronic device. The method includes detecting an interruption such as a key release for stopping the output of audio data, and verifying Pulse Code Modulation (PCM) data of the audio data. If there is a gap between an endpoint of the PCM data and a given reference value, the device reduces the gap by revising the endpoint of the PCM data.

Abstract: An approach is provided for measuring, identifying, and removing at least one sinusoidal interference signal (Ak·ej(?kt+?k), Ak·ej(?·?k?t+?k)) in a noise signal (w(t), w(?·?t)). A frequency range to be measured is split into a plurality of frequency bands (?) via a Fast Fourier Transform (FFT) filter bank. For each of the frequency bands (?), an autocorrelation matrix ({circumflex over (R)}?) is determined, wherein parameters of the autocorrelation matrices ({circumflex over (R)}?) are variably adjusted based on whether the at least one sinusoidal interference signal (Ak·ej(?kt+?k), Ak·ej(?·?k?t+?k)) is to be measured, identified, or removed and further based on at least one averaging. The autocorrelation matrices ({circumflex over (R)}?) are jointly utilized for one or more of measuring, identifying, or removing the at least one sinusoidal interference signal (Ak·ej(?kt+?k), Ak·ej(?·?k?t+?k)) in the noise signal (w(t), w(?·?t)).

Abstract: A noise reducing circuit includes a variable low-cut filter disposed at an upstream of a sound signal switching section and has a variable cutoff frequency, and a control circuit which controls the cutoff frequency of the variable low-cut filter to a first cutoff frequency lower than a cutoff frequency of a low-cut filter disposed at downstream of the variable low-cut filter when a switching instruction is not issued from a switching instructing section, and increases the cutoff frequency of the variable low-cut filter to a second cutoff frequency higher than the first cutoff frequency when the switching instruction is issued. The switching of the sound signal switching section is executed after a predetermined period elapses since the switching instruction is issued, and the control section decreases the cutoff frequency of the variable low-cut filter to the first cutoff frequency after the switching of the sound signal switching section is completed.

Abstract: Disclosed herein are an audio processing apparatus and method. In an embodiment, if a playing mode that abruptly changes the level of audio being played has been input, the data of the audio is processed to mitigate the abrupt change in the level of the audio and converted into analog signals, and the analog signals are output. In an embodiment, if a playing mode that causes a jump from the current track of the audio being played to another track is input, the audio data is divided by an exponential function of 2 before the jump to the another track is completed. In another embodiment, if a playing mode that rapidly moves a playing position to another location on the same track has been input, the audio data is divided by a specific exponential function, and is then multiplied by the exponential function after the playing mode has been completed.

Abstract: Noise reduction for a switching amplifier system having a differential output stage and demodulator filter responsive to complementary PWM signals includes generating in-phase PWM signals and gradually adjusting their duty cycle between a low duty cycle and the full duty cycle of the complementary PWM signals, generating full duty cycle PWM signals and gradually shifting their relative phase between in-phase and out-of-phase; and in response to a turn-on signal, adjusting the in-phase PWM signals from low to full duty cycle and shifting the relative phase from in-phase to out-of-phase, and in response to a turn-off signal shifting the relative phase from out-of-phase to in-phase and adjusting the in-phase PWM signals from full to low duty cycle for maintaining balanced charge on the demodulation filter to reduce audible noise.

Abstract: An audio subsystem having a waveform generation circuit that generates a power-up signal for controlling an electric signal used to drive a speaker during a power-up period in which the power-up signal has a positive second derivative during a first sub-period of the power-up period and has a negative second derivative during a second sub-period of the power-up period. The first sub-period spans at least one-fourth of the power-up period, and the second sub-period spans at least one-fourth of the power-up period.

Abstract: An audio output driver includes an audio amplifier for generating an amplified signal. A virtual ground generator generates a virtual ground signal in response to a virtual ground reference. A combiner produces an output signal, based on the amplified signal and the virtual ground signal, that is coupled to an audio output device. A voltage equalizer equalizes the virtual ground reference and the output signal when the supply voltage compares unfavorably to a supply voltage threshold.

Abstract: An output-level-controlling converter device, including a ramp generator, used to generate a ramp signal; and an analog-to-PWM converter, said converter is used to perform conversion digitally for a reference signal by making use of said ramp signal, and output a pulse-width-modulation signal; and a pulse width detector, used to detect a duty cycle of said pulse-width-modulation signal, and output a gain control voltage signal based on said duty cycle, and when said duty cycle is close to 0% or 100%, said ramp generator is used to increase a voltage amplitude of said ramp signal based on a voltage value of said gain control voltage signal, hereby increasing or decreasing said duty cycle of said pulse-width-modulation signal for reducing voltage gain of said reference signal.

Abstract: Disclosed is a circuit for preventing an output of a pop noise, which occurs from an audio amplifier when a power switch of an electronic device loading the amplifier is turned on/off. The circuit may comprises an analog switch for switching an electrical connection between an audio amplifier and a speaker, and a signal delay circuit capable of respectively delaying times that the operating states of the analog switch and the power supply are changed when the power switch is turned on/off, and it is structured such that the analog switch is already opened state at the time that the power supply is on/off. Accordingly, it is possible to prevent the pop noise from being outputted through a speaker connected to the amplifier. The circuit of the invention can be applied to a variety of electronic devices having an audio amplifier.

Abstract: A circuit for suppressing audio noise having a common node electrically connected to an output terminal of a preamplifier and an input terminal of a postamplifier is disclosed, in which the preamplifier is provided power by a second voltage supply. The circuit for suppressing audio noise includes a first and a second pulldown switch, a first control switch and a voltage detecting circuit. In which, the first and the second pulldown switch conduct audio noise passing the preamplifier to the ground during the early and the later stage after the second voltage supply is turned on and the voltage is stable, respectively. In addition, the voltage detecting circuit detects whether the voltage is stable or not for deciding whether the circuit for suppressing audio noise must be disabled or not. If the circuit is disabled, the audio signal directly sent to the postamplifier from the preamplifier.

Abstract: A system is provided for use in an audio signal processor to reduce the order of the loop to remove sound artifacts from an audio signal that includes an input for receiving an audio input signal a control loop of order greater than one configured to process the audio input signal and to output a Pulse Width Modulated audio output signal, a circuit for performing a gradual reduction of the order of the control loop such that prior to entering a shut down state the order is reduced to a single order and a circuit to disconnect a Driver Circuit from the Pulse Width modulated signal operated by a timing device designed to switch at the moment of zero average output value.

Abstract: A noise elimination circuit of a audio output device includes a sound card for receiving a digital audio signal and transforming it to an analog audio signal; an audio reproduction apparatus such as a audio output device connected to the sound card for receiving the analog audio signal; a power supply connected to the sound card for providing a working voltage thereto; a capacitor connected between the power supply and ground; and a discharging circuit also connected between the power supply and ground, for discharging deposited current in the capacitor when the audio output device is cut off. The discharging circuit is controlled according to the state of the power supply.

Abstract: An audio output apparatus includes: an audio codec outputting an analog audio signal corresponding to a digital audio signal from a system controller; a switch unit having a first end coupled to the audio codec through a capacitor, and a grounded second end; and a switch controller triggered by a trigger signal to output a control signal to a control end of the switch unit such that the switch unit couples the capacitor to ground in response to the control signal. The trigger signal is generated by one of the system controller, the audio codec, and a power circuit supplying electric power to the system controller, the audio codec and the switch controller upon occurrence of a condition associated with pop noise, and is outputted to the switch controller before the pop noise is generated, such that the pop noise is conducted to ground via the switch unit.

Abstract: A system and process for muting the audio transmission from a location of a participant engaged in a multi-party, computer network-based teleconference when that participant is working on a keyboard, is presented. The audio is muted as it is assumed the participant is doing something other than actively participation in the meeting when typing on the keyboard. If left un-muted the sound of typing would distract the other participant in the teleconference.

Abstract: A circuit for generating a large RC time-constant includes an input node for receiving an input signal making a transition from a first state to a second state characterized by a first time-constant, and an output node for providing an output signal making a transiting from the first state to the second state in response to the input signal. The circuit also includes a first MOS field effect transistor coupled between the input node and the output node. The circuit further includes a first capacitor coupled between the output node and a ground node. A switch circuit is connected to a gate of the first MOS field effect transistor. The switch circuit is configured to bias the MOS field effect transistor to operate in saturation mode and the transition of the output signal is characterized by a time-constant associated with this large output resistance and the capacitor coupled to the output node.

Abstract: A circuit, system and method provide the suppression of pop at power up of audio amplifiers. The output driver is tri-stated at power up and is enabled after a predetermined time constant. In one embodiment, the output driver includes a MOS transistor pair connected in a push-pull configuration and switches that are under the control of a delay circuit. the. The output driver and the delay circuit may be part of a power amplifier in an audio system. The delay circuit may be implemented using mixed analog and digital signals or a digital controller configured to receive a clock frequency and execute a machine readable program code. The delay circuit is responsive for the start-up behavior of the audio system.

Abstract: An audio power amplifier includes a differential amplifier circuit that serves as an input circuit. The differential amplifier circuit includes a signal GND (SG) terminal that receives a SG voltage, and an audio signal input terminal that receives an audio signal. A SG voltage generation circuit is provided to output the SG voltage. The SG voltage generation circuit includes a voltage follower amplifier that outputs a current, a reference voltage source that is input to the voltage follower amplifier, and a current control circuit that controls the current output from the voltage follower amplifier. The SG voltage rises in a prescribed manner while suppressing a pop sound during its transition.

Abstract: A first situation indicating that the system is in a power-on situation or an un-mute situation, or a second situation indicating that the system is in a power-off situation or in a mute situation, is detected. When the first situation is detected, a differential PWM signal including a plurality of pulses each having a gradually increased or reduced width and the subsequent pulse train of 50% duty cycle pulses is generated and, if the output of an audio processor is in a stable situation, sent to the amplifier via a multiplexer. When the second situation is detected, the differential PWM signal including a plurality of pulses each having a gradually reduced width and the subsequent pulse train of no signal is generated and, at the same time, the generated pulses are sent to the amplifier via the multiplexer.

Abstract: A noise estimation unit estimates a noise signal in an input signal. A section decision unit distinguishes a target signal section from a noise signal section in the input signal. A noise suppression unit suppresses the noise signal based on a first suppression coefficient from the input signal. A noise excess suppression unit suppresses the noise signal based on a second suppression coefficient from the input signal. The second suppression coefficient is larger than the first suppression coefficient. A switching unit switches between an output signal from the noise suppression unit and an output signal from the noise excess suppression unit based on a decision result of the section decision unit.

Abstract: Provided is a sound processing device including: a sound input unit for dividing an input sound into predetermined time units; a sound processing unit for encoding the input sound thus divided; a noise detecting unit; and an output control unit for replacing encoded data on the input sound with silent data according to detection results of the noise detecting unit. Also provided is an input sound processing method including: encoding an input sound; judging whether or not the input sound contains a noise; and replacing a noise portion contained in the encoded input sound with silent data.

Abstract: An audio amplifier is provided. The audio amplifier includes an amplifier, a biasing circuit, and a time-delay circuit. The amplifier circuit is for amplifying audio signals. The biasing circuit is for providing a bias voltage to the amplifier circuit to actuate the amplifier circuit. The time-delay circuit is for receiving a pulse signal and delaying the bias voltage to avoid a sudden actuation of the amplifier circuit based on the pulse signal. The time-delay circuit comprises a first input for receiving the pulse signal, a first resistor coupled to the first input, a first output coupled to the biasing circuit, a first BJT whose base, emitter, collector are respectively coupled to the first resistor, ground, and the first output.

Abstract: An audio amplifier, amplifying the audio signal, includes a first filtering circuit, and a second filtering circuit. The first filtering circuit generates an inverting driving voltage to drive a load according to the audio signal. The second filtering circuit generates a non-inverting driving voltage to drive the load according to the inverting driving voltage. The first filtering circuit and the second filtering circuit filter out signals with frequencies greater than a pre-determined frequency.

Abstract: An audio reproducing apparatus includes a power supply, an amplifier, a speaker, and a controller. The power supply is for supplying a voltage. The amplifier is for receiving the voltage and audio signals, amplifying the audio signals, and outputting amplified audio signals. The speaker is for reproducing sound after receiving the amplified audio signals. The controller is for receiving the voltage and generating a control signal to enable the amplifier. The controller includes a generator and a delay unit. The generator is for receiving the voltage and generating the control signal. The delay unit is for delaying the time of transferring the voltage from the power supply to the generator.

Abstract: An audio amplifier includes a timing control circuit, an amplifying circuit, and a bias control circuit. The timing control circuit generates a first power down signal and a second power down signal, in which the first power down signal is asserted before the second power down signal is asserted. The amplifying circuit receives a bias voltage to amplify an audio signal and is deactivated when the first power down signal is asserted. The bias control circuit provides the bias voltage for the amplifying circuit and is deactivated when the second power down signal is asserted.

Abstract: An audio amplifier includes an amplifying circuit, a bias control circuit, and a decoupling device. The amplifying circuit amplifies an audio signal. The bias control circuit provides at least one bias voltage for the amplifying circuit according to a power down signal, in which the power down signal represents that the audio amplifier is powered on or powered down. The decoupling device reduces the damping phenomenon of the bias voltage caused by powering on or powering down the audio amplifier.

Abstract: An electronic audio device with a digital audio output channel in which an amplifier output voltage is gradually ramped up and down to avoid causing a popping sound when the device is turned on and off. This is accomplished without employing any additional hardware, by incrementally changing a digital input word applied to a digital audio source, such as a DSP, so as to gradually change the amplifier output voltage between a minimum, such as zero volts, and a DC working voltage. On powering up, the amplifier is only turned on after the digital word is applied, but while it still results in a minimum amplifier output, and on powering down the amplifier is turned off after it's output has been ramped down, but before removing the digital input word. Sources and output channels can also be switched over by powering down, and then powering up, following the same method.

Abstract: A multi-channel decoding method includes: receiving an input signal to generate a first channel output signal and a second channel output signal, wherein the input signal is mixed with a specific clock signal; and gradually changing an amplitude of the specific clock signal from a first value to a second value when switching from a first mode corresponding to a first number of channels to a second mode corresponding to a second number of channels. Systems utilizing the method and another method further comprising calibration are also disclosed.

Abstract: An pop noise eliminating circuit includes a power source, a grounding terminal, a speaker, an audio amplifier that has two opposite ends respectively connected with the power source and the first end of the speaker, a delay unit that has one end electrically connected with the power source, a first power control switch that has a control end electrically connected with the delay unit, a first conduction end electrically connected with the other end of the speaker, and a second power control switch that has a control end electrically connected with the delay unit, a first conduction end electrically connected with the grounding terminal, and a second conduction end electrically connected with a second conduction end of the first power control switch.

Abstract: An apparatus and method for minimizing the quantization noise as muting are provided, and particularly applied to a Delta-Sigma modulator that is used to process digital-to-analog conversion. By means of a zero-sampling detection circuit and a dynamic gain mechanism, a dynamic gain is introduced to minimize the quantization noise occurred as muting. The method preferably includes a first step for receiving the signals by the Delta-Sigma modulator inputted from an audio decoder, and a next step for detecting signal zero by a zero-sampling detection unit and counting the number of the signals with signal zero. The mute state is entered when the number of signal zeros reaches a pre-set number. At the moment, the signaling route is switched to another route with dynamic gain mechanism. Further, the dynamic gain mechanism is activated for producing a dynamic gain, which will be fed back to the input end of the modulator.

Abstract: A mute circuit has a resistor net configured to include a plurality of resistors connected in cascade between two reference voltage terminals, the resistor net being capable of outputting one of divided voltages from between the adjacent resistors, a selecting circuit configured to control selection of the divided voltage outputted from the resistor net based on logic of a selecting signal, a signal propagation determining circuit configured to monitor a voltage level of the divided voltage selected by the selecting circuit using an alternating test signal, and determine whether a signal indicating the monitored result propagates or not at the same cycle as that of the test signal, a memory circuit configured to store data corresponding to an output signal of the signal propagation determining circuit in association with the selecting signal, a first switching circuit configured to switch whether a DC blocking capacitor is charged or not according to the divided voltage outputted from between specific resisto

Abstract: A first amplifier amplifies a first audio signal. A synthesizer circuit synthesizes an output signal of the first amplifier with a second audio signal. The first amplifier is arranged such that a first state in which the first amplifier amplifies a signal with a set gain and a second state in which the first amplifier outputs a fixed bias voltage can be seamlessly switched. A signal processing unit is disposed upstream of the first amplifier, subjects a third audio signal to a predetermined signal process, and outputs it as the first audio signal. When a state of the signal processing unit is switched, the first amplifier is changed from the first state to the second state, the state of the signal processing unit is switched in the second state, and subsequently the first amplifier is switched from the second state to the first state.

Abstract: A sound signal switchover means capable of preventing pop noise sound in an audio system from being generated is down-sized, and a time constant of a time constant unit for the changeover of the sound signals can be varied, thereby enabling the switchover to be implemented with greater smoothness. A sound signal selection means (12) having a plurality of switches (SW 1a? to SW 2b?) for switching over the sound signal to the sound signal having the different output level is provided between a sound input source, and a sound output means. When switching over the sound signal to the sound signal having the different output level, the sound signals before and after the switchover coexist and the switchover is implemented at that point in time. A time constant unit (8) is made up of a SCF built in an IC, and the time constant ? can be controlled to be freely adjusted by a clock signal Fclk obtained by dividing a reference signal generated in a VCO (6) by a variable frequency dividing rate.

Abstract: A pop noise suppression apparatus for eliminating popping noise generated upon initiation or shutdown of an audio output circuit comprises a switch component and a control circuit. The switch component allows the audio output circuit to provide audio through the output of the audio output circuit. The control circuit provides a mute signal for a first period of time in to response initiation or shutdown of the audio circuit. The control circuit comprises a capacitor to be charged upon initiation of the audio output circuit or to be discharged upon shutdown of the audio output circuit. A length of the first period of time during which the mute signal is provided depends on a second period of time to charge or discharge the capacitor.

Abstract: An audio system that reduces or eliminates click and pop noise during power up and power down operations. In particular, the audio system includes an amplifier with an input adapted to receive an input audio signal and an output adapted to produce an amplified output audio signal for an associated speaker. The audio system further includes a noise reduction circuit adapted to smoothly apply and remove a DC voltage to and from the output of the amplifier in a manner that reduces or eliminates click and pop noise from being generated by the associated speaker. The DC voltage at the output of the amplifier may be derived from a DC reference voltage source and/or from the input audio signal.

Abstract: In an audio output device and controlling method therefor, the audio output device includes a power source, an audio processing unit and a power correction unit. The power source provides power for the audio output device. The audio processing unit processes audio signals. The power correction unit is coupled between the power source and the audio processing unit. The power correction unit corrects the supplied power by slowly charging or discharging for causing a frequency of a pulse audio signal being lower than 20 Hz, wherein the pulse audio signal is correspondingly obtained by the audio processing unit processing a power changing produced by turning on or turning off the power source.

Abstract: A PWM signal generator is operable to generate a first pulse signal and a second pulse signal at least one of before and after generating the first pulse signal. A duty ratio of the second pulse signal is gradually changed. A low-pass filter is operable to convert the first pulse signal output from the PWM signal generator into an analog acoustic signal. The low-pass filter is operable to convert the second pulse signal output from the PWM signal generator into the analog acoustic signal having an inaudible frequency.

Abstract: An audio amplifier is provided. The audio amplifier includes an amplifier, a biasing circuit, and a time-delay circuit. The amplifier circuit is for amplifying audio signals. The biasing circuit is for providing a bias voltage to the amplifier circuit to actuate the amplifier circuit. The time-delay circuit is for receiving a pulse signal and delaying the bias voltage to avoid a sudden actuation of the amplifier circuit.

Abstract: A digital offset is combined with an audio signal in the digital domain to cancel an output offset caused by one or more analog components processing the same audio signal. In this manner, the offset at the output of the audio signal path (e.g., at a power amplifier output) is reduced or eliminated. Consequently, audible artifacts, such as click-and-pop artifacts, can be reduced or eliminated. In audio devices operating in ground-referenced capless mode, power consumption is reduced because of reduced or eliminated direct current (DC) leakage current through speakers or headsets of such audio devices. In some circumstances, the digital offset in the digital domain may be applied at substantially all times of operation of the audio signal path.

Abstract: An audio output device and method capable of preventing generation of pop noise by a relatively simple and small-sized circuit configuration and control timing. A D/A converter converts a digital audio signal to an analog audio signal. A non-inverting amplifier amplifies the analog audio signal. A signal output from the non-inverting amplifier is amplified by inverting amplifiers of two stages with a first timing. A signal output from an inverting amplifier is input to a speaker amplifier by a switch. The output signal of the inverting amplifier is output to a speaker with a second timing subsequent to the first timing. The output signal of the inverting amplifier is amplified by the speaker amplifier and output to the speaker. With a third timing subsequent to the second timing, the output of each of the inverting amplifiers is stopped and the output of the speaker amplifier is stopped.

Abstract: A multiple-channel audio processor (10) and an associated plurality of power stages (22) in an audio system are disclosed. The audio processor (10) includes a plurality of audio amplifier channels (22), each of which includes a pulse-code-modulation (PCM) to pulse-width-modulation (PWM) conversion function (25), which generates PWM signals for application to the plurality of power stages (22). The audio amplifier channels (20) each also include an interchannel delay function (28) for delaying the PWM edges relative to other channels (20), for reducing noise. The audio amplifier channels (20) each also include delay adjust circuitry (32) for gradually increasing and decreasing the interchannel delay of the channel (20) on startup and shutdown. This permits a single control terminal (VALID) at the processor to globally enable and disable all of the power stages (22).

Abstract: An audio signal processing apparatus for outputting an input digital audio signal as a positive phase PWM signal and a negative phase PWM signal. The resolution of the input digital audio signal is converted to a low resolution and noise shaping is performed to generate a positive phase digital signal (REF_P) and a negative phase digital signal (REF_N). Both signal patterns are compared at a buffer and pattern comparator section when muting. If the signal patterns match, a selector outputs a set value having 50% duty instead of the digital signals to optimize timing for switching to 50% duty when muting.

Abstract: An n-channel integrated circuit device (n is an integer of 1 or greater) for muting an audio signal includes a control circuit configured to generate a control signal and a delayed control signal, a charging and discharging circuit configured to charge and discharge a time constant control terminal according to the control signal and the delayed control signal, an N-th voltage-to-current converting circuit (N is an integer from 1 to n) configured to generate a (2N?1)-th current corresponding to a voltage on the time constant control terminal and a (2N)-th current corresponding to an intermediate voltage, a (2N?1)-th mirror circuit configured to copy the (2N?1)-th current to generate (4N?3)-th and (4N?2)-th intermediate currents, a (2N)-th mirror circuit configured to copy the (2N)-th current to generate (4N?1)-th and (4N)-th intermediate currents, a (2N?1)-th selecting and combining circuit configured to combine a (2N?1)-th mute control current using the (4N?3)-th intermediate current and the (4N?1)-th interm