Multiple example valve amplifiers are provided. A first example valve amplifier is provided which comprises (i) a valve power amplifier switchable between a high-power mode and a low-power mode and (ii) a loudspeaker simulator circuit, the valve amplifier being configured such that the valve power amplifier drives the loudspeaker simulator circuit in the low-power mode. A second example valve amplifier is provided which comprises a switched-mode power supply, SMPS, system), the SMPS system comprising (i) an SMPS and (ii) circuitry configured to enable an output impedance of the SMPS to be switched between first and second output impedances, the first output impedance being lower than the second output impedance.

Multiple example valve amplifiers are provided. A first example valve amplifier is provided which comprises (i) a valve power amplifier switchable between a high-power mode and a low-power mode and (ii) a loudspeaker simulator circuit, the valve amplifier being configured such that the valve power amplifier drives the loudspeaker simulator circuit in the low-power mode. A second example valve amplifier is provided which comprises a switched-mode power supply, SMPS, system), the SMPS system comprising (i) an SMPS and (ii) circuitry configured to enable an output impedance of the SMPS to be switched between first and second output impedances, the first output impedance being lower than the second output impedance.

Disclosed are a hybrid mode based audio processing method and an apparatus therefor. A hybrid mode based audio processing apparatus according to an exemplary embodiment of the present disclosure includes a signal converting unit which converts a digital signal of an input sound source into an analog signal; a mode controller which analyzes the input sound source, sets an amplification mode according to the analysis result, and generates an amplification control signal to control the amplification mode; an amplifying unit which amplifies the analog signal in the amplification mode set based on the amplification control signal; and an audio output unit which outputs an audio corresponding to the amplified analog signal.

An audio device for amplifying an audio signal enables a user to instantly switch between two or more active amplifying components, thereby allowing the user to evaluate the effect of a particular active amplifying component in the audio device. In one example, the audio device is an audio vacuum tube preamplifier, and has a circuit configuration that facilitates A/B comparison between two or more preamp tubes by hot switching between preamp tubes in the audio signal path. The input to the two or more tubes is switched between each tube by the listener on demand without pause or interruption to the music or program.

Disclosed are a hybrid mode based audio processing method and an apparatus therefor. A hybrid mode based audio processing apparatus according to an exemplary embodiment of the present disclosure includes a signal converting unit which converts a digital signal of an input sound source into an analog signal; a mode controller which analyzes the input sound source, sets an amplification mode according to the analysis result, and generates an amplification control signal to control the amplification mode; an amplifying unit which amplifies the analog signal in the amplification mode set based on the amplification control signal; and an audio output unit which outputs an audio corresponding to the amplified analog signal.

A vacuum tube and transistor amplifier natural sound field tone dividing system includes: a front-end circuit for receiving and processing an input signal to thereby generate an audio signal; a transistor power amplifying circuit connected to the front-end circuit and adapted to process a low-frequency signal in the audio signal and play the low-frequency signal with a first player; and a vacuum tube power amplifying circuit connected to the front-end circuit and adapted to process a medium-frequency signal and a high-frequency signal in the audio signal, play the medium-frequency signal with a second player, and play the high-frequency signal with a third player, wherein the transistor power amplifying circuit and the vacuum tube power amplifying circuit are independent of each other.

A single-ended Class-A amplifier includes an amplification component (e.g., a vacuum tube) having at least an output terminal, a reference terminal and a control terminal. The control terminal receives a time-varying input signal. The amplification component responds to the time-varying input signal to vary an output voltage on the output terminal and to vary a current flowing between the output terminal and the reference terminal. A load is AC-coupled to the output terminal. A steered current source has a voltage input coupled to the output terminal and has a steered current output coupled to the output terminal. The steered current source is configured to increase the steered current to provide current to the load when the output voltage on the output terminal of the amplification component increases and to decrease the steered current when the output voltage on the output terminal of the amplification component decreases.

A bias circuit includes a first transistor, a second transistor, a first resistor and a second resistor. The first end of the first transistor is coupled to a first voltage source. One end of the first resistor is coupled to the second end of the first transistor, and the other end of the first resistor is coupled to the control terminal of the first transistor. The first end of the second transistor is coupled to a second voltage source, and the second end of the second transistor is coupled to the control terminal of the first transistor. One end of the second resistor is coupled to the other end of the first resistor, and the other end of the second resistor is coupled to the control terminal of the second transistor.

A bias circuit includes a first transistor, a second transistor, a first resistor and a second resistor. The first end of the first transistor is coupled to a first voltage source. One end of the first resistor is coupled to the second end of the first transistor, and the other end of the first resistor is coupled to the control terminal of the first transistor. The first end of the second transistor is coupled to a second voltage source, and the second end of the second transistor is coupled to the control terminal of the first transistor. One end of the second resistor is coupled to the other end of the first resistor, and the other end of the second resistor is coupled to the control terminal of the second transistor.

A bias circuit includes a first transistor, a second transistor, a first resistor and a second resistor. The first end of the first transistor is coupled to a first voltage source. One end of the first resistor is coupled to the second end of the first transistor, and the other end of the first resistor is coupled to the control terminal of the first transistor. The first end of the second transistor is coupled to a second voltage source, and the second end of the second transistor is coupled to the control terminal of the first transistor. One end of the second resistor is coupled to the other end of the first resistor, and the other end of the second resistor is coupled to the control terminal of the second transistor.