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 solid-state semiconductor guitar amplifier system/method mimicking the audio performance characteristics of conventional vacuum tube guitar amplifiers is disclosed. The disclosed system/method incorporates solid-state semiconductor circuitry implementing an input audio preamplifier (IAP) having asymmetric gain control (AGC) that feeds wave shape transformer (WST) circuitry implementing a piecewise/diode breakpoint (PDB) transform that emulates a conventional vacuum tube voltage-current transfer (VIT) characteristic. A breakpoint threshold controller (BTC) determines the offset associated with application of the PDB operation to the audio signal. Once the PDB transform has been applied to the audio signal, it is further processed by pick attack sag compressor (PAC) circuitry that applies positive sag control (PSC) and negative sag control (NSC) compression envelopes to the overall signal shape before presenting the resulting peak compressed signal through an audio volume control (AVC) and conventional solid-state semiconductor speaker power amplifier (SPA) for application to an audio speaker.

To improve voice sound quality using a vacuum tube amplifier. A reactive load that has impedance characteristics, in which impedance characteristics in a first frequency band includes a first impedance characteristic pattern selected from a plurality of first impedance characteristic pattern candidates on the basis of a type of a vacuum tube amplifier, and impedance characteristics in a second frequency band includes a second impedance characteristic pattern selected from a plurality of second impedance characteristic patterns on the basis of the type of the vacuum tube amplifier, outputs a signal that responds to a sound signal output from the vacuum tube amplifier in accordance with the impedance characteristics and performs correction on an output signal of the reactive load.

An amplifier stage uses a loaded transistor amplifier circuit including a load that causes greater second order harmonic distortion energy than third order harmonic distortion energy to be produced in said loaded transistor amplifier circuit for amplifying a source audio signal to produce an audio output signal. The spectrum of the fundamental orders of harmonic distortion is adjusted to improve perceived sound quality or listening enjoyment.

A solid-state semiconductor guitar amplifier system/method mimicking the audio performance characteristics of conventional vacuum tube guitar amplifiers is disclosed. The disclosed system/method incorporates solid-state semiconductor circuitry implementing an input audio preamplifier (IAP) having asymmetric gain control (AGC) that feeds wave shape transformer (WST) circuitry implementing a piecewise/diode breakpoint (PDB) transform that emulates a conventional vacuum tube voltage-current transfer (VIT) characteristic. A breakpoint threshold controller (BTC) determines the offset associated with application of the PDB operation to the audio signal. Once the PDB transform has been applied to the audio signal, it is further processed by pick attack sag compressor (PAC) circuitry that applies positive sag control (PSC) and negative sag control (NSC) compression envelopes to the overall signal shape before presenting the resulting peak compressed signal through an audio volume control (AVC) and conventional solid-state semiconductor speaker power amplifier (SPA) for application to an audio speaker.

A power amplifier includes a class-D amplifier and an input signal supplier. The class-D amplifier includes an input portion and a switching device. The switching device is switched according to an input signal that is input to the input portion so that a current is supplied to a load from a power source via the switching device. The input signal supplier supplies the input signal to the input portion of the class-D amplifier, calculates a virtual output voltage to be output from a virtual power source having a prescribed internal impedance characteristic when a current to flow through the load is output from the virtual power source, and adjust an amplitude of the input signal according to the virtual output voltage.

Various examples are directed to analog vacuum tube emulator circuits. In various examples, a vacuum tube emulator circuit may comprise a first circuit and a second circuit. The first circuit may be effective to receive, a first voltage, a second voltage, and a third voltage. The first circuit may be effective to develop, at an input of the first circuit, a first current based on the first voltage, the second voltage, and the third voltage. The first circuit may output the first current to an output node. The second circuit may be effective to receive the first voltage, the second voltage, and the third voltage. The second circuit may be effective to develop, at an input of the second circuit, a second current based on the first voltage, the second voltage, and the third voltage. The second circuit may output the second current to the output node.