A guitar holder with a built-in guitar amplifier for enabling convenient guitar practice and/or play with a compact, space-saving footprint. The guitar holder may comprise any of a variety of guitar holders, including but not limited to a guitar stand and/or a guitar wall hanger.

A transducer system has a transducer configured to receive an incident signal and produce an output signal as a function of the incident signal. As known in the art, the output signal has a −3 dB point. The transducer system also has circuitry operatively coupled with the transducer. The circuitry includes an amplifier with an output configured to produce an amplified signal as a function of the output signal. In addition, the circuitry further has a positive feedback loop and a negative feedback loop that both are electrically coupled between the transducer and the amplifier. The positive feedback loop is configured to move the −3 dB point in a first frequency direction. Conversely, the negative feedback loop is configured to move the −3 dB point in a second frequency direction. Preferably, the first and second frequency directions are different.

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.

The present disclosure is directed to the creation, modification, and selection of a plurality of audio profiles in programmable audio amplifiers. Embodiments of the present disclosure include an input device, a programmable amplifier device, a controller, and an output device. In certain embodiments, the audio amplifier device is pre-programmable and/or re-programmable and can comprise an enclosure, a processor within the enclosure, a receiver communicatively connected to the processor, and a controller external to the enclosure, with the controller being communicatively connected to the processor.

The present disclosure is directed to the creation, modification, and selection of a plurality of audio profiles in programmable audio amplifiers. Embodiments of the present disclosure include an input device, a programmable amplifier device, a controller, and an output device. In certain embodiments, the audio amplifier device is pre-programmable and/or re-programmable and can comprise an enclosure, a processor within the enclosure, a receiver communicatively connected to the processor, and a controller external to the enclosure, with the controller being communicatively connected to the processor.

A current-averaging audio amplifier for vehicles. The current averaging audio amplifier is connectable to a DC power source and a load, and may generally comprise a power input to receive a DC electrical power from the DC power source. The system may further include a voltage converter, such as a boost converter, connected to the power input, such that the voltage converter can receive electrical power from the DC power source. The system also includes a rechargeable battery coupled to the voltage converter, such that the voltage converter charges the rechargeable battery. An audio amplifier can be powered by the rechargeable battery and connectable to supply power to the load, wherein the average power supplied by the rechargeable battery to the audio amplifier in a finite time interval differs from the average power supplied by the DC power source to the voltage converter.

A current-averaging audio amplifier for vehicles. The current averaging audio amplifier is connectable to a DC power source and a load, and may generally comprise a power input to receive a DC electrical power from the DC power source. The system may further include a voltage converter, such as a boost converter, connected to the power input, such that the voltage converter can receive electrical power from the DC power source. The system also includes a rechargeable battery coupled to the voltage converter, such that the voltage converter charges the rechargeable battery. An audio amplifier can be powered by the rechargeable battery and connectable to supply power to the load, wherein the average power supplied by the rechargeable battery to the audio amplifier in a finite time interval differs from the average power supplied by the DC power source to the voltage converter.

This application describes time-encoding modulator circuitry (200), and in particular a PWM modulator suitable for use for a class-D amplifier. A forward signal path receives a digital input signal (Din) and outputs an output PWM signal (Sout) and includes a first PWM modulator (101). A feedback path provides feedback to an input of the first PWM modulator (101). The feedback path includes an ADC (203) which receive a first PWM signal (Sa) derived from the output PWM signal. The ADC (203) includes a second PWM modulator (401) which generates a second PWM signal (Sb) based on the first PWM signal. A controller (201) controls the second PWM modulator such that a PWM carrier of the second PWM signal is phase and frequency matched to a PWM carrier of the output PWM signal.

A matching circuit structure for effectively suppressing the low-frequency clutter of a power amplifier of a mobile phone, falling within the technical field of radio frequency Pas is provided. The circuit structure includes an input end, a blocking capacitor, a power amplifier (PA), an output matching network and an output end connected in series; and the matching circuit structure further includes a negative feedback network connected in parallel to a transmission end of the PA; the negative feedback network includes a resonant capacitor, a resonant inductor and a matching inductor; the resonant capacitor and the resonant inductor are connected in parallel to form a frequency selecting network, and the frequency selecting network is connected in series with the matching inductor and to the ground. The matching circuit structure above can be used to effectively suppress the low-frequency clutter of a power amplifier.