An audio preamplifier includes a first stage including a first triode of a first vacuum tube in a common cathode configuration configured to perform a first gain function favoring one of low frequencies and mid-range frequencies in response to user input; a second stage including a second triode of the first vacuum tube in a common cathode configuration configured to perform a second gain function favoring one of low frequencies and mid-range frequencies in response to user input; a third stage including a first triode of a second vacuum tube in a common cathode configuration configured to perform a tone-shaping function favoring one of low frequencies and mid-range frequencies in response to user input; and a fourth stage including a second triode of the second vacuum tube in a follower configuration configured to perform a tone stack function in response to user input.

Methods, apparatus, systems and articles of manufacture are disclosed for audio equalization. Example apparatus disclosed herein include a volume adjuster to apply equalization adjustments to an audio signal to generate an equalized audio signal, the equalization adjustments output from a neural network in response to an input feature set; a thresholding controller to: detect an irregularity in a frequency representation of the audio signal after application of the equalization adjustments, the irregularity corresponding to a change in volume between adjacent frequency values exceeding a threshold; and adjust a volume at a first frequency value of the adjacent frequency values to reduce the irregularity; an equalization (EQ) curve generator to generate an EQ curve to apply to the audio signal when the irregularity has been reduced; and a frequency to time domain converter to output the equalized audio signal in a time domain based on the EQ curve.

A system and method for optimizing the low-frequency sound rendition of an audio signal, implementing variations in a plurality of parameters of the audio signal according to the volume level of the signal chosen by a user, in particular filtering or compression parameters, or parameters relating to the harmonics of the audio signal, while seeking to optimize the dynamics and the bandwidth of the audio signal according to the volume, in order to provide an optimal rendition to the user.

A variable-resolution graphic equalizer providing an improved interface for controlling gain values across the entire audio spectrum using many narrow-band filters (e.g., 120). It allows user selection of a frequency range for graphic equalization and automatically maps a reduced and fixed number of sliders to the selected range based on the number of filter bands falling within the selected range. In an audio processing system, specific user interface regions are highlighted to display selected frequency ranges and corresponding selected sliders to allow for rapid and precise equalization of the full audio spectrum using the many narrow-band filters.

There is provided a method of determining filter coefficients for an audio filter system including a number, N2, of filter paths for enabling processing of N audio channels, one filter path per channel, wherein each filter path includes at least one audio filter for performing the processing of the corresponding channel. The method includes providing a common set of filter design parameters for a pair of audio filters belonging to different filter paths, including phase difference information representing an inter-channel phase difference and frequency information representing a frequency value as filter design parameters; and determining filter coefficients for the pair of audio filters at least partly based on the common set of filter design parameters.

A display system includes a head-mounted display unit and a detachable speaker unit. The head-mounted display unit outputs visual content to a user and provides a visual pass-through of a real environment to the user. The detachable speaker unit is detachably coupleable to the head-mounted display unit for providing aural content to the user. At least one of the visual content or the aural content is changed according to a position of the detachable speaker unit relative to the head-mounted display unit.

An adjusting system and an adjusting method for equalization processing are provided. Frequency band energies of sound receiving signals are obtained. The frequency band energies correspond to different frequency bands, respectively. Target gains corresponding to frequency bands are determined according to the frequency band energies. Frequency responses of filtering processing with respect to a plurality of center frequencies are obtained. Equalization gains corresponding to the frequency bands and having the least gain error are determined. The gain error is related to a difference between the amplitude obtained after the equalization gains are reflected on the frequency responses corresponding to the filtering processing and the target gains. The equalization gains are inputted into the filtering processing according to the corresponding frequency bands. Accordingly, the impact of the filtering processing can be reduced.

A sigma-delta analog-to-digital converter (ADC) is disclosed. The sigma delta ADC has an analog input and a digital output. A sigma-delta modulator input is coupled to the analog input and a sigma-delta modulator output. A first filter having a first filter input is coupled to the sigma-delta modulator output and a first filter output. A second filter having a second filter input is coupled to the sigma-delta modulator output and a second filter output. The sigma-delta ADC operates in a first and second mode. In a first mode, the first filter output is coupled to the digital output. In a second mode, the second filter output is coupled to the digital output.

An electronic device and an equalizer adjustment method thereof for adjusting gain settings of an equalizer according to the volume of the output signal are disclosed. The method includes the steps of: setting a volume gain value table including a plurality of volume values through a gain value setting module, which are a first volume value to an Nth volume value with volume incrementally increasing, each of the plurality of volume values including a set of correction parameters which including a plurality of compensation gain values corresponding to a plurality of target frequencies, respectively; storing the volume gain value table in a storage module; obtaining a volume of the output signal; loading the volume gain value table according to the volume of the output signal to obtain the corresponding set of correction parameters; and adjusting gain value settings of an equalizer for different frequencies of sound.

Systems, methods, and apparatus are provided for equalization preference learning for digital audio modification. A method for listener calibration of an audio signal includes modifying a reference sound using at least one equalization curve; playing the modified reference sound for a listener; accepting listener feedback regarding the modified reference sound; and generating a weighting function based on listener feedback. A listener audio configuration system includes an output providing a sound for listener review; an interface accepting listener feedback regarding the sound; and a processor programming an audio device based on listener feedback.