Example embodiments provide a process that includes one or more of receiving an audio signal at a feedback compressor circuit, determining how much to attenuate the audio signal when a power level of the audio signal exceeds a threshold power level, combining the audio signal with an auxiliary attenuation signal from an auxiliary attenuation source and a compressed attenuation signal from the feedback compressor circuit to create a combination signal, and generating an audio output signal of the feedback compressor circuit based on the combination signal.

An amplifier circuit comprises a first gain circuit path configured to provide a first signal gain to an input signal, a second gain circuit path configured to provide a second signal gain to an input signal, an auxiliary gain circuit path configured to provide an auxiliary signal gain to an auxiliary input signal, wherein the auxiliary signal gain is equal to the first signal gain minus the second signal gain, a summing circuit configured to sum the second gain signal path and the auxiliary signal path, and logic circuitry configured to change an output of the circuit between the first gain circuit path and the sum of the second gain signal path and the auxiliary signal path, and set the auxiliary input signal equal to the input signal before the changing.

In some embodiments, a method for performing enhancement on an audio signal to generate an enhanced audio signal in response to feedback indicative of amount of compression applied to at least one frequency band of the enhanced audio signal. In typical embodiments, the enhancement is or includes bass enhancement. Examples of other types of enhancement performed in other embodiments include dialog enhancement, upmixing, frequency shifting, harmonic injection or transposition, subharmonic injection, virtualization, and equalization. Other aspects are systems (e.g., programmed processors) and devices (e.g., devices having physically-limited bass reproduction capabilities, such as, for example, a notebook, tablet, mobile phone, or other device with small speakers) configured to perform any embodiment of the method.

In some embodiments, a method for performing enhancement on an audio signal to generate an enhanced audio signal in response to feedback indicative of amount of compression applied to at least one frequency band of the enhanced audio signal. In typical embodiments, the enhancement is or includes bass enhancement. Examples of other types of enhancement performed in other embodiments include dialog enhancement, upmixing, frequency shifting, harmonic injection or transposition, subharmonic injection, virtualization, and equalization. Other aspects are systems (e.g., programmed processors) and devices (e.g., devices having physically-limited bass reproduction capabilities, such as, for example, a notebook, tablet, mobile phone, or other device with small speakers) configured to perform any embodiment of the method.

A linear amplifier includes a pre-amplifier configured to amplify an input differential signal, a post-amplifier configured to amplify an output signal of the pre-amplifier, an amplitude detector configured to detect an amplitude of an output signal of the post-amplifier, and an output voltage corresponding to the detected amplitude, a comparator configured to control a tail current source of the pre-amplifier such that when the output voltage of the amplitude detector is less than or equal to a reference voltage, a tail current of the pre-amplifier is set to a constant value, and when the output voltage of the amplitude detector is larger than the reference voltage, the tail current is reduced to make the output voltage of the amplitude detector equal to the reference voltage.

A linear amplifier includes a pre-amplifier configured to amplify an input differential signal, a post-amplifier configured to amplify an output signal of the pre-amplifier, an amplitude detector configured to detect an amplitude of an output signal of the post-amplifier, and an output voltage corresponding to the detected amplitude, a comparator configured to control a tail current source of the pre-amplifier such that when the output voltage of the amplitude detector is less than or equal to a reference voltage, a tail current of the pre-amplifier is set to a constant value, and when the output voltage of the amplitude detector is larger than the reference voltage, the tail current is reduced to make the output voltage of the amplitude detector equal to the reference voltage.

A sensor is configured for measuring skin conductance. An amplifier is used to convert the skin conductance into an analog output voltage which is then converted into the digital domain by an analog-to-digital converter, so that an increase in the tonic skin conductance and the phasic skin conductance response are obtained in the digital domain. The amplifier has a non-linear logarithmic gain, with a decreasing gain for increasing skin conductance values. The sensor enables detection of increases in both tonic and phasic signals over a wide range of skin conductance. This allows the use of a lower resolution, and therefore lower cost, analog-to-digital converter.

A sensor is configured for measuring skin conductance. An amplifier is used to convert the skin conductance into an analog output voltage which is then converted into the digital domain by an analog-to-digital converter, so that an increase in the tonic skin conductance and the phasic skin conductance response are obtained in the digital domain. The amplifier has a non-linear logarithmic gain, with a decreasing gain for increasing skin conductance values. The sensor enables detection of increases in both tonic and phasic signals over a wide range of skin conductance. This allows the use of a lower resolution, and therefore lower cost, analog-to-digital converter.

Example embodiments provide a process that includes one or more of receiving an audio signal at a feedback compressor circuit, multiplying the received audio signal with a power feedback signal to create a product audio signal, wherein the feedback signal comprises a low-pass filtered signal, applying a power amplifier to the product audio signal, and providing the amplified product audio signal as an output signal to a speaker.

Example embodiments provide a process that includes one or more of receiving an audio signal from a feedback path of a feedback compressor circuit, determining whether an auxiliary attenuation value applied to the feedback compressor circuit has changed since a last audio signal was received, responsive to determining the auxiliary value has changed, determining a current operational state value of the LPF needs to be modified based on the changed auxiliary attenuation value, modifying the operational state value of the LPF, and applying the audio signal to the modified LPF.