Abstract: Methods and apparatus provide for: a rectification circuit operating to convert a source of AC power into a final DC power source; a rectification filtering capacitance operating to at least partially smooth a voltage of the final DC power source, which exhibits a voltage sag and recovery characteristic in response to time-variant current drawn therefrom; a power amplification circuit drawing power from the final DC power source and producing an output signal, for driving a speaker, having audible characteristics influenced by the voltage sag and recovery characteristic of the final DC power source; and a control circuit operating to continuously vary, in response to user input, one or more parameters of the voltage sag and/or recovery characteristic of the final DC power source.

Abstract: Methods and apparatus provide for: a rectification circuit operating to convert a source of AC power into a final DC power source; a rectification filtering capacitance operating to at least partially smooth a voltage of the final DC power source, which exhibits a voltage sag and recovery characteristic in response to time-variant current drawn therefrom; a power amplification circuit drawing power from the final DC power source and producing an output signal, for driving a speaker, having audible characteristics influenced by the voltage sag and recovery characteristic of the final DC power source; and a control circuit operating to continuously vary, in response to user input, one or more parameters of the voltage sag and/or recovery characteristic of the final DC power source.

Abstract: Methods and apparatus for producing first and second drive signals from an input signal such that each drive signal is about 180 degrees out of phase with respect to the other; variably altering at least one of the first and second drive signals such that their respective magnitudes may be unbalanced to a varying degree; and producing an output signal from the first and second drive signals such that it includes harmonic distortion when the first and second drive signals are unbalanced.

Abstract: Methods and apparatus contemplate: an output transformer having at least first and second separate primary windings and at least one secondary winding, each winding including a first (in phase) end and a second (out of phase) end; at least first and second active elements, each having at least a pair of power terminals and a control terminal, one power terminal of each active element being coupled to a common node; and a switching circuit operable to change a circuit configuration of the first and second primary windings and the active elements between a class A mode and a class A/B mode.