Abstract: An amplifier circuit is disclosed suitable for feeding a loudspeaker system having plural drivers. The amplifier circuit has an output stage and plural output connectors such that there is an output connector for each driver, wherein the output stage is connected separately to each output connector for independent connection to each driver. A method of feeding a loudspeaker system having plural drivers with an amplifier circuit having an output stage is also disclosed.

Abstract: An amplifier circuit is disclosed suitable for feeding a loudspeaker system having plural drivers. The amplifier circuit has an output stage and plural output connectors such that there is an output connector for each driver, wherein the output stage is connected separately to each output connector for independent connection to each driver. A method of feeding a loudspeaker system having plural drivers with an amplifier circuit having an output stage is also disclosed.

Abstract: A push pull amplifier is disclosed having upper and lower output devices operating in a mode in which the devices drive a load alternately. The amplifier includes bias means for providing a bias current to the output devices at all times. The bias means is incorporated in a feedback loop and is arranged such that transitions from load current to minimum bias current in the upper and lower output devices are sufficiently gradual so that harmonic frequencies generated by the transitions are within the capability of the amplifier under all signal conditions. The feedback loop includes a non-linear transform circuit for each upper and lower output device to prevent the bias current reducing to zero. The feedback loop also includes a linearity control circuit for controlling the harmonic frequencies in the upper and lower output devices.

Abstract: A push pull amplifier is disclosed having upper and lower output devices operating in a mode in which the devices drive a load alternately. The amplifier includes bias means for providing a bias current to the output devices at all times. The bias means is incorporated in a feedback loop and is arranged such that transitions from load current to minimum bias current in the upper and lower output devices are sufficiently gradual so that harmonic frequencies generated by the transitions are within the capability of the amplifier under all signal conditions. The feedback loop includes a non-linear transform circuit for each upper and lower output device to prevent the bias current reducing to zero. The feedback loop also includes a linearity control circuit for controlling the harmonic frequencies in the upper and lower output devices.

Abstract: A method of constructing an acoustic filter incorporates a technique in which the filter is modelled with one or more distributed two port elements. The or each distributed element is defined by a characteristic impedance and length and includes a waveguide filter which does not require damping. The or each filter section is characterized in that it has at least two resonances which are used to shape a specified response for the filter. A substantially reactive acoustic filter constructed according to the method and a loudspeaker system incorporating such an acoustic filter are also disclosed.