Abstract: Disclosed is a loudspeaker apparatus having at least one support surface provided therein adjacent to a complaint surround for providing lateral support thereto, the surround mounting the diaphragm of the speaker to a speaker frame for permitting longitudinal movement of the diaphragm with respect to the frame. The support surface may be used with a variety of surrounds. A second support surface may also be provided. The support surfaces may be contoured to achieve a desired response from their engagement with the surround. A negative air spring is formed from a pair of opposed support surfaces contoured to form a necked region therebetween for deformingly engaging a surround formed as a resilient member. The negative air spring negatively balances, or counterbalances the diphragm against the box pressures with the enclosure. The resilient member is formed as a tube for containing a fluid such as air therein. The pressure within the resilient member is controlled in response to a variety of parameters.

Abstract: An inverter for an audio amplifier. The inverter comprises a current damped feedback loop for actively damping oscillations caused by an output inductor within the inverter. A forward compensator is provided to compensate for the frequency response of the actively damped filter. The resulting inverter generates an output voltage that tracks an input voltage thereof with improved frequency response within the frequency range of interest.

Abstract: An inverter for an audio amplifier. The inverter comprises a current damping feedback loop for actively damping oscillations caused by an output inductor within the inverter. A forward compensator is provided to compensate for the frequency response of the actively damped filter. The resulting inverter generates an output voltage that tracks an input voltage thereof with improved frequency response within the frequency range of interest.

Abstract: An audio frequency amplifier having a switching converter comprising source and sink rectifiers configured for sourcing and sinking current, in which the source and sink supply voltages of the rectifiers track the audio frequency signal being amplified. The amplifier has a circuit or element for discharging the output capacitors of the source and sink rectifier as necessary to prevent floating of the source and sink supply voltages. The discharging element can be a locking capacitor or one or more Zener diodes connected across the source and sink supply voltages. The discharge circuit can be one or more switching transistors connected across the freewheeling diodes of the source and sink rectifiers to actively pull the source and sink voltages down to discharge the output capacitors and thereby prevent floating. Low voltage rated parts can be used in the output stage amplifier, and in certain configurations a high voltage low current preamplifier stage can be eliminated.

Abstract: A system for increasing the quality of the sound available from a broadcast, frequency modulated, radio frequency, stereophonic signal. Sound quality is promoted by: (1) so switching between available antennas that the signal available from the antenna receiving the incoming signal which is stronger and contains the least multipath distortion is processed into audio output signals, and (2) at least partially blending stereophonically related audio input signals into a monophonic signal if the modulation of the incoming first and second audio signals decreases below a selected threshold value and if: (a) the multipath distortion in the incoming signal reaches or exceeds a preselected threshold value, or (b) the strength of the incoming signal decreases to, or falls below, an also preselected threshold value.

Abstract: A video processor for generating an improved video display by synthesizing high frequency components of a received video signal in a manner that the frequencies of the synthesized high frequency components are greater than the upper frequency limit of the received video signal. A selected higher frequency band of the received signal modulates a continuous wave signal having a selected frequency so that the upper sideband frequency components of the modulated output are greater than the video signal upper frequency limit. The lower sideband components of the modulated output are removed and the upper sideband components are then added in phase with the original video signal to generate a composite signal having a greater bandwidth than the original received signal for generating the improved video display.

Abstract: A tuner includes circuitry for conditioning an audio signal including (i) a pilot signal canceller, (ii) a noise limiter, (iii) a notch filter, and (iv) a de-emphasizer; as well as an attenuator for RF signals. In an exemplary embodiment, an AM stereo pilot signal canceller utilizes a 25 Hz signal which is added or subtracted from the left and right channels to eliminate the pilot signal. The noise limiter includes a capacitor which is switched into the feedback circuit of an operational amplifier when the input is at a selected level. The diverting of the feedback signal to the capacitor causes the amplifier to saturate thereby removing the noise from the signal. The notch filter includes first and second band pass filters which are centered at a selected frequency, e.g. 10 kHz, for removing a 10 kHz beat note. The passed band is phase shifted so that it is 180 degrees out of phase with the original signal and then added back with the original signal to remove the selected band.