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LYRUS AUDIO

LYRUS is the only genuine high performance Class D
amplification technology on the world market.

Up until now all brands of Class D amplification technology have only been suitable for driving subwoofers. Halcro's head physicist Bruce Candy has perfected Class D technology to the point it is now audiophile quality. Bruce gave a paper at the October 2004 AES in San Francisco which revealed the genuine high performance qualities of the technology. This was supported by a paper written by Bruce Candy and the Applied Maths Department of the University of Adelaide which proved the technology in the form of pure mathematics. This paper is being published in the "SIAM (Society for Industrial and Applied Mathematics)", one of the worlds most prestigious Applied Maths journals.

Lyrus Technical Class-D Description
Written by Bruce Candy

Class-D amplifiers convert an input signal to a power 1-bit digital output signal, that is the output signal is either a 1 (say +70V) or a 0 (say -70V). The rate at which the output switches is much higher than audio frequencies (say 500kHz). This rate is controlled by a reference clock signal. The ratio between the average time spent at +70V and -70V varies in proportion to the input signal. That is if the input signal is say more than 0V, then the output correspondingly spends more time on average at +70V than -70V and so on. This ratio is also controlled by the clock signal. The 500kHz switching signal is removed by analogue filters so that only the average signal passes to the loudspeaker, and as stated, this is controlled to be in proportion to the corresponding input signal.

Class-D amplifiers (analogue) suffer from intrinsic distortion, that is, even with "perfect electronic components" the circuits mathematically generate distortion. This intrinsic distortion increases rapidly with both increasing power and frequency. Thus at high powers, class-D amplifiers hitherto are substantially inferior to well designed traditional class-A or -AB or -B amplifiers.

The Lyrus™ circuits contain patented distortion canceling circuitry so that at high powers the Lyrus™ class-D amplifiers are on a par with well designed traditional class-A or -AB or -B amplifiers. Technically the intrinsic distortion can be attributed to an intrinsic time distortion (advanced phase) which varies in a non-linear manner with signal level (level squared law). The Lyrus™ circuits introduce a compensating time variation to the reference clock signal which controls when the output signal switches.

More technically, the clock signal is a triangular-wave which acts as a reference to the pulse-width modulator and the symmetry of the triangular-wave is varied by the input signal to produce the required corresponding phase compensation.

The Lyrus™ amplifiers produce about 1/5th to 1/10th of the distortion of typical well designed competitors at high powers.

Bruce Candy
Physicist - Lyrus™ Designer