Sharp - SM-A75H(BK) DSP - digital sound processor

SHARP OPTONICA SM-A75 INTEGRATED A/V AMPLIFIER

The SHARP SM-A75, part of the Optonica audio component line, is a compact and versatile surround amplifier and audio/video control hub. Each of its four channels delivers at least 25 watts into an 8-ohm load with total harmonic distortion not exceeding 0.8% when all four channels are driven simultaneously, as would occur in a typical surround system. The SM-A75 can also be used in standard two-channel stereo mode, in which the rated power rises to 35 watts per channel. The specified frequency range at rated power and distortion level is 30 Hz to 20,000 Hz for the front channels and 30 Hz to 15,000 Hz for the rear channels.

The SM-A75’s preamplifier section has inputs for turntable, CD player, cassette deck, turntables, television, two auxiliary sources, two video recorders, and a videodisc player. There are also tape and video recording outputs. The front panel features two small knobs for tone control and a pair of buttons for volume control. The digital circuits adjust gain in 2 dB steps. A small DUBBING MODE button links the two video recorders for two-way recording or for duplicating videodiscs to video recorder 1. The RCA connectors on the front panel mirror the connectors of video recorder 2 on the rear of the amplifier, simplifying temporary connection of a second video recorder to the system. There are also two stereo headphone jacks, one for the front channels and one for the rear channels.

A fundamental feature of the Optonica SM-A75 is its surround audio processor. The front-channel signals can be combined in a matrix to produce left-right difference signals (L - R and R - L). Each of these signals can then be processed through its own 16-bit digital delay system, adjustable in 1 millisecond steps from 1 to 92 ms. A tunable fraction of each delayed signal can also be fed back through the delay system to provide a more spacious sound. After amplification, the delayed signals drive the rear speakers (surround).

The SM-A75’s digital memories store the key parameters (delay times, feedback amount, frequency response, and relative level of the rear channels) for eleven preset surround models and up to three user-programmable modes. The factory presets include three modes for music programs, HALL, LIVE, and STAGE; two for movies, THEATER and SF (presumably “science fiction,” a genre in which unusual sound effects might be expected); three for sports, STADIUM, RINGSIDE, and GAME; two base surround modes, MATRIX and PRESENCE; and standard Dolby Surround. The preset parameters are stored in a...