Sony PS-2251
Direct drive with no belt, no idler, no pulley — and a rumble figure of −58 dB that Sony was happy to shout about.
Overview
The PS-2251 was Sony's declaration of independence from the mechanical middlemen that sat between a motor and a platter on most turntables of the era. Sony's own advertising, which ran in Audio (July 1973, p.13) and High Fidelity (October 1973, p.63), made the pitch blunt: no belts, no pulleys, no idler wheels, just a motor spinning at the record's speed. That direct-drive approach was the whole selling proposition, and Sony leaned on it hard.
The rumble number is the one that sticks. Sony claimed −58 dB (NAB) — a figure the company argued was even better than the spec sheet suggested, because a slow-turning motor puts its residual noise at a lower frequency, where the ear is less sensitive. Whether or not you buy that reasoning wholesale, −58 dB was a serious number for a consumer deck in 1973, and it came from the absence of the intermediate drive parts as much as from the motor itself.
Speed accuracy was handled by an AC servo system. Sony's ad copy argued AC servo was superior to DC servo on the grounds of uniform magnetic field strength, and claimed the resulting speed was unaffected by variations in line voltage or line frequency. A built-in pitch control allowed ±4% adjustment, with a self-illuminated strobe to return the platter to a precise 33-1/3 or 45 rpm.
The tonearm was supplied as part of the package — statically balanced, with viscous-damped cueing and effective anti-skating. The whole assembly sat on a wood base with an independent spring suspension intended to isolate it from externally caused vibrations. Collectors should treat the lower number as the earlier advertised price and the higher one as the corrected figure; both appear in period print.
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