Sony ps-x70 (1978-1981)

Name: Sony ps-x70
Brand: Sony

A full-auto direct drive turntable from Sony's original PS-X series, built with quartz control and a high-inertia die-cast platter.

Overview

The Sony PS-X70 is a full-auto direct drive turntable made from 1978 to 1981. It debuted the PS-X series alongside the PS-X50. It became one of Sony's best-selling turntables, with tens of thousands built. It was a high-end consumer model with some advanced engineering for its time: a DC servo-controlled linear BSL (slotless) motor, crystal lock phase control, and a dedicated logic circuit for function sequencing. It was priced at ¥79,800 in 1978, and Sony's brand history lists it as a "Legendary Product."

Specifications

Production years	1978 to 1981
Product type	full-auto direct drive turntable
Manufacturer	Sony
Original price	¥ 79,800 (1978)
Wow and flutter	0.025% WRMS
Signal-to-noise ratio	75dB (DIN B)
Speeds	33 and 45 rpm
Speed accuracy	±0.002%
Speed control range	±10%
Turntable	32 cm aluminum die-cast platter
Turntable weight	2.2 kg (including mat)
Moment of inertia	340 kg/cm²
Motor Type	DC servo controlled linear BSL (slotless) motor with Magnedisc velocity detection
Start-up characteristic	1/4 turn or less to full speed
Drift time	0.0003% / h or less
Tone Arm Effective length	235mm
Tone Arm Total Length	330mm
Overhang	14 mm
Arm Height Adjustment Range	± 3 mm
Needle pressure adjustment range	0 to 2.5g (0.1g interval)
Anti-skating range	0 to 2.5g
Shell dead weight	11.0g (SH-155)
Usable cartridge weight limit (including shell weight)	11.0 ~ 19.5g
Usable cartridge weight limit (with auxiliary weight)	19.0g ~ 27.5g
Tonearm balance	static balance
Cable capacitance	45pF/m
External dimensions	480 x 165 x 420 mm
Weight	13 kg

Design

The PS-X70 uses a DC servo-controlled linear BSL (slotless) motor to get rid of torque unevenness. A Magne-disk velocity detection system generating 512 wave signals handles speed control. There is a crystal lock (X-tal lock) phase control circuit, and a quartz drive strobe light for calibration. The tonearm is the PUA-7, a simplified version of the PUA-9. It has a J-shaped arm pipe of carbon-charged aluminum alloy and a hardened cemented carbide pivot shaft (5 mm diameter) with a mirror finish. The bearings are a Longs pan design with a single straight shaft. The cabinet is SBMC (Sheet Bulk Molding Compound), and the base has viscous-filled, height-adjustable insulator feet. The headshell connector uses a 4-clamp locking nut with wedge effect, and the internal wiring is Litz wire with urethane coating. The rest of the feature list: logic IC-controlled operation, electromagnetic quick-stop braking, audio muting, tonearm safety clutch, viscous damped cueing, direct-read anti-skating and counterweight, feather-touch controls, and a removable spring-loaded dust cover. Record-end detection uses a luminous sensor, so no lateral pressure lands on the stylus.

Context

The PS-X70 was one of the original models in Sony's PS-X series and one of the company's best-selling turntables, and it earned a place among its "Legendary Products." The materials, textures and functional design all got careful attention. The PUA-7 tonearm can handle high-quality moving-coil cartridges, which shows Sony meant it as a serious audiophile turntable despite the automated features.