Sony TC K50 (c. 1978)

A cassette deck from Sony's late-1970s lineup, built around recording precision and automation.

Overview

The Sony TC K50 is a cassette deck introduced around 1978, made for high-fidelity recording and playback. It has an automatic music sensor (AMS) for track detection, memory stop/play for repeating sections, and a real-time LED peak program meter with a fast 1 msec response. It supports Dolby NRIC noise reduction. The circuit is integrated with other amplifier stages, which cuts the part count and improves reliability. The tape selector is a 3-stage switching type with independent bias and equalizer settings, so each tape type gets its own optimized setup.

Specifications

Heads	Erase: 1, Recording/Playback: 1 (special 3-stage S&F head)
Motor	BSL Green Motor
Signal-to-noise ratio	59 dB (Dolby off, Peak Level, Dual Cassette)
Frequency response	30 Hz ~ 18 kHz ± 3 dB (Dual Cassette)
Wow and flutter	0.045% wrms
Total harmonic distortion	1.0% (Dual Cassette)
Power consumption	15W
Power	AC 100V 50/60Hz
External dimensions	Width 430 x Height 155 x Depth 290 mm
Weight	6.5kg
Original price	¥67,800 (c. 1978)

Design

The TC K50 uses a special 3-stage solid core S&F head. Sendust alloy gives it excellent magnetic saturation linearity, and ferrite adds superior high-frequency response and low core loss. The BSL Green Motor is a slotless design, which eliminates torque unevenness and helps speed stability. An integrated IC with built-in electronic switches reduces component count, which improves reliability and sound quality. The peak program meter has 20 segments in two colors (red/yellow), with 1 msec attack time and real-time peak hold. The deck also has a Rec Mute function, an MPX filter, and separate volume controls for line-out and headphone. An optional timer allows unattended recording and alarm playback.

Market

The Sony TC K50 commonly needs belt replacement. Service kits are listed with three belts and a roller. Units advertised as serviced typically include new belts, so this is a standard restoration step.

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