The TC-D5 was the machine that while clearly not being a “personal stereo cassette player” in the accepted sense of the term contributed immensely to the development of the Walkman idea and the Walkman range. Launched in 1978, it immediately became a favourite of senior people in the Sony company as a source of high quality portable music, despite the lack of suitable lightweight headphones, its large size and its high price. This provided the idea for a cheaper, smaller version that could be sold cheaply enough to become widely popular. Text copyright © Walkman Central. Unauthorised reproduction prohibited.
The TC-D5 was not the first Sony portable stereo cassette recorder, there had been many models aimed at both the amateur and the professional user, though they had all been fairly large and heavy, similar in both size and scale to the domestic cassette decks of the period. They were typically based around the mechanicals of the larger machines and had included mains power units and full-sized loudspeakers, all factors not conducive to small size and low weight. Text copyright © Walkman Central. Unauthorised reproduction prohibited.
The TC-D5 was different to these models and the design was clearly focused on portability. It operated on batteries only, had only a small “monitor” loudspeaker and most importantly, used a mechanism specially developed for small machines. However, the TC-D5 was first and foremost a high quality product, and none of these factors were allowed to detract from this. The signal processing circuits required a higher voltage than the two “D” sized batteries allowed, so a DC-DC converter was employed to step up the 3V to 12V, enough to power high-grade amplifiers and the excellent limiter and Dolby B processor that the machine included. Of particular note, and most important, were the microphone amplifiers, which offered low noise and a wide dynamic range, making the TC-D5 the perfect choice for outdoor recording, news gathering and other such tasks. Also of interest was the head which was made of ferrite. This material not only has excellent electrical properties, it is also very hard and resistant to wear, reducing the need for frequent readjustment. Text copyright © Walkman Central. Unauthorised reproduction prohibited.
The best electronics in the world would have been wasted if the mechanical sections of the machine had not been of equal quality. A big problem with any portable machine is that of wow and flutter, random tape speed changes that slur the sound and lend it a diffuse, wavering quality. Large, stationary recorders can be fitted with large flywheels and powerful motors to minimise these effects, but in portables this is not only impractical due to the size and power constraints, it also is counter productive as large rotating masses become unstable when the machine is moved or carried. Text copyright © Walkman Central. Unauthorised reproduction prohibited.
To avoid these problems, the TC-D5 used the “disc drive” principle. The capstan flywheel was small and driven at its edge by a motor whose axis was at 90 degrees to that of the capstan spindle. The capstan was fitted a bevelled rubber tyre and the motor had a cone-shaped extension to its shaft to match. The two were held in contact by light spring pressure, which also held the capstan securely in its lower bearing. A pickup coil inside the flywheel bearing measured the speed that the capstan rotated at and this information was used to regulate the speed of the motor. The electronics could respond quickly, and this, combined with the low and well-damped rotating mass, effectively made the tape speed absolutely stable and unaffected by movement, tape friction, temperature and battery voltage. Text copyright © Walkman Central. Unauthorised reproduction prohibited.
The rest of the mechanism was built to a level of precision to match, and in plan was little larger than the cassette. Despite its specialised nature, similar mechanisms appeared in other Sony models, for example the FX-412 TV/radio/cassette, though this had a conventional belt drive for the capstan. Text copyright © Walkman Central. Unauthorised reproduction prohibited.
The exterior of the TC-D5 had to be tough for the machine to be useful as a portable. The front panel was a single die-casting, complete with a finger recess to aid operation of the tape transport keys. The top and bottom were black painted metal and the rear edge (on which the machine was likely to put down on when used with the carrying strap) was protected with a thick rubber block. The battery compartment had a simple but sturdy catch so that batteries would not fall out if the machine was jarred. Simple controls and large meters (illuminated if necessary) also helped to make the TC-D5 useful for its intended role. The limiter could be used to prevent tape overload, whilst chrome tapes were automatically sensed and adjusted for. Minor controls, such as that for switching the Dolby system in and out, were placed inside the cassette compartment (but visible from the outside) where they could not be knocked. In the original version, normal, ferrichrome (a Sony speciality) and chrome tapes could be used. Sony’s own tapes were recommended but the machine could be adjusted by the dealer to suit any make of tape. Text copyright © Walkman Central. Unauthorised reproduction prohibited.
Despite its high price, the TC-D5 was a very successful model and remained in production in various forms for over 20 years. The TC-D5M was a popular variant, this used a Sendust head which while being not as wear-resistant as the original ferrite one but did allow Metal tapes to be used. There were also two versions aimed at the professional user, the TC-D5 Pro and TC-D5 Pro 2. The Disc Drive servo would eventually become a part of the better Walkman models, where its compact size and superior stability gave the Sony machines an extra edge over their imitators. The idea of a very high quality recorder would also appear later in the Walkman range with the WM-D6, which aimed to offer the same quality in an almost pocket-sized package. Text copyright © Walkman Central. Unauthorised reproduction prohibited.