Sony MODEL-770
A portable stereo tape deck that ran on rechargeable nickel-cadmium batteries and cost $750. Professional field recording in a package you could carry.
Overview
The price is the first thing that stops a collector: $750, as listed in period tape-equipment literature. For that you got a portable stereo deck - not a console, not a rack unit, a machine built to be carried - running on built-in rechargeable nickel-cadmium batteries. The ServoControl motor and Vari-Speed control were the headline engineering. The deck also had three speeds, a built-in peak limiter, Sony's own noise reduction system, remote start-stop control, sound-on-sound, and tape/source monitoring.
The transport specs were serious for a portable. Frequency response ran 20 to 22,000 Hz at 7½ ips, ±2 dB, with a signal-to-noise ratio of 58 dB without the noise reduction engaged. Wow and flutter came in at 0.09% at 7½ ips. Those figures made the 770 a candidate for location work rather than casual home recording.
Sony's advertising in the period was not shy about any of this. Audio (March 1969, p.55) carried the claim of "better-than-studio specs" alongside the response and noise figures. With the noise reduction engaged, the same advertising listed the 770-2 variant at 58 dB or better and the 770-4 at 56 dB or better, peak level to unweighted noise. DB-Magazine (March 1969, p.36) put the whole package at 24 lbs. 11 oz. and used "stereo on location" as the sales angle. These are manufacturer claims, not independent lab results. They are the company's numbers, repeated across placements.
The 770-2 and 770-4 designations point to head configurations rather than separate machines. The "-2" and "-4" track variants show up throughout the period advertising. The same material confirms a full 7-inch reel capacity, and the deck could run from its self-enclosed rechargeable pack or from AC. Beyond that, documentation thins out quickly.
Collectors chasing one today should expect the usual battery-deck caveats: nickel-cadmium packs of this vintage are almost certainly dead or leaky, and the ServoControl motor and Vari-Speed circuitry are the parts that matter most to a restoration. No reliable market pricing or common-failure data has surfaced in the available documentation, so treat any asking price as a negotiation starting point. What the 770 represents is clearer than what it costs: a moment when Sony decided a genuinely portable stereo deck with professional ambitions was worth building — and priced it accordingly.
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