KLH Model 40 (1969)
The tape deck that launched consumer Dolby noise reduction — and the demo that made jaws drop at the New York Audio Show.
Overview
The KLH Model 40 was a two-speed open-reel tape deck introduced in 1969. It holds a place in audio history that has little to do with its transport and everything to do with what sat inside it: the Model 40 was the first consumer tape machine to incorporate Dolby "B" Type noise reduction, licensed from Dolby Laboratories.
The deck was designed around a single obsession: making 3¾ ips sound like something other than 3¾ ips. KLH built the Model 40 "especially for use at the tape speed of 3¾ ips," which they claimed had been optimized by the Dolby System to allow an audible noise reduction of 10 dB at that speed. For anyone who fought hiss on slow-speed tape in the late sixties, that number was the whole pitch. The machine also ran at 7½ ips, giving owners a conventional high-fidelity option, but the 3¾ setting was the reason it existed.
The feature set reads like a serious recordist's deck rather than a consumer toy: a single calibrated VU meter that reads both channels simultaneously, individual level-controlled mike and auxiliary inputs for each channel with full mixing capability, a master record level knob, automatic rewind and shut-off. A walnut base was an optional extra — the deck itself was sold without it.
What made the Model 40 famous, though, was the demonstration. KLH introduced the deck at the New York Audio Show with a comparison between one of Victor Campos's carefully selected 15-ips studio tapes and the 3¾-ips copy made on the Model 40. When enough recorders reached the public to get a meaningful reaction, that reaction was, in the magazine's words, "one of enthusiastic acceptance." Consumer tape noise reduction effectively launched from this deck.
The Model 40's place in the KLH line is worth noting for collectors: it was a Dolby showcase first and a tape deck second, and the company clearly knew it.
For collectors today, the Model 40 is a historically significant piece — the first consumer Dolby B recorder — but it is also a 1969 electro-mechanical device. Buyers should expect to service the transport and verify the noise-reduction boards, and should treat any listing that doesn't show the deck powered up and running tape with caution. The deck's value lies in its provenance as much as its performance.
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