Sanyo DCA-1700X
A decoder-amp that promised four channels out of your ordinary stereo records — for a price that undercut almost everyone.
Overview
The DCA-1700X is one of those early-Seventies quadraphonic gadgets that makes sense only if you remember the pitch: you already had two channels, and Sanyo wanted to sell you the illusion of four. The unit was a solid-state stereo pre-main amplifier with a built-in quadrasonic synthesizer, and its whole reason for existing was to decode four-channel information that Sanyo claimed was already hiding inside ordinary two-channel discs, tapes, and FM multiplex broadcasts. Feed it a stereo source and a second pair of speakers, and it would spread the sound into a four-speaker array.
The power figures depend on whom you ask and how they measured. Sanyo's own literature rated the DCA-1700X at 80 watts at 4 ohms and 60 watts at 8 ohms, while a period trade listing put it at 70 watts total music power at 4 ohms and 56 watts at 8 ohms, both at 0.8% THD. Collectors should treat the 40-watt rms figure as the honest one — the "80 watts" and "70 watts" numbers are music-power ratings, not continuous output, and they flatter the amp considerably.
What the DCA-1700X actually did was decode matrix-encoded quadraphonic material. That placed it in the thick of the first quad wave, alongside far more expensive boxes from Marantz and Sansui — the Sanyo undercut the Marantz 2440 by a hundred dollars and the Sansui QS-500 by ninety. For a buyer dipping a toe into four-channel without committing to a whole new amplifier, that was the appeal.
Frequency response was specified broadly: 10 Hz to 100,000 Hz ±2 dB, with a power bandwidth of 15 Hz to 100,000 Hz ±1 dB. Those numbers look impressive on paper and say more about the wideband silicon of the era than about audible performance — no one hears to 100 kHz, and the figure mainly signals that the amp wasn't rolling off early. Inputs covered four-channel tape, two phono, and two auxiliary sources, so it could sit at the center of a system fed by a turntable, a tape deck, and a tuner without a separate preamp. The phono section was specified at 2.5 mV sensitivity into 50 kilohms, with a signal-to-noise ratio better than 75 dB below rated output.
Sanyo's advertising framed the DCA-1700X as the cheapest route to four-channel: the company billed it as all the equipment needed, plus a pair of speakers, to upgrade any two-channel system, and it could also serve as a second stereo amplifier for discrete four-channel eight-track or reel-to-reel tapes. That dual role — synthesizer for stereo sources, straight amp for discrete tape — was the practical argument. The catch, as with all matrix quad, was that the rear-channel separation was modest by nature; the format itself, not the Sanyo, set that limit. The unit was also sold in bundles: one period promotion paired the DCA-1700X with an FMT-1400K tuner, a DCA-1400 amplifier, and a TP-805 turntable for $579.80, throwing in speaker systems to sweeten the deal.
The DCA-1700X is a curiosity now rather than a sought-after collectible. Quadraphonic hardware has a devoted but small following, and matrix decoders are the least glamorous corner of it — the discrete-tape and CD-4 crowd gets most of the attention. Values reflect that: these turn up cheaply, often untested, and buyers should expect the usual vintage-solid-state issues rather than any documented model-specific failure. It's a piece for someone who wants a working example of early-Seventies quad ambition and doesn't mind that the format lost the war. As a stereo amplifier alone it's competent; as a time capsule of the four-channel moment, it's more interesting than its spec sheet suggests.
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