Nakamichi 670ZX (c. 1979–1980)

A 9 kg slab of aluminum and crystal heads that treats a plastic cassette like a master tape.

Overview

The Nakamichi 670ZX is a three-head, single-well compact cassette deck with full-logic auto-reverse, built in Japan. It listed in Japan at ¥188,000 around 1980, roughly $1,150 at the time. The dating is muddy. One page heading files it under 1984, while period advertising and the original pricing point to 1979-1980. At least one source claims it was first sold in 1979 and discontinued a year later. The safest read is that the 670ZX belongs to the turn of the decade, and the 1984 figure should be treated with suspicion.

Where it sat in the lineup isn't in dispute. The 670ZX filled the niche between Nakamichi's mid-tier decks and its flagships. It was the machine for someone who wanted the ZX-series technology without paying Dragon money. It's routinely described as having bridged the gap between broadcast equipment and home audio. The Dragon overshadows it in popular memory, but the 670ZX represented the bleeding edge of what cassette reproduction could do in its era. It was never cheap or casual.

Key Features

The Discrete Three-Head Array: P-8L, R-8L, and E-8L

Recording, playback, and erase heads are completely independent, each optimized for its own job rather than compromised into a shared record/play head. The playback head is a P-8L, a 0.6-micron narrow-gap type made of crystal. Nakamichi's own literature credits it with flat reproduction into the ultra-high frequencies, response down to 10 Hz, and no characteristic degradation even after 10,000 hours of use. The record head is an R-8L with a 3.5-micron gap, also crystal. Erasure comes from an E-8L direct-flux double-gap head. That layout gives real-time monitoring off the playback head during recording, with no generational loss.

Auto Azimuth Alignment with a 400 Hz Test Routine

This is the hallmark of the ZX series and the 670ZX's headline trick. A secondary playback head continuously watches high-frequency response while motorized actuators trim the angle of the main P-8L head. The calibration itself is semi-automatic. The deck records a built-in 400 Hz/0 dB test signal, plays it back, converts the reproduced sine wave to a square wave, and a phase-discrimination circuit detects whether the channels are early or late relative to each other. The play button stops blinking when alignment is done. HiFi-Stereo (February 1980, p.13) called Auto Azimuth Alignment "undoubtedly the most advanced and sophisticated innovation in cassette-recorder technology," launching "a new era in high-fidelity recording." That's the manufacturer's framing echoed in a period ad, but the mechanism was genuinely unusual for a consumer deck. Owners report sustained channel separation of 37 dB or more at 1 kHz and crosstalk beyond 60 dB, even on imperfect tapes.

Frequency-Distributed Double Capstan Transport

Tape travel runs at 4.8 cm/s (1⅞ ips) through a frequency-distributed double-capstan system driven by direct-drive servo motors, with servo-controlled reel motors handling tension. The two capstans are deliberately different diameters so their flutter peaks don't land on top of each other. That shows up in the spec: wow and flutter of 0.04% or less (WTD RMS). The full-logic transport changes sides during auto-reverse without a pause. A C-MOS logic control section drives a motor-linked control cam that moves the head base and pinch roller through six control buttons. Nakamichi also fitted a pad lifter, which takes the cassette's pressure pad out of the equation and suppresses the characteristic changes it introduces.

Frequency Response, Noise, and Distortion

With ZX (metal) tape the deck is rated 10 Hz to 22 kHz ±3 dB. On SX and EXII formulations it's 10 Hz to 20 kHz ±3 dB. Overall signal-to-noise runs 60 dB or greater at 0 dB (WTD rms), and the distortion figures are 0.8% or less on ZX tape, 1.0% or less on SX/EXII. Erasure rate is 60 dB or more at saturation level. Some modern listings claim Dolby S support, but Nakamichi's own documentation describes a generic Dolby NR system with dedicated record and playback circuitry, so treat the Dolby S claim as unverified. What is documented is the 3-position tape selector (EX, SX, ZX), independently switchable 120 μs/70 μs equalization, a 105 kHz bias frequency, and an MPX filter.

Recording Amplifier and Double NF Circuit

The record amplifier eliminates the coupling capacitor between amp and record head entirely, running the connection direct and DC. A double negative-feedback circuit is applied to the capacitors in both the record and playback equalizers. Dedicated Dolby circuitry for record and playback enables after-monitoring. The high-output headphone port drives 45 mW into 8 ohms.

RAMM, Manual Queuing, and the Small Conveniences

RAMM (Random Access Music Memory) handles automatic cueing for up to nine tracks. For manual work, pressing Pause/Queue during fast-forward or rewind drops the speed to about a third, and holding the FF/REW button again cuts it to roughly a fifth. That's handy for hunting a passage by ear. There's a one-touch Rec-Mute that cuts the input signal mid-record, a tape start memory function, a high-speed shut-off, and pitch control good for approximately ±6% of playback speed. The pointer-type level indicator covers the full span from the −40 dB noise floor to the +7 dB saturation point, and the front panel uses a vacuum fluorescent display.

Chassis, Rack Mounting, and Rear-Panel Details

The chassis is a resonance-damping type, using aluminum alloy with high vibration-damping characteristics combined with resin molded parts, and the body itself is aluminum. Dimensions are 482 × 143 × 340 mm at approximately 9 kg. A removable rack-mount adapter gives the deck a 19-inch EIA-standard panel with 2¼-inch screw pitch, so it fits a rack as easily as a shelf. Around back there's a voltage selector for other-market versions, switchable between 120 V and 220-240 V, plus a dedicated power terminal for Nakamichi's Black Box Series accessories (up to 125 mA). The optional RM-200 Remote Control Unit, sold separately at ¥6,000, handles transport functions remotely.

Collectibility & Value

Working 670ZX decks typically trade between $600 and $1,000, with fully restored examples commanding more. A serviced unit was listed at $1,600 in 2024. Parts and consumables turn up regularly: belt sets around $30, upgrade kits near $90, even individual knobs at $15. Collectibility is growing, driven by renewed interest in quality tape playback and the ZX-series reputation. Enthusiasts group the 670ZX with the 682ZX, 1000ZXL, ZX-7, ZX-9, and CR-7 as some of the finest-sounding decks ever built.

The known trouble spots are seized azimuth motors, hardened pinch rollers, dried lubricants, and capacitor aging in the power supply. The head-movement complexity means regular demagnetization and professional alignment aren't optional. One technician's write-up flags a Dolby level calibration discrepancy on these decks, calling it an old Nakamichi error, so any restoration should be checked against a known reference. Service manuals circulate through enthusiast communities, and some parts remain available from specialty restoration suppliers. Plenty of examples come to market unserviced, and some sellers move them as non-working, so budget for a proper going-over.