The Nakamichi Dragon is an audio cassette deck that was introduced by Nakamichi in 1982 and marketed until 1994. The Dragon was the first Nakamichi model with bidirectional replay capability and the world's first production tape recorder with an automatic azimuth correction system; this feature, which was invented by Philips engineers and improved by Niro Nakamichi, continuously adjusts the azimuth of the replay head to minimize apparent head skew and correctly reproduce the treble signal present on the tape. The system allows the correct reproduction of mechanically skewed cassettes and recordings made on misaligned decks. Apart from the Dragon, similar systems have only been used in the Nakamichi TD-1200 car cassette player and the Marantz SD-930 cassette deck.
At the time of its introduction, the Dragon had the lowest-ever wow and flutter and the highest-ever dynamic range, losing marginally to the former Nakamichi flagship, the 1000ZXL, in frequency response. Competing models by Sony, Studer, Tandberg and TEAC that were introduced later in the 1980s sometimes surpassed the Dragon in mechanical quality and feature set but none could deliver the same mix of sound quality, flexibility and technological advancement. The Dragon, despite inherent issues with long-term reliability, remained the highest point of compact cassette technology.
Development and production Background Philips introduced the Compact Cassette in 1963. The new format was intended primarily for dictation and had inherent flaws – a low tape speed and narrow track width – that precluded direct competition with vinyl records and reel-to-reel tapes. The cassette shell was designed to accommodate only two heads, ruling out the use of dedicated recording and replay heads and off-tape monitoring that were the norm in reel-to-reel recorders. In 1972, however, Nakamichi introduced a cassette deck that outperformed most domestic and semi-professional reel-to-reel recorders. (originally published at AudioEnz, August 5, 2011) Ordinary cassette decks of that period struggled to reproduce on ferric tape and 14 kHz on chromium dioxide tape; the Nakamichi 1000 could record and reproduce signals up to 20 kHz on tapes of either type. It was the first three-head cassette deck, the first with discrete (mechanically, magnetically and electrically separate) record and replay heads, closed-loop double capstan drive, off-tape monitoring, calibration of recording levels and bias, and a convenient manual adjustment of replay head azimuth.
While its competitors struggled to approach the performance of the 1000, Nakamichi continued research and in 1981 presented their next flagship, the 1000ZXL. The new deck has a slightly narrower dynamic range and slightly higher wow and flutter than some competitors, but exceeded them in frequency response and low recording distortion, and was praised for subjective musicality. Its price of was too high for the consumer market; the uprated "gold" version, which was priced at $6,000, became the most expensive cassette deck in history. This was a halo model, a vehicle for selling the company's numerous less expensive decks. Although Nakamichi released several models with experimental functionality, overall the company's approach to design was conservative. All models below the 1000 and 700 series followed the same general design and used the same dual-capstan transport that was introduced in 1978. Nakamichi consistently refrained from copying its competitors' latest solutions and features, refused to employ adaptive biasing and Dolby S, The interviewee, Paul Wilkins, is the co-owner and executive of Bowers & Wilkins, former Nakamichi dealer and current Nakamichi repair specialist in the UK. and did not make autoreversing decks until introduction of the Dragon. Autoreversing was desirable but bidirectional autoreversing tape transports of the 1970s suffered from inherent head azimuth instability, which caused irrecoverable treble roll-off. This issue had to be resolved before attempting to build a true high-fidelity autoreversing deck.
Azimuth problem
In magnetic recording, "azimuth" denotes the orientation of the magnetic head gap – a narrow, vertical slit that spans the height of the track – with respect to the direction of tape travel. "Absolute azimuth", the angle between the gap and the direction of tape travel, must be set at precisely ninety degrees for correct replay of treble signals. In practice, the main goal is perfecting the "relative azimuth" – the angle between the recording and replay magnetic gaps, which must be as low as possible. A two-head deck, in theory, has zero relative azimuth at a given point in time but in the long term its absolute azimuth drifts away from ninety degrees. The advantage disappears when a two-head deck replays tapes recorded on equipment with an unknown absolute azimuth error.
Azimuth errors, or tape skew, affect cassette decks much more than reel-to-reel tape recorders running at higher speeds. A cassette deck claiming a frequency response up to 20 kHz must have an azimuth error less than 6' (arc minutes). Above this threshold, losses in high-frequency response steeply rise; at 20' the head is practically unable to reproduce any treble. These losses cannot be recovered with conventional analog filters. Another inherent drawback of cassettes is the instability of tape positioning relative to the mechanism. The direction of tape travel often deviates from the deck's plane of reference. Sometimes a cassette will play acceptably in one direction but not the other; sometimes azimuth error will audibly vary as the tape plays. Mechanical improvements in tape transport cannot remedy this problem because it stems from minor defects and wear of the cassette shell.
Bidirectional autoreversing cassette tape transports are particularly prone to azimuth errors. Simple transports that use fixed four-track replay heads – the industry standard for car and personal stereos – can be properly aligned in one direction only, leaving the other direction vulnerable to unpredictable random errors. Transports that use rotating two-head assemblies were usually equipped with independent alignment screws for forward and reverse directions. Rotation, however, subjects heads to mechanical stresses that quickly cause audible azimuth errors. Rotating assemblies cannot physically fit separate recording and replay heads; this drawback limits fidelity and rules out tape-source monitoring and tape calibration functionality. The third, more flexible alternative is unidirectional transports that reverse tapes by physically flipping the cassette. Philips and Akai tested this approach in the early 1970s and it was abandoned until the introduction of Nakamichi UDAR (Unidirectional Auto Reverse) decks in 1984.
Search for solution
In 1976, John Jenkins of International Tapetronics invented a novel azimuth correction system for multitrack studio recorders. Two outermost tracks of the Jenkins recorder were reserved for the reference sine wave signal. With properly aligned heads, two sine waves recorded in phase should also replay in phase. If the replay head is skewed, the output sine waves will differ in phase. A DC motor governed by a servo regulator continuously adjusts the azimuth of the replay head to minimize the difference between two signals. Thus, claimed Jenkins, his recorder was able to compensate for replay azimuth skew of any nature.
In 1978, Albert Rijckaert and Edmond deNiet of Philips patented an azimuth correction method that did not require dedicated reference tracks and could be retrofitted to any existing recording format. Its inventors proposed splitting each channel of the replay head into two half-width sub-channels; one magnetic subsystem would read the upper half of the track and the other would read the lower half, and the difference between their outputs would comprise the error signal. The system would work if and when the recorded signal has enough treble content; it would not work reliably with recordings with very little treble content and would not work at all with blank tapes. One year later, Rijckaert and de Niet patented a complete azimuth control system. Their servomechanism used a piezoelectric transducer and functioned in a manner similar to the device described in Jenkins' patent.
A practical, production-ready design of the RijckaertdeNiet head for cassette recorders was patented by Niro Nakamichi in November 1981. Fitting two replay sub-channels into 0,6 mm of a cassette track was a challenging task; according to the patent, each of two cores had to be made up of and thick lamination stacks; the windings had to be hidden in narrow grooves cut into the sides of the thickest stacks. The patented servo system, which was soon commercialized as the Nakamichi Auto Azimuth Correction (NAAC), analyzed only treble signals in the 2–8 kHz range; the deadband of the control loop was set with a simple diode limiter. The servomechanism was driven by an electric motor and used a complex gear train terminating in a wedge that pushed the pivoting replay head.. The primary application was filed in Japan in November 1981.
Unlike the RijckaertdeNiet system, the NAAC analyzed only the innermost (right) channel of a stereo tape. The outermost (left) channel should have been reproduced with a conventional full-track magnetic system. According to Nakamichi, the left channel of a cassette tape is more prone to dropouts and wear, and should not be used for extracting azimuth information; as a side benefit, a simplified control loop has to deal with only one error signal. A unidirectional, azimuth-sensing head would employ three magnetic subsystems – one full-track and two half-track – a bidirectional NAAC replay head would employ six. Bidirectional recording was not an option because a fixed, pivoting replay head would require two erase heads and two recording heads – too many for the limited space of the cassette tape guide. Niro Nakamichi and Kozo Kobayashi, lead designer of the Dragon, settled for a conventional three-head configuration with unidirectional recording only.
Introduction
The Nakamichi Dragon, the first production cassette deck built around Rijckaertde Niet and Niro Nakamichis's inventions, was introduced in North America in November 1982. At a price of , it replaced the far more expensive and already discontinued Nakamichi 1000ZXL as the company's flagship model. The name Dragon broke Nakamichi's tradition of using plain numeric model codes and was coined by company founder Etsuro Nakamichi, who died in the same month.
The deck was well-received by the press, scoring far above the competition. It became the new reference against which all competition was judged and remained so until the end of production.: "the ultimate consumer-cassette machine ... new plus ultra deck". Competing products dubbed "Dragon slayers" of the late 1980s like Revox B215 or Tandberg 3014 or the flagship TEACs surpassed the Dragon in mechanical quality or functionality, but no one could beat it altogether. The combination of sound quality, function set and technology attained by Nakamichi in 1982 remained the apex of the cassette deck industry.
The only other auto-azimuth deck was released in 1983 by Marantz, which was then a Japanese subsidiary of Philips. The Marantz SD-930 had a unidirectional, three-head tape transport, a stereo azimuth-sensing replay head with four magnetic subsystems, and the proprietary Marantz Auto Azimuth Correction (MAAC) servomechanism with a piezoelectric actuator. It was manufactured for a short time in small numbers and remained almost unknown to the audiophile community and the press. In 1985, it was examined and tested by the German magazine Audio, which ranked it the worst of eight competing products.
Later years