Nakamichi Dragon


The Nakamichi Dragon is an audio cassette deck introduced by Nakamichi in 1982 and marketed until 1994. The Dragon was the first Nakamichi model with bidirectional replay capability and world's first production tape recorder with automatic azimuth correction system. This feature, invented by Philips engineers and improved by Niro Nakamichi, continuously adjusts replay head azimuth to minimize apparent head skew and thus retain treble signal recorded on tape. The system allows correct reproduction of mechanically skewed cassettes, and cassettes recorded on other, often misaligned, decks. Apart from the Dragon, similar systems have only been used twice, in the Nakamichi TD-1200 car cassette player and the Marantz SD-930 cassette deck.
At the time of introduction the Dragon had a record lowest wow and flutter and a record highest dynamic range, losing marginally to the former Nakamichi flagship, the 1000ZXL in frequency response. Competing models by Sony, Studer, Tandberg or TEAC, introduced later in the 1980s, sometimes surpassed the Dragon in mechanical quality or 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

In 1963 Philips introduced the Compact Cassette. The new format, intended primarily for dictation, 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 use of dedicated recording and replay heads and off-tape monitoring that were the norm in reel-to-reel recorders. However, in 1972 Nakamichi introduced a cassette deck that easily outperformed most domestic and semi-professional reel-to-reel recorders. Ordinary cassette decks of that period struggled to reproduce 12 kHz on ferric tape or 14 kHz on chromium dioxide tape; the Nakamichi 1000 easily recorded and reproduced signals up to 20 kHz, on tapes of either type. It was the first three-head cassette deck, the first cassette deck with 'discrete' 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 the competitors struggled to approach the performance of the model 1000, Nakamichi continued research and in 1981 presented their next flagship, the 1000ZXL.. The 1000ZXL had slightly narrower dynamic range and slightly higher wow and flutter than some competitors, but won the contest with its unprecedented frequency response and record low distortion. Its price of 3800 US dollars was too high for the consumer market; the uprated "gold" version, priced at 6,000 dollars, 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 did release a few 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 blueprint and used the same dual-capstan transport introduced in 1978. Nakamichi consistently refrained from copying the competitors' latest solutions and features, refused to employ dynamic biasing and Dolby S, 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.

The azimuth problem

In magnetic recording, azimuth denotes the orientation of magnetic head gap - a narrow vertical slit spanning the height of the track - with respect to the direction of tape travel. Absolute azimuth, the angle between the gap and direction of tape travel, must be set at precisely ninety degrees - this is a prerequisite for correct replay of treble signals. In practice,the main goal is perfecting the relative azimuth - the angle between recording and replay magnetic gaps, which must be as low as possible. A two-head deck, in theory, has zero relative azimuth - but only at a given point in time; in the long run its absolute azimuth drifts away from the ninety-degree mark. The advantage disappears when a two-head deck needs to replay tapes recorded on other equipment with its own, unknown, absolute azimuth error.
Azimuth errors affect cassette decks much more than their reel-to-reel cousins running at higher speeds. A cassette deck claiming frequency response up to 20 kHz must have azimuth error less than 6' ; above this threshold treble losses steeply rise, and at 20' the head is practically unable to reproduce any treble. These losses cannot be recovered with conventional analog filters. Another inherent drawback of cassette format is the instability of tape positioning relative to the mechanism. The actual direction of tape travel often deviates from the deck's plane of reference. Sometimes a cassette will play fine in one direction, but not the other; sometimes azimuth error will audibly vary as the tape plays through a single side. Mechanical improvements in tape transport cannot remedy this problem, because it stems from minor defects and wear of the cassette shell itself.
Bidirectional autoreversing cassette tape transports are particularly prone to azimuth errors. Simple transports employing 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 at mercy of unpredictable random errors. Transports employing rotating two-head assemblies were usually equipped with independent alignment screws for forward and reverse directions. However, rotation subjects heads to mechanical stresses and inevitably changes their absolute azimuths. Rotating assemblies cannot physically fit separate recording and replay heads; this drawback severely limits fidelity and rules out tape-source monitoring and tape calibration functionality. There was a third, more flexible alternative - unidirectional transports that 'reversed' by physically flipping the cassette. This approach was tested by Philips and Akai in the early 1970s and was abandoned until the introduction of Nakamichi UDAR 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, two output sine waves will differ in phase. A DC motor governed by servo regulator continuously adjusts 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 azimuth correction method that did not require dedicated reference tracks and could be retrofitted to any existing recording format. Inventors proposed splitting each channel of replay head into two half-width subchannels. One of two magnetic subsystems should read the upper half of the track, another the lower half; the difference between their outputs is the error signal. One year later Rijckaert and de Niet patented a complete azimuth control system. Their servomechanism employed a piezoelectric transducer and functioned similar to the Jenkins patent - if and when the recorded signal has enough treble content. It would not work reliably with recordings having very little treble content, and would not work at all with blank tapes.
A practical, production-ready design of the RijckaertdeNiet head for cassette recorders was patented by Niro Nakamichi in November 1981. Fitting two replay subchannels into mere 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 0.2 mm and 0.4 mm thick lamination stacks; the windings had to be 'hidden' in narrow grooves cut into the sides of the thicker stacks. The patented servo system, soon commercialized as the Nakamichi Auto Azimuth Correction, analyzed only treble signal in 2–8 kHz range; deadband of the control loop was set with simple diode limiter. The servomechanism was driven with an electric motor, and employed a complex gear train terminating with a wedge that pushed the pivoting replay head.
Unlike the RijckaertdeNiet system, the NAAC analyzed only the innermost channel of a stereo tape. The outermost channel should have been reproduced with a conventional full-track magnetic system. Nakamichi reasoned that the left channel of a cassette tape is too prone to mechanical damage and dropouts, and should not be used for extracting azimuth information; as a side benefit, simplified control loop has to deal with only one, not two, error signals. A unidirectional azimuth-sensing head would employ three magnetic subsystems, a bidirectional NAAC replay head would employ six. Bidirectional recording was not an option, because a fixed replay head would then 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 first production deck built around Rijckaertde Niet and Niro Nakamichis's inventions, the Nakamichi Dragon, was introduced in North America in November 1982. The Dragon, then priced at "only" 1850 US Dollars, replaced the far more expensive, already discontinued Nakamichi 1000ZXL as the company's flagship model. The name Dragon, breaking with Nakamichi's tradition of using plain numeric model codes, was coined by company founder Etsuro Nakamichi who coincidentally died in the same month.
The deck was very well received by the press, scoring far above the competition. It became the new reference, against which all competition was judged, and held this place until the end of production. "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 impregnable, an absolute highest point of cassette deck industry.
The only other auto-azimuth deck was released in 1983 by Marantz, 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 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 Audio magazine, and was ranked worst out of eight competitors.

Later years

In 1985, Nakamichi attempted to develop the Dragon marquee into a premium sub-brand, and released the Nakamichi Dragon-CT turntable, but the line of cassette Dragons turned out a dead end. Manufacturing and aftermarket servicing of azimuth-sensing heads and transports was too expensive and too difficult even for the company that invented them. After the Dragon, Nakamichi released only one NAAC-equipped model, the TD-1200 car stereo. The 'junior' line of Nakamichi autoreversing decks, released in 1983–1985, employed unidirectional transports that physically flipped the cassette and lacked azimuth correction. The 1986 Nakamichi CR-7 - a new flagship deck manufactured along the older Dragon - had unidirectional transport with manual azimuth controls. By 1988 development of high-end cassette decks was over. These models were a concession to a very thin circle of enthusiasts - too small to make any profits. Their value as halo drivers for selling low-cost consumer decks quickly eroded with the spread of digital technologies. Any further improvements in analogue tape, if possible at all, required substantial research expense - but by that time corporate resources were already committed to digital.
In 1990 Nakamichi outsourced transport manufacturing to Sankyo and discontinued all models built around Nakamichi's own unidirectional tape transports, but the Dragon remained in production until 1993, and sales in Japan continued a least into 1994. The number of manufactured Dragons remains undisclosed, but given the eleven-year production run and worldwide sales network, it was very large for a halo product. By 1996 rising costs of Japanese labor and declining market forced Nakamichi to shut down cassette deck production. The company made a mistake by banking on a digital format that failed to get substantial market presence, and in 1997 the Nakamichi family sold the dying business to Grande Holdings.

Design features

Appearance and ergonomics

The Dragon faceplate, clearly descending from models ZX-7 and ZX-9, differs from them in the arrangement of secondary controls and recording level meter. Oversized transport and calibration control buttons, arranged in rows like shingles, acquired three-dimensional profile. The Dragon has a well-developed calibration panel and automated fader, but otherwise its function set is minimalistic, assuming fully manual operation. Tape selection is fully manual, with independent settings for bias and equalization; this allows recording Type II and Type IV tapes with 120μs time constant. Reviewers rated Dragon ergonomics positively but noted many minor quirks and inconveniences. Deep window of the cassette well is too small; right-side buttons, including the important noise reduction and EQ switches, are too small, hard to read but easy to press accidentally. Resolution of the LED meter, like that of all segmented displays, is too coarse for precise adjustment. Finally, Nakamichi continued its tradition to give cryptic names to standard tape types.
Recording channel calibration is performed separately for left and right channels in a sequence similar to ZX-7 and ZX-9, except that optimal relative azimuth is set by the NAAC automatically. Once the NAAC reaches equilibrium, which takes no more than 15 seconds, the user aligns recording channel gain to match the tape's sensitivity, using 400 Hz test tone. Then, the user aligns bias using 15 kHz test tone. Reviewers noted that manual calibration in the Dragon was as good as automatic systems of its competitors. Manual process takes more time, but allows control over frequence response to suit the user's taste. Calibration, however, cannot remedy faults of low-grade ferric tape, "which would be bad choices for the Dragon anyway".

Tape transport

Nakamichi designers always followed "performance first, convenience second" philosophy. This approach led them to adopt discrete three-head layout with independently adjustable recording and replay heads, while the rest of the industry adopted tightly joined head assemblies. Next, they created a robust double-capstan "diffused resonance" tape transport, and Nakamichi's trademark pressure pad lifter - a tiny improvement that substantially reduced scrape flutter and modulation noise. The Dragon added yet another innovation - direct drive of both capstans with low-cogging brushless DC motors. Capstans, traditionally, had unequal diameters and different flywheel masses. Their quartz-controlled speeds were spread apart to ensure that the trailing capstan always lagged behind the leading capstan by 0.2%, in either forward or reverse mode, to proper tension the tape and isolate it from the cassette shell. The third motor spun both tape spools, the fourth motor drove the NAAC servo, and the fifth one smoothly raised and lowered the head assembly. Both pinch rollers were enclosed in wraparound tape guide blocks. A side benefit of complex five-motor arrangement was that the transport did not use belts or springs.
The Dragon's "discrete" heads were rated for 10000 hours replay or recording time. To prevent early formation of wear groove, which usually destroys left channel audio, the heads were pre-slotted at the tape edges. This standard feature of reel-to-reel studio recorders has never been used in cassette decks before. Cores of recording and replay heads were made of Nakamichi's "crystalloy", double-gapped erase head used a ferrite and sendust core. The two-track recording head has a gap of 3.5 micrometers, the four-track, six-channel replay head has a gap of 0.6 micrometers. Theoreticall, the latter allows reproduction of frequencies up to 40 kHz.
Nakamichi auto azimuth correction operates continuously in either replay or recording mode and is able to correct azimuth errors up to 12'. The NAAC has no memory: each tape eject, and each change of replay direction resets current setting and returns the replay head to default position. The systems is reactivated immediately upon pressing play button. If the detected azimuth error lies within deadband limits, the head remains stationary; higher error values engage servomechanism action. When the recorded signal has sufficient content, adjustment to less than 1' azimuth error takes from 1 to 5 seconds and usually gets unnoticed by the listener. If the recorded signal contains very little treble energy, the system detects uncertainty and slows down, or does not engage at all. It is not completely fool-proof, and can be confused and disturbed with unusually strong ultrasonic signals, or very fast audio frequency sweeps. Such unnatural, non-musical signals cause "some hunting" as the NAAC tries to seek nonexistent or quickly changing target.

Audio signal path

The Dragon's replay audio path contains six identical head amplifiers: two for forward direction, two for reverse, and two for the NAAC control channel. Each head amplifier is an active filter employing a discrete JFET front stage AC-coupled to an operational amplifier in inverting configuration. This was the first time when Nakamichi used op amps, rather than discrete transistors, in head amplifiers. Their feedback networks shape up low and middle-frequency parts of the IEC equalization curve, and crudely approximate its treble part. The signal then passes through CMOS switches that select either forward or reverse channels, and is then routed to noise reduction ICs, where the treble equalization is completed. The Dolby B/C compander is a true "double Dolby", with two NE652 ICs in replay path and two more in recording path. A similar arrangement, excluding bidirectional replay features, was later used in Nakamichi CR-7. Recording path, traditionally for upper-range Nakamichi, has individual analogue bias adjustment, and no Dolby HX Pro, or any other kind of dynamic biasing.

Reception and reviews

Independent measurements

The Dragon's wow and flutter announced by Nakamichi were an absolute record for the period, twice as low as those of Nakamichi 1000ZXL. Independent tests confirmed manufacturer's figures; according to Stereo Review, test results revealed performance not of the Dragon, but of the professional transport that recorded the test tape. In 1985-1988 ASC, Onkyo, Studer and TEAC reached a similar level of wow and flutter, but the Dragon's achievement was still the best in industry. Long-term speed stability of the Dragon was exemplary, but that was typical for all quartz-controlled transports. Likewise, the Dragon's absolute speed error was typical for the industry, and presented no audible distraction.
According to Stereo Review measurements, the Dragon's dynamic range for Type I, II and IV tapes equalled 54, 56.5 and 59 dB respectively. These were record high figures for cassette machines, beating Tandberg 3014 and Revox B215 in comparative tests by 4-5 dB. The Dragon's replay audio path generated far less treble noise; tape hiss reproduced with the Dragon appeared subjectively queter and euphonic. Maximum output levels of the Dragon, were also the best in class, marginally better that those of the Tandberg but almost 4 dB better than those of the Revox.
The lower boundary of the Dragon's frequency response, measured to within ±3 dB, extends to 1112 Hz. Nakamichi claimed that special shape of their heads substantiall reduced contour effect, effectively suppressing low-frequency headbump, or poletip resonance. This was true only for the replay head. Combined recording and replay frequency response, according to independent testers, exhibits the familiar comb-like resonant pattern. The lowest and most prominent peak lies at around 15 Hz; it can be suppressed with a user-defeatable subsonic filter.
The upper boundary for low-level signals extends to 2224 kHz depending on tape type. This is much lower than the record set by Nakamichi 1000ZXL, and is typical for all flagship models of the 1980s. Significance of this parameter was often overstated by hi-fi enthusiasts; professionals did not rate it as important because any professional deck easily exceeded the 20 kHz mark. More important was the high-level frequency response, which was largely limited by the tape and tape-head interaction. Here, the Dragon demonstrated very good performance, again marginally better than Tandberg and significantly better than the Revox with Type I and Type IV tapes.

Controversy about equalization

Reviewers who examined the Dragon's frequency response noted its abnormal behavior in the upper treble. The Dragon played back test tapes with a prominent treble boost, reaching +4 dB at 18 kHz. This would audibly brighten up music recorded on standard equipment. Noel Keywood wrote that Dragon's brightness would benefit most tapes recorded on inferior decks, yet might be at times annoying or outright unpleasant.
Nakamichi's signature treble boost was well known to the press before the Dragon. The controversy has been discussed in American journals in 1981–1982. The root of the problem was hidden in the language of the IEC standard enacted in 1978 and based on the original, outdated 1963 Philips specification. The standard was written in terms of remanent magnetic flux recorded on tape. Flux, the principal metric of recorded signals, cannot be measured directly. It can only be picked up with a magnetic head, which converts faint magnetic field into electric current, losing some energy in the process of conversion. Replay head losses rise with frequency and usually cannot be reliably calculated due to complexity of underlying phenomena. To make things easier for the industry, the IEC tacitly allowed manufacturers to use the output of the IEC reference replay head as the measure of recorded signal. Losses in the reference head had to be compensated with a reciprocal treble boost during recording. This arrangement became a norm in the industry, but was never properly formalized. By 1981 improvements in tape head technology made the IEC reference head obsolete; new top-of-the-line replay heads had far lesser treble losses and did not need as much pre-emphasis, yet test tapes were routinely made to suit the old reference head. Overall, test tape tape production was in disarray, which worsened compatibility issues. Classic Philips calibration tapes were technologically obsolete and inconsistent from sample to sample. Newer TDK tapes were even more inconsistent, and different from Philips tapes, while TEAC tapes were different from either Philips or TDK. All were recorded with undocumented pre-emphasis, and with slightly different azimuth.
Nakamichi never subscribed to the informal convention. The company followed the Philips and IEC standards literally, and insisted that losses in replay head must be compensated in replay audio chain. Pre-emphasis in the recording chain should only compensate for recording losses; anything else, according to Nakamichi, was unacceptable. The company insisted that estimation of treble losses in well-engineered heads presents no problems. As a result, Nakamichi's recording chains and Nakamichi's calibration tapes were consistently duller than the competition, and Nakamichi's replay chains were consistently brighter. The competition, in turn, was gradually improving their own replay heads, and tacitly adopting Nakamichi's approach. BASF, a principal player in the IEC and manufacturer of the IEC Type I and Type II reference tapes, backed Nakamichi with a statement that, as of December 1981, Nakamichi decks were fully compatible with BASF-made reference.

Overall ratings

Throughout the 1980s, high fidelity magazines called Dragon the best cassette deck ever tested. In comparative tests by Audio and Stereo Review, only the Revox B215 equalled the Dragon in sound quality. The Revox surpassed the Dragon in mechanical aspects, and probably in long-term durability, but lacked autoreversing, auto azimuth adjustment and the versatility of manual calibration. Flagship decks by ASC, Harman Kardon, Onkyo, Tandberg and TEAC, and the auto-azimuth Marantz SD-930 were distinctly inferior. Whether the Dragon was Nakamichi's best deck or not is debatable. According to Paul Wilkins of Bowers & Wilkins, the 1000ZXL was the most complicated, the less expensive CR-7 was an even match for the Dragon in sound quality but, again, lacked auto reverse and auto azimuth functions.
These functions, particularly auto azimuth, changed the playing field in favor of the Dragon. It wasn't just another precision recording machine: it was a universal player that was able to digest almost any cassette recorded by almost any other deck, and consistently make the best of it. This attracted affluent yuppie buyers and sealed the reputation of the Dragon as a desirable status symbol. In the late 1990s, after Nakamichi went down, their products acquired cult status. Barry Wilson of Stereophile compared it to the role of Harley-Davidson among motorcyclists, or the Gibson Les Paul among guitarists. McIntosh amplifiers or Linn turntables were just as desirable, but none could beat Nakamichi in the number of loyal owners. Worldwide numbers are unknown, but there were around 130000 Nakamichi decks sold in the United Kingdom alone By 1998, fans already formed vibrant internet communities; their online activity disseminated and reinforced the belief in "legendary" "Nakamichi warmth". The Dragon, in particular, was revered as "the Holy Grail of what could be accomplished at 1 7/8".
In the 21st century, reputation of the Dragon is reinforced by collectors, internet traders and very narrow circle of repair technicians. Critics say that the "legend" of the Dragon did not pass the test of time. The complex five-motor transport, once hailed as "a masterpiece of engineering" and an "engineering tour de force", was inevitably not as robust as simpler unidirectional transports. The Dragons sold at internet auctions all need extensive repairs; the number of Nakamichi service technicians is small and shrinking, and the parts can only be scavenged from other, already dead, Dragons. Cost of complete overhaul in the 21st century is comparable with the price of a new deck in the 1990s.

Reviews and comparative tests