Manufacturer's Specifications
Frequency Response: 20 Hz to 21 kHz, to 22 kHz with metal tape.
Harmonic Distortion: 0.8%.
Signal/Noise Ratio: 66 dBA with Dolby B NR, 72 dBA with Dolby C NR.
Separation: 37 dB.
Crosstalk: Down 60 dB.
Erasure: 60 dB.
Input Sensitivity: Line, 50 mV.
Output Level: Line, 1 V; headphone, 45 mW at 8 ohms.
Flutter: 0.019% wtd. rms, 0.04% wtd. peak.
Dimensions: 17 3/4 in. (450 mm) W x 5-5/16 in. (135 mm) H x 11-13/16 in. (300 mm) D.
Weight: 21 lbs. (9.5 kg).
Price: $1,850.00.
Company Address: 1101 Colorado Ave., Santa Monica, Cal. 90401.
The Nakamichi Dragon cassette deck is an exciting combination of innovative design, convenience features and outstanding performance. The centerpiece of the innovations is the fascinating NAAC (Nakamichi Auto Azimuth Correction) system which automatically adjusts the play head to match the azimuth of the material already recorded! Most readers are probably familiar with Nakamichi's scheme for automatically adjusting the record head to match the play head, and that approach ensures the best performance for each deck and tape combination. In the past, however, many have commented on the fact that tapes made on one deck might not sound their best when played on any other model, because of azimuth discrepancies. Only by careful and tedious work could the play head's azimuth be matched to what was on the tape.
With NAAC, however, the Dragon senses the azimuth of the recorded material and adjusts the play-head azimuth to match, obtaining the best possible response. The concept is fairly simple, as many good ideas are, both the implementation is something to marvel at. The head core for one of the stereo channels is actually split into two cores, both still just the total width of one track. The two core outputs are fed through bandpass filters into the rest of the NAAC system:
Waveform squaring circuits, a phase comparator, an operational amplifier and drivers with a motor to shift the play head into position for zero phase deviation. The bandpass filter restricts signals to the range from about 3 kHz to a bit above 15 kHz, ensuring that accurate phase and angular deviation information can be obtained.
The Dragon is Nakamichi's first auto-reverse deck, and NAAC is operational in the reverse-play direction as well, automatically compensating for such effects as changing tape skew. The transport drive system is of dual-capstan design, unusual in that each capstan is driven directly, with the motors locked to a quartz crystal reference. The supply capstan (in either direction) runs 0.2% slower than the take up capstan to maintain the proper tape tension over the heads.
A number of other features are most easily introduced by describing the front panel. The right center is dominated by an array of fairly large, angled, rectangular pushbuttons which are grouped by function.
On the top row are playback functions (reverse play, stop and forward play). Just below are the rewind and fast-forward buttons, flanking the button which actuates the "Cue" function during fast wind. As on other Nakamichi decks, this moves the head closer to the tape, to make the fast-wind "chatter" audible, and reduces the winding speed (to one-third normal with one push, to one-sixth normal if the winding button is held down). Cueing direction can be reversed by pushing the opposite fast-wind button; pressing the appropriate play button selects which tracks the "Cue" function will scan. Green lights indicate which of the buttons in these top two rows are actuated.
The next two rows are for recording functions. First are the "Rec Mute," pause and record buttons, with red LED indicators. (There is no reverse recording function.) On the bottom row is the fixed, button-like "Auto Fader" with direction-indicator lights. It is flanked by the "Down" and "Up" fade buttons themselves. There are two rates of fade, with the faster rate obtained by a second, light push or a single hard one. The fade indicator arrows change intensity to show the direction and level of fading.
To the right of the control buttons are the tape selection and calibration controls: Left and right level pots for three tape types grouped beneath the test button marked "Level (400 Hz)," and left and right bias pots for each tape type grouped beneath the "Bras (15 kHz)" button.
Between these test-signal buttons is a smaller, "Reset" button which shuttles the tape back to the counter zero point. Beneath that are the tape type selector buttons.
Unfortunately, these are marked only with Nakamichi's own tape designations: "EX" (normal, IEC Type I), "SX" (chrome, Type II) and "ZX" (metal, Type IV). Each is flanked by its bias and level pots.
The Dragon's calibration procedure is slower than the automatic setups used by some decks, but as accurate.
After setting the tape type and switching the monitor to "Tape," you actuate the record/pause and "Rec Mute" but tons to disable the inputs. This also sets the counter to 0000.
Start the tape, push the "Level (400 Hz)" button, and set the level-adjust pots for a zero indication on the meters, whose scales expand during this test. Next, push "Bias (15 kHz)." The NAAC system immediately adjusts the play head to compensate for any tape skew, etc., between it and the record head. Then, channel bias levels are adjusted for zero. A push of the "Reset" button returns the deck to the 0000 counter point. After a short familiarization period, this procedure seemed simple and direct.
On the right side is a vertical row of four knobs ("Master," "Left" and "Right" recording gain, and "Output") and seven buttons. The latter are for "Monitor (Tape/Source)," "Eq ilsec (120/70)," "Dolby NR (Off/On)," Dolby "B-Type/C Type," "MPX Filter (Off/On)," "Subsonic Filter (Off/On)," and "Auto Rec Pause (Off/On)." Most of these are self-explanatory, though the helpful inclusion of a subsonic filter is worth noting. "Auto Rec Pause," however, is an unusual convenience, automatically switching from record to record/pause mode if there is no input signal for 40 seconds. With this, you need not stand by, waiting (im)patiently to stop the deck when the music ends.
In addition to its "Auto Rec Pause" feature, the Dragon will also check for silences in playback. When "Auto Rev" is enabled, if there is a blank of more than 40 seconds, the deck fast-winds to the end of the side being played, and then starts play in the other direction if the reverse controls are set for that. This eliminates the need to fast-wind manually past long blank spaces at the end of a side, common in classical recordings.
In the center of the front panel are the four-digit, LED counter and the 20-segment, vertical bar-graph level meters which read from -40 to +10. During tape calibration, the meter scale is expanded for finer resolution. The counter reads from 9999 to-999.
Between these two displays and the main transport controls are five small buttons in a vertical array: Three are for the counter--"Reset," "Memory (Off/On, Stop/Play)"--and the other two are for auto reverse, "Off/On" and a switch to select continuous play or a single auto-reverse cycle.
Above the window in the cassette-compartment door are LED arrows which show the direction of play. These glow red in recording (forward only), green in play, and flash whenever the NAAC system is adjusting play-head azimuth to match the tape in use.
At the far left are a large "Power" button, small "Timer" buttons ("Off/On, Play/Rec"), a large eject button, and a headphone jack.
On the rear panel are gold-plated line in/out phono jacks, a socket for the optional RM-20 remote control, and a d.c. power jack for such Nakamichi accessories as the MX-100 microphone mixer.
Removing the metal top and side cover revealed a few p.c. boards supported and surrounded by a rugged, metal chassis frame. The soldering on the boards was excellent.
Interconnections were made with multi-conductor cables, ending in plugs and sockets or wirewrap. All parts and adjustments were labeled.
Measurements
The playback responses were well within 2 dB of reference for both equalizations and for both directions of play, with the exception of the 18-kHz points at +3 dB with the 70-uS tape. Most of the points for this equalization were within ±0.5 dB, excellent results. Play speed was about 0.07% fast in forward play and about 0.1% fast in reverse play, excellent figures. Average playback-level indications were 0.5 dB high. Record/playback responses were checked for approximately three dozen formulations. Excel lent results were possible with all of them after using the built-in calibration-with the exception of low-bias Type I tapes (non-premium), which would be bad choices for the Dragon anyway.
The supplied Nakamichi EXII, SX and ZX tapes were used for all of the detailed testing that followed. The swept-frequency responses were taken at Dolby level and 20 dB below that for the three tapes, both with and without Dolby C NR. Figure 1 shows the resultant plots, and Table I lists the 3 dB down points for all of the traces. Of particular note are the general flatness, the extended responses at both ends of the band (especially at Dolby level with Dolby C NR), and the good Dolby tracking at -20 dB. The peak at 20 kHz with the EXII tape is somewhat high, but calibration was purposely done rather quickly; slightly more bias would bring it down. It must be noted, however, that bias calibration must be done without Dolby NR for the most stable playback of the 15-kHz tone and its tracking by NAAC. A check of responses with Dolby B NR showed them to be excellent, with very good tracking over a range of levels.
Fig. 1--Frequency responses with (solid lines) and without (dashed lines) Dolby
C NR, using Type I (Nakamichi EXII), Type II (Nakamichi SX) and Type IV (Nakamichi
ZX) tapes.
Fig. 2--Record/playback response of Nakamichi 582 cassette deck with misaligned
record head (top) vs. playback of same tape on Dragon with NAAC system (bottom).
Vertical scale: 5 dB/div.
A number of tests were conducted to learn more about the performance of NAAC. The earlier playback response tests showed that the system would align the play head to the 12.5-kHz test-tape tone within 15° to 20° of phase, equivalent to an azimuth accuracy better than 1' (1/60 degree). This is excellent.
Pink noise was recorded on a separate Nakamichi 582, with its record head purposely misadjusted to cause a loss of almost 20 dB at 15 kHz, as shown in the top trace in Fig. 2. (The relative rise in level for the 16- and 20-kHz bands was from tape noise.) The cassette was then transferred to the Dragon, and the bottom trace shows the response after NAAC operated for about five seconds. Next, the pink noise to the 582 cassette deck was purposely band-limited to 50 Hz to 12.5 kHz to simulate a run-of-the-mill recording (Fig. 3, top), and then the record head was misaligned (middle).
The bottom trace shows how the Dragon operated on the response of the simulated poor deck's tape to achieve correct alignment--further proof of the success of this amazing system. In checking the response limits of the deck, it did appear that NAAC might do some "hunting" with a test signal of 20 kHz or so, which is above its normal response band. This was not considered a defect; there is no known music consisting of a single, 20-kHz tone. There was also some hunting at the start of the swept-frequency response tests, but with a slower sweep rate NAAC had no tracking problems. This was also, of course, a nonmusical condition, and the pink-noise tests indicated what it would do under normal (non-test) conditions.
Table II lists various record/playback test results, and they are all excellent, with the exception of the multiplex filter which had its 35.4 dB notch at a higher frequency. I suspect that, in the rush to get this first-of-its-kind unit out, this simple adjustment was overlooked. The subsonic filter was 3 dB down at 15.8 Hz and 22 dB down at 10 Hz. The level-adjust pot (400 Hz) had a range of-6.1 to +4.5 dB relative to zero indication for ZX tape. The bias pots could set the 15-kHz level anywhere from -8 to +6 dB with the same tape. There was some bias in the right channel output in "Tape" but none in "Source." The 400-Hz (396.7-Hz actual) and 15-kHz (15.24-kHz actual) tones both had less than 1.0% distortion, quite acceptable for the purpose. In the process of running tests with pink noise, it was noted that Dolby C tracking was not affected by the bandwidth of the noise source. (Such effects had been observed with other decks with Dolby C NR). Reference to the frequency responses confirmed that the roll-offs above 20 kHz were very sharp, reducing the likelihood that the Dragon would have any mistracking caused by above-band energy, such as might be generated by a synthesizer. This was another design nicety which showed up without the manufacturer having made any mention of it.
Table Ill lists the distortion figures for the three tapes at 400 Hz with Dolby C NR over a range of levels from 10 dB below Dolby level to the points where HDL3 reached 3%.
The results are excellent, especially so for the EXOI and ZX tapes. Table IV shows the excellent signal-to-noise ratios obtained for all three tapes. Table V lists the figures for HDL3 versus frequency, from 50 Hz to 6 kHz with ZX tape, both at Dolby level and 10 dB lower, again using Dolby C NR. The results are outstanding--the best overall for a deck to date.
Tests were also run at Dolby level using Dolby C NR with both EXII and SX tapes, and those results were also impressive. In general, distortion figures without Dolby NR were, as usual, 30% higher.
Table VI lists a number of input/output characteristics, all substantially to specification as expected. All of the values listed stayed within acceptable limits from 20 Hz to 20 kHz.
The two sections of the master input-level pot tracked together within a dB for 50 dB from maximum, which is very good. The output-pot sections tracked to the same criterion for about 30 dB, which is acceptable. The output polarity matched the input polarity both in "Source" and "Tape" monitor, a desirable configuration.
The thresholds for most of the segments on the level meters were quite accurate, but the lowest ones were about 3 dB too sensitive compared to the zero reference. The bar graph response was slower than that of true peak-responding meters, but the zero segment showed a faint glimmer at 30 mS, which is quite fast. The decay time was 1S for 20 dB, shorter than the IEC standard. The frequency response of the meter was down 3 dB at 47 Hz (on the high side) and 21.6 kHz (just fine).
Fig. 3--Nakamichi 582 cassette deck's response to pink noise rolled off at
10 kHz, with correct record-head alignment (top); 582 with record head out
of correct azimuth alignment (middle), and Dragon's response with off-azimuth
tape from 582 (bottom). Vertical scale: 5 dB/div.
Fig. 4--Record and playback of the opening passages of Respighi's Feste Romane
on a correctly aligned 582 (top) and playback on the Dragon of the same passages
recorded on an incorrectly aligned 582 (bottom). See text. Vertical scale:
10 dB/div.
There was no measurable change in play speed with any line voltage from 110 to 130 V. Speed variations appeared to be less than 0.005%; better instrumentation would be necessary to get more accurate figures. In the reverse play direction, the results were the same. The flutter at any point in a cassette was 0.014% or less, wtd. rms, and 0.028% or less, wtd. peak. In reverse play, the figures were slightly higher, but still better than specified. The Dragon even operated up to specification with a cassette known to be of poor quality. Fast-winding time averaged 51 seconds for a C-60 cassette. All mode changes, including shutoff at the end of the tape, took less than a second.
Table I--Record/playback responses (-3 dB limits).
Table II--Miscellaneous record/playback characteristics.
Table III--400-Hz HDL3 (%) vs. record level (0 dB = 200 nWb/m).
Table IV--Signal/noise ratios with IEC A and CCIR/ARM weightings.
Table V--HDL3 (%) vs. frequency using Dolby C NR.
Table VI--Input and output characteristics at 1 kHz.
Use and Listening Tests
Tape loading was a simple drop-in. Access for head cleaning and similar maintenance was fairly good with the door cover in place, very good with, the cover removed.
The Dragon was very quiet in all its modes, including the cam-drive positioning of the heads. It was interesting to watch the smooth shifting of drive components as tape direction was reversed.
The instruction manual was lucid and quite complete, although some users might desire more technical back ground. It had a number of helpful, pertinent notes, and the illustrations were well done and well tied to the text.
All controls and switches were completely reliable throughout my testing. The angled buttons looked slightly odd, but they were very easy to use, especially with their bright indicators. The arrangement was one of the best I've used, and the angling seemed just right. However, the small, black pushbuttons blended into the panel, putting their in/out status in doubt at times. This was judged most important for the Dolby NR and EQ pushbuttons, where an error would not be immediately apparent.
Setting recording levels was easy, with the bright, vertical bar-graph meters and the three input level pots. The knobs on the individual channel pots were smallish, in contrast to the "Master" gain control, but their friction was low.
Other features that particularly appealed to me included flying-start (punch-in) recording, the "Auto Fader," "Cue," and "Auto Rec Pause." It goes without saying that the NAAC system operated ah the time, trimming play-head azimuth as needed.
The opening passages from Respighi's Feste Romane, one of the records used for the listening tests, was taped twice on a Nakamichi 582-first with the record head correctly aligned, then with the record head set to drop the 15-kHz response by 10 dB on a normally aligned playback head. This second version was played on the Dragon, and its maximum-level spectrum (Fig. 4, bottom) compared with playback on the aligned 582 (Fig. 4, top). There are a few minor discrepancies, but it can be seen that, as the listening indicated, NAAC had aligned the Dragon's play head to restore the original high-frequency spectrum.
Neither ear nor meter detected any noise pulses on the tape when switching into record or pause modes. However, switching from record to stop generated just a slight click, so far down in the noise that it's only audible when using Dolby C NR.
Listening to the Dragon's playback of tapes made from favorite discs was most enjoyable. The sound was clean, even at quite high levels, and a drummer friend was particularly impressed with the bass tightness and clarity.
It's tempting to make some sort of cute remark about a deck called "Dragon," but it's much more important to call attention to the value of its exciting, auto-alignment innovation, NAAC. That, and its superbly low distortion and flutter, excellent calibration facilities for all premium tapes, flat and wide frequency responses, superior reverse-play performance, and many convenience features, all make the Dragon--even with its $1,850 price tag--certain to interest high-end audiophiles and professionals, particularly for normal-speed duplicating.
--Howard A. Roberson
(Audio magazine, May 1983 )
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