Denon DTR-2000 DAT Deck Review

Denon’s DTR-2000 is one of the first consumer-level digital audio tape (DAT) recorders available in the U.S. through normal channels. By incorporating the Serial Copy Management System (SCMS), it enables users to make as many direct, first-generation digital dubs of CD’s and other digital program sources as they wish, while limiting the ability to make digital copies of copies. It also features an advanced version of Denon’s 20-bit Super-Linear digital-to-analog (D/A) converter, called the Lambda SLC. Priced at $1,000, the DTR-2000 comes with a full-function remote control and complements its analog connectors with both optical and coaxial digital inputs and outputs.

While a number of manufacturers have recently adopted one form or another of 1-bit d/a conversion, Denon has chosen instead to remain with the eight-times-oversampling, 20-bit Lambda SLC system originally developed for its top CD players. The Lambda enhancement is designed to minimize the zero-crossing distortion that is characteristic of most multibit d/a converters. Nonlinearity is reduced still further by very careful factory adjustment of the converter’s most-significant-bit (MSB) registers. At the other end of the process, a high-speed analog-to-digital (a/d) converter is used to quantize analog input signals.

Apart from the power switch and the buttons that control the tape transport, the front panel of the DTR-2000 contains only one visible control, which is used to set the recording level for taping from an analog source. (Digital-to-digital recording does not require a recording-level control, since the signal is just a stream of pulses representing binary numbers.) All the other pushbuttons, switches, and controls are neatly concealed behind a flip-down front panel.

Despite their diminutive size, DAT cassettes can hold up to 2 hours of music at the normal 48- and 44.1-kHz sampling rates, or 4 hours at the lower-fidelity 32-kHz sampling rate. Cassettes are inserted into the deck through a motorized tray like those used in most CD players. The transport mechanism inside the deck is similar to that of a miniature VCR and uses the same helical-scan principle. The high tape-to-head speed needed for multimegahertz frequency response (in digital terms, the system’s throughput is 2.77 megabits per second) is achieved with a pair of heads mounted in a rapidly rotating drum set at an angle to the longitudinal direction of the tape.

Although the DTR-2000’s loading design precludes watching the tape as it creeps from spool to spool, the deck’s fluorescent counter provides a far more accurate way to tell where you are on the tape. In addition to displaying the program selection number, the counter can be switched to provide any of four different digital readouts: elapsed time from the start of the tape, elapsed time in the current selection, remaining time to the end of the tape, and conventional (nontimed) counter units, which can be reset to zero at any time.

Signal levels are shown on at wenty-two-segment-per-channel fluorescent peak-reading display, calibrated from - 60 to 0 dB with a single over indicator. When using a DAT deck, you have to avoid the old analog habit of squeezing out a few extra decibels of “signal-to-hiss” ratio by letting the deck’s indicators “run into the red.” Once all 16 bits of the digital signal are 1’s, no larger number (that is, greater signal level) can be processed. The DTR-2000’s built-in analog limiter prevents true digital overload, but such circuits inevitably produce some distortion of their own. You should be careful to keep the recording level down to a point where the over indicator lights only very occasionally if at all (preferably never).

Program selections up to No. 99 can be found by pressing the appropriate numbered buttons on either the deck or its remote control. The tape automatically fast-winds (at 250 times normal playing speed) in either direction to the start of that program and begins play from there. The repeat button will rewind and replay the entire tape as many as sixteen times without further attention, but if you wish to hear a specific selection again you must manually punch in its number and hit the play button each time.

In normal use a program number’s start id code is automatically written into the tape's subcode fields—as is an end id code after the last recorded selection. The DTR-2000 also has a manual mode override that lets you enter or erase start, skip selection, and end subcodes for yourself. To facilitate the exact placement of these inaudible electronic markers, the DTR-2000 provides not only a conventional cue-and-review feature but also a pair of fine cue buttons that inch the tape back and forth at half the normal speed. After manually modifying the subcodes, pressing renumber runs through the tape, renumbers your selections in order, and rewinds the tape again.

To create smooth segues between selections, the DTR-2000 has a digitally controlled fade-in/fade-out facility. The front-panel headphone jack has a level control, and there is a channel-balance control for analog recordings. A three-position switch selects among analog, optical digital, and coaxial digital inputs. The deck provides for automatic activation by an external timer.

The Denon DTR-2000 measures 17-1/16 inches wide, 12-1/16 inches deep, and 4Vs inches high, and it weighs a little less than 16 pounds. Price: $1,000.

Lab Tests

We measured the performance of the Denon DTR-2000 using both Sony and Japan Audio Society (JAS) calibrated tapes, the CBS CD-1 test disc, and our Audio Precision System One test equipment. Whether it was playing back a calibrated tape or going through either the analog or the digital input/output chain, the deck’s frequency response between 20 and 20,000 Hz was so flat that it would be pointless to graph it. In the worst-case condition (using the analog input and output circuitry), one channel was down by 0.31 dB at 20,000 Hz; most deviations throughout the audible spectrum were within a few hundredths of a decibel.

Playback signal-to-noise ratio (S/N), measured against a totally quiet input track, was in excess of 100 dB even without weighting, which certainly confirms the very low noise content of the DTR-2000’s audio output. On the other hand, since a digital silent (“infinity zero”) track does not exercise the d/a converter, the A-weighted dynamic range and the unweighted quantization-noise figures, which were within a few decibels of the theoretical 98.08-dB limit for a 16-bit system, represent more realistic—but still excellent—performance measurements.

Distortion was approximately 0.003 percent for both playback and recording through the digital inputs. Through the analog inputs, the total harmonic distortion plus noise (THD + N) was 0.0015 percent (the a/d converter adds some slight distortion of its own), but a more accurate picture can be gained by looking at the accompanying graph A, where it can be seen that the “knee” of the distortion curve is actually reached at a recording level of —1 dB. Above this point the analog limiter kicks in. Even with this, however, at 0 dB the distortion is an order of magnitude lower than is obtainable when recording on conventional analog cassettes.

Channel separation at 1,000 and 10.000 Hz was more than respectably high on an overall record-playback basis, remaining more than 56 dB at 10.000 Hz. In playback alone, where the analog input circuitry was not active, it was better than 80 dB at the higher frequency. The A-weighted S/N’s of 87 and 85 dB through the analog inputs, while very good, were not outstanding. A good idea of the deck’s relative performance recording through the analog and the digital inputs can be gained by comparing the sets of traces in graph B. The overall linearity of the a/d and d/a converters was excellent down to -50 dB, and the error did not exceed 1 dB until the level dropped below -90 dB.

There was, of course, no wow-and-flutter to measure in the DTR-2000, and its input and output levels were entirely normal. We detected a minuscule speed error (0.02 percent) on the AP’s frequency counter, but it could not conceivably be audible. Fast-winding speeds were fast indeed. The deck ran through a 120-minute tape in 39 seconds in normal fast wind and in 27 seconds when the button was held down for even faster rewind.

Comments

We found the human engineering of the DTR-2000 excellent, though we never tried to use it with the fold-down panel closed. Its controls were responsive and quick, and the recording-level knob had a fine feel. The level display was exceptionally readable.

Even after repeated trials, we are uncertain whether we could repeatable detect any audible differences at all between the input and output signals of the DTR-2000. The frequency response is so accurate, the signal-to-noise ratio so high, and the distortion so low that when we thought we had found some passage on which we heard a difference, even when recording CD’s through the analog inputs, a moment later we were doubtful whether it was not our imagination. One very keen-eared listener thought he detected a very slight roughening of some already “edgy” CD passages, and there may have been the very slightest difference in stereo imaging, but we would not be prepared to swear even to this, despite matching levels between the original and the copy to an accuracy of one-twentieth of a decibel. Suffice it to say, therefore, that we found the Denon DTR-2000 to be a superb recorder and reproducer of music that we can heartily recommend to the most critical of audiophiles.

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