I think it will be best if I state my basic position on the subject of DCC up front. before any discussion of our tests of the Marantz DD-92. This is essentially a political product. Not a technological one. (The same is true of all other DCC decks. needless to say.) DCC would never have happened if R-DAT had not run into serious political trouble in the consumer market. R-DAT is small, cute, and cuddly; it is versatile and practical; its audio fidelity is indisputably state-of-the-art; its linear PCM coding is uncompromised; it is the perfect digital recording/playback medium for our time. DCC is bigger, cruder, clumsier, much less lovable; its operation depends on low bit-rate coding. which is still being hotly debated as to audio quality; its backward compatibility with the Philips audio cassette —for playback only!— is of small consequence because everybody has at least one cheap cassette deck for that purpose (not to mention making copies for the car stereo. which a DCC deck cannot do).



R-DAT blows away DCC in every way. but the marketeers got tired of fighting the paranoid political opposition to the perfect recording/copying medium and abandoned the consumer market (though not the professional market). DCC is what tries to fill the resulting vacuum; it is claimed to be audibly perfect while circumventing bit-for-bit copying of linear PCM recordings.

It has been argued that R-DAT would have remained prohibitively expensive for the mass market even if there had been no opposition to it. That argument is contradicted by the universal abundance of cheap VCRs, based on the same sophisticated rotary-head technology as R-DAT. The irony is that DCC may never come down in price to the mass market level because, according to recent reports, the manufacturing costs of the supposedly simpler DCC magnetic head have been disastrously underestimated. It would be poetic justice if DCC failed and consumers started to demand cheaper R-DATs. That said I must now state that the Marantz DD-92 is in many ways an admirable piece of engineering, proving what can be done when a resourceful industrial giant, namely Philips, decides to do an end run around a headon unyielding technological/political problem. I am quite impressed -with a few reservations. The basic idea behind low bit-rate coding—more illuminatively called perceptual coding—is that you can't possibly hear a mosquito circling around a jackhammer in action. so why not record only the jackhammer and use fewer bits? The assumption is that Only so many bits will fit into so many seconds on the medium (tape, laserdisc, etc), which may not be true as the media tech-nology advances but is a practical fact for here and now. The trick is to capture absolutely everything that the keenest ears ca11 hear. no matter what the musical or other program material happens to be, and to throw away only what they surely cannot hear. There are a number of rival coding schemes purporting to do exactly that; the Philips algorithm is called PASC {Precision Adaptive Subband Coding) and uses 4-to-l data reduction. By farthe best and most complete explanation of the system appeared in the September 1991 issue of Audio, by none other than our own Contributing Editor at Large. David Ranada. My congenital reluctance to do once again what somebody else has already done with great skill has been frequently reiterated here, so I shall simply refer the reader to that excellent article and blithely proceed with my own evaluation.

The Marantz DD-92 is thc flagship DCC deck of the Philips line and l00ks it. Cosmetically the unit is in the top-of-the-line Marantz idiom. meaning the massive gold look with thick, crackle-finished end caps and a smooth, slightly curved fascia, plus lots of bells and whistles. Only the remote control unit looks a bit chintzy. The cassettes are the same size as the ordinary ones but a little more high-tech-looking and equipped with a sliding metal shutter like a 3 1/2" computer diskette. The microprocessor-controlled displays in the front-panel window are amazing- they tell you in real time everything that's going on, everything you need to know, and a few things you don’t need to. I'd say that those who judge audio equipment by the controls will be happy.

The most important thing I wanted to find out about the unit was whether or not PASC data reduction resulted in any audible change in the signal. David L. Clark, whom I have always found to be reliable, had already reported in the April 1992 Audio that PASC was audibly transparent, so I was at least emotionally prepared to find likewise. I copied the entire 33-minute length of the Stravinsky Sacre from CD to DCC via S/PDIF; then I also copied the Bach Toccata in F-sharp Minor, onto the same tape as I did an undistinguished but superbly recorded jazz cut from a dmp CD. The Stravinsky has very dynamic, heavily orchestrated passages alternating with soft, delicate ones using only a few instruments; the harpsichord is supposed to be especially difficult for low bit-rate coders to reproduce; the jazz selection contained percussive sounds with clean attack/decay against a quiet background. I set up the ABX double-blind comparator with the CD player and the DCC deck as the signal sources; I matched the levels very carefully and synchronized the CD with the tape for each comparison. Three different experienced listeners -I was one of them— spent about two hours each trying to hear differences. Each of us believed to have zeroed in on very subtle differences as long as A and B were known; in the X tests, however, we got completely random results. Based on this admittedly limited experiment, DCC appears to be transparent.

I understand that David Ranada, who years ago found precisely the right music to identify the sonic Achilles' heel of the unlamented Copycode, is trying to do the same with DCC and other perceptual coding schemes. It stands to reason that 4-to-l data reduction should throw away some audible music now and then, even if very rarely, since the algorithm is most unlikely to anticipate every possible musical combination in the world. So far, however, no one has come up with the music that will confound PASC, at least not in print with documentation. It should be added that this is not a trivial, hairsplitting, audio-freak issue; perceptual coding in some final standardized form will definitely be needed for the data-intensive multichannel audio formats of the future (see the Mark Davis interview in our last issue) and for digital broadcasting; there is no way around it. We must find the all-around best code or face another stupid format war, which could become the most counterproductive in the history of the industry. AT&T claims they have something significantly better than Philips, Sony, and the rest; the silico11 implementation, however, may turn out to be costly. Dolby also has a coder. Eventually there will have to be a showdown and a shakeout.

After 0ur listening tests, I decided that it made little sense to test the operation of the PASC, although Audio Precision has a complete test protocol to do so on the "System One Dual Domain". The coder drastically alters the signal, and I was not particularly interested in electronically trackgin the procedure as long as it turned out to be sonically transparent. On the other hand, I was interested in testing the A/D and D/A converters used in the Marantz DD92, as they are supposed to preserve the integrity of the signal in their conversions.

The A/D converter turned out to be quite good but not state-of-the-art. Its full-scale THD + N averaged aproximately -91 dB across the audio spectrum, showing little fluctuation with frequency. That’s just a tad short of 15 bits; Marantz calls it a Bitstream Sigma-Delta converter with 18-bit resolution. Ahem... The linearity of the ADC was excellent, departing departing the 0 dB line only below the -80 dB level; the error at -90 dB was +0.5 dB.

The D/A converter performance was not nearly as good —and this is the top-of-the-line Philips BitstreamDAC 7 in the differential mode. Full-scale THD + N versus frequency stays between -88 dB and -93 dB hum 20 Hz to 2 kHz. then goes into orbit: -79.5 dB at 8 kHz. -64 dB at 18 kHz! N0 it isn‘t jitter because with the S/PDIF input reduced to -20 dB it goes away; normalized to full scale it then looks like a -95 dB DAC up to 10 kHz, and the normalized 18 kHz distortion is also a much more respectable -84 dB. This is gain-related analog distortion, almost surely, and it isn‘t necessery. Remember, there are DACs that can give you that -95 dB performance at full scale and at all frequencies. Len Feldman, reviewing the Marantz DD-92 in the March 1993 issue of Audio, shows pretty much the same curve I obtained but leaves it without the slightest criticism. Bob Harley in the July 1993 Stereophile doesn't even mention full-scale THD + N versus frequency in his review of the Marantz DD-92; at this point i think he avoids that measurement because i keep insisting on it. After that I must add that the gain linearity of the DAC was superb, requiring n critique.

To sum up, the Marantz DD-92 delivers the sonic performance claimed for it and is overall a pretty sexy toy from the point of view of the average knob-twiddling audiophile, but it has some enseasurable shortcomings that aren't easily forgiven at the $1200 price. For $1200 I'm sure that Philips with their present-day technology could produce a DAT deck that would need no apology and no convoluted political reasoning behind it. On the other hand, if PASC turns out to be the perceptual coding scheme of the future-frankly, I doubt it— then the total effort will have been more than worthwhile, and the Marantz DD-92 will be remembered as a11 industry milestone.
The Audio Critic, Late summer 1993, issue no. 20





Specifications Marantz DD92
D/A conversion: Bitstrem DAC-7 Differential mode 1 bit pulse density modulation with 20 bit 8 times oversampling digital filter
A/D conversion: Bitstream Sigma-Delta modulation 64 times oversampling with 18 bit resolution

Frequency response Digital:
48kHz sampling: 10-Hz - 22kHz +/- 0,2dB
44.1kHz sampling: 10Hz - 20kHz +/- 0.2dB
32kHz sampling: 10Hz - 14.5kHz +/- 0.2dB
Analog (Type II tape): 20Hz - 18kHz +/- 3dB

Signal to noise ratio (A-weighted)
Digital (playback):
>103dB (Marantz DD92)
>101dB (Marantz DD82)
Analog (no NR, Type II): >59dB
Dolby B Improvement: up to 10dB
Dolby C Improvement: up to 20dB

Dynamic range
Digital (playback): >100dB

Total Harmonic distortion
Digital (playback):
<0.03% at 1kHz (Marantz DD92)
<0.035% at 1kHz (Marantz DD82)

Channel separation
Digital (playback): 100dB at 1kHz

Wow and flutter
Ditigal: below the limit of measurement
Analog (WRMS): .015%

Output level and impedance
Analog fixed: 2V / 1.5 kOhm
Analog variable: 0-2V / 1.5 kOhm
Digital co-axial: .5V p-p/75 Ohm
Digital optical: Toslink-19 dBm

Power supply
/01 version: 110-120/220-240V AC 50/60Hz
/02 version: 230V AC 50/60Hz
/05/07 version: 240V AC 50/60Hz
U version: 120V AC 50Hz 35W

Dimensions:
Width:
456mm (including side panels, Marantz DD92)
420mm (Marantz DD82)
Height: 132mm
Depth: 344mm
Weight:
13kg (Marantz DD92)
8.2kg (Marantz DD82)