Nakamichi OMS-2A CD-player Review

The OMS-2A is Nakamichi’s least expensive CD player, although its $499 price would probably place it in the top half of most other CD player lines. It shares many of the basic circuit features of the more expensive Nakamichi CD players, including a “Shunt-fed Analog De-Glitcher” designed to improve the resolution of low-level signals and thereby retain the ambience of the program. It uses a true 16-bit digital-to-analog (d/a) converter, with double over-sampling at 88.2 kHz followed by a digital filter and a five-pole analog filter. The combination is said to provide much better group-delay characteristics than is possible using a “brick-wall” analog filter alone.

Like Nakamichi’s higher-priced CD players, the OMS-2A employs a “multi-regulated” power supply for maximum channel separation and to keep digital noise out of the analog circuits. Its three-spot laser pickup is also similar to those used in the other Nakamichi players, and the entire drive mechanism is floated from the main chassis on springs to isolate it from external shock and vibration.

Although the OMS-2A appears deceptively simple at first glance, it has most of the convenience features one expects in a CD player. It can be programmed to play up to fifteen tracks in any desired order, and either the programmed sequence or the entire disc can be repeated indefinitely. Track skipping in either direction is also provided, but there is no direct access to indexed program segments. Fast forward and reverse search are provided only on the supplied wireless remote control. A disc can be scanned at two speeds, with the program audible when this mode is entered from play.

The OMS-2A’s display is considerably simplified, however. Normally it shows only the number of the current track. Successive operations of the display button cycle it through its other modes, which show the remaining time on the disc and the elapsed time in the current track. When a disc is first loaded, the display shows the total number of tracks and the total playing time for 3 seconds each. Small lights in the display window show the status of the memory and repeat features. During programmed operation, the display shows both the track number and its position in the programmed sequence. The front panel of the OMS-2A contains a stereo headphone jack with its own volume control.

The Nakamichi OMS-2A measures 17 inches wide, 12-3/4 inches deep, and 3 inches high, and it weighs 11-1/4 pounds. It is finished in black with gold panel markings.

Lab Tests

With a standard EIA load of 10.000 ohms and 1,000 picofarads of capacitance connected to its outputs, the Nakamichi OMS-2A delivered an output of 2.32 volts from a 0-dB (maximum-level) test recording. The channel imbalance was only 0.07 dB. The frequency response was ruler-flat from 20 Hz to several kilohertz and rose slightly at the highest frequencies, with small superimposed ripples. The two channels differed slightly at the high frequencies, although they were never more than 0.5 dB apart.

The channel separation was 95 dB at the low and middle frequencies, decreasing slightly to 90 dB at 10.000 Hz and 87 dB at 20,000 Hz. Dynamic range (defined as the ratio of the 0-dB output to the total distortion content of a — 60-dB, 1,000-Hz test tone) was 103 dB. Distortion was typically negligible at normal listening levels. The interchannel phase shift increased from a few degrees at low and middle frequencies to 34 degrees at 20,000 Hz.

The cueing of the OMS-2A was slower than that of most other current CD players; it took 6 seconds to go from Track 1 to Track 15 of the Philips TS4 test disc. But it had no trouble with the transition between Tracks 17 and 18, which have no silent interval between them, and it did not clip any of the opening syllable of Track 18. The maximum levels of the calibrated defects on the Philips TS5A test disc were tracked without difficulty. The player’s resistance to physical impact was very good on its side, good on the top.

Comments

Our measurements showed the Nakamichi OMS-2A to be at least the equal of most other machines in its price class in respect to the basic parameters of frequency response, distortion, noise, and channel separation. In the important qualities of defect tracking, cueing accuracy, and impact resistance, it was also an excellent performer. None of this came as a surprise given the company’s recognized dedication to making products of the highest quality.

Unlike some people, we have never found significant differences in sound quality between CD players (as distinguished from the CD’s themselves, which differ at least as much as LP’s ever did). It was also not surprising, therefore, to find that the OMS-2A sounded no better (or worse) than any other current, good-quality CD player we have used.

Nakamichi stresses the ability of the OMS-2A to reproduce the lowest program levels in their correct proportions, in contrast to the many CD players that tend to “lose” the signal as its level becomes very low, cutting it off abruptly instead of allowing a natural gradual decay into the background noise. Although we did not detect any differences in this respect with music programs, listening to single test-tone signals at levels down to —100 dB confirmed that the OMS-2A did produce a smooth reduction in volume as the signal approached its minimum level. With some other good CD players, the signal volume tended to stabilize at about —80 to — 90 dB before disappearing abruptly at —100 dB. To put this distinction into perspective, however, it should be said that a — 90- or —100-dB level is barely audible with one’s ear placed against the speaker and the gain of a 350-watt amplifier turned to maximum—and then only in a very quiet room! Unless you are one of those persons who are hypersensitive to this effect, its significance would seem to be somewhat exaggerated.

The most obvious difference we noted between the Nakamichi OMS-2A and most other CD players we have used was the relatively limited visual information displayed while a disc was playing. The OMS-2A’s display can show just about everything that any other player can, but not simultaneously. Perhaps it is just that we have become accustomed to seeing both the track number and the elapsed time on the displays of CD players, but we would have preferred the OMS-2A to have a more conventional display. More than offsetting this minor quibble was the excellent headphone volume provided by the player, which drove the AKG K340 phones we were using to very high volume levels without difficulty.

Overall, the Nakamichi OMS-2A is certainly a first-rate CD player that is worthy of the name it carries, and when all factors are considered it is reasonably priced. If you listen to CD’s, as opposed to watching the colored lights on equipment panels, you should find it an eminently satisfactory choice.

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