Onkyo DX-G10 CD-player
One word best describes Onkyo's DX-G10 Compact Disc player: "imposing." We hasten to add that this description does not apply to the controls, which are as easy to use as those of most other CD players. Instead, what impresses us is the solidity and conservatism-with one exception-of the unit's design and construction.
There is only one major innovation in the unit, but it's an important one: This is the first CD player we've tested that uses true 18-bit linear digital-to-analog converter (DAC) integrated circuits. These chips, made by Burr-Brown of Arizona, are used with their full factory-recommended trimming circuitry and are individually calibrated in production for each player. The trimming circuit adjusts the four least-significant bits in the converter for maximum linearity (which leads to minimum distortion). The initial reference current used by each DAC to establish the "scale" of the conversion process is stabilized by a unique regulator using an LED/phototransistor link. Working backward in the circuit path, the digital input to the DACs comes from the player's four-times-oversampling digital filter. The DACs and the filter are connected by fiber-optic data links for maximum circuit isolation and minimum noise. There are separate regulated power supplies (including separate power transformers) for the disc-transport and electronics sections.
For minimum noise (and to make the volume-setting operation available on the supplied wireless remote control), the G10's back-panel variable output and the front-panel headphone output are controlled by a motorized potentiometer. In addition to the variable output, there are a fixed output, a coaxial (pin-jack) direct-digital output, and a fiber-optic direct-digital output. The remote duplicates every front-panel function except the power switch and the large knob labeled shuttle search.
Best used in conjunction with the pause control, shuttle search controls the G10's audible-scan cueing function and is continuously variable in speed in both directions: The further you rotate the knob left or right, the faster the player scans backward or forward, respectively. This takes some getting used to, especially since the knob is spring-loaded to return to the center "neutral" position. But once you get the hang of it, you'll find it difficult to go back to the standard two-speed scan buttons found in other CD players. Very fast track-to-track access is provided by the linear-drive mechanism for the laser assembly. The laser scanner itself is a three-beam device.
Most of the unit's other controls are behind a flip-down door running across the bottom of the front panel. These controls include a numerical keypad used to directly enter track cues and to enter selections in the player's 20-slot programmed-playback memory. Two repeat modes are available: whole disc (or program) and A-B looping. Index points can be reached upward or downward, in sequential order, using a pair of buttons, and the cueing system can also find specific times either within a track or in relation to the entire disc's playing time. The vacuum fluorescent display can be dimmed or shut off altogether with another button. A mode control cycles the track/time display through three settings: time remaining in the track, time elapsed in the track, and time remaining on the disc or in the programmed sequence. Lastly, for those concerned with absolute phase, a press of a button inverts the polarity of the outputs. Since the inversion is performed digitally, before the bit stream is fed into the DACs, the two digital outputs are also affected by the polarity button.
More surprising than the use of 18-bit electronics is the G10's size and weight: At approximately 50 pounds, the G10 is certainly the most massive CD player we have tested, in addition to being the largest. The weight comes mainly from the cast steel-alloy chassis, a construction used for strength, rigidity, and vibration isolation. The effectiveness of the design was shown by our informal "shock" tests, which consisted of blows to the top and side of the unit while it was playing a disc. Our fists reached their threshold of pain before play was interrupted.
As could be predicted from the use of high-quality 18-bit DACs, the G10 provided some outstanding lab-test results, even though our sample was an extremely early production unit (with a Japanese model number). For example, Diversified Science Laboratories reports that the unit's harmonic distortion at 0 and - 24 dB was consistently below our already inaudible reporting threshold of 0.01 percent. Linearity was also outstanding, especially at the lower levels. Despite the lab's finding that the player skipped once at the 800-micrometer point during the surface-obstruction test, use of our pressing of the tracking-test disc (they are all slightly different) showed perfect tracking performance at that damage level. All the other electrical measurements were also good or better, and they show that, with the 18-bit G10, we are finally approaching true 16-bit performance.
As could also be predicted by the sound quality of contemporary CD software-which can provide, at best, only 16-bit performance-we were unable to hear anything in the G10's superb sound quality that could be definitely attributable to the use of 18- rather than 16-bit converters. We thought we could hear a difference when toggling the phase-in-version feature with the remote, but, in addition to being an uncontrolled test, any audible differences with this feature cannot be attributed to the increase in DAC resolution. If your ears are better than ours or if your music software actually is accurate to 16-bits (which is extremely unlikely, considering the comparatively poor conversion accuracy of professional digital recorders), you may be able to hear the two-bit difference. In any case, the lab measurements, the solid feel, the luxurious construction, and the smooth, accurate sound quality of the DX-G10 prove that it represents the state of the art in CD-player design and construction.