Linn Sondek CD12 CD Player Page 2
The CD12's parallels with Linn's LP12 Sondek turntable aren't at all coincidental. The CD12 is the first Linn product since that venerable classic to bear the "Sondek" designation, which Linn says it reserves for one product every quarter century or so. They've produced CD players before, but this one is something special, they say.
It certainly looks it. This isn't just another black box. The compact chassis is machined from two plates of solid aluminum alloy to a tolerance of about 1 micron—a process that takes Linn's sister company, Castle Precision Engineering, about eight hours per chassis. The parts are then hard-anodized. The resulting case looks and feels like jewelry, but Linn points out that these processes produce sonic advantages as well: The mass and rigidity of the chassis, when tightly bolted into a single unit, makes the CD12 resistant to acoustic vibration, and the anodizing optimizes heat transfer and offers electrical insulation.
The drawer is of chrome-plated aluminum alloy, and locks solidly in place when closed. The drawer is also the only means (other than the remote, of course) of controlling the player, as there's nary a knob or button on the CD12's face—optical sensors detect "nudges" against the drawer. The machine understands a hard shove to mean Open or Close, while a gentle nudge is interpreted as Play—or, if a CD is already playing, as Next Track. A nudge will also stop play—but only after you've become sensitized to the control system. It takes a few tries to learn the differences between a Next nudge, a Stop nudge, and an Open shove. Pause is handled solely through the remote.
Linn calls the CD12's transport functions the "CD Engine"; this part of the mechanism is isolated from the digital and analog circuitry in its own carved-out section of the chassis. The CD Engine is constructed from anodized aluminum, in this case an extruded assembly that is then precisely machined.
The laser assembly is a Philips unit incorporating an integrated photo-diode RF amplifier, said to improve the 8-to-14 modulation (EFM) signal to the servo/decoder circuitry, which is controlled with digital signal processing (DSP). Linn claims this allows the servo circuitry to react quickly to disc irregularities, including warp and eccentricity. CDs are clamped to the turntable using a Linn-designed magnetic puck. The laser mechanism is decoupled from the main chassis, which, Linn says, helps prevent the servo mechanism from needing to correct vibration-caused tracking errors. The circuits for the laser drive, spindle motor, and DSP/microprocessor control are all isolated from one another.
The CD12 employs four specially selected 20-bit Burr-Brown PCM-1702U-K D/A converter chips operated in dual-differential mode. Though extensive measures are taken to reduce jitter, Linn claims that no one can totally eliminate it; that the best one can hope to do is reduce jitter's impact to the point where it no longer affects the critical digital and analog signals. To this end, Linn has developed what they call "clockless" construction—which doesn't, of course, mean that the CD12 has no word clocks, "only that the precision of the clocks driving the DAC has no effect on sound quality"—a pretty tall order.
Digital filtering is provided by a Pacific Microsonics PMD-100—an HDCD filter, of course. The 6dB attenuation required by the HDCD license is performed in the analog domain, which, Linn maintains, sounds better than doing it digitally. In addition, the player can be programmed to offer eight different levels of HF dither, ranging from the factory-set minimum amplitude mode to a minimum white triangular-PDF mode.
The CD12 uses a version of Linn's Brilliant Switch Mode Power Supply (SMPS), which converts incoming AC to high-voltage DC. Fast electronic switches convert the DC back to AC at a higher frequency (about 1000x the 60Hz mains frequency). A transformer isolates and transforms the high voltage down to the required output voltages, where fast rectifiers convert them to DC, which is then filtered by small capacitors. There are 16 stages of power-supply regulation in the CD12's SMPS, which is isolated from the rest of the player's circuitry in its own pocket of the chassis.