Linn Karik/Numerik CD player Robert Harley October 1994
Back in January 1992 (Vol.15 No.1), I reviewed the Linn Karik CD transport and Numerik digital processor pair, the first digital components from Linn Products of Scotland. I found them eminently musical, technically sophisticated, and worthy of a Class A recommendation in Stereophile's "Recommended Components."
Although the Karik's mechanism and electronics remain unchanged, the unit is now a CD player as well as a transport. Linn simply installed a D/A board without increasing the $3395 retail price. Two significant changes have been made to the Numerik: it's gotten a new pair of DACs and a radically different power supply. Numeriks shipped at the time of this writing have both these revisions fitted as standard; owners of older Numeriks (serial numbers below 1354) can have either or both changes made to their units by their Linn dealer.
Linn made available to me a Karik CD player (footnote 1) and three Numerik processors for this Follow-Up. The processors were a standard Numerik, a Numerik with the new DACs and the older power supply, and a Numerik with both the new power supply and the new DACs. Having three units for audition allowed me to evaluate the effect of each modification independently.
The Numerik's new DACs are a pair of Burr-Brown PCM1702s—a 20-bit ladder DAC similar to the Burr-Brown PCM63s found in the original Numerik. Replacing the DAC is simply a matter of inserting a pair of small pcbs with the new DACs mounted on them into the sockets that once held the PCM63s. The new DACs cost $295, including installation.
Linn calls the Numerik's new power supply "...one of the most exciting developments in our company's history." The supply, modestly called the "Brilliant," is used in Linn's Kairn preamplifier and Kremlin tuner, as well as in the Numerik processor, and operates in a way radically different from conventional linear supplies (see later). Retrofitting a Kairn, Kremlin, or Numerik with the "Brilliant" supply costs $550, and is performed by a Linn dealer. All Kairns, Kremlins, and Numeriks now shipping have the new power supply already installed.
Karik CD player: The original Karik was introduced as a transport, to be used with an outboard digital processorµsually the Numerik. Then, in early 1993, Linn converted the Karik into a full-fledged CD player by adding an internal D/A section; so, since the retail price was the same, it was possible for someone to get into a Linn digital front-end by spending $3395 instead of $5790 (the cost of a Karik/Numerik pair) in one shot. Karik owners could have music now, and add a Numerik processor later if they wanted.
The Karik's D/A section—a very small board mounted above the main circuit board—is built around a Crystal CS4328 1-bit DAC. A shielded enclosure encases the DAC and some associated electronics to protect them and the analog circuits from the noise radiated from the transport electronics. Analog output is from two pairs of RCA jacks mounted on the rear panel.
The Karik's transport mechanism, designed by Linn from the ground up, features four motors, a replaceable laser, a diagnostic output for verifying the transport's performance, and a clamping device that secures the disc from the top.
PCM1702 DAC: The PCM1702 DAC is a 20-bit ladder DAC housed in a much smaller package than its brother, the ubiquitous and excellent PCM63. Burr-Brown is encouraging manufacturers to switch from the 63 to the 1702, which is less expensive, easier to make, and may be the basis for Burr-Brown's forthcoming surface-mount DAC. Perhaps not coincidentally, Burr-Brown raised the price of the PCM63 when the 1702 was released.
Technically, the 63 DAC appears to outperform the 1702. Where the 63's linearity is specified at ±0.3dB typical, 1dB max, the 1702 is guaranteed to ±0.5dB (typical), with no maximum linearity error. Similarly, the 63 has a guaranteed gain error of less than 2%, compared to 3% for the 1702. In addition, the bipolar offset spec is looser on the 1702, and no minimum dynamic range is specified. Finally, the signal/noise ratio has been relaxed on the 1702, and the output current accuracy isn't specified.
These may be interesting specifications, but what really matters is how the new DACs perform in the listening room (see below).
"Brilliant" Power Supply: All power supplies convert Alternating Current (AC) voltage into Direct Current (DC) voltages, which then become the voltage "rails" that power the audio circuits. Virtually all power supplies in audio products are called linear supplies: the voltage of the incoming AC is first changed to an appropriate value with a generally large, heavy transformer; they then rectify the incoming AC (turning AC into DC), filter the DC to remove traces of the AC, and almost always regulate (hold constant) the DC output voltage. The regulator input is DC that can shift in voltage; its output is (ideally) rock-steady DC, regardless of fluctuations at the input. A 12V output regulator may have an input voltage of 15V, with the difference in voltage dissipated as heat.
Another type of supply is called the switching power supply (SPS), where the incoming AC is immediately rectified, eliminating the need for a large, heavy transformer. Transistors that turn on and off very quickly are then used to produce a very-high-frequency AC waveform by "chopping" the DC voltage. Because of the high frequency, a very small transformer, with subsequent rectification, can then be used to produce the appropriate-value voltage rails. The chopping-transistor duty cycle can be used to regulate the output voltage.
Switching supplies are much more efficient than linear supplies: they consume less energy, run cooler, are smaller and lighter, and don't need as much heatsinking. Because of these attributes, switching supplies are used in computers and many other electronic products.
Footnote 1: The Karik referred to in this review was fitted with the new switching power supply.—John Atkinson