Solid State Preamp Reviews

Also, since the signal is not attenuated before entering the active circuitry, source components with extremely high outputs could have been problematic. "We had to do a fair amount of work to ameliorate this potential problem," Hansen said. "With a typical source of 2V to 4V balanced output, the distortion is around 0.001% to 0.002%. Increasing the input to 8V RMS, as some digital products produce, will bring the distortion up to around 0.008% to 0.01%."

Hansen chose to set the input impedance at a high 1M ohm per phase (2M ohms balanced). "You know how, when you load a moving-coil cartridge up to 47k [ohms], everything just sounds more open and alive? We believe the same thing is true of any input. We chose 1M ohm per phase because it sounded best to us—I believe that if something's good, more is better, and that's the amount that sounded truest to us. On the other hand, if something's bad, don't use it—which is our philosophy on feedback."

The KX-R has the usual Ayre virtues, including Ayre Conditioner powerline RFI filtration. It also has an AyreLink circuit, which allows other AyreLink-equipped gear to be connected via ordinary two-line phone cables. Turning on any AyreLink component turns them all on and, when AyreLink-equipped sources are brought to market, turning on the source will also switch the KX-R to that input. The KX-R also comes equipped with a remote control that, if somewhat large, is convenient for everyday use.

The KX-R doesn't have an external power supply. Instead, each part of the circuit resides in its own milled compartment: The control section, the audio circuit, and the power supply are therefore isolated from one another by substantial aluminum barriers. Hansen had to have made special transformers to get the KX-R to match the MX-R's shape; while the models are the same size, the KX-R's front panel is on what would be a side panel of the monoblock.

Solid air
In my line of work, unpacking and setting up new gear is usually relatively unexciting. The KX-R was different. For one thing, it's deceptively small for its 40-lb weight, so just unpacking it was an adventure. Then, the rear panel is laid out logically—at least, according to Charles Hansen. In electronic terms, he's right: the signal paths are short. However, the mirror-image layout on the rear panel of four single-ended inputs, four balanced XLR inputs, two balanced XLR outputs (no SE option), and two balanced XLR tape outputs might confuse ordinary mortals—especially as they're not labeled but numbered. The owner's manual suggests you make notes of what you plugged into where.

Those notes will come in handy at the next stage of setup, which is "activating" those inputs. On power-up, if no inputs have been activated, the KX-R automatically enters Setup mode, its display flashing "Set 1 Unused." On either side of the display is a scroll wheel: the one on the left scrolls through the inputs, the one on the right through a list of names you can apply to the input, ranging from the generic (CD, DVD, Digital) to the specific (all Ayre models). Advanced users can input custom names, if they wish. Other adjustments accessible in Setup mode are of gain offset, channel balance, and bypass (for integration with a surround-sound processor).

Only the inputs that have been named, and thus activated, can receive a signal. When an input is unused, the KX-R removes it from the circuit and lifts its ground (as it does to inputs not currently in use)—which prevents noise from bleeding through to the active input and the rest of the audio circuit.

Once an input has been activated, the two scroll wheels revert to their primary functions: the left one is the source selector, the right controls volume. These wheels are actually optical encoders that send pulses to stepper motors that operate custom-designed, "applied-force" rotary switches with silver contacts. (These motors emit an audible and weighty thump in operation.) The front panel also sports Standby and Mute touch switches.

All of these functions, and many more, are also actuated by the remote control. The KX-R's volume control has 61 steps of 1dB each—see "Measurements" sidebar—which effectively meant that I got precisely the level I wanted every time—I never had to settle for "almost right."

At first I paired the KX-R with my Musical Fidelity Nu-Vista 300 power amplifier, which has only single-ended inputs, so I had to use an XLR-to-RCA adapter, which cost me 6dB of gain—not that I noticed any problems owing to that. Later, Ayre sent me a pair of MX-Rs to audition with the KX-R. My primary source was Ayre's C-5xe universal player; the speakers used included Wilson WATT/Puppy 8s, Avalon Indras, and Thiel CS3.7s.

Spinning on the air
Ayre claims that the KX-R benefits from break-in, and that, because each input uses a different path on the input circuit board, each requires its own break-in period. Maybe so in their Boulder listening room, but the KX-R sounded good from the go in Brooklyn. I mention this because I sometimes get queries from readers about break-in, asking how long they should "cook" a component before listening to it. My response is pretty much Play it, and count as a blessing every dollop of improvement. The KX-R started out in the front rank; if it gets even better, well, lucky Ayre customer!