Solid State Preamp Reviews

The challenge for Ayre's Charley Hansen was formidable. Having already designed a world-class preamplifier—the highly acclaimed $7100 K-1 (see Wes Phillips' review in March 1997)—Hansen set out to offer audiophiles "80 to 90%" of the K-1's sound and build quality at a price more of them can afford. Not that the new K-3 is a piece of "budget" gear. It's not. But at $4500, the fully loaded K-3, complete with phono section and remote control, is within reach of many.

The "base price" version, minus the MC/MM phono section ($1000) and remote ($250), is an even more reasonable $3250...but in this day and age, who would order one without a phono section and remote? No one I know. I reviewed the complete package.

Description
Like the K-1, the K-3 is an all-FET (field-effect transistor), zero-feedback, discrete balanced design. In fact, the two preamps share virtually identical circuit topologies—and that includes the fully balanced phono stage, which WP declared to be the best he'd ever heard at the time.

So where did the designer make his compromises? Hansen is a "build and listen" kind of guy; he eliminated all signal-path wiring in the "price-no-object" K-1 because he could hear the sonic improvements, subtle though they were. But the increased sonic purity and lower noise floor came at a cost: in order to execute the design, Hansen had to position the main circuit board almost flush against the back panel, so the high-quality Cardas RCA and balanced Switchcraft XLR input and output jacks could be soldered directly to it. In addition, the four discrete-resistor, stepped-attenuator volume controls (two per channel for balanced operation) also had to be mounted directly to the board—a complex engineering feat requiring a series of nylon ladder belts and drive pulleys that looked to be straight out of the Gyro Gearloose design handbook.

Hansen has opted for a more conventional layout in the K-3, though the input and output jacks are still soldered directly to a circuit board. The biggest differences are the two short runs of Cardas wire to and from the volume control. The wired configuration saved a great deal of money. Hansen also uses a somewhat lower-quality "G10" circuit board, more in line with industry standards, instead of the special high-speed board used in the K-1. That saved some more. Other cost-cutting measures include using polypropylene and foil (instead of polystyrene and foil) capacitors.

Hansen was not about to completely do away with what he considers to be one of the keys to the K-1's ultra-pure, high-resolution sound: the four expensive, custom-made (by Shallco), "military-specification," solid-silver contact/solid-silver wiper, 46-position stepped-attenuator volume controls (two are needed per channel in a balanced design—one each for the plus and minus parts of the signal), which are accurate to 0.01dB and, according to Hansen, are also "silly" expensive.

Instead, he was able to bring the cost down by designing a less expensive "mil-spec" version of the volume control that still uses solid silver contacts and silver wipers. The difference is fewer steps—31 (mostly in 1.5dB increments) instead of 46—which allows for two sets of contacts on a single wafer. Two wafers instead of four, and both mounted concentrically on a single shaft, cut a great deal of the cost without cutting the sonic benefits. Finally, Hansen reduced the number of inputs from six to four.

Otherwise, the K-3 is a very close cousin to the K-1, and is housed in the same high-quality chassis and fronted with the same ½"-thick, handsome, polished-aluminum fascia (black is also available). As with the K-1, the power supply is outboard, connected via a nondetachable umbilical cord.

Controls are minimal. In addition to volume, there are rotary source and tape selector knobs—custom-made, solid silver Electro-Switch devices that, though not "mil-spec," are "top quality," according to Hansen—and a Mute/Play switch. That's all. The rear panel features two balanced pairs of XLR and two unbalanced pairs of RCA jack inputs, and both balanced XLR and single-ended RCA outputs. Like the K-1, the K-3 features a tricolored LED that glows red on turn-on, switches to green when the unit is "ready" but muted, and goes blue when passing signal. Whatever happened to "green for go"? Read Hansen's explanation in the K-1 review.

Enough inputs?
If you're analog-impaired, the K-3 gives you four high-level inputs—two balanced, two not—plus a tape loop. That should be sufficient for most audiophiles. Even with the optional phono section, which connects to one of the balanced inputs, the three remaining inputs should suffice for most of you. Ayre offers high-quality XLR/RCA adapters ($75/pair), which you might need to connect unbalanced components to one of the balanced jacks, and Ayre Reference Series balanced-configuration phono interconnects ($475 per 1.5m set). I was supplied with a DIN/XLR set for the Graham tonearm and RCA/XLR adapters for the Immedia arm, which is hard-wired with RCA plugs. Most cable companies will custom-terminate phono cables for balanced performance.

Circuit design
Since the K-3 shares the K-1's circuit design, I'll be brief, and recommend you read Wes Phillips' review. The line section is a DC-coupled, zero-feedback design with a simple three-stage topology: a differential input (which also converts unbalanced inputs to balanced) followed by a cascode stage, and finally a buffer that lowers the impedance so the unit can effectively drive almost any amp to which it is connected, no matter how far away.

The low-noise phono section uses essentially the same topology as the line stage. It has enough gain for any cartridge currently available, and includes a totally passive, zero-feedback RIAA circuit, which allows the high and low parts of the equalizer to be split into two independent sections instead of being tied together in the usual feedback loop. There are two gain blocks: high-frequency EQ is accomplished in one, low-frequency EQ in the other. The result is, according to Hansen, "ruler-flat, dead flat response from 100Hz to 20k." We'll see what Technical J. Norton's measurements show. The remote control circuit does not use a microprocessor, so there's no high-frequency garbage bouncing around inside the chassis. This innovation clearly required lots of work by Hansen, but since he'd already done it for the K-1, passing it on to the K-3 was no sweat—unless you ask his accountant.

Each stage of each channel has its own regulation for each half of the balanced signal, though the pre-regulator found in the K-1's outboard power supply has been left out of the K-3, to...? Right. Save money. The power supply features a beefy toroidal transformer, and two smaller toroidal transformers used as filter chokes. Also on board are the same high-speed Schottky rectifier diodes used in the K-1. The unit as originally delivered featured an internal-ferrite-ring common-mode power-line filter; this was subsequently changed to a new, sexy, nonmetal device that Hansen is looking into patenting.

What sound?
Cartridge loading and gain setting (factory-set to 50dB, but you can opt for 40dB or 60dB via supplied resistors) require removal of the chassis top-plate, so before firing up the K-3 I got a good look at its innards. The layout is clean and functional, with no integrated circuits. Ayre supplies clearly marked plastic bags containing tiny loading and gain resistors that fit into circuit-board–mounted screw fixtures. You'll need to work carefully and with a pair of miniature needle-nose pliers, a tweezer, or, as Wes Phillips suggests, a hemostat. (But why would anyone have one of those lying about? And is burnt hemp resin as bad for electronics as Bill Bennett claims?)

I began listening to the K-3 about six months ago, and, as I write this, I haven't stopped (save for a few detours for comparison's sake). Let me put it to you this way: after a few weeks' break-in, the line stage was as close to the old "straight wire with gain" as I've heard in my listening system.