Solid State Preamp Reviews

The experience left me doubting my ears. After I'd performed all the measurements of Ayre Acoustics' KX-R preamplifier ($18,500) to accompany Wes Phillips's review in our November 2008 issue, I spent a weekend listening to it. To my astonishment, the sound of my system with a Transporter D/A processor feeding the preamplifier was better than when the DAC fed the power amplifier directly. Through the KX-R, images sounded more tangible, and the sound was better focused, despite the signal's having been passed through not just another set of interconnects but also through the preamp's input and output socketry, switches, a volume control, printed circuit-board traces, and active and passive parts. Logically, you'd think that having nothing in the signal path would have less of a degrading effect than so many somethings. But no, that was not what I heard, much as I would have preferred otherwise.

A preamplifier is the port of entry through which you gain access to the sources you've so carefully assembled. It's also the gate through which all of your music passes. So while its sonic performance is obviously critical, you'd also better assess how it feels, how it looks, and how it operates—you're going to be in an intimate relationship with it for a long time. Before choosing a preamplifier, therefore, take some time to drive it around the block, or at least shake hands with it. Use your imagination as much as your ears.

Asked how to make a guitar, the celebrated luthier Wayne Henderson offered a straight-up answer: "Just get a pile of really nice wood and a whittling knife. Then you just carve away everything that isn't a guitar." (footnote 1)

The making of a preamplifier seems more or less the opposite. You start with a simple volume control and a couple of jacks, then add whatever you think constitutes a preamplifier. Choices might include electronic source switching, line-level gain, phono-level gain and equalization, tone controls, tone-defeat switches, a balance control, a headphone jack, an iPod input, and maybe even a digital-to-analog converter with a USB receiver. The sky is pretty much the limit.

In the early 1970s, Stereophile's founder, J. Gordon Holt—a man I used to describe, with all due respect, as having been clothed by the haberdasher to the homeless—said that Audio Research's SP-3 tubed preamplifier was "the closest thing available, in fact, to the ideal straight wire with gain" ie, it would amplify the signal without editorializng in any way. Back then, the SP-3 cost $595. Today it would cost around $3500. But TAD's C600 dual-mono, solid-state, balanced preamplifier costs more than 10 times that: $42,000.

It was the strangest thing. In the fall of 2008 I was comparing Ayre Acoustics' then-new KX-R line preamplifier with no preamplifier at all—I was feeding the power amplifier directly with the output of the Logitech Transporter D/A processor. (Levels were matched for the comparisons, of course, made possible by the fact that the Transporter has a digital-domain volume control.) Being a rational being, I knew that the active circuitry of a preamplifier, as well as the extra socketry and cables, would be less transparent to the audio signal than a single piece of wire. I wanted to determine by how much the Ayre preamp fell short of that standard.

I was setting up for some musical demonstrations I was to present for a Music Matters evening at the ListenUp! store in Boulder, Colorado, in May 2011. For these events, an audio store invites manufacturers (and the occasional journalist) to demonstrate to local audiophiles the musical benefits of high-end audio playback. In Boulder, I was to share the store's big listening room with Dave Nauber, president of Classé Audio, who had set up a system with B&W Diamond 802 speakers, a Classé stereo amplifier, and a preproduction sample of Classé's new CP-800 preamplifier ($5000), all hooked up with AudioQuest cable. I unpacked my MacBook, with which I was going to play the high-resolution master files of some of my Stereophile recordings, and looked around for a DAC. There wasn't one.

I asked for a sample of the K-5xe so I could do a Follow-Up to Sam's review, but other review commitments kept getting in the way. When I finally spent some time with it (S/N 10J002), I found the sound a little on the robust, forward side, which made system matching problematic. Then, as I was about to spill some ink on the K-5xe, I got an e-mail from Charlie Hansen letting me know that the development of the QB-9 USB DAC had led them to rethink the K-5xe's design, and that Ayre would be sending a sample of what would be called the K-5xe^MP. After a longer delay than I had anticipated, the K-5xe^MP, priced at $3500, arrived for review.