Moon W-5 power amplifier: $4795
Although the W-5's front panel is rectangular, the main chassis' profile is elliptical, with flat top and bottom and massive curved heatsinks on the side panels. Tubular shafts run along each side, connecting the upper ends of the four spiked towers on which the amp sits. These shafts make it surprisingly easy, given adequate muscle, to move and position this 72-lb brick on its built-in spikes.
The chassis' stiffness and solidity are impressive. Under the lid and behind the *"-thick front panel are two hefty 1000VA toroidal transformers; each amp channel has four 22,000µF smoothing capacitors, a roomy and clean printed circuit board, and eight TO-3-cased power transistors arranged as four sets of matched pairs. The power transistors are bolted to an extrusion mounted to the inside of the curved heatsinks, which form the side walls of the chassis. Generous heatsinks are mounted to many of the smaller transistors on the pcb. Overall, this is an impressively executed design.
There are no front-panel controls other than the blue power indicator. The rear panel has a rocker switch for power and a pushbutton for reset. I found that the rocker turned the amp off just fine, but the reset button also had to be pushed to turn the unit back on. This behavior seems normal but is not described in the manual. Also on the back panel are four RCA jacks and a pair of XLRs. The available input options are three: 1) balanced using the XLR input jack; 2) balanced via a pair of coax interconnects, using both the inverting and noninverting RCA jacks; and 3) single-ended using either the inverting or noninverting RCA input jack, with the unused input shorted. Shorting plugs for the unused RCA jacks are provided. One advantage of this arrangement is that bridging this fully differential amplifier is easily implemented by feeding a single preamp output, via a Y-connector, into the inverting input of one channel and the noninverting input of the other.
My first experience of the W-5 was with my late, lamented Apogee Duettas, and it was memorable. The folks at SimAudio suggested that the amp was a great match for electrostatics and other planar speakers, and from turn-on, the Moon amp gripped the Duettas' normally overripe bottom end and eliminated any trace of bass flab. These speakers have a decently extended low end, and in my room require a bit of taming in order not to too heavily tilt the spectral balance. In the past, I've cured this by blocking the bottom 6" of the rear of the bass ribbon (as suggested by Martin Colloms in a now-ancient review). More recently, I've deftly shaped the bass response with a Z-Systems rdp-1 digital equalizer.
The Moon amp made all these machinations superfluous. It forced the Duettas to behave in the amplitude domain like a well-controlled conventional woofer, yet the system was not deprived of its particular transient and dipolar radiation characteristics. The midrange sounded honest and clear, with the crossover to the treble ribbon more difficult to detect than ever. The high frequencies, too, were excellent, with suitable luster and no glare. Whether fed from analog or digital sources, from the P-5 or any other preamp, the Moon W-5 was simply the best amp for the Apogees that I have experienced.
I've recommended Exotic Dances from the Opera (Reference RR-71CD) as a sonic blockbuster, but I didn't know how right I was until I used the Moon W-5 (and P-5) with the Apogees. Listening from about 20' back (much more than my usual 12' listening distance), I could clearly "see," with my ears, the whole symphony orchestra arrayed before me—wider and deeper than the room, each orchestral voice in its place. Wow!
Running the amp with a range of other speakers helped define the character that had been suggested by its performance with the Duettas. The Moon W-5's bass control and tightness were steadfast. The bass was also powerfully extended. For speakers that benefit from such control—ie, most domestic speakers that behave in a nonlinear fashion at very low frequencies—the Moon W-5 is the perfect mate. In fact, because of this control, usable bass response is extended into regions the speaker had heretofore not entered. I noted this advancement with the Gershman GA-P520x and the Coincident Super Conquest. Believe it or not, even the tiny Celestion MP-1 gained new authority. The W-5 was not quite as suitable a mate for speakers with highly damped low-end responses, whether sealed boxes or transmission lines: The Moon W-5 starved the PMC IB-1S Monitor's bass to the point of anorexia.
Most of my listening was done with the Genesis 500 speakers, whose in-built woofer amplifiers rendered moot the Moon W-5's bass control, but whose transparency revealed details about the amp's personality. In the midrange and high frequencies, the W-5 sounded clear and uncolored but slightly dry. This made for a relaxed, laid-back presentation that nonetheless did not lack for detail and resolution. The recent re-remastering of Solti's recording of Wagner's Ring (Decca 455 555-2) was so enticingly projected that I did something I hadn't done in decades: I listened to the whole thing in four consecutive evenings! Yes, there's less hiss than in the original transfers, but there's also much more detail, which the Moon/Genesis combination reveals. Spatial presentation also benefited and was, with this and similar recordings, wide and deep. Perhaps the most consistently satisfying feature was the treatment of dynamics. Subtle gradations were well reproduced, but—remarkably—progressively larger Wagnerian gradations were equally well treated.