Simaudio Moon P-5 preamplifier & W-5 power amplifier:
Page 3 In my experience, and even with high-powered amplifiers, the ability of an amp to make large dynamic transitions without any change in the tonal characteristics or ambient flavor is unusual. The Moon W-5 is one of those few amps that can convey a real "jump" with no loss of detail or focus.

Comparisons: The comparisons I made of the W-5 with three other amps reminded me of Goldilocks and the Three Bears. First we tried Papa Bear, the Bryston 7B-ST monoblocks: more assertive and full in the bass, with a bit more sparkle in the treble. This difference made the W-5 a better match with the Duettas, but made the Brystons happier with the Genesis 500s and the PMC and Coincident speakers. Large dynamic contrasts were more distinctly terraced with the W-5, but one could argue that they were more seamless with the Brystons—a toss-up, the outcome of which was greatly influenced by the tonal balance of the partnering speaker.

Next I visited Mama Bear. The Sonic Frontiers Power-2 seemed relatively mellow in the bass and softer in the treble, but with a glowing presence in the midrange that the Moon W-5 lacked. Those features were advantageously mated to the Genesis 500s. The Power-2, however, lacked the sheer, gutsy power of the W-5 on the Duettas, and was somewhat generous in the midbass with the Coincidents.

Finally we come to Baby Bear, the McCormack DNA-1, which was a bit brash in the treble and could not control the bass as well as did the W-5. It was, however, decidedly more lively and gripping. In fact, the dryness and slight reticence of the Moon W-5 became distinct in these direct comparisons. Thus, this amp was "just right." Though it was preferred in some contexts, it wasn't in all.

Moon P-5 line preamplifier: $3995
The Moon P-5 is built on two identical chassis: one each for the audio circuitry and power supply. Like the Moon W-5, each chassis is elliptical in cross-section, with the lateral surfaces formed into heatsinks that run from front to back. Two power cables, one for the analog audio circuitry and another for the digital control circuitry, connect the two chassis. Both cables are captive to the preamp.

After power-up from a rear-panel switch on the power supply, all functions are controlled from the deceptively simple front panel or the impressively potent remote control. The lone front-panel knob controls volume, and each channel's level is clearly indicated on the display panel. The knob's action is delightfully smooth, with appropriate inertia. Operation of this digital optical encoder is accompanied by the subtle, unobtrusive ticking of the internal relays that do the work.

The volume is stepped in units from "0" to "50," but these are on neither a purely log nor a purely linear scale. SimAudio has selected, from 256 available increments, close spacing (for low-level precision) for numeric values 1 to 35, and progressively wider spacing for 35 through 50. No specific volume increments are specified. Almost all of my listening was with settings below 30, and I never needed or wanted an unavailable intermediate setting.

The other front-panel controls—Monitor, Mute, Input, Display, and Standby—were operated by soft, positive-detent pushbuttons. While the operation of the monitor switch is self-evident, the mute switch reduces volume to one tenth the level set with the volume control—sufficiently low to permit a phone conversation, but not full silence. Thus, although I tried to use Mute to keep the unit warm between listening sessions, there were quite noticeable soft whispers from my default source (FM). A touch of the volume knob restores output to the preset level without requiring further use of the Mute button.

The Input button, touched once, changes the display to indicate the selected input (CD, A1, A2, A3, A4, A5); pushed again, it steps through each input in sequence. Finally, the Display button toggles the display on or off for critical listening, and the Standby button turns off all output and display, but keeps the audio circuitry and the power supply warm and ready.

The rear of the P-5 power supply has two outputs to supply power for the preamp, and two to provide power for an optional external phono stage, all in the form of XLR jacks. The rear of the P-5 preamp is arranged in quasi-symmetrical fashion: Across the middle are two rows of RCA jacks for inputs CD, A1, A2, A3, A4, and Tape Out. Flanking this group on the left and right, according to channel identity, are XLRs for balanced input A5, XLRs for balanced output, and RCA jacks for the singled-ended output. The power-supply cables are on the extreme left.

Inside, the P-5 is just as clean and tasteful as the W-5. There is a double tier of smoothing caps across the front edge and a parallel array of input/output relays across the back. Otherwise, the single pcb appears to be L/R symmetrical. On each side, long stacks of resistors flank hidden, damped, and shielded mechanisms that softly click as the volume control is adjusted. Discrete transistors and integrated circuits are given breathing space, and eight local regulators are mounted to the lateral heatsinks, as are the output stage devices. Overall construction and parts qualities were impressive, and fully appropriate for $4000.

The remote-control wand is an imposing device. Framed by a fluted extrusion that emulates the side panels of amp and preamp, the wand is about 9.5" long and quite hefty. In addition to performing all the functions available on the P-5's front panel, the remote can adjust interchannel balance (indicated by the front-panel display) and provide direct input selection (as opposed to the stepping control on the front panel). It can also control other components—such as CD players, tuners, and decoders—with compatible RC-5 protocols. The remote's appearance suggests, but the sparse manual barely hints at, its capabilities.