Simaudio Moon P-5 preamplifier & W-5 power amplifier Kalman Rubinson July 2002

Kalman Rubinson followed up on the Moon P-5 preamp in July 2002 (Vol.25 No.7):

I approach a Stereophile Follow-Up as a reality check, and the return of Simaudio's Moon P-5 preamplifier to my system was a big one. In re-reading my review of the Simaudio W5 power amplifier and the P-5 in our March 1999 issue, I saw that I had found both to sound sleek and powerful, but ever so slightly velvety and dry at the top end compared to, say, the Sonic Frontiers Line-2 with its more silky treble. Aside from that, I had found little to distinguish the sound of these two excellent preamps.

So, after many months of living with SF's Line-3, auditioning a few other preamps, and confirming that the updated W5 was quite similar to its predecessor, I was anxious to hear the P-5 again. I used it with a number of amps, and with both the B&W Signature 800s and my resident Revel Ultima Studios. I also asked Simaudio's Lionel Goodfield to tell me what changes might have been made in the P-5 since my last review sample. His numbered replies are in italics below.

"1) The values of the resistor array ladder in the gain section were changed to 'even out' the progression of the selectable gain settings. Keep in mind that the audio signal passes through only one selected resistor in this array at any given time. As well, this change results in the virtual elimination of small 'popping' sounds when the gain level is changed."

These changes were transparent to me. The nonlinear spacing of the gain steps was acknowledged as a "feature" in the original, but it wasn't a problem then, and the changed spacing wasn't either. Over the usable range of settings (15-30 out of the total range of 1-50), I never lacked for just the right setting with either sample. Moreover, I had two P-5s for the full review, the second supposedly corrected to reduce the relay clicks by reducing input offsets. Well, the clicks associated with gain change were just noticeable and not annoying. They still are. If the spacing of the gain steps is more even, that's okay.

"2) Amount of overall gain was increased for added flexibility."

In my original review, I used volume settings below 30 with the Apogee Duettas, and now used similar settings with the 800s and Studios. Because the P-5 was still dead quiet, the extra gain cost me nothing, and might be useful in some systems.

"3) The amounts of current traveling through different stages of the P-5 were altered to improve sonics."

Ah-ha! Something vague but significant: a change in sound! Well, there was an audible difference between the old P-5 and the new, and I can say this even though I didn't have them side by side for a direct comparison. My audio memory isn't supernatural, but there's no way the new P-5 could have matched my description of the originals. Those units could be distinguished from the Sonic Frontiers preamps by their ever-so-slightly dry and closed-in treble. With more extraverted speakers and sources, they sounded more natural than the SFs. With others, the old P-5 could make voices seem recessed.

Well, the new P-5 was having none of that. Through the analytical 800s or the more self-effacing Studios, the new P-5 was absolutely grain-free, spacious, and open. Compared to the SF Line-3 or, indeed, a bypass, it was apparent that the new P-5's treble had shed its final veil. If anything, it seemed a bit more alive and forward than the SF, although whether one or the other was less colored in comparison to a bypass shifted with my selection of source components and recording.

"4) A new DC servo correction circuit was implemented for the purpose of maintaining a DC output level as close to 0V as possible. This circuit uses no coupling capacitors, which we believe add colorations to the sound."

I don't know how much of an effect this might be having because the original, if I recall correctly, abjured coupling capacitors as well. The small but significant improvement in the P-5's rendition of treble voices seems to have been accomplished without compromising any of its other outstanding performance features. The new P-5's midrange, bass, imaging, and soundstage remained state-of-the-art.

"5) In terms of physical changes—dimensions remain unchanged; the standard finish is a black faceplate with a pewter-colored Moon logo. Alternatively, we offer an optional silver faceplate with a gold-colored logo."

As I recall, the original units had a silver finish; whether one prefers the new black units is a matter of taste. I didn't care for the feel of the somewhat granular finish on the black volume-control knob. On the other hand, I tended to use the remote control almost exclusively, particularly since the new remote is an improvement over the original. The original was an imposingly large, straight extrusion with large buttons, but its features were labeled less than explicitly and it was uncomfortable in the hand. The new remote, though still hefty, has more but smaller buttons, clearer labeling, and a waisted shape that invites one to clasp it. Unlike its predecessor, this remote made it easy to make single steps in volume and required no reading of an instruction manual before I was using it effectively with the P-5, the Meridian 508.24 CD player, and other components. A real improvement.

"6) The MSRP remains $3995."

Okay. That's fair.

"7) In terms of factory upgrades, the main circuit board has to be changed; customers should contact our factory using our toll-free number, (877) 980-2400, or visit our website."

Hmmm. If you like your current P-5, I dunno that an upgrade is the route to go. From my observations, the new one was subtly better, primarily in its more open and revealing treble, but if your older P-5 is a good match for your system, an upgrade could be a step in the wrong direction. On the other hand, if you feel a need to draw just a bit more presence and intensity from your system, then go for it.

"8) Finally, these changes are the result of various developments over a period of over three years....The changes didn't all come into being at once."

I had no hesitation in recommending the earlier P-5, and it's clear to me that the new version is a more evolved preamplifier. Despite the creeping advance of criteria, the Simaudio Moon P-5 remains at the top of the heap.—Kalman Rubinson