SimAudio Moon W10 Monoblock Review

Category: Amplifiers

Review: SimAudio Moon W10 Monoblocks.

Aesthetics / specs / setup:
The ‘Sim’s’ as they shall be referred to during the remainder of this review, are a fully balanced differential mono-block amplifier capable of producing 750 watts into 8 ohms and 1400 watts into 4 ohms.
According to the SimAudio website ( the amp uses "technology featuring a no overall feedback circuit and bipolar output devices”.

Aesthetically the Sim’s are very handsome and quite minimalist in appearance. They adopt an integral framework, which provides both lifting handles and spiked feet, allowing for easy handling and lifting from the top of the amplifier and at the same time negates the need for a spiked amp stand.

The amps run cool and do not therefore require hefty heatsinks as found on Krell amps, for example. The result being a relatively light and compact amp at a mere 71 LBS each.

The amps have both balanced and single ended inputs, use a small nipple switch for on/off operation, and disappointingly lack a second set of speaker binding posts. Other than that there isn’t much else to remark on as far as aesthetics and connectivity are concerned.
Initially I used the amps with their integral brass spikes into the carpet. This arrangement doesn’t provide much clearance on the underside of the amp and I was a little concerned about ventilation. Coming from the Krell MD300, I was half expecting a black scorch mark on the carpet, but after an hour or so of operation it was evident that these amps run exceptionally cool. The main reason for their relative efficiency is that the design runs class A for the first 10 watts only, thereafter switching to AB.
Having recently moved my system into another part of the room, I no longer have a dedicated amp circuit, so I have a less than optimal arrangement with both amps pulling juice from the same wall outlet. Pulling juice is probably not an appropriate term for these puppies, with a peak current rating of 85 amps each, or 35 amps continuos, it’s more a case of draining than pulling.

Let me give a little background on the decision to buy these amps. I’m using Magnepan 3.6R speakers in quite a large room. I’ve learned the hard way through extensive trial and error that these speakers need gobs of power to come alive. I wont list all of the amps that I’ve tried, but 200w/channel Cary V12 Monoblocks, Krell FPB200 and most recently Krell’s MD300 monoblocks, have all been through my system. Non of these so-called ‘muscle’ amps ever really got to grips with the Magnepans in a way that could be described as ‘authoritative’. Of course the Krell MD300’s came closest, with their 650 watts into the Maggie’s 4 ohms, but they always sounded lean through the midrange, and a little lacking in musicality. So the Sim’s on paper at least, seemed to remove any lingering doubts of having insufficient power on hand.

I had company on the day these amps arrived, so I courteously offered Steve the sweet spot for the first few tracks. The amps were stone cold, having been sitting in the back of a UPS van on a 20 degree day. They clearly needed some gentle coaxing to get them up to room temperature. However, with the amps cold, and me sitting some 4 or 5 feet away from the sweet spot, I could tell within the first few notes that there was something special at work. I could hear a warmth and depth to the sound that no other amp has produced in my system to date.
After 30 minutes or so of warm up, I assumed position in the sweet spot, anxious to see if my off-axis initial impressions were supported from the critical listening spot. They were, but with a small reservation or two. There was tremendous depth and sweetness to the sound, but with a slight smearing in the midrange, and slight lack of clarity. This gave instruments a slightly more homogenized sound without a clearly delineated soundstage.
Listening to the instrumental track 3 on the Ani De Franco’s Reckless CD, there wasn’t the same attack, bloom and decay to the acoustic guitar notes. It didn’t have the impact that was evident with the Krell amps that had just been replaced.
It was a little irritating to have this apparent deficiency, but I tried to focus more on the strengths that these amps clearly have over the Krells.
I’ve never heard amps fill up the soundstage like these do. A few days before they arrived, I’d been experimenting with speaker position, and moved them apart by almost 18 inches, to approximately 8’ between inner edges. This seemed too much, and though there was a nice sense of scale and stage width, the leanness that the Krells had exhibited in my system seemed to be exaggerated. With the Sim’s in place, the soundstage became completely populated without any apparent leanness and with good center fill energy.
Bass was deep and tight. There’s a sense of weight and authority that I thought was probably max’d out when I added the Krells, but the Sim’s provide more, and in spades. There is also naturalness to the bass that I haven’t heard before. Playing tracks from the ‘Steve Green Trio’ CD, which is my reference for the reproduction of acoustic bass, the instrument sounded so tight and defined, yet notes had all the bloom and reverberation that you would expect to hear from a ‘real’ and ‘live’ instrument.
I enjoyed this ‘new’ presentation for a few hours then set about trying to correct some of the weaknesses. I moved the amps off the carpet and sat them on marble slabs, still using the integral spiked feet. This seemed to pull a little fullness and bloom out of the midrange and tightened focus a little. Later, I added large brass cones under the chassis of each amp, effectively making the integral feet redundant. This further increased focus and added back the dynamic ‘snap’ and impact, acoustic guitar strings now had that sense of attack, bloom and decay that I’d missed with the amps spiked into the carpet.
A week later, I removed the marble slabs and used the large brass cones under the amp chassis and into the carpet. The change was subtle yet apparent and this arrangement so far has brought the best results.
The top end of these amps is also excellent. There is great extension and clarity, yet with a sweetness to the sound that is generally found in only the best solid state amps. I have some room acoustic problems that need to be resolved resulting in a slight glare at the higher frequencies and a little ringing through the midrange. But I have a sufficient handle on those problems to know when it’s the room and not the equipment. I don’t detect anything in these amps that is anything less than first class reproduction of sound, across the frequency spectrum. The Krells presented a tad more depth to the soundstage, but this may have been a product of the leaner midrange, when all said and done.
The Krells presented the stage level with the front of the speaker and pushed it backwards. The Sim’s present the sound slightly forward from the front of the speaker and stretches back almost as far as the Krell, so overall, there is a greater sense of depth and 3 dimensionality with the Sim’s.
Bass performance was very good with the Krell, but better with the Sim’s, the sense of weight and authority is first rate.
The midrange is where the Sim’s really excel. They provide a full, liquid and coherent soundstage that fills up the space between speakers providing a seamless whole.
The highs are clear and precise without drawing unwanted attention in a way that can quickly become fatiguing.

These are by far the best amps I’ve heard in my system. I can’t get enough music right now, which tells me one important thing, these are very musically engaging amps!
However, I believe that the full potential of the Sim’s is not being realized presently, due to my poor AC installation. That will be rectified in the next week or so and I’m hopeful for another step forward in performance.
I would heartily recommend these amps to anyone requiring extra weight and authority in their system without losing any sense of realism or finesse.


I bought these amps brand new and have owned them for about three years now and I feel exactly as you do.

For the first year I owned them I was listening to Maggie 3.5r's (which I love). Since then I've been listening to Vandy 3A Sigs and have never looked back. Just smooth music that's always beautiful to listen to. Fantastic sound stage.

I'm sure I'll be upgrading equipment over the years but I don't see myself ever replacing these amps. They are built like a tank and will probably last forever.

Enjoy your music!
I have had a W-5 for 3 years now. Basically one half of your monoblocks but same insides.Anyways I drive 1.6qrs and the Sim's are perfect for Maggies.
They take many days to break in.
You were astonished after a few hours.,wait for about 6 months uninterruped power.
I get real grumpy when the power goes out,like real pissed off cause the sound is thin and congested for about 3 days.
Good conditioning really helps them and dedicated outlets.I use a Z-cube and a Audio Magic Stealth, both these conditioners do not limit power to Sim's. Most conditioners limit and restrict the Sim's'dynamic' power .
Good choice.
Happy listening,
Thanks for the comments. Peter, I'll check out the power conditioners that you mentioned. I use a PS 600 for the source components and need something for the amps that isn't current limiting.
The comment you made about them sounding thin and congested for a few days after the power goes off, that's totally wild, and fits exactly with what I'm experiencing. The first week I had them switched on and off regularly while I messed with isolation. Then I left them on, and after a few days the whole sound seemed to change, more depth, detail and clarity....I wondered what the heck was going on, now I know!


I too have a fondness for Sim Audio, their W5 being my first high-end component. (Guess I should blame them for all subsequent purchases :-) Unfortunately, due to various constraints when 2 ch and HT needed to merge in one room, the W5 had to take a vacation. After two long years of remodeling another residence (can't do it like I used to), we are nearing the move-in date when the Sim will once again take center stage driving the mains for the HT. Just hope nothing has dried out (as they talk about how caps can degrade) And I'm also looking forward to a shoot out between the W5 and the Clayton M70 monos in the main rig (the Clayton's better be on their best behavior! - I sense I may be missing the effortlessness of the W5, tho the Claytons are way sweet too).

Congrats on the W10's, Rooze, - I can only imagine. I came close on several occasions to adding another W5 (I've got this thing for the mono look) but never could quite swing it. Oh well, I still feel fortunate to have the one.

Leave 'em powered up,