NuForce’s Reference 18 Mono Power Amplifier

NuForce’s Reference 18 Mono Power Amplifier
And now, what we’ve all been waiting for…


 October 2010


Disclosure. Again. I work for NuForce. In keeping with my standing as a spoiled insider, my comments about my employer’s new amp will likely be the first to appear. The properly cynical reader will see reviews elsewhere. If they’re other than raves, I’ll eat a marzipan facsimile of my keyboard. And I make this promise without yet having heard the Ref 18. I’m that confident!

I first got wind of NuForce’s ne plus ultra amp many months ago. Launch dates came and went. Not having asked – this is only a guess – I suspect that no NuForce product has been so long in gestation. I do know for a fact that Jason Lim and crew set great store by it. 

My first NuForce amps, a pair of Series 9 monos, which I acquired for review before my present involvement, incorporated the initial-version (V1) amplifier board. That early pair sounded better to me than my huge, power-mad Mark Levinson 33H monos, which soon departed the listening room. What with their flesh-ripping heatsinks, 33H haulage is a two-man operation. I managed solo with the help of a Sears hand-truck I hesitated buying but have since often used, for one aesthetically gratifying example, positioning rocks in our garden. In case you were wondering. 

Back indoors, in the MLs’ stead, two tiny, greener-than-green switcheroos held me in thrall. This was the best-resolved, most transparent, harmonically spot-on, grain-free sound I’d yet achieved. But, as a purely visual matter, it was difficult coming to terms with the Nines’ lemur-versus-hippo aspect. I found the contrast unsettling. 

But got over it soon enough and graduated in due course to the Reference V2 and V3 Special Edition Nines. Rather than leaping from apples to kiwis to plums, the Nines grew more refined in a clearly related fashion. 

With respect to looks, I suggested in an earlier report that the Ref 9V3SE belongs in a museum’s modern design department. Apart from its beefier case, doubled expanse, touch-sensitive on-off strip, and topside’s NUFORCE badge, the Ref 18 repeats the Ref 9V3SE’s angled façade (as do other recent NuForce products). An enlarged capacitor board, to which its designers attribute a good measure of the Ref 18’s supremacy, accounts for the unit’s width. 

As matters stand

Having found the Ref 9V3SE wanting in no respect whatever, comparisons promise to be interesting. I was concerned that my first pair of Nines could not deal with the challenging impedance, first, of my Wilson WATT/Puppies, and latterly, my Wilson Sophia W/Ps – given as a nominal 4 ohms, with 2-ohm dips. If indeed the Nines pooped out, I was never able to detect those moments. I’d recommend these little beauties to anyone, with the exception, perhaps, of those among us who crave coloration. We all make mistakes. That’s why they put erasers on pencils. 

In the way of sweet-spot happiness, the Ref 9V3SEs have provided a true, unmediated view of the recording, be it honey-sweet, astringent, lucid, congested, holographic or billboard-flat. When the source is right, my heart takes flight. They’ve provided me with as many delightful moments as any sane sound buff could possibly expect. As I say, this should prove a most interesting comparison. 

An authoritative voice 

Bob Smith, NuForce’s Magic Cube and speaker designer, discusses the new capacitor board:

“Beginning with its implementation in the Reference 18 Mono Power Amplifier, NuForce’s Cross-Matrix Array (CMA) capacitor board has been designed to improve power delivery to its new, large-chassis amps. In order to describe the CMA’s distinctions, some background is in order.

“Typically, for an amplifier to deliver large amounts of electrical current on demand, an equal amount of current is held in reserve within its power supply’s filter-capacitor stage. This being the generally accepted case, conventional thinking would have us believe that, in order to be maximally effective, these current-delivery systems need to reside in larger or, alternatively, a greater number of capacitors. In practice, however, we have discovered that the matter is considerably more complex.

“Along with other amplifier components, a capacitor possesses features that are often hidden from obvious view. In engineering terms, we refer to these concealed aspects as parasitic parameters. In the case of capacitors, inductance and resistance comprise the principal parasites. In practice, these combine with capacitance to produce an unwelcome resonance at certain frequency bands. Among other potential negative effects, if left unattended, this resonance can also reduce the speed of power delivery significantly below what theory would otherwise suggest. Simply using larger sizes or quantities of a single value, as is commonly done, will also lead to a single resonant frequency of a large magnitude. Clearly, from a design standpoint, this is a worst-case arrangement. 

“To overcome these problems, the CMA employs high-quality capacitors of numerous values in a quasi-random pattern in order to spread resonances over a wide range of low-amplitude frequencies. The capacitors are arranged so that their polarities are reversed with respect to each other in order to minimize stray magnetic fields, and hence, to reduce parasitic inductance. By lowering inductance, any remaining resonance is elevated to frequencies where its elimination becomes an easier task.

“Finally, low-value resistors combine with capacitors in strategic locations in order to dampen residual resonances. In engineering terms, the resonant peak’s Q, i.e., steepness, is reduced to a value of 0.707 or lower. To put that another way, these low-Q values represent circuit damping to a degree where resonance no longer exists.

“This is no mere marketing gambit. In terms of audibility, the CMA’s stable, high-speed current delivery to the amplifier stage translates to improvements the end-user will cherish.” 

We speculate

The Ref 18’s RMS power ratings are those of the 9’s: 175 watts into 8 ohms, and 335 watts into 4 and 2 ohms respectively. I’ve never paid much attention to these figures. (Truth be told, I looked them up for this report.) Inadequate power hasn’t been an issue with the NuForce amps I’ve used, nor indeed with any of their predecessors, including, years ago, a pair of Crown Macro Reference, probably capable of jump-starting a John Deere combine. If I hear the Ref 18 sounding better than the Ref 9, the difference may have to do with superior speed and resolution, perhaps imaging, harmonic texture and, who knows, an enhanced sense of clout. Idle speculation. Pay it no mind.

I’ve already hit upon the ideal test track – more like an obstacle course: a remarkably well recorded performance ofEonta by Iannis Xenakis (1922-2001), an elegant essay in eye-crossing ferocity for piano, three trombones and two trumpets, mode CD 217, Xenakis Edition Volume 11, with pianist Aki Takahashi and members of the Calithumpian Consort. This is harsh, aggressive, abrasively modernist stuff assembled by way set theory “to determine the choice of pitches,” etc. Yes, that sort of thing. Xenakis is an original I take as a restorative in brief, bracing doses. On a good, wide-range system, Eonta raises gooseflesh. The Ref 9V3SE pair performed flawlessly and my Sasha W/Ps are what they are and I don’t deserve them. 

Your reporter dodges the blahs

Writing about audio gear often involves postponing “serious listening” until a proper burn-in runs its course. Speakers, electronics, cables, outlets, just about anything relating to audio: designers tell us their stuff sounds its best after this or that maturation period, which can range from a few to a few hundred hours. For the Ref 18, it’s a recommended 75. A couple of scheduling missteps earned me the Milpitas office’s demos rather than the factory-fresh pair I thought I’d be getting. Just wire up these beauties and listen –– ever so seriously –– an impatient enthusiast’s dream come true.

Helping hands

I’ll be doing my listening via a system that has changed only with respect to the amps. After-market items and tweaks remain: 

Dedicated Oyaide outlets; Nordost power cords; BlackNoise Modelo 2500 and Modelo Extreme line filters; AudioQuest Ground Controls; NuForce speaker cables; NuForce Magic Cubes (a less expensive version of Bob Smith’s Black Box, which I expect to be writing about before long); Acoustic Revive RR-77 Schumann Resonance Generator; Acoustic Revive RD-3 Disc Demagnetizer; Acoustic Revive RIO-5 II Negative Ion Generator; four wall-hung Acoustic Revive RWL-3 Room Tuning Panels. 

Rather than positioning the wider Ref 18s on either side of the CDP, which is how I arrayed the Ref 9V3SE pair, I’ll be stacking one Ref 18 over the other. I did ask. The amps produce almost no heat, so stacking’s no problem, nor is EMF, RFI, STD or COPD. The CDP and amps will sit on two 19 x 15-inch, quartz-crystal-based Acoustic Revive platforms, intended for use as speaker underboards. (They’re too small for my speakers and I like them too much to let them lie idle.) 

And now, what we’ve all been waiting for…

At 16 pounds per, the Ref 18’s weight is a tick less than double that of the Ref 9V3SE. A hinged wood crate and ample padding account for the 60-pound shipping weight. NuForce packaging has always been competent, minimal, and attractive. The crate takes panache a long stride beyond.


NuForce’s chiseled “New Look” set my 9V3SEs apart from their rather prosaic predecessors. In terms of fit and finish, I’d grade them with an A. The Ref 18 gets an A+. The case’s execution is flawless. (When you turn the amp on, a tastefully dim NuForce appears in the touch-sensitive strip.)

Soundwise, the Ref 18 bears a not unanticipated resemblance to the Ref 9V3SE. And so it should. Both amps employ the Version 3 (V3) amplifier board. As, again, no surprise, I hear superb transparency, resolution, dynamic finesse, textural integrity and a rock-steady, well-detailed soundstage. 

But differences? I think so. Morton Feldman’s Why Patterns? and Crippled Symmetry, (Hat Art CD 2-6080 / two discs), call for flute, alto flute, bass flute; piano, celesta; glockenspiel, vibraphone (Eberhard Blum, Nils Vigeland, Jan Williams). Feldman’s For Philip Guston, (Dog w/a Bone DWAB02 /four discs), requires a similar ensemble: flute, alto flute, piccolo; piano, celesta; vibraphone, marimbaphone, glockenspiel, chimes (Petr Kotik, Joseph Kubera, Chris Nappi).

This is quiet music, skeletally spare, lengthy and lush, For Philip Guston especially so. The listener leans into the sound and breathes in the volupté. Both releases are beautifully recorded. One relishes the textures and feather-stroke attacks. I’ve enjoyed these productions before, of course, but never so much as now. To a slight but significant degree, the instruments’ textures have a deeper nap. A term like luminous would not be out of place. The music’s edges melt into the air. To what to ascribe an enhancement? Perhaps the new capacitor board along with a few refinements in circuit routing, whatever. When it comes to an understanding of how electronics work, it’s a dead heat between me and my shoe. But I can say with assurance that even at low levels, a sure hand delivers the sound. 

As an extreme in contrast, quiet passages notwithstanding, Xenakis’Eonta rattles the listener’s bones – one ferocious piano, two trumpets, three trombones, closely mic’d. And I played it at a level I wouldn’t inflict on Chemical Ali. This and the final movement of Carl Nielson’s Fourth Symphony, the one with the dueling tympani (San Francisco Symphony, Herbert Blomstedt conducting; London CD 421 524-2, released in 1988), demonstrate what I set out to test: the Ref 18’s control of outsized events. I hear no congestion, nor does the soundstage congeal or distort. 

After submitting the above comments for posting, I played a disc just for the pleasure of it. I’d done my “critical listening,” or so I thought. However, the just-for-the-fun-or-it experience was, without exaggeration, downright transformative, and something I have to discuss in this space. First, the music: a CD of works for percussion Lou Harrison (1917-2003), a West Coast free spirit somewhat in the mold of Harry Partch, composed between 1939 and 1842. The disc, entitled Labyrinth, features the Maelström Percussion Ensemble, Jan Williams conducting, hat[now]ART 105, recorded at the Slee Concert Hall, University of Buffalo, in 1997, by Hat’s inestimable Peter Pfister, definitely on the short list of my favorite recording engineers. The disc was released in 2000 in an edition of 3000. If you can find a copy, go for it. 

I played Labyrinth No. 3 (1941) at a high volume. Harrison’s inspiration and aesthetic look toward Asia, and in this work especially, the influences reveal themselves in a wealth of techniques and means –– metal, drums, wood, who knows what else –– that quite dazzle the ear, more so now than ever. In terms of the image’s size and detail, its timbres and textures, especially the low drums’ tunefulness absent a hint of overhang, in short, everything we love about great sound, sums to an experience I can only describe as unique. The amps make the difference. I decompressed with a few of those gorgeously recorded Haydn string quartets (the series on Tacet) I’ve been writing about lately. Again, that sense of richer textures. Not quite up to a slap in the head, but there. Oh yes. 

Our musical tastes likely differ. I’ve mentioned in other reports that nothing bores quite so much as the writer’s account of what he played. Trust me when I report having listened to enough canned sound to be as sure of my impressions as human frailty allows. 


Nothing about the Ref 18 took me by surprise or storm. What the amp does so well is consistent with what I’ve come to expect. I hear the Ref 18’s advances as both real enough to set it apart and remarkably familial. Were I shopping for a pair of high-end monos, the difference in MSLP between the new amp and the leader it replaces ($5k and $7.6k) is close enough in heft to send me in the Ref 18’s direction. (I did just specify “high end,” where tickets in this range are relatively modest. Some phono pickups cost more.)

You’ve no reason in the world to believe anything I’ve written here. I did predict at the outset that other reviewers will tell you how good the Ref 18 is. If you find me trustworthy, great. On the other hand, if you see me as a company shill, by all means wait for other opinions. As always, NuForce will honor its 30-day return policy and offers moreover a trade-in allowance on other NuForce amps. (There! I’ve done my marketing bit.)

Manufacturer Info:
NuForce Reference 18 Mono Power Amplifier,

Price: $7600/pair
382 South Abbott Avenue
Milpitas, CA 95035
Online Store: 
Phone 408 890 6840
Fax 408 262 6877



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