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This review first appeared in the July 2008 issue of fairaudio.de and can be read in its original German version here. It is herewith translated and presented to an English-only audience through a mutual syndication arrangement with fairaudio.de. As is customary for our own reviews, the writer's signature at review's end has a link below it to his e-mail should you have questions or feedback you wish to send. All images contained in this review are the property of fairaudio.de or NuForce. - Ed.


Reviewer: Ralph Werner
Sources: Analog - turntable - Acoustic Solid MPX; tone arms - Phonotools Vivid-Two, SME M2 12"; cartridge - Denon DL-103, Ortofon MC Rondo Bronce, Shelter 501 MK II, Zu Audio DL-103; digital -audiolab 8000CD
Amplification: integrated - Lua 4040C, Myryad MXI 2080; preamplifier - bel canto PRe 3, Funk LAP-2; power amplifier - bel canto M300 monos, Myryad MXA 2150, SAC il piccolo monos
Loudspeakers: Elac FS 247, Thiel CS 2.4, Volent Paragon VL-2, WLM La Scala monitor, Zu Audio Druid Mk4
Cables: Low-level -Ecosse Baton + Symphony, Funk BS-2, van den Hul Integration Hybrid, Zaolla Reinsilber; phono - fis Audio Phono, WSS Silver Line; high-level - Ecosse SMS2.3, Ixos 6006 Gamma, Zu Audio Libtec
Racks & Stands: Creactiv, Taoc, Liedtke Metalldesign Stand
Review component retails: €3.290 for the preamp; €1.390 per monaural amp

I hear the outcries already: "Now they're reviewing compact systems!" So what if we did? I'm sure we'll get there too. Just not today. What might look like an executive mini rig above is actually a full-fledged pre/power combo; a two-chassis P-9 preamp by NuForce plus matching 8.5 V2 Reference monos. Not that Herr Merz of Marvel Audio, German importer for NuForce (and distributor for Einstein, Marten and Jorma) is any stranger to such misapprehensions. At many hifi events, attendees ping pong between his Marten speakers and Einstein source only to fail seeing his amplification electronics: "When I point at the NuForce monos, they're invariably aghast. They figured those would be power supplies to other components."


Force of habit. After all, those who cruise the upper hifi strata do envision big, heavy and ideally hot-running boat anchors when thinking amplifiers, be it tube or transistor; not half width, 5cm low minis à la NuForce. Time to adapt. It takes no surreal powers of prognostication to define the future of amplification: class D. Small and cool. Now add smart. Cause for melancholia, is it? Not really, certainly not if price/performance ratios are factored in. Regardless of NuForce's own claims, it's intuitive that class D's higher efficiency (smaller power draw, insignificant heat) translates also economically. There are lower production and logistics costs; neither giant transformers nor bristly heat sinks allow for smaller, lighter enclosures etc. If the world works as it should, Adam Riese would predict that end user pricing should slide down as well. Now only the performance would have to hit. Hard.

P-9 preamplifier
Let's start at the beginning and the preamp. And forget class D. Our So-Cal design team from around San Francisco runs this circuit in class A with discretely built-up operational amplifiers in a twin cascode array. Even the power supplies are 'conventional', i.e. not switch mode as in the monos. A base criterion of ex Spectral Audio designer Demian Martin for this machine seems to have been, isolate, shield and protect. That's apparent already in the twin chassis whose halves communicate via an umbilical which I nearly relegated into the drawer "PC/notebook".

The lower box with the two controls and central display houses all the noise-generating stuff, i.e. three power supplies plus control processors. The upper box merely includes the relay-switched inputs, an Alps pot and the preamplification circuit proper. This 'dirty/clean box' concept isn't novel but still timely and quiet: NuForce claims an S/N ratio of 100dB across the entire band whose -3dB down point hovers at 2.5MHz (!), with THD + N between 20 and 20 at ca. 3/1000th.

Five RCA inputs feed into RCA or XLR outputs, with the latter only pseudo symmetrical. Input switching occurs with the left knob which doubles as stand-by switch when pushed. The right volume knob goes mute instead. Complete power up/down occurs around back. As to volume, its twin control implementation confused me for a spell due to the third knob on the other chassis which impacts signal voltage as well. But why? Well, it turns the Alps pot directly whereas if you twirl down low on the dirty box, it sends a code signal to the second box to prompt it turning the Alps. One could have skipped one of these knobs but then would have lost the controls' triangulation.

The real kicker of this story is probably that it enables remote control over volume without introducing dirt into the hallowed halls of the low-level signal since reception and processing of the latter occur exclusively in the upper box. If only the remote allowed for finer step progressions. Then everyone would be happy. As is, this remote is unusually cool and six-cornered for something new. Even the buttons aren't moronically tiny and everything is solid metal. Anything else? Certainly, but our focus was supposed to be on the monos...

Reference 8.5 V2 monos
NuForce never tires of reminding us that its amplifiers aren't digital but analog switching amps. While correct (nice), it's the case with all class D amps. Nevertheless, another maker of analog switching amps told me how his website instead uses the term "digital amplifier" since more people goggle for that. While I ruminated on terms even more often fed into search engines than either of these, NuForce is to be commended for remaining factual. As they are for not repackaging designed-elsewhere modules into pretty bling. This outfit runs its own R&D department, has four patents in matters audio amplification under its belt and even its packaging jobs suggest anti-bling – solid but certainly no material worship.


'Normal' switching amps run a fixed high-frequency saw-tooth carrier wave to modulate the audio signal such as to produce a square wave of the same frequency as the saw tooth wave but with squares of various widths (class D) which encode the frequency and amplitude data of the music to switch the output transistors accordingly. The fact that the transistors are switched fully on or off eliminates the permanent quiescent current throughout to generate class D's high operational efficiency - about 85% in NuForce's case. Conventional class A ovens throw this away as heat. Of course with class D, the HF garbage of the carrier wave has to be subtracted from the audio signal at the outputs via a filter. NuForce posits that's where compromises enter.


They claim class-leading performance in switching matters in four discrete ways. There's higher bandwidth without phase errors. Both are compromised by common class D solutions due to the interactions of the output filter's LC network and the speaker's fluctuating impedance. NuForce claims to have implemented a negative feedback loop which taps directly off the speaker terminals (hence post filter) and a new form of modulation (not fixed sawtooth wave but self oscillation). The core argument is that the feedback loop includes the (error-producing) output filter.

A common issue with class D designs is that the phase-inverted feedback signal can generate amplifier instabilities since the output filter creates its own phase errors which the NFB loop doesn't account for. This can create full 360-degree phase shifts to invert feedback phase back to signal phase to cause oscillation. The patented NuForce solution is claimed to disable such behavior while linearizing the behavior of the output filter. Then there's a < 10 milliohm output impedance for a high damping factor regardless of frequency, the latter claimed to enable very low distortion specs mostly irrespective of output voltage (0.05% THD+N during power peaks). While on power peaks, this small box claims to make short-term 288, 576 and 1125 watts into 8, 4 and 2 ohms respectively. For RMS, there's a permanent 160, 200 and 200 watts. The 'ideal' power doubling into halved impedances thus exists only momentarily.


Input connections for the monos are toggle-switched XLRs or RCAs which sound identical, period, hence stop fretting over what's superior. There's one output terminal pair per amp (more wouldn't fit) and the power mains is on the back as well. There's a small pop on power down over the speaker but most will leave these amps on permanently with their negligible idle draw of 13 watts. The Reference 8.5 V2 monos can be had in black or silver, the P-9 preamp additionally in copper. Those lusting after more power can convert an 8.5 into a 9, the next model up. This upgrade consumes €1.100 and buys a heftier power supply with a power increase of 100 watts per side.


Sound
I looked forward to the NuForce monos since they'd create an opportunity to contrast my work horse Bel Canto e.One M300 monos, another class D design based on Bang & Olufsen ICEpower whose €2.600/pr sticker competes squarely against NuForce's €2.800/pr. Needless to say, the €4.800/pr SAC il piccolo monos too would make an appearance as a design I'm much impressed by and run as a personal reference. My colleague Jörg meanwhile relates to the Myryad MXA 2150 stereo amp in like fashion. It wouldn't take much to pin the two Yankee challengers under my arm and walk 'em over to him.


How about the preamp? Yeah, I did listen to it, too. It proved the best within reach, albeit at €3.300 also 50% costlier than Bel Canto's own e.One Pre3. But this surcharge buys more and pretty much across the board, tonally down low, on high and in the middle. Bass is squarely great - pressurized, contrasted and most of all fast, with a very agile core character. With hi-hats more finely resolved (something I could personally overlook), even the insight into the vocal band is higher than over the Bel Canto pre. But is it resolution per se? Or more tone textures? Not sure. For example, Björk's "Anchor Song" consists solely of voice and brass and over the NuForce P-9, the latter sounds brassier in a good way. As though individual sounds were tracked more closely. The brass sounds are more precisely rendered without tipping their timbre more toward the light or dark. But there's more than just increased brassiness which often is a negative and something I've heard as such even on this number while here it's high praise indeed. Dimensionality too is enhanced with the NuForce pre. There's greater insight and instruments are more precisely allocated their positions. That'll suffice. For further comparisons, I'd leave the P-9 running to swap out amps since relying on top neutrality ahead of the amps has never yet been a bad thing.

Now it was down to 2 x 2 monos, both class D, at nearly identical prices yet sonics remained dissimilar. If my imagination was to transform me temporarily into a field general who surveys the horizon of frequency response from his hill while rendering commentary on the landscape... I'd talk of a gently upwards sloping Bel Canto plain with a middle plateau shelved down at the end. The NuForce cartography begins like the Bel Canto, with a brief rise and beyond that, flat flat plains. The Netherlands? Though I'd not spot a dike in the distance, wouldn't there be a nearly imperceptible rise 2/3rd into the flatlands? Should I clean my glasses? Enough with poetry, let's look more closely.


I fancy the Bel Canto M300s for three reasons: 1/ They look the business as a very handsome design. 2/ They never misbehave to go on my nerves. They simply play music and only analytical listening might suggest that the top is a bit charming and rounded off, a minor error which often turns into an asset in real life. 3/ Their midrange is very balanced and natural - while, granted, the bass doesn't pressurize as it does with certain transistor brutes but that's nothing you couldn't live with.


Greater acceleration in the bass is then what the NuForce Ref 8.5 V2s deliver. Impulses in the bassment gain in angularity to enhance rhythmic liveliness. I also hear a bit more bass over the NuForce amps. That said and regardless of indoctrinations on extreme damping factors, I don't hear extreme iron-fisted control of the woofer's voice coil. While dryness is quite good, "never heard before" articulation is an empty claim. And it didn't require the take-no-prisoners SAC Piccolos in that regard to make the point. Even the control exerted by Myryad's MXA 2150 stereo amp is higher to generate more impact from the upper bass on up. Which is quite impressive particularly when a dirty electric guitars gets thrown in the room from below. Not that it has to become a steady diet but it's sterling in the right doses. So the NuForce mono bass is agile and rhythmic but not ultimately powerful or articulated - good but the true virtues of these switching amps sit elsewhere.


That'd be the outrageous clarity and transparency which operate above the lowest bass out into the bat realm. This was obvious from cold out of the box: "Like clear water". Should an old-timer counter with yesteryear's Malaria hit "Cold clear water", I'd correct the verbiage to "well-tempered clear water". While the sound is lively and fresh, I'd not confuse it with cold. It's the lack of grey veiling as well as the absence of graininess and over-articulated edges which produce exceptionally detailed insight into tonal hues and inner subtleties. Hence voices, instruments (and oh yes, violins!) gain in richness, detail, nuance or micro info over the e.One M300s - albeit being also a bit lighter. Well-recorded female vocals are rendered with a bit more body over the Bel Cantos but also along the motto "you needn't know the full 100%". "But you should get at least 95%" counter the NuForces to coerce the lady closer to her microphone. The resultant balance accords a live-feel in-room presence without getting tiresome from hyper presence.


A while back, I visited a van Gogh exhibit and even this cultural bottom feeder remembers something about it: I inspected these expensive canvasses from as close as possible, nose to the glass. This rendered tons of color, even the master's fingerprint on thickly layered oils, but the picture per se vanished. While the explosion of colors was fascinating, how those color hues related to one another was lost from this perspective. I had to step back until, at a certain distance, the color party turned into a sunflower. Naturally, similes always overdraw but in principle, this one holds. Proper viewing distance is key to create the appropriate perspective. 30 meters removed, you'll make out a yellow spot. At 30 centimeters, it's all spots. At about 3 meters though, you'll appreciate both the image and how it's been painted. With the NuForce amps, the perspective matches: You neither lose detail nor the big picture.

Clarity and transparency dominate the treble. Aside from the greater midrange resolution, this might be the biggest differentiator to the Bel Cantos. Where those say less to occasionally round over aggressive attacks, the Reference 8.5 V2s draw the straight line. It's because there's no distortion or grating that this doesn't interfere even over the long haul. Hence I personally relate well to the manufacturer's broad bandwidth claims. It's truly a very open sound.


As with their staging, something always seemed to sparkle when the NuForce monos ran the show - as though the air between the speakers got electrically charged. The lateral panorama is nicely broad and even height is rather tall. Ditto for depth even though there I've heard deeper. Wearing my pedantic hat, I might want for a bit more sorting, more edge definition, image accuracy and, relatedly, greater insight into the stage rear. Granted, this is scaling the ivory tower. But that's the definition of hifi reviewing. Even from those abstracted heights, there's very little to criticize dynamically, particularly in the micro range. It seems to be a veritable obsession with the NuForce amps to peel out minute level changes similar to the expanded color scale in the midband.


They position themselves as a new force in the hifi sector, these folks. And their dog hunts. NuForce sits at the top of an amplifier technology which has future dominance written all over it -- class D analog switching – and presents it with a very high price/performance conviction to turn the technology suitable for high fidelity. I find it courageously simpatico how demure NuForce has styled its challengers. Competitors would have blown far more hot air into the enclosures for more impressive sizing and weight. That the highly neutral NuForce P-9 preamp with its potent bass outweighs the monos will really take old-time high-enders for a loop. Get used to it. At least sonically, the NuForce entry-level mono amp offering Reference 8.5 V2 is anything but a bantam weight.


Psych profile of the NuForce Reference 8.5Vs:
  • Tonally neutral with a small tendency toward the light. Bass is agile and rhythmic, well defined but not ultimately dry. The mids are exceptionally transparent and differentiated, drawing from an enhanced color palette and detail retrieval without harshness or grain. A few will ask for a bit more body. The treble is a straight line, not too much, not too little: open, clear, clean and defined.
  • Music is freely in the room on a large, particularly broad scale. For usually rather more money, improvements are possible in matters of outline definition, sorting and stage depth.
  • Anything related to tempo – percussion & drums, piano hammer falls, plucked strings – is exceptionally immediate, a solid guarantee against boredom.
  • Dynamically impervious, period.

Facts:
P-9 preamp
  • Weight: 7,7 kg
  • Dimensions: 21,5 x11 x 35,7cm HxWxD (stacked)
  • Finish: silver, black, copper
  • Power consumption: 9 watt Standby
  • Inputs: 5 x RCA (impedance 10 kOhm)
  • Outputs: RCA und XLR (pseudo), (impedance 100 Ohm)
  • Max output: 7 Volt
  • Other: two-box concept

Mono Reference 8.5 V2 (per)

  • Weight: 3,6 kg
  • Dimensions: 21,5 x 5,5 x 35,5cm HxWxD
  • Finish: black or silver
  • Power consumption: 13 Watt Standby
  • Inputs: RCA and XLR (impedance: 45 kOhm)
  • Outputs: single pair of binding posts (output impedance ca. 10 Milliohm)
  • Max output: 160/200 watts into 8/4 ohms
  • Other: can be upgraded to Reference 9
  • NuForce website
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