Brian Kahn is the longest tenured writer on staff at HomeTheaterReview.com. His specialties include everything from speakers to whole-home audio systems to high-end audiophile and home theater gear, as well as room acoustics. By day, Brian is a partner at a West Los Angeles law firm.
quickly become a major player in the audiophile grade, Class D
amplification market over the past five years. While the NuForce
product line is now quite extensive, ranging from amplifiers to
headphones, the company is best known for their Class D mono block
amplifiers, the latest version of which is the Reference 9 V3 Special
Edition reviewed here. The NuForce amplifiers differ from traditional
amplifiers in that they are a "switching amplifier" or "switched power
supply amplifier." Most switching amplifiers on the market today are
digital switching amplifiers that are considered by most to be a Class
D design. The NuForce amplifiers distinguish
themselves from this group of amplifiers by utilizing a closed-loop
system with analog modulation driven by the audio signal. A traditional
analog amplifier is controlled by fixed frequency, carrier based pulse
width modulation. The NuForce topology is said to greatly increase
efficiency, bandwidth, control (damping), phase problems, linearity and
signal to noise ratios.
V3 series released in October 2009 is NuForce's third generation
amplifier. Owners of V1 or V2 series amplifiers can have their
amplifiers upgraded to V3 for a relatively modest fee. In the case of
my V2 Special Edition amplifiers the cost to upgrade them to V3 Special
Edition was only $400. Of course you can buy a brand new V3 Special
Edition for $5,000. The only difference between the upgraded and new
amplifiers is the face plate; the upgraded units will have an old style
faceplate with the new "V3" moniker and the new units will have
NuForce's new three dimensional faceplate.
describes the V3 circuit as having an improved feedback path and better
control over a wider bandwidth. The V3 circuit has different power spec
than the V2: 175 watts RMS into eight-Ohms as opposed to the V2's 190
watts. However, into four-Ohms the V3 has 335 watts of RMS power as
compared to the V2's 300 watts. V3 has lower gain than V2 due to design
optimization with the new feedback control system. NuForce notes that
the lower gain allows the preamplifier's volume control to be run at
higher level which produces better sound quality with many of the
preamplifiers on the market today. The V3, like prior generations of
NuForce amplifiers is offered in both standard and Special Edition
versions; the Special Edition features an custom designed capacitor
array instead of the standard dual big capacitors design. While I have
never had both the standard and Special Edition versions of the same
amplifier for comparison, NuForce claims sweeter highs and a smoother
midrange set in a more coherent and deeper soundstage.
I first saw a NuForce Reference 9 I was surprised by their diminutive
extruded aluminum chassis' which measure eight and a half inches wide,
14 inches deep and nearly two inches tall, and weigh in at eight pounds
a piece. Most of the monoblocks I have had in my system over the years
were large, heavy units. These traditional monoblocks can be visually
impressive but they can also be difficult to move and find a place to
set up. This is where Class D amplifiers can have a large advantage; I
can easily carry both units under my arm and then set them up in the
same amount of space as a traditional source unit.
extruded aluminum chassis on the Reference 9 amplifier series is
reasonably solid and well finished but will not be confused with a
Rowland, McIntosh or similar component. There are no half inch thick
metal panels or surfaces polished to a mirror finish. The images I have
seen of the new faceplate style indicate an upgraded aesthetic for
those who need eye candy to go along with their ear candy. The
amplifiers have both single ended and true balanced XLR inputs and a
set of Eichmann Cable Pod binding posts.
used the NuForce amplifiers in my dedicated two channel system,
utilizing Logitech's Transporter and Classé CDP-202 as sources. During
the course of this review, I switched pre-amplifiers from Conrad
Johnson's excellent CT5 to another tube unit, McIntosh Laboratories'
C-500 (review pending). I spent a lot of time listening to the
Reference V3 Special Edition amplifiers with both preamplifiers but my
listening notes were done with the McIntosh preamplifier in the system.
The speakers I used in this review were Martin Logan Summit's and
Acoustic Zen Adagio's. All connections were made with Kimber Select
cables, single ended with the Conrad Johnson preamplifier and balanced
from source to amplifier with the McIntosh. Power conditioning was
courtesy of a Richard Gray Power Company 1200 and power cables were
small size of the amplifiers allowed me to easily fit the amplifiers on
a single Billy Bags amplifier stand. The Eichmann Cable Pod binding
posts may provide a good electrical connection but did not provide the
tactile reassurance of a more traditional 5-way binding post. The
layout of the amplifier itself forced me to feed my spade fitted
speaker cables from above the amplifiers, if the back of the amplifiers
extend past the shelf you may be able to access the binding posts from
the bottom, side access will be tight with most speaker cables.
Regardless, the Eichmann Cable Pod binding posts kept a firm grip on
the Kimber speaker cables throughout the course of my review.
any serious listening I let the amplifiers break in for over a couple
of weeks, including six straight days of non-stop music. These
amplifiers need a seriously long time to break in, close to 200 hours
seemed to do the trick for me. I also left them on unless it was going
to be days between listening sessions as I found that it took over an
hour for them to fully warm up to maximum performance levels.
Read more about the performance of the Reference 9 V3 on Page 2.
"Hallelujah" from Jeff Buckley's Live at Sin-e (Sony) is a well recorded piece that I have listened to on many systems including in my house with the V2 version of the NuForce amplifiers. The overall sonic character of the V3 amplifier is very similar to the prior V2 amplifier, with some small but noticeable improvements. The V2 Special Edition that I had previously reviewed was already an excellent amplifier, but like any other component there is always room for improvement. As before, the amplifier was fast and detailed while maintaining tonal accuracy. I recall thinking that the prior V2 version as having similar sonic characteristics to Halcro's pricey MC amplifier series but slightly less refined. The V3 is noticeably more refined and would give the Halcro a run for the money in that regard. What does that mean to the listener? On this track I found the Jeff Buckley's voice and guitar to be slightly more palpable and three dimensional than before and with a greater sense of presence. Through both the MartinLogan's and the Acoustic Zen's I noticed a deep soundstage. The high end was even more improved than the midrange. My listening notes indicated that the V2 Special Edition could be slightly forward in the higher regions; the new V3 was more extended and sweeter, and I never had the sense that even with the Adagio's ribbon tweeter that the amplifiers upper limit had been reached.
An album I have been listening to lately is the all-time classic, Dire Straits' Brothers in Arms (Warner Brothers). I have this album stored as a full resolution FLAC file and access it via my Logitech Transporter. I went in and sat down for a closer listen, selecting the track "Money for Nothing." I immediately noticed that even at higher volumes the higher frequencies remained strong and open, becoming ever so slightly harsh only at insanely loud levels. Most wouldn't push these amps to this level of output but I wanted to see just how far I could take it and my ears seemingly gave out before the amps did. There's lots of power coming from these relatively small amps.
On the other end of the audio spectrum, I listened to a couple of albums I have been using lately to test the lower end: The Black Eyed Peas' latest album, The E.N.D. (Interscope) and the ubiquitous It Happened One night by Holly Cole (Blue Note Records) . The synthesized bass line in "Boom Boom Pow" was sharp. I was particularly impressed by the NuForce's control over the Adagio's woofers as there was absolutely no smearing of the bass notes. The bass notes appeared to have more weight than with the prior V2 version but still were a bit shy of the bass powerhouses such as the Krell FTB series of amplifiers. The acoustic bass on Holly Cole's "Train Song" from her album It Happened One Night (Blue Note Records) is an often used demo as it provides some reasonably detailed, well recorded and reasonably deep bass notes. The NuForce amplifier's speed and clarity were great assets here. The leading edges of the notes were sharp, and the decay was naturally extended. The NuForce also did quite well with female vocals. Holly Cole's voice seemed to come from a spot a just behind the plane of my speakers with a good sense of air and space.
Throughout my listening sessions the constant factor with the NuForce was a sense of quickness. The amplifiers always seemed to be quick to respond to any change in the input signal. After the amplifiers were fully broken in they also leaned slightly towards the warm side yet they were very revealing; on some systems they may be too revealing of system shortcomings. When listening to CD's I often felt like the amplifiers were lacking the ultimate level of refinement I have heard in the absolute best of amplifiers. However, this already narrow gap in refinement levels was dramatically narrowed when I listened to some 24 bit FLAC files. I joined the Bowers & Wilkins Society of Sound. I downloaded Peter Gabriel's newest album, Scratch My Back. Gabriel's vocals had a sense of presence and realism that I had not heard with any of the CDs I listened to. The violins on the track "Listening Wind" were particularly lush and vibrant. With both the instruments and vocals there was a significantly greater sense of presence.
My impression is that slower amplifiers may hide the lower resolution sources by a very slight smearing of details which may sound similar to, but not the same as, the sonic qualities often described as "liquid" or "organic". The NuForce amplifiers are true to the recording, whether or not this means they are true to the music will depend on the quality of the recording, perhaps more so than with other gear, as the inadequacies of the recording are likely to be revealed by the speed and detail of these amplifiers.
The NuForce Reference 9 V3 Special Edition speakers can be ruthlessly revealing and will require careful system integration. The slight reduction in power between the V2 and V3 series may cause problems if your preamplifier is passive or low gain. Likewise, inefficient speakers may also not be suited to these amplifiers if concert level volumes are demanded. Another speaker compatibility issue may arise if you have partially active speakers. In the past I have had speakers whose powered sections were not activated by a Class D amplifier.
Sonically, the amplifiers perform extremely well and are among the best sounding amplifiers I have had in my system including class-A, class-AB and class-D. However, they are not 100 percent neutral and consistent throughout the frequency range. The variation is slight but I found their sonic character to gain warmth as you move from the lowest to highest frequencies. Personally, I found this slight deviation from absolute neutrality to work well as I liked my lows to be cool and controlled and my highs to be warm and extended.
The NuForce Reference 9 V3 Special Edition improves upon the already excellent NuForce Reference 9 V2 Special Edition amplifiers which I purchased over a year ago. The difference between the V2 and V3 is evolutionary rather than revolutionary. The differences were not huge but they were noticeable and appreciated as they addressed some of the items that came to mind when I listened to the V2's and wondered, "This is good but wouldn't it be great if they could also...." The biggest improvements came at each end of the frequency range with more controlled bass on the one end and warmer, more extended highs on the other.
The reduced gain allowed my preamplifiers to work in their optimum volume range; however the reduced gain may prove incompatible with low gain or passive preamplifiers or with inefficient speakers. Thankfully NuForce offers an in-home audition program so you can try the amplifiers out on your own system. If you are looking for an amplifier that will give you a lush and smooth midrange that will hide the imperfections in the recording or your system, look elsewhere. The NuForce Reference V3 Special Edition amplifiers will let you see deep into your music, bringing out more of the information that would otherwise be buried by less detailed products. The Reference 9 V3 Special Editions, being a touch on the warm side, let speed and detail shine without the analytical sterility normally associated with these characters. All in all, the NuForce Reference V3 Special Edition won't sugarcoat a bad recording but they will coax a ton of enjoyable musical detail out of high quality recordings and if you have high resolution recordings, this amplifier will let their increased resolution really shine through.