NuForce has 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.
 

The 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.

NuForce 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.

When 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.

The 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.

The Hookup
I used the NuForce amplifiers in my dedicated two channel system, utilizing Logitech's Transporter and Classe 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 from Kimber.

The 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.

Performance
Before 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.