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Reviewer: Srajan Ebaen
Source: Zanden Audio Model 2000P/5000S
Preamp/Integrated: ModWright SWL 9.0SE; Bel Canto Design PRe2; Eastern Electric MiniMax; AudioZone PRE-T1 copper [on review]
Amp: Decware Zen Taboo; 2 x AudioSector Patek SE; Canary Audio CA-308 [on review]; Fi WE421A [on review]
Speakers: Zu Cable Definition Mk1.5 with new external bass attenuator (retro-fitted)
Cables: Zanden Audio proprietary I²S digital cable; 2 x Stealth Audio Indra; Zu Cable Varial [on review]; 2 x Cerious Technologies interconnect [on review]; Zu Cable Ibis; Crystal Cable Reference power cords; Z-Cable Reference Cyclone power cords on both powerline conditioner
Stands: Grand Prix Audio Monaco four-tier
Powerline conditioning: 2 x Walker Audio Velocitor S
Sundry accessories: GPA Formula Carbon/Kevlar shelf for transport; GPA Apex footers underneath DAC and preamp; Walker Audio SST on all connections; Walker Audio Vivid CD cleaner; Furutech RD-2 CD demagnetizer; WorldPower cryo'd Hubbell and IsoClean wall sockets
Room size: 30' w x 18' d x 10' h [sloping ceiling] in long-wall setup in one half, with open adjoining living room for a total of ca.1000 squ.ft floor plan and significant 'active' cubic air volume of essentially the entire (small) house
Review component retail: $1,200/ea.
 

As a new force in analog switching amps, this aptly named firm from Milpitas/CA is aggressively going after the high-value, compact, high-power amplifier market. Rather than repackaging Tripath, Hypex or ICEpower boards, NuForce engineer Nguyen's prior position as chief bottle washer in charge of developing the Tomahawk missile power system made him heavy enough to whip up his own proprietary (now patent-pending) wrinkle on Class D amplification.

Hot on the heels of the Reference 8 monos which our own Edgar Kramer described as "... delivering 100 watts of 2-8-ohm RMS power with 1152 watts of 2-ohm peak power that may just about fit in your trouser pockets", the new Reference 9s offer 160/300/350 watts into 8/4/2-ohm RMS and peak ratings of 325/650/1300 watts respectively. With <10 milliohms of full bandwidth output impedance, the damping factor for an average speaker works out to in excess of 4000. Claimed S/N ration is an impressive 120dB at 100 watts, input impedance 47K and gain 26dB. At 7lb and 8.5" w x 14" x 1.8" h, the Reference 9 is a lightweight otherwise and fully encased in a brushed/anodized aluminum clamshell of either gold, silver or black.

Switchable RCA and true balanced XLR inputs plus 5-way binding posts and the ubiquitous power inlet make up the rear, with a 474K/250V filter cap across the outputs and connecting leads wrapped, inductor-like, around a hollow tube of ceramic-type substance, indicating significant HF filtering right before the speaker terminals [upper right].

Four transistors are direct-coupled to an unfinned heatsink with a hollow air channel in the back. The two halves of the board are veritably stuffed with surface mount parts to eliminate most flying-lead connections.

Distortion is claimed to be load-invariant i.e not vary with power draw and reactive speaker behavior. Even under short-term peak power demands, THD+N is said to remain below 0.05% while phase shift is claimed to be nearly fully absent, period. The use of a switch-mode power supply explains the lack of weight. The hefty power transformer necessary for a traditional linear power supply of a 300-watt/4-ohm amplifier has been chucked. The regulated SMPS includes over-current and short-circuit protection to conform with "all leading safety and industry reliability standards". Where NuForce claims to differ from other Class D amplifiers is in its closed-loop architecture that avoids "spurious interactions between a speaker's complex impedance and back-EMF with the amplifier's resonant output filter".

The Reference 9s need to remain properly grounded during operation and connected to a load while fed signal. Because the speaker output terminals are floating with a 24V DC offset, care must be taken with unusual connections (such as summing the outputs from two Ref 9s through a subwoofer). Normal operating temperature is ca. 45 degrees Celsius but continuous use in confined spaces could increase this as high as 60 degree. A one-year warranty with parent company NPhysics is supplied.