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A decade ago, many predicted that amplifiers with switching or class-D (footnote 1) output stages would come to dominate high-end audio. In a post–Peak Oil world in which the price of energy would always continue to rise, a class-D amplifier's very high efficiency in converting AC from the wall outlet into speaker-driving power would be a killer benefit. Although a conventional push-pull class-B amplifier has a theoretical efficiency of 78.5%, which would seem usefully high, this efficiency is obtained only at the onset of clipping; the need for the output devices to carry a standing bias…
The M2 is relatively hefty, but offers a superb level of fit'n'finish, as well as a high maximum continuous output power of more than 200Wpc into 8 ohms. In common with NAD's amplifier philosophy, more power—300Wpc into 8 ohms—is available for short-term transients. Also reflecting NAD tradition, the M2 offers optional Soft Clipping, selectable with a rear-panel switch and realized in the digital domain. The M2 uses three power supplies, all switch-mode types: one for each channel's output stage, and a third for the input stage and control section.
Technical details
In its simplest…
I wasn't sure what to expect from the M2. My experience of class-D amplifiers has been somewhat limited, but from that experience I anticipated taut, dry lows, somewhat threadbare highs, and a flattened soundstage. I got none of those things. Instead, when I fed the M2 the 24-bit/88.2kHz master files of Cantus's While You Are Alive (CD, Cantus CTS-1208), the soundstage was wide and deep, the high frequencies silky smooth, the lows warm and rich.
With iTunes playing back CD data, well-balanced rock recordings such as Mary Chapin Carpenter's version of Jagger and Richards' "Party Doll,"…
Sidebar 1: Specifications
Description: Solid-state, stereo integrated amplifier with remote control, four digital and two analog inputs, digital processor loop, RS-232 port, 12V trigger input and output, and soft clipping. Digital input sample rates accepted: 32–192kHz at up to 32-bit word length. Clipping power: >250Wpc into 8 ohms (>24dBW). Maximum continuous power: >200Wpc into 8 ohms (>23dBW), >250Wpc into 4 ohms (21dBW), >300W into 2 ohms (18.8dBW). IHF dynamic power: 300Wpc into 8 ohms (24.8dBW), 450Wpc into 4 ohms (23.5dBW), 600W into 2 ohms (21.8dBW). Maximum…
Sidebar 2: Associated Equipment
Digital Sources: Ayre Acoustics C-5xeMP, dCS Puccini disc players; Apple Mac mini (G4 processor, 1GB RAM) running OS10.4.11 for media storage & playback with iTunes 9.0, used with Bel Canto USB Link 24/96.
Power Amplifier: Simaudio Moon Evolution W-7.
Loudspeakers: Aerial Acoustics 20T V2, PSB Synchrony One.
Cables: Digital: Kimber Illuminations Orchid AES/EBU, AudioQuest VSD-4, Stereovox XV2 S/PDIF, Belkin Gold USB 2.0. Interconnect: AudioQuest Wild DBS, Ayre Acoustics Signature (both balanced). Speaker: AudioQuest Kilimanjaro, K2. AC: PS…
Sidebar 3: Measurements
The NAD M2 is not the first power D/A converter to have crossed my test bench: the Sharp SM-SX100, reviewed by Michael Fremer in July 2000 had that honor. But as I wrote at the time in the measurements section that accompanied that review, "On the face of it, an amplifier accepting digital input data and operating entirely within the digital domain is a very attractive idea. But as Sharp's SM-SX100 reveals, it takes heroic engineering to make it work, and there are still some compromises involved, particularly in achieving sufficient dynamic range."
The…
It's difficult to believe that the former top model of Vandersteen Audio's line of loudspeakers, the Model 5, has been in production in one form or another since 1997. Time passes quickly when you're having fun. Like all Vandersteen speakers, the 5 was and remains a good value and performance proposition. For all the 5's high technology and excellent performance both measured and audible, its price now starts at under $20,000/pair (up from about $10,000/pair when the 5 was introduced in 1997), including a built-in, proprietary powered subwoofer in each cabinet, and a sophisticated…
The fully balanced crossover network—with crossover frequencies at 100Hz, 600Hz, and 5kHz—uses the highest-quality, best-sounding components Vandersteen could find. Richard V. said he was surprised by the differences in sound quality different types of connectors made; after trying all of the types commercially available, he decided to make his own. His biwirable terminals, mounted in a barrier strip with machined Teflon insulation, are positioned so that the connectors can be soldered directly to the crossover board, which is located directly behind the terminal panel, inside the cabinet.…
Soundstages were as wide and deep as was appropriate to the program material, but their height was less than fully realized—not surprising, given the Model Seven's height of only 3' 8". Still, the sonic pictures extended well north of 44", just as their width and depth pushed well beyond the physical boundaries of the baffles—but if you're used to line-source arrays—or tall, well-integrated speakers, as I am—the low ceiling of the Sevens' soundstage will be noticeable. That single minor limitation is easily forgotten, however, given the clarity, coherence, and transparency of the three-…
Sidebar 1: Specifications
Description: Four-way loudspeaker with powered subwoofer. Drive-units: ¾" rear-firing aluminum-alloy dome tweeter; 1" dual-chamber, carbon-fiber sandwich, composite-dome tweeter; 4.5" carbon-fiber/balsa composite-cone midrange unit; 7" carbon-fiber/balsa sandwich composite-cone midbass unit; 12" dual-motor, push-pull aluminum-cone subwoofer. Subwoofer amplifier: built-in, 400W, with 11-band room-response compensation. Frequency response: 22Hz–40kHz, ±2dB. Nominal impedance: 4 ohms (+4, –0.5 ohms). Sensitivity: 83.5dB/W/m.
Dimensions: 44" (1117.6mm) H by 14" (…