In the January 2015 edition of “Music in the Round,” I reviewed NAD’s latest Masters Series preampliﬁer processor and multichannel power ampliﬁer, respectively the M17 and M27. I was taken with both, but the M27 made a special impression. In many ways, it personiﬁed what a modern power amp should be: quiet, transparent, cool running, and compact. Its neat package of seven 180W channels inspired me to consider that stereo or mono versions of such a thing could supplant the ungainly monster amps I was using in my main system. So I asked NAD to send me not just one but two samples of their new two-channel power ampliﬁer, the Masters Series M22: Although this is a review of a stereo ampliﬁer, I did want to have my front three speakers identically voiced.
The Masters Series M22 is based on a version of Hypex Electronics’ model NC400 NCore ampliﬁer module that has been customized for NAD. Fundamentally, the M22 is a pulse-width-modulating (PWM) ampliﬁer that’s DCcoupled from end to end, lacking even an output-blocking relay. (The M22 uses much faster electronic protection instead.) DC protection also includes a useful 12dB/octave high-pass characteristic at 2Hz, not by means of a traditional DC servo but via a feed-forward design that derives a low-passed signal from the input and subtracts it from the main signal at a later stage. The NCore design makes use of negative feedback, and uses a modulator that was linearized using a mathematical analysis of oscillator behavior. The distortion and output impedance remain low throughout the audioband. The M22’s speciﬁcations are impressive, particularly in terms of continuous power output and distortion—250W into 8 ohms, both channels driven, and <0.003%, respectively—even without reference to the ampliﬁer’s weight of only 19.6 lbs. But that’s not uncommon these days. What struck me is that, aside from the power-output specs, which are correlated with Ohm’s law, none of the specs are differentiated by load impedance, which counters standard practice. Given that speaker loads are complex, consisting of resistive and reactive elements, load-invariant amps are likely to suit a wider range of speakers, and perform better across the audioband with each of them. And as I expected, the M22 performed well with my two sets of quite different speakers. But I’m getting ahead of myself . . . The M22s arrived in NAD’s standard packaging for its Masters Series models: outer and inner cardboard boxes and, inside the inner box, upper and lower blocks of some soft-covered material, formed to ﬁt the M22’s contours. This unknown material is much more dense and reassuring than any comparable packing substance I’ve seen. (Note that the M22’s shipping weight is more than half again that of the amp itself.) Cutouts in the forms accommodate boxes for the M22’s accessories: a power cord, a leather-cased USB drive ﬁlled with documentation, and four magnetic footers. The amp itself, as it emerged from its velour bag, felt more like a solid block of sculpted metal than an electronic device. I put the M22 in place, slipped the footers under its generously sized pointy feet, and appreciated that the latters’ magnetism kept them in place even when I moved the amp around.
Setup and Operation
Connections were made with AudioQuest Earth XLR interconnects, AudioQuest Oak speaker cables, and a KubalaSosna Emotion AC cord. I ﬂipped the rear power switch on, and the NAD logo on the M22’s front panel glowed amber to indicate that the amp was now in standby mode. To turn the M22 on and play music required that I gently—but not too gently—stroke the soft-touch standby switch that’s recessed on the amp’s top front edge. (I’d had difﬁculty getting the same switch on the M27 to work consistently well, and now took greater care.) My ﬁrst touch was evidently too light, so I repeated it; the M22 remained off. More trials taught me that a light touch was ﬁne, and that the M22 took a few seconds to respond: Pressing the switch again too soon only kept it in standby. (Without tactile feedback from the switch, and with a delayed response from the amp, why would users not hit it again? And why use such a nonstandard, no-feedback switch in place of something simpler?) That’s not my only gripe about the M22’s switching. Apparently catering to EU demands, the M22 arrives conﬁgured to switch itself into standby after about 30 minutes without an audio signal. That’s an effective way to conserve energy, but, unlike many US amps, the M22 can’t then detect the reappearance of a signal and switch itself out of standby—you have to switch it back on again manually. Unless you’re a real power miser, I recommend following the simple steps outlined in the manual to deactivate this function. Okay. Start again. I ﬂipped the rear power switch on. The NAD logo glowed amber to indicate standby mode. A gentle stroke of the standby switch and—after a short wait— the music came alive.
I found it more than a bit uncanny to open my eyes and see that only this one little box was powering two quite large speakers
Bowers & Wilkins’ 800 Diamond speakers (unofﬁcially, the D2 versions) and I have cohabited in my Manhattan listening room for some years now; I know them well enough that even small changes in my system’s sound are easily perceived—sometimes vividly so. Compared to my experience with the other three amps I had on hand (details to follow), the M22 immediately conjured a big, wide soundstage populated with colorful instruments and voices. Individual sounds were natural and balanced, and not conﬂated with the surrounding ambience. Images, too, were stable. Moreover, I found it more than a bit uncanny to open my eyes and see that only this one little box was powering two quite large speakers and ﬁlling my room with the San Francisco Symphony and Chorus (led by Michael Tilson Thomas), soprano Isabel Bayrakdarian and mezzo Lorraine Hunt Lieberson, and the pipe organ of Davies Hall, in Mahler’s Symphony 2, Resurrection (2 SACD/CDs, SFSO Media 821936-0006-2), all at full cry: >100dB spl! Obviously, the M22’s compactness need not earn it any special treatment in evaluations of its sound. I then turned to 2L’s high-resolution recording of “Come Away, Death,” from Gerald Finzi’s song cycle on Shakespearian texts, Let Us Garlands Bring, to hear the voice of mezzo-soprano Marianne Beate Kielland, the piano of Sergei Osadchuk, and their acoustic and musical relationships (free 24-bit/192kHz PCM download from SACD/CD, 2L 2L-064-SACD). Through the NAD M22, Kielland’s voice was pure and cleanly delineated, with a notable presence in the room. Osadchuk’s piano stood apart from Kielland, a bit farther from me, but with requisite body and detail. Together, they sounded as if recorded in a fairly large space with a moderate amount of reverberation that never blurred the music—a little more present than through some other ampliﬁers. Satisfying as this was, just two performers recorded with a moderate amount of ambience was not going to reveal much about soundstage size, width, or depth. For that, one turns to larger ensembles with lots of voices, such as the aforementioned Mahler symphony. Even listening to only the two-channel DSD tracks of the Resurrection, I could easily discern the locations of solo singers, instruments, and chorus, beginning at the plane described by the speakers’ front bafﬂes and receding in ranks from there. Admittedly, the distance from that plane to the back of the stage didn’t seem as deep as I’ve experienced with this recording and other amps—but then again, I can’t measure those depths, or compare my perception of them to the live event. Nonetheless, I could clearly visualize all the movement and other shenanigans artfully devised by Gregorio Paniagua for his and Atrium Musicæ de Madrid’s La Folia de la Spagna (SACD, Harmonia Mundi HMC 801050) as they popped up or scurried around the soundstage. Spectral balance via the M22 was natural, characterized by a notably full but taut and extended bass with plenty of slam, a balanced midrange with distinct presence, and transparent, detailed treble with nary a glint of sharpness. Consequently, pop and rock recordings had impact and snap. Dire Straits’ eponymous ﬁrst album (SACD/CD, Universal Japan UIGY-9634) sounded fresh, with impulsive bass beats and an almost in-your-face presence that, despite its studio genesis, gripped as if it were live. Despite this 1978 recording’s greater presence and clarity through the M22, tape hiss was smooth and unobtrusive. More modern stereo recordings, such as Sara K.’s Hell or High Water (SACD/CD, Stockﬁsch SFR 357.4039.2), lacked for nothing other than, perhaps, the deeper stage audible from this disc’s multichannel tracks. That was not at all surprising—and when I later listened to those multichannel tracks with my three front speakers, powered by both M22 review samples, even that minor issue evaporated. I also took an M22 up to Connecticut, where, in my weekend system, it drove a pair of Monitor Audio Silver 8 speakers with equally satisfying results. Again the soundstage was spacious and detailed, if a bit less deep than I prefer. Reinstalling the Bryston 9BSST2 power amp resident there restored that depth. On the other hand, the M22 didn’t quibble with the Silver 8s, as had the identically priced Benchmark Music Systems AHB2 that I reviewed in November 2015,2 and there were no shifts in spectral balance. In fact, the M22 offered a sound that was barely more muscular than but otherwise identical to that of the M27.
Back in Manhattan, after listening with satisfaction to the M22 driving the stereo pair of B&W 800 Diamonds, I decided to act on an evil thought from a while back. I asked NAD’s Greg Stidsen, “Is it possible to bridge the M22 and make it into a hugely powerful but reasonably priced compact monoblock?” His reply: “Because the M22 uses a fully balanced architecture, all you need are a pair of XLR Y-cords . . . the right channel positive becomes the mono + speaker connection and the left channel positive becomes the – speaker connection.” Sure enough, packed with the second M22 were a pair of just such Y-cords and a note: “You now have a fully balanced dual-mono system with 600W per channel (into 8 ohms) continuous power and about 1,000W IHF dynamic power. Make sure your speakers are up to the task!” The B&W 800 Diamonds’ recommended ampliﬁer power is 50–1000W into 8 ohms on unclipped program; they were up to it, but my ears were not. With the single M22, I had no problem playing the 800 Diamonds as loudly as I could enjoy. In the brief moments I could tolerate a bit more, I detected a glazing-over of the choral voices in the Finale of Mahler’s Resurrection. Was it just my ears overloading? No, because with the bridged M22 minimonsters, the chorus sounded pristine—until my ears and my neighbors cried for mercy. That tells me that I could live happily with a single M22; others, with more maniacal demands, might see a great opportunity for a bridged pair.
Direct stereo comparisons of the M22 with the other amps revealed two issues in the NAD’s sound: The soundstage was slightly shallower and it seemed a bit closer to the listening position. I heard little to distinguish the M22 from Parasound’s Halo A 31 except that the NAD lacked a tiny bit of warmth and soundstage depth. Those same differences were greater with McIntosh Laboratory’s MC303, but even so, saying which was more accurate will entirely depend on the choice and placement of speakers and the room’s acoustic, and even more on your taste in sound. The Benchmark AHB2 set itself apart from the other three amps with its copious soundstage depth and a slightly more distant presentation, but while I felt an abiding sense of its accuracy and neutrality, it failed to be as lively or exciting as the NAD.
Overall, NAD’s Masters Series M22 power ampliﬁer acquitted itself with distinction. Despite its small size, it has all the wallop necessary for staggering volume levels, and, if necessary, can be bridged to meet even more outsize demands. The M22 is more than fair value in view of its compact size, excellent build quality, a tolerance for driving difﬁcult loads, and, most of all, its transparent sound. It is an outstanding ampliﬁer in every way, and I could happily live with it.
Credits: Kalman Rubinson