Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click this link.
If you’re a regular reader of the SoundStage! Network websites, you know that we, and especially our founder and publisher, Doug Schneider, are big fans of Purifi Audio’s Eigentakt amplifier technology. Those class-D amp modules provide high power with extremely low distortion and, most important, extremely neutral and musically satisfying sound—as I discovered in September 2020, when I reviewed NAD’s Masters M33 integrated amplifier-DAC, which is based on the Eigentakt amp. The subject of this review is NAD’s Masters M28 multichannel power amplifier ($4999, all prices USD), which boasts seven channels of Purifi Eigentakt technology.
To the eye, there’s little difference between the Masters M28 and the earlier Masters M27 ($3999, discontinued), which I reviewed in April 2014—except for the “M28” screened onto the top of the black front panel, they’re outwardly identical. They have the same black top panel with 12 large, square, grilled vents. The black top and front panels provide a nice contrast to the thick, brushed aluminum of the rest of the M28’s case—seven years on, the result is still a handsome, modern-looking amp. The M28’s spiked feet can be set on magnetized discs (provided) to keep the spikes from scratching the surface the amp is placed on. The M28 and M27 have identical dimensions of 17.1″W x 6.2″H x 15″D, but at 33 pounds the M28 outweighs its predecessor by two pounds. The M28 is warranted for two years for parts and labor—not all that long for a product for which its manufacturer clearly has high-end aspirations.
A capacitive-touch button at the front of the top panel selects between Standby and On. This takes a little getting used to—the button provides no tactile feedback, and after it’s touched, there’s a slight delay before the M28 powers up. The light surrounding the NAD logo on the left of the front panel glows amber in Standby, white for On, and red to indicate a short circuit.
The M28 retains the same input and output connections as the M27: for each of its seven channels, a single-ended (RCA) and a balanced (XLR) input, and a pair of high-quality speaker binding posts. Each channel’s inputs and outputs are neatly and vertically aligned, the former above the latter. A small toggle switch selects between each channel’s single-ended and balanced inputs.
Also on the rear panel are a three-bladed IEC power socket for the provided cord, a rocker switch for mains power, a fuse bay, an LED for each channel indicating Normal or Fault status, a 12V trigger input, and an LED level button for dimming or darkening altogether the front-panel power indicator. This last button can also be held down until that front light flashes, to toggle the M28 between normal operation and Auto, which puts it into Standby mode after 30 minutes of receiving no source signal.
The M27 and the M28 may look identical; the key difference between them is that the M28’s Purifi Eigentakt amp modules replace the M27’s Hypex Ncore amps. As they do for their Masters M33 integrated amplifier-DAC, NAD builds the Eigentakt amp modules themselves, under license from Purifi. This allows them to ensure that the quality of each module is at least as good as the reference, to maintain the M28’s overall performance. Because the Eigentakt amp is low in gain, NAD adds a gain stage to bring it up to 28dB to ensure better compatibility with other components. The M28 also has a complex active power supply claimed to act more like a power amp that outputs DC, and to maintain the correct output voltage over a wider range of input voltages than a linear power supply.
The M27 was specified as outputting 180Wpc of continuous power and 300W of peak power into 8- or 4-ohm loads, all channels driven. The M28’s specs indicate a bump in power: 200Wpc into 8 ohms or 340Wpc into 4 ohms, both ref. rated THD, 20Hz-20kHz, all channels driven. The specified IHF dynamic power into 8 ohms is 280Wpc, all channels driven, or 560W, one channel driven. Of course, manufacturers’ power-output specs don’t always indicate an amp’s actual performance. While NAD seems to specify their amplifiers more conservatively than do many other manufacturers, the M28’s output specs are still open to interpretation—therein lies the rub with multichannel amplifiers. Outputting large amounts of continuous power through all channels is difficult and impressive, but is rarely required in real-world situations. An amp’s ability to direct more power dynamically to one or a few channels is often more revealing of what it can actually do. Judging by the specs provided by NAD, the M28 can do this.
The M28’s specified total harmonic distortion (THD) is ≤0.003% ref. 20Hz-20kHz (250mW to rated power), with a damping factor of >750 (ref. 8 ohms, 50Hz and 1kHz). Its claimed signal/noise ratios, A-weighted, are: >102dB (ref. 1W, balanced), >97dB (ref. 1W, single-ended), >124dB (ref. rated power, balanced), and >120dB (ref. rated power, single-ended). Finally, its specified frequency responses are 20Hz-20kHz, ±0.1dB; and 3Hz-60kHz, -3dB.
I used the Masters M28 primarily with the excellent Masters M17 V2i surround processor, which NAD had also provided. This meant that I had NAD’s top-model surround preamplification to complement their best multichannel amplifier. The speakers were my usual MartinLogan array—Classic ESL 9 mains, ElectroMotion ESL C center, Motion 4 height speakers—supplemented by a pair of Definitive Technology’s BP9080x surrounds. In addition to the seven speakers driven by the M28, the system was completed by a pair of JL Audio E-Sub e112 powered subwoofers.
The rest of the system comprised an Oppo UDP-205 4K Ultra HD universal BD player that also pulled occasional duty as a DAC-preamp, and an Intel NUC computer running Windows 10, Roon, and Qobuz. I used interconnects and speaker cables from Analysis Plus, AudioQuest, Clarus, and Nordost, and power cords and power conditioners from Blue Circle Audio, Clarus, ESP, and Zero Surge.
A surround-sound system playing multichannel recordings, especially film soundtracks, presents the listener with so much auditory information from multiple directions that minor imperfections in the amplifier’s sound quality can easily be hidden or overlooked. So I began evaluating the NAD Masters M28 by listening to two-channel recordings of music.
The M28 was able to differentiate the extremely subtle changes in inflection and processing of Lana Del Rey’s voice in “Mariners Apartment Complex,” from her Norman Fucking Rockwell! (16-bit/44.1kHz FLAC, Polydor/Qobuz). As she transitions from verse to chorus, or even from line to line, the character of her voice can change from wispy and ethereal to more direct, the latter with a great deal of presence. The M28’s ability to differentiate among and reveal these nuances was unlike anything I’d previously experienced through a multichannel amp in my system.
The M28 reproduced well-recorded voices with amazing accuracy and presence in general, but was also able to do the same with the instruments in Del Rey’s “Venice Bitch.” Whether it was the softly strummed guitar in the foreground or a violin in the background, every instrument had striking realism and precision, regardless of its position on the soundstage. Satisfied that the M28’s reproduction of stereo recordings was top-notch, I moved on to multichannel recordings.
The M28’s sound with all seven of its Eigentakt amps cooking was second to none, as I learned when I played the new Dolby Atmos soundtrack of the Ultra HD BD edition of Peter Jackson’s The Lord of the Rings: The Fellowship of the Ring. In the underground city of Moria, when the members of the Fellowship are surrounded by screeching, scuttling orcs, those sounds coming from all directions were handled superbly, the M28 never sounding harsh or grating at reference levels. As the Fellowship then runs toward the Bridge of Khazad-dûm, fleeing the approaching Balrog, the subwoofers handled most of the bass—but the other channels still had to deal with a good amount of low end, and the M28’s sound was never strained in any way. All the while, Howard Shore’s wonderful score filled the front of the soundstage and wrapped around to the sides of the room with the fidelity of a high-resolution music recording, even with the thunderous crashes of the crumbling underground caverns surrounding me and the realistic whoosh of arrows flying past my head.
I can’t overstress how coherent in all dimensions was the soundfield re-created by the M28. Although I was playing my favorite film soundtracks at extremely high levels, the sound was always a perfectly balanced mix of enveloping music score, Foley effects, and dialog, each element precisely placed in a 360° soundstage to support and enhance a stunning cinematic experience. The M28 displayed the kind of precision and fidelity I’d normally expect from a reference-quality stereo amplifier at this price—yet there I was, experiencing that level of performance from all seven channels of a multichannel amp.
The NAD Masters M28 costs $1000 more than the M27, and easily bested its predecessor when driving my two MartinLogan ESL 9 main speakers alone. The ESL 9s require a bit more power and control than the M27 could provide, and the M27’s exceedingly clean sound could occasionally sound a touch lean in comparison to the M28’s more-fleshed-out yet still neutral sound. Nevertheless, the M27 performed admirably in my system for several years. After all, I have the 1000W Anthem M1 monoblocks to drive the ESL 9s; the M27 had only the less demanding center-, surround-, and height-channel speakers to deal with.
My current reference multichannel amp is a model I consider a benchmark in its price range: the SensaSound TPO-7300 ($4900). It’s specified to output 200Wpc into 8 ohms, all seven channels driven, and even though it’s a class-AB behemoth weighing 99 pounds—compared to the class-D M28’s relatively svelte 33 pounds—their sounds were very similar. Both the M28 and the SensaSound were more than capable of driving my 5.2.2-channel home-theater speaker array to reference levels—I heard little difference in their sounds with most film soundtracks. There were, however, a few subtle differences: The M28 sometimes revealed more microdetail, which resulted in a slightly deeper, more holographic presentation. The TPO-7300’s sound was occasionally a bit weightier, and gave more scale to the rich orchestral score of The Fellowship of the Ring. But these differences were minor and intermittent, depending on which movie I was watching—and listening to.
To get a better idea of how these amps compared with each other, I hooked them up to my pair of ML ESL 9s in a stereo-only configuration with my Oppo UDP-205 BD player as a preamplifier-DAC, a component with whose sound I’m very familiar. What I heard with two-channel recordings was similar to what I’d heard from the two amps with multichannel film soundtracks, but to an even greater degree. The SensaSound sounded undeniably richer with Lana Del Rey’s “Venice Bitch,” but pushed the instruments more toward the speakers, with less center fill between them. And while voices were more prominent and had more presence through the TPO-7300, they also sounded slightly forced, with greater sibilance, than through the NAD. Everything just seemed more balanced with the NAD, with no part of the audioband, or any voice or instrument, emphasized at the expense of any other. When I reviewed the SensaSound in September 2019, I thought it set a new standard for sound quality in a $5000 multichannel amp. The NAD M28 costs only $99 more and sounds better. The SensaSound is still a fantastic amp at its price, but the NAD is even more fantastic for little more, and thus is an even better value.
The Masters M28 was slightly more revealing than even my more powerful two-channel reference amps, the Anthem M1 monoblocks ($7500/pair)—its dead-neutral character made the Anthems sound ever so slightly rich. The Anthems admittedly have more power in reserve when that’s needed, but other than when I listened at insanely high volume levels, it was a toss-up. Keep in mind that a pair of Anthems costs half again as much as an M28—for five fewer channels! The M28’s reproduction was so neutral that it greatly reminded me of the fantastic-sounding and near-perfect-measuring Bryston 4B3 ($6795), which I reviewed in June 2017. Although it’s been a while since I had the Bryston in my system, its powerful, extremely linear, yet eminently musical sound remains burned into my aural memory.
NAD’s Masters M27 is a very good multichannel amplifier that provides seven channels of relatively high power with clean, transparent sound, at a competitive price—but I found its successor, the M28 to be truly exceptional, with more power and even more neutral, better balanced sound, for only $1000 more. The M28 was so good that I had a hard time hearing any shortcomings in its performance.
When I reviewed the NAD Masters M33, I proclaimed it the front-runner in the $5000 category of integrated amplifier-DACs. Now, the Masters M28 is my pick for front runner among $5000 multichannel amps. You’d be hard-pressed to find another amp in its price range that will provide as much power and sound as good with films or music. In fact, it would give many stereo power amps in its price range a run for their money.
The M28’s sound is, in the best sense, extremely neutral—if you want an amp that will inject some sort of coloration to “correct” the sound of your system, look elsewhere. But if you want an amp that you can just plug in and get sound that’s perfectly neutral and natural regardless of what you play, look no further. NAD’s Masters M28 is an outstanding multichannel amplifier, and one of the best now available at any price.
. . . Roger Kanno
Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click this link.
- Speakers: MartinLogan: Masterpiece Classic ESL 9 (front mains), Motion ESL C (center), Motion 4 (height). Definitive Technology BP9080x (surrounds).
- Subwoofers: JL Audio E-Sub e112 (2)
- Amplifiers: Anthem M1 (monoblocks), SensaSound TPO-7300, NAD Masters M27
- Surround processor: NAD Masters M17 V2i
- Sources: Intel NUC computer running Windows 10, Roon, Qobuz; AudioQuest JitterBug jitter reducer; Oppo Digital UDP-205 4K Ultra HD universal BD player
- USB link: AudioQuest Carbon
- Speaker cables: Analysis Plus: Black Oval 12, Blue Oval, Silver Apex. Clarus Aqua Mark II.
- Interconnects: Analysis Plus: Chocolate Oval-In, Silver Apex. Clarus Aqua Mark II. Nordost Quattro Fil. DH Labs (HDMI).
- Power cords: Clarus Aqua, Essential Sound Products MusicCord-Pro ES
- Power conditioners: Blue Circle Audio PLC Thingee FX-2 with X0e low-frequency filter module, Zero Surge 1MOD15WI
NAD Masters M28 Multichannel Amplifier
Price: $4999 USD.
Warranty: Three years parts and labor.
Lenbrook Industries Limited
633 Granite Court
Pickering, Ontario L1W 3K1
Phone: (905) 831-6333