Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click this link.

Purifi’s Eigentakt class-D amplification technology first came to our attention when SoundStage! Network founder and publisher Doug Schneider raved about the performance of an engineering evaluation sample utilizing the company’s OEM modules. We subsequently reviewed several Eigentakt-based products from NAD, including the C 298 stereo amplifier, the M28 multichannel amplifier, and the M33 integrated amplifier-DAC. I personally reviewed the latter two, and all three products received SoundStage! Network Reviewers’ Choice awards when they were published. The C 298 and M33 went on to win SoundStage! Network Product of the Year awards.

NAD recently released an Eigentakt-based stereo/mono power amplifier in the Canadian company’s Masters Series, replacing its earlier Hypex Ncore-based Masters M22. At $3749 (all prices in USD), the M23 isn’t cheap, but considering that the M22 was priced at $2999 when it debuted almost eight years ago, and how prices of electronics, like most things, have been increasing in recent years, this price seems quite reasonable. After a delay of a few months due to the usual supply-chain issues and high demand for this amp, Lenbrook Industries, NAD’s parent company, was able to send me a review sample.

Description

The NAD Masters M23 shares the same elegant styling as other Masters components, including the multichannel M28 I previously reviewed. Its contrasting brushed-silver alloy and matte-black surfaces set the standard for aesthetics in this price range. It is gorgeous, yet still classy and understated.

Although it doesn’t have the extreme build quality of some components from ultra-high-end manufacturers, it is still very solidly built. Measuring 17″W × 5.25″H × 17″D and weighing 21.4 pounds, the M23 is relatively compact and light for a 200Wpc amplifier, but this is not unusual for a class-D design. The spiked feet can be placed on the provided magnetic discs to prevent scratching the surface it’s placed on.

The top panel is mostly black, with eight large, square vents, each covered by a black wire mesh, running down the center in two rows. The faceplate is largely covered by a black panel that protrudes about a half inch from the brushed-silver base. Its only feature is the illuminated NAD logo at the top left, which glows amber in standby mode, bright white when on, and red in protection mode.

The model number is silkscreened very lightly on the top edge of the black front panel, just in front of a capacitive-touch standby button. This control takes a little getting used to, as it provides multiple functions. Auto standby and auto-sensing on modes can be selected by holding the standby button for various lengths of time, and the power indicator flashes a different number of times to confirm the mode selected.

Connections on the back panel are placed symmetrically to the left and right, with the XLR and RCA inputs near the center and the speaker outputs on either side. There’s enough space between them to keep cables neatly separated. Small toggle switches allow selection of the XLR or RCA inputs and Low (19dB), Mid (24dB), or High (29dB) gain levels in stereo mode (25dB, 30dB, and 35dB in bridge mode) and a 12V trigger input is provided. A slide switch can be used to select bridge mode (mono) and a small button is provided to adjust the brightness of the LED power indicator. The three-prong IEC power inlet is on the left side along with a mains power rocker switch and ground terminal.

As with all its Eigentakt-based amplifiers, NAD builds each pair of amplification modules for the M23 in-house under license from Purifi. This means NAD can leverage its substantial engineering and manufacturing resources to ensure the quality of each module rather than relying on an external supplier. NAD also uses its own switch-mode power supply and gain stage to make the Eigentakt module more compatible with the company’s components. Rather than simply attenuating the incoming signal, the M23’s gain selector switches between the three levels of gain within the gain stage. The M23 also features a mirrored layout of components to maintain as much separation as possible between the channels with the only common connection being to the shared power supply.

As is typical for NAD products, a thorough list of specifications is provided for the M23. The highlights include a power output of greater than 200Wpc into 8 ohms or 380Wpc into 4 ohms, and greater than 700W into 8 ohms in bridge mode. The damping factor is said to be >800, THD is <0.00069% (XLR), and the signal-to-noise ratio is >127dB (200W into 8 ohms).

I was impressed by the specifications of the M23. Based on previous measurements of the similarly designed M28 and C 298, I had little doubt that the extensive suite of measurements by the SoundStage! Network measurement specialist, Diego Estan, would show that the M23 mostly meets, and in some cases exceeds, the claims of the company.

In addition to the noteworthy specifications, the M23 and its Masters brethren are some of the best-looking amplifiers I have ever had in my system, and their visual appeal challenges that of some of the very best high-end competition.

Setup

I connected the NAD Masters M23 to my Anthem STR preamplifier-DAC in place of my reference pair of Anthem M1 monoblock amplifiers. An Intel NUC computer running Roon and streaming Tidal was my main source, and the system was completed by a pair of MartinLogan Masterpiece ESL 9 speakers. For the review process, I removed my dual JL Audio E-Sub e112 powered subwoofers from the system, but used the STR preamp both with and without its built-in ARC Genesis room-correction system. The system featured Shunyata Venom-X XLR interconnects and speaker cables, an AudioQuest Carbon USB link, a JitterBug jitter reducer, and various power products from Clarus, ESP, Zero Surge, and Blue Circle Audio.

One thing I noticed about the M23 during my review was that it sounded a little thin when first turned on from cold, and took at least 10–15 minutes for its performance to stabilize. Thus, I disabled the auto-sensing standby option and left the amp powered on for a period of time before doing any critical listening.

I primarily used the XLR inputs for connection to my preamplifier, and set the gain switch on the M23 to the Mid setting.

The sound

It probably won’t come as a surprise to anyone who has read my previous reviews of NAD’s Eigentakt-based amps that I found the performance of the M23 to be nearly flawless. And I’m not the only one who feels this way about Purifi’s Eigentakt amplification technology: Evan McCosham was similarly impressed by NAD’s C 298 power amplifier, and Doug Schneider was “bowled over” by the performance of the Eigentakt engineering sample amplifier provided by Purifi.

So what was it about these amplifiers that impressed us so much? Nothing, really. And by that, I mean these Eigentakts essentially had no sonic signature. We all found that they seemed to perfectly amplify the incoming signal and send it—totally unadulterated—to the speakers. You can see this objectively in Diego’s measurements. Subjectively, the result was a sound that was detailed and highly resolving, while at the same time both natural and relaxed. Connecting the Masters M23 to my Anthem preamp and MartinLogan loudspeakers, there was a sense of rightness to the sound from the get-go. Even though I did not initially engage ARC Genesis room correction, I thoroughly enjoyed listening with the M23 in my system, no matter what I listened to or for how long.

I recently stumbled upon Colin Hay’s Man @ Work (16-bit/44.1kHz FLAC, Compass Records / Tidal), on which he reworks mostly acoustic versions of songs from his former band, Men at Work. The new arrangements and performances are not particularly revelatory, but the immediacy and presence of Hay’s vocals on “Overkill” were dazzling through the M23. Backed by only acoustic guitars, his voice was singularly clear and present and totally arresting in its purity. There isn’t much depth or width to this recording—the instruments and vocals were placed relatively close together, toward the middle between the two speakers—but there was an absolutely breathtaking clarity to the sound through the M23.

Billy Idol’s live version of “White Wedding” on VH1 Storytellers (16/44.1 FLAC, Capitol Records / Tidal) isn’t exactly an audiophile-quality recording either, but the utter coherence imparted by the M23 made it sound as if Idol and guitarist Steve Stevens were standing between the two speakers in my room. The individual notes of each pick by Stevens and the strumming of the chords were all clearly delineated from one another, and the clapping of the crowd in unison to the music was placed in perfect relation to the players, slightly behind and spread evenly from speaker to speaker. Idol’s vocals were not as lucid as those of Hay on “Overkill,” but they were still mad detailed, displaying every bit of the raspy, snarling character of his voice.

“Break My Soul (The Queens Remix)” by Beyoncé and Madonna (24/44.1 FLAC, Columbia Records / Tidal) is filled with unrelenting wave upon wave of EDM beats and rhythms that will slam your speakers and your room if your system is capable enough. But it is also an intricately mixed and complex track. The M23 filled my room with sound: the opening, echoey vocals expanded in all directions and the finger snaps were imaged well outside the left speaker. Both lead and backing vocals emanated precisely from points throughout the soundstage, from side to side and front to back, with the samples of Madonna’s “Vogue” set well back behind the speakers. The sample of Big Freedia’s “Explode” is buried slightly in the mix, yet the intelligibility of the rapid-fire rapping was astounding through the M23, and the catchy beat was always taut and punchy. At times, I did wish that the M23 had a tad more fullness in the bass, but I found the overall transparency and neutrality of the sound to be astonishing.

The NAD M23 sounded simply fantastic in my system in its own right, but engaging the ARC Genesis room-correction system built into my Anthem STR preamplifier did offer some worthwhile improvements. The deep bass became slightly more prominent without taking away from the overall neutrality, and the upper bass and lower midrange became a little clearer, further enhancing the astonishingly precise imaging and retrieval of low-level detail I had heard so far. The guitars on “Overkill” became even more vivid, as did Hay’s vocals; some sibilance I had noticed earlier on the final verse was somewhat tamed. However, these were relatively minor changes, and only slightly enhanced the already impressive performance of the M23.

I also compared the sound through the balanced XLR inputs versus the single-ended RCA inputs and could not discern any consistent differences in performance between them.

Comparison

Lest there be any doubt, the NAD Masters M23 is one of the finest amplifiers I have had in my system, and in many respects it comes close to—or even surpasses—the performance of many of the much more expensive amplifiers I have auditioned. Compared to my reference Anthem M1 monoblock amplifiers ($3999.99 each), the M23 was slightly more transparent throughout the entire frequency range, resulting in clearer image outlines and a more coherent soundstage. Relatively speaking, there was a minor lack of bass that some might attribute to a slight coloration in the sound of the Anthems. The M1s are much more powerful, with a rating of 1000Wpc into 8-ohm loads, but my MartinLogan ESL 9 hybrid electrostatic loudspeakers were driven fairly easily by the M23’s rated 200Wpc, and I suspect that most loudspeakers will perform similarly well with the NAD.

Lang Lang’s “Somewhere (Dirty Blvd.)” featuring Robbie Robertson (24/44.1 FLAC, Sony Music / Tidal) is an extremely varied composition that at times sounds like a multitracked studio pop recording and at other times like a live recording of a full orchestra. Compared to the M1s, the M23 painted a clearer picture of each section of the orchestra and their relative positions. It wasn’t that the individual sections seemed further apart, but that the space between them—and between individual instruments—was darker and quieter, resulting in more sharply defined image outlines. There are only a few instances of extremely deep bass in this recording, but the M1s did manage to dig a little deeper with the timpani; however, the M23 countered with better articulation of each strike of the drums, making each beat sound slightly different.

I observed similar differences between these two amps with the powerful Allegro con brio from Beethoven’s Symphony No. 7 in A Major with Daniel Barenboim conducting the West-Eastern Divan Orchestra (24/48 FLAC, Deutsche Grammophon / Tidal). Even though the prominently featured string sections are full of chaos and fury in this boisterous movement, the M23 was still able to provide a clearer rendering of the full layout of the orchestra. And while the Anthems had a touch more bass weight and depth, I didn’t really miss it as the overall presentation was so clean and composed. Engaging ARC Genesis room correction also did not significantly tip the balance in favor of either amp. The NAD did benefit from a slightly fuller bass presentation, but ARC mainly served to marginally enhance the performance of both amps to a similar degree.

If I didn’t already own a pair of Anthem M1s, the other amplifier I would be happy to have as my long-term reference is the Bryston 4B³. It has a superlatively transparent sound combined with excellent bass, and a healthy power rating of 300Wpc. Although it has been a long time since I’ve had the Bryston in my system, I would say that it is roughly the equal of these two amps, with a similarly neutral sonic signature that is somewhere between that of the NAD and the Anthem. However, like a pair of the Anthems, the 4B³ costs twice as much as the NAD at $7495.

Conclusion

I’ve had the privilege of hearing a lot of truly excellent amplifiers in my system over the past few years, and the NAD Masters M23 is one of the very best. In fact, it compares very well to my Anthem M1 monoblocks and the Bryston 4B³—my two favorite amps in the upper four-figure price range. While I still prefer the sound of my Anthems, I don’t consider the Bryston or the M1s to be substantially better in any area of performance. And since the M23 is roughly half the cost of those two other amps, it is a screaming bargain, and a great-looking one at that.

. . . Roger Kanno
rogerk@soundstagenetwork.com

Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click this link.

Associated Equipment

• Speakers: MartinLogan Masterpiece Classic ESL 9.
• Preamplifier: Anthem STR.
• Power amplifier: Anthem M1 (monoblocks).
• Digital sources: Intel NUC computer running Windows 10, Roon, and Tidal; AudioQuest JitterBug jitter reducer.
• Speaker cables: Shunyata Research Venom-X, Analysis Plus Silver Apex.
• XLR interconnects: Shunyata Research Venom-X, Analysis Plus Silver Apex.
• RCA interconnects: Nordorst Quattro Fil.
• USB link: AudioQuest Carbon.
• Power cords: Essential Sound Products MusicCord-Pro ES, Clarus Aqua.
• Power conditioners: Blue Circle Audio PLC Thingee FX-2 with X0e low-frequency filter module, Zero Surge 1MOD15WI.

NAD Masters Series M23 Stereo/Mono Amplifier
Price: $3749.
Warranty: Three years, parts and labor.

NAD Electronics International
633 Granite Court
Pickering, Ontario L1W 3K1
Canada
Phone: (905) 831-6555
Fax: (905) 837-6357

Website: www.nadelectronics.com