Integrated Amp Reviews

High-quality playback of digital audio is evolving in two opposed directions. One is where a smart wireless loudspeaker, like the KEF LSX or DALI Callisto 6 C, needs to be connected to a simple source of data. The other is where a smart amplifier takes the data from wherever it needs and sends it to a pair of dumb loudspeakers. NAD's Masters Series M32 integrated amplifier ($4848 with its optional MDC DD-BluOS module), which I reviewed in May 2018, is a great-sounding example of the latter approach.

In the spring of 2019, NAD introduced the Masters Series M10 ($2749). At first I assumed that the M10 was a stripped-down, less-powerful version of the M32, but the new amplifier offers a unique set of features.

Like the M32, the M10 offers analog and digital inputs, but here the BluOS functionality, with its network, Wi-Fi, and Bluetooth connectivity, is included rather than optional. Yes, both amplifiers use a digital output stage, but while the M32 uses a "DirectDigital" amplifier that takes a digital signal as its input, the M10's "Hybrid Digital" amplifier takes in an analog signal. The M10 also offers 50W less power than the >150W claimed for the M32. But NAD specifies that the M10 will offer "Dynamic Power"—ie, when the power demand is short-lived, as it would be with musical transients—of 160W into 8 ohms and 300W into 4 ohms.

The M10 includes multiroom capability and is compatible with home control systems from Crestron, Control4, and Lutron. But more significantly for Stereophile readers, purchasers of the M10 receive a free license to use Dirac Live Room Correction with their new amp. (This can be upgraded to a paid Dirac Live Full Frequency version.) The M10 is supplied with a USB microphone that can be used to measure the responses of the owner's loudspeakers at the listening position; the Dirac app then creates a digital filter to optimize the sound, after which the amplifier's digital signal processing corrects the signal on the fly.

Design
The M10 is a small, elegant-looking amplifier—it is just 8.5" wide—finished in black with the front and top panels formed from "Gorilla Glass." The top panel has an illuminated NAD logo, with a color that indicates various things that are happening inside. (In operation it shines a chaste white.) The front panel comprises a full-width, color TFT touchscreen with a proximity sensor—it senses when your finger is close and offers you items to choose from the menu. The menu itself is too complicated to describe here; suffice it to say that it allows a wide range of functions, including tone controls and crossover frequency for one or two subwoofers (see the screenshot). When the M10 receives streamed audio, the display shows the album cover art, artist, album, composer, and track name. When the M10 receives S/PDIF digital audio and analog signals, the display shows a large pair of white-on-black VU meters.

As well as two pairs of terminals for loudspeakers and the usual 15A IEC power jack, the crowded back panel has two pairs of RCA jacks for analog input signals; a pair of preamplifier output RCA jacks; a pair of subwoofer output RCA jacks; coaxial and optical S/PDIF input ports; an HDMI port for connecting any TV that supports HDMI Control (CEC) and Audio Return Channel (ARC) functions; a combined Ethernet port and Type A USB port; a standby button; a switch for turning the M10 into a bridged-mono amplifier; and various service and trigger jacks. The M10 has Wi-Fi and Bluetooth connectivity; its USB port can accept thumb drives containing music files; and it can access music files stored on a network-attached drive using the BluOS Controller app or Roon. The M10 supports all the common file formats, including MP3, AAC, WMA, OGG, WMA-L, ALAC, OPUS, DSD, FLAC, WAV, and AIFF, with sample rates up to 192kHz and 16–32 bit depths. It can unfold MQA-encoded data and also supports Spotify, Amazon Music, Tidal, Deezer, Qobuz, HDTracks, HighResAudio, and many more streaming services, as well as internet radio.

Inside the box, the M10's brain is an ARM Cortex-A9 processor running at 1GHz. Analog signals are digitized and all the audio data are converted to analog with a 32-bit ESS Sabre DAC chip. While this can decode data sampled up to 384kHz, the maximum rate the M10 can handle is 192kHz. As mentioned above, the M10's output stage is based on the well-regarded Hypex nCore modules, which take negative feedback from after the class-D stage rather than before, to better control the loudspeakers.

Setup
Though I didn't try doing so, the M10 can be voice-controlled by Amazon's Alexa and Apple's Siri. As the M10 doesn't have a conventional remote control, it needs to be connected to a network, either Wi-Fi or Ethernet, for full functionality. Following the excellent instructions in the manual—supplied on a USB thumb drive—I connected the M10 to my network with Wi-Fi using the BluOS Controller app running on an iPad mini. As appears to be the norm these days, the amplifier contacted homebase to see if its firmware needed to be updated. It did, so I waited while the update was downloaded and installed—the NAD logo on the top panel flashes red during this process—after which the M10 rebooted itself and was ready to play music. I later used a wired network connection but didn't hear any difference between the two modes (footnote 1).

play CDs, as I didn't have a long-enough coaxial cable I connected the AES/EBU output of my Ayre disc player to a VSP digital format converter so I could send the data to the M10 via a 15' Toslink optical connection. While the BluOS app can be used to access a music library, I mostly used the Roon app—Roon recognizes the M10 as a Roon Ready zone—to send music data to the M10 via the network. Roon also recognized the NAD as an Airplay device, which I used to listen to internet radio from my Mac mini. I used four pairs of loudspeakers during my auditioning: the inexpensive PSB Alpha P5s that I reviewed in the October 2019 issue and that were my personal 2019 Product of the Year; my long-term reference KEF LS50s; my vintage Rogers LS3/5a's; and the Q Acoustics Concept 300s, which I review elsewhere in this issue.

Listening
Before installing the M10 in my system, I had been listening to my resident pair of KEF LS50s driven first by a pair of Lamm M1.2 Reference monoblocks, then by the Vandersteen M5-HPA monoblocks I had used with the Vandersteen Quatro Wood CT loudspeakers that I reviewed in the November 2019 issue. The latter had their high-pass frequency set to 20Hz so they would, in effect, be driving the KEFs virtually full-range. As you might expect, these very much more expensive amplifiers—the Lamms cost $32,490/pair, the Vandersteens $15,800/pair—set a high bar for the M10. Both made the KEFs sound considerably larger, more authoritative than you might expect from what are relatively small speakers. In particular, the Vandersteen M5-HPAs proved a particularly synergistic if unlikely match. I further explore the performance of this amplifier in my review of the Q Acoustics Concept 300 elsewhere in this issue.

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Footnote 1: Twice during the review period, the M10 stopped recognizing my network. Rebooting it with the front-panel menu command resolved whatever the problem had been.