Integrated Amp Reviews

When I started listening to the NAD M10, therefore, I was anticipating a marked diminution in sound quality—even veteran reviewers aren't completely immune from expectation bias. Using the KEFs, I played some reference CDs, including André Previn's performance of Rachmaninoff's Symphony No.2 with the Royal Philharmonic Orchestra (Telarc 80113) that I had auditioned with the Vandersteen speakers and amplifiers. Following the Previn performance, I cued up the DSD64 file with Iván Fischer and the Budapest Festival Orchestra performing the same symphony (Channel Classics 21604) with Roon. (Roon transcoded the DSD64 data to 24/176.4 PCM, and I couldn't see how to tell the app to send the original DSD data to the M10, footnote 2.) With both recordings, I was surprised by a) how much I was enjoying the music, and b) how little the NAD's presentation fell behind in comparison with the Vandersteens. Yes, the low frequencies sounded less extended, less authoritative with the NAD, even with the Dirac Live EQ for the KEF LS50s enabled—see sidebar, "Trying Dirac Live Room Correction"—but what there was of the midbass carried sufficient weight for me not to miss the M5-HPAs too much, and the M10's upper bass was impressively articulate.

My longtime test for bass articulation is the repeated 16th-note bass line in "Last Train Home," from Pat Metheny's Still Life (Talking) (CD, Geffen GEFD 24145-2). It is difficult for a reflex loudspeaker system to keep the onset of each bass note distinct from the overhang of the previous one, and this can be exacerbated by the amplifier used. With the KEFs driven by the M10, however, each note was clearly defined and, if I had to swear to it, better defined than with the Vandersteen amplifiers.

Stereo imaging precision with all the speakers I used with the M10 was excellent, with acoustic objects palpably positioned in the soundstage. Metheny's electric sitar in "Last Train Home" hung in space just to the left of center, and the individual voices in the song's wordless bridge were clearly delineated. While there wasn't quite as much soundstage depth as with the expensive Vandersteens, the M10 still scored well with this aspect of performance.

As the M10 will decode MQA files, I enabled the Core decoder function in Roon and streamed an MQA file of Mozart's Violin Concerto No.4 from Tidal, with Marianne Thorsen and the TrondheimSolistene (24/44.1 FLAC, 2L 7041888521624). Roon authenticated the stream as "MQA Studio 352.8kHz," unfolded it to 24/88.2 data "with MQA Signaling," and sent it to the M10, which rendered it as a stream sampled at 352.8kHz. The sound was excellent. However, even though the M10's manual says that playback of MQA files will result in a green or blue indicator being shown both on the amplifier's front panel and on the BluOS app's screen, this didn't appear. That said, both when I streamed the violin concerto from Tidal with BluOS or selected the MQA-encoded files on a USB thumb drive plugged into the M10's rear-panel port, the MQA indicators appeared correctly, along with the Tidal logo in the former case. These indicators only operate, therefore, when the M10 is acting as both the MQA core decoder and renderer, as it does when using the BluOS app for playback but not when Roon is performing the first unfold.

Digital comparisons
As regular readers will know, I am not a fan of Bluetooth use for music transmission. Even so, when I sent music files to the M10 via Bluetooth, it worked well enough, the amplifier switching to the Bluetooth signal when I pressed Play on my iPhone or iPad.

I had intended to perform some comparisons between the M10 fed digital data via the optical link from the Ayre player and the same data sent via AES/EBU to my reference DAC, a PS Audio DirectStream DAC (Snowmass firmware) that I purchased following Art Dudley's review in September 2014. The output of the PS Audio was sent to the M10's analog input via 12' single-ended AudioQuest interconnects. However, as the NAD digitizes its analog inputs, the PS Audio's reproduction was affected first by the A/D conversion and then by the M10's D/A conversion. I therefore connected the M10's preamplifier outputs to the Vandersteen monoblocks using unbalanced/balanced adaptors and alternated this connection with a balanced connection from the PS Audio.

Using Roon to send the same music to both the NAD and PS Audio with the levels matched with the 1kHz warble tone on Editor's Choice (16/44.1 AIFF file, from Stereophile STPH016-2), the PS Audio was softer-balanced in the highs than the NAD, the M10's treble sounding more forward. However, the PS Audio DAC excelled in the pre- sentation of space. Even with the MQA unfold/upsampling rate restricted to 176.4kHz rather than to the full 352.8kHz, the DirectStream decoded more of the recorded ambience on the 2L Mozart Tidal stream.

On the Pat Metheny track, the chugging bass line had a touch more upper-bass energy with the PS Audio, and though the electric sitar and Lyle Mays's acoustic piano was sweeter-sounding, the soundstaging overall was more palpable than it had been with the NAD. But to put this comparison into perspective, with its network bridge card the PS Audio DirectStream costs $5999, more than twice the price of the NAD M10, and while it has a similar if smaller touchscreen, it is just a DAC. No amplifier.

Luxman comparisons
As coincidence would have it, the Luxman SQ-N150 that Ken Micallef very favorably reviewed in December 2019 arrived at my place for measurement as I was wondering what amplifiers I could compare the M10 with. While the Luxman is an integrated amplifier around the same size as the NAD and, at $2795, is priced similarly, it is otherwise as different as it could be. It uses tubes, has analog inputs only, and offers a maximum power of just 10Wpc into 8 ohms. (It does have a headphone jack, which the M10 doesn't.)

For the comparisons, I used my PS Audio DirectStream DAC with its single-ended output set to its maximum and matched the levels from both amplifiers with the 1kHz warble tone on Editor's Choice. With the PSB Alpha P5s the sound was sweetened, with a mellower top end than with the M10. Orchestral violins sounded lush. While the Luxman's low frequencies were richer, the passages where the double basses dig down in the third movement of Beethoven's Symphony No.4, with Simon Rattle conducting the Berlin Philharmonic Orchestra (24/192 WAV file, Berlin Philharmonic download, BPHR 160091), sounded thickened, less distinct, with the tubed Luxman compared with how they did with the class-D NAD. In addition, the low-powered Luxman was close to running out of power on climaxes with SPLs in the high 80s, while the NAD was still coasting at these levels.

Substituting the KEF LS50s for the inexpensive PSBs, the highs remained sweeter than with the NAD but the lows acquired a touch more authority. The double bass on "Autumn Leaves" from Cannonball Adderley's classic Somethin' Else (24/94 ALAC files ripped from the Classic Records DVD reissue, DAD1022), which sounded a little dry on the NAD, was warmer with the Luxman. Stereo imaging was equally well-defined with both amplifiers driving the KEFs, but the solo woodwinds in the mysterious opening of the Beethoven symphony's first movement were clearly set farther back with the NAD. This is the opposite of what I would have expected, given the prevailing meme that tube amplifiers offer excellent soundstage depth.

I enjoyed the two days I spent living with the Luxman SQ-N150. It offers the virtues of a classic tubed amplifier without any of the vices, other than restricted maximum power. Overall, however, even without considering its digital and network functionality, NAD's M10 offers a more neutral tonal balance, greater transparency, and as much power as I would ever need with the speakers I choose to use.

Conclusions
NAD's Masters Series M10 may be small, but don't let that fool you. Hidden within its unassuming exterior are a powerful, transparent, clean-sounding amplifier, a versatile streaming DAC, and the ability to optimize the sound of its owner's preferred speakers. Voted EISA's "Smart Amplifier of 2019–2020," the M10 was described as "a true master of modern music playback." Amen to that sentiment: Other than a pair of loudspeakers, the relatively affordable M10 offers everything serious audiophiles and music lovers need to enjoy their music.

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Footnote 2: Peculiarly, although the M10 is specified as being able to play DSD data, when I copied the DSF files to a USB thumb drive and plugged it into the M10's rear-panel port, the files weren't recognized, even though all the hi-rez PCM files on the drive were identified as such and could be played with the BluOS app.