Yamaha MX-D1 digital power amplifier Page 2

The main virtue of solid-state is usually a well-damped bass. When properly executed, such bass has a punchy weight with enough textural subtlety to not sound "one-notey" and monotonous. Few tube amplifiers in my experience can match a good solid-state design's weight and control in the bass. Then again, few solid-state amps can match tubes' textural and harmonic performance in the same region. The best amps of each technology narrow the gap between the two, but still fall short of the other side's special strength. So partisans of solid-state and tubes stand their respective grounds, each extolling their side's virtues and ignoring its vices.

The Yamaha MX-D1 didn't sound stereotypically "digital"—in other words, it didn't sound clinical, cold, or two-dimensional. Nor did it sound harsh, mechanical, or edgy, as did the first few generations of CDs and their players. But it sure had a unique sonic fingerprint—one well buried within a musical presentation that was remarkably transparent and easy to live with.

What about the music?
The MX-D1 arrived while I was still auditioning the Verity Audio Sarastro loudspeaker (see review in the March 2005 Stereophile). I hooked up the amp and resumed listening to Classic Records' 200gm edition of Willie Nelson's Stardust, which had been sounding particularly stunning through the Sarastros. Now what I heard was a quite different rendering of that album, though not startlingly so. The first differences I noticed were more at the periphery than at the foundation of what constitutes effective amplifier performance.

Specifically, the system's overall timbral presentation had shifted slightly toward the cool—from the moderately golden to the somewhat platinum. Nelson's acoustic guitar exhibited more string and less body, and the sounds from his vocal cords and head were more emphasized than those seeming to emanate from his chest. Usually, that sort of presentation is accompanied by sharper transients and a tendency toward etchiness, but not here. In fact, transient presentation and image definition were subtly softer, which added up to an initial sensation of stupendous transparency and delicacy. Behind them was inky-black silence and noticeably prolonged decays of reverberations that at last gracefully disappeared into velvety nothingness. The MX-D1 also exerted great control over the Sarastro's woofer, and seemed to produce a somewhat cooler, leaner, less prodigious midbass that complemented the Sarastro's excess in that area.

As you might imagine, that sonic snippet from a new amplifier cold out of the box made me more than mildly enthusiastic about the MX-D1's performance.

The soundstages of familiar LPs and CDs were presented differently through the Yamaha than they had been through the Musical Fidelity kWs, the front of the stage beginning with the plane of the speakers' front baffles and arrayed in a somewhat flatter, less semicircular shape from left to right, especially in the stage corners. The MX-D1's soundstage could hardly be described as flat, however—it developed outstanding depth, with remarkable image clarity in the farthest corners on familiar recordings, as if a slight, almost invisible haze had been lifted.

This MX-D1 was subjectively quiet, producing some of the "blackest" backdrops I've heard—though its measured level of noise will be interesting, given its switch-mode power supply and PWM amplifier circuitry. Whatever remnants of the carrier frequency might be measurable, I couldn't hear them.

My review of the Sarastros completed, I replaced them with my Wilson Audio WATT/Puppy 7s and listened via the MF kWs until I'd reacclimated myself to the sound of my reference system. I then reinserted the Yamaha, which produced results similar to those it had with the Sarastros, and confirmed a particular characteristic of the amp that I thought I'd heard before.

I've been getting into Björk's Medulla (45rpm LPs, One Little Indian TPLP358; also available on hybrid and single-layer SACD and DVD-Audio). Built on electronically manipulated but well-recorded a cappella tracks, including mouth percussion, Medulla seems to have been mixed to give the impression of being a personal, internal dialogue on which the listener is eavesdropping. The album seems to flow directly from inside Björk's head to the listener's ears.

Like its dead-silent backdrops, the MX-D1's ability to project depth to the very corners of the soundstage helped deliver this sensation of seeing into a very private, mysterious world. After a half dozen plays I switched back to the kWs, which confirmed what I'd suspected was the MX-D1's single strongest character and fault: It had difficulty producing solid, focused images. What had at first impressed me as transparency and freedom from etch and hardness was really its inability to draw a focused line in the sonic sand and say, "Here is where the image has been drawn."

The other side of the fence—a worse problem typical of many budget solid-state amplifiers—is images that are too etched, too literal, too cardboard-cutout to be convincingly realistic. I'll take the MX-D1's imaging over the hard, etched variety any time—but why be forced to make that choice if you can afford not to?

Speaking of inner mind adventures, Cisco's recent reissue on 180gm vinyl of Joan Baez's In Concert (Vanguard VSD-2122), a favorite of mine when originally issued back in 1962, had me wondering where my 15-year-old head was at back then, to be able to sit transfixed through both sides.

Don't get me wrong: I still have a great deal of respect for Baez, who was all of 19 when this album was recorded. She sings in that angelic, impossibly high-pitched warble, with a ghostly vocal delicacy and purity that are nothing short of astounding. But the medicinally effete somberness of some of the proceedings can make the skin crawl. Still, Baez's eerie readings of the haunting ballad "Geordie" and Malvina Reynolds' "Clear Skies Initiative"—I mean "What Have They Done to the Rain?" (send in those letters!)— almost make up for a ghastly "Kumbaya."

The recording, possibly made at New York's Town Hall, is a fabulous Vanguard Stereolab job of stupendous transparency, clarity, dimensionality, and sense of ambient space. Through the Yamaha MX-D1, Baez's voice had a rich Merlot-like finish, with appropriately soft and delicate sibilants and a nice blend of body and head—but she just wasn't sufficiently in focus, not placed solidly enough on the soundstage, and therefore not as convincingly realistic as she should have been, or as this recording is capable of conveying. There wasn't enough "there" there. That lack of image focus and, especially, solidity—compared to a reference that, at $23,000/pair, costs more than five times as much—was the only serious shortcoming I could consistently find in the MX-D1.

That's not to say that the amp was otherwise "perfect" and without personality—no amplifier is. The MX-D1 will not appeal to every listener or be appropriate in every system, but it offers an attractive, well-balanced blend of qualities: nimble, extended, well-defined bass; an effervescent sense of rhythm'n'pace; a reasonably evenhanded timbral balance that fell on the lean side; and, thanks to its pitch-black noise floor, notably superior resolution of ultra-low-level detail. Even so, the bass focus was not all it should have been, which meant that image solidity suffered, and sometimes the bass became a bit woolly and just too big.

But music breathed freely through the MX-D1, thanks in part to its vast reserves of power and ultrawide dynamic range, which it expressed with ease at both ends of the scale and in between. Still, just as a tube amp will sound and feel different from a solid-state one, the MX-D1's unique sonic signature may or may not be explained by its measurements. Most important, when I listened to LPs, the MX-D1 didn't make me think I was listening to "digital."

The Yamaha MX-D1 offers enormous reserves of power, low distortion, wide dynamics, bandwidth that's almost "DC to light" (well, 1Hz–100kHz, anyway), and, subjectively at least, ultra-low noise—all in an attractive, compact, cool-running package. Unlike early, anemic-sounding switch-mode power-supply amplifiers that promised power on the test bench that they couldn't deliver to a pair of actual speakers, the MX-D1 never seemed to run out of gas. Whether or not this was due to Yamaha's Active Power Control System, the MX-D1 always sounded ready to deliver more power if needed—at least driving the two high-efficiency speakers I used. I would have liked to have heard it with the 81dB-efficient mbl 101s.

The MX-D1's problem with image focus was essentially a "passive," continuous fault that was noticeable in direct comparisons with a reference costing more than five times as much, but was easy to ignore over the long haul. Otherwise, the Yamaha proved an attractive performer with a well-balanced, spacious, thoroughly musical presentation. If its faceplate didn't say "digital" and it was built on a larger chassis with a boat anchor of a power-supply transformer, no doubt more audiophiles would pay attention to this intriguing product. But even if you're a diehard vinyl fanatic, if you like and need power, the MX-D1 is definitely worth a listen.

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georgehifi's picture

"so to examine the MX-D1's performance at low signal levels, I used an active sixth-order low-pass filter with a 20kHz bandwidth and a floating input."

Wow, with this almost brick wall filter territory at 20khz on it's output and you can still see the switching noise embedded in the square wave. https://www.electronics-tutorials.ws/filter/fil57.gif
Would have been eye popping to see it au naturel, an unrecognizable square wave most likely

"so I caution readers (and Yamaha) not to take the specific graphs as representing anything more than broad-brush pictures of the amplifier's behavior."

Pretty useless having these graph shots if they don't represent what coming out of the output of these Class-D's for readers to see what being fed to their speakers.
There never used to be a problem measuring with the AP gear showing the results without filter when Class-D was first being measured, like with the Anthem M1 Class-D

Cheers George