NAD 218 THX power amplifier
By Robert J. Reina   •   August, 1999 The story of New Acoustic Dimensions, aka NAD, begins in the late 1970s. The company was founded as a dealer distribution collective to design and market reasonably priced serious high-end gear to cost-constrained audiophiles. By eliminating needless features and focusing manufacturing in low-cost production facilities, NAD has successfully delivered audiophile-quality gear for 20 years at prices little more expensive than mass-market department-store schlock.

As the owner of three pieces of NAD electronics at various times over the last 15 years, I've been impressed with the character and the consistency of the NAD sonic signature: a tuneful and dimensional sonic presentation with a balanced palette of shortcomings that, being subtractive and euphonic, have been consonant with the musical experience.

Serious design
The 218 THX—designed in the UK and manufactured in China—is the flagship of a series of high-powered basic stereo amplifiers that represent a new design approach for NAD: the marriage of massive power supplies with an amplifier design consistent with the company's traditional goals of performance and affordability. A Holmgren toroidal transformer coupled with a bank of multiple small reservoir capacitors (as opposed to a small number of large ones) endows the amp, claims NAD, with a very low source impedance and the ability to respond very quickly to repeated demands for current. The 218's input/driver stages (operating in pure class-A supplied by its own independent power supply) use current-mode feedback to achieve wide open-loop bandwidth. Three Panasonic output devices are used in parallel for each half of the complementary output stage. There is a servo for DC offset, and the only capacitor in the signal path is a selected film type at the input.

The 218 THX features balanced and unbalanced inputs; via the former, it passes THX certification requirements for power output and input sensitivity. There is also the ubiquitous NAD "soft clipping" button, which the company effectively calls the "party switch." When the switch is engaged, the amplifier filters out the high-frequency edges that squarewaves produce when the amp goes into clipping, and thus protects the speakers from excessive HF energy. During my listening sessions I noticed no difference in sound when this switch was engaged, but as the amplifier puts out 225Wpc into eight ohms (780W when bridged for mono operation!), I'm certain I never approached its rated power limit, even during high-volume peel-the-paint-off-the- tests.

Speaking of current-delivery capability...when I first hooked up this amplifier to my main reference system, I didn't realize that the unobtrusive power switch on the front panel was engaged. As I began to gently plug in the unit's AC cord, a bolt of bluish-gray lightning shot from the outlet into the cord, causing this stunned reviewer to drop the cord and recheck the faceplate of the amp. Nope, it still said NAD, not Krell.

Serious sound
A THX-certified amplifier of this power rating for $1099 is impressive indeed, but how did it sound? On first turn-on, NAD's trademark tonal balance was immediately recognizable: a rich, tubelike, dimensional presentation, most of whose flaws were euphonic or subtractive, and consonant with the musical experience. On well-recorded vocal works, all voices, male and female, had a rich, supple palpable quality, much as one would expect from a more expensive tube amplifier. On Bill Berry's For Duke (M&K Realtime RT-101), the trumpet was reproduced with the requisite blend of blat and burnished metal. The tenor sax solo on "Take the A Train" was naturally throaty and chesty without seeming colored.

As the program material ascended the frequency scale, the NAD began to lose its hold on definition. The highs were not rolled, dark, or distorted, but there was a noticeable if gradual loss of detail resolution as the frequency climbed. On Charles Wuorinen's percussion extravaganza, Ringing Changes (LP, Nonesuch H71263), the NAD's high-frequency deficiency did not detract from the realism of the drums—there was just a relative lack of information when compared with other amplifiers' renditions of this track. With less information conveyed, it was more difficult to unravel the subtleties of this complex work.

The thick, overripe midbass I noted in the 218 THX was reminiscent of every NAD amplifier I've heard since the original 3020 integrated. The double-bass sections of orchestras sounded overly prominent, and rock and blues recordings with generously mixed bass guitars suffered from a bit of overhang in the 80-100Hz region. This would not be an issue were the 218 THX an inexpensive NAD integrated—in fact, it may be overly kind to some bass-shy bookshelf speakers—but on a highly revealing system with full-range loudspeakers, the NAD's midbass performance emerged as its greatest weakness.

The 218 THX's biggest surprise emerged from beneath the midbass: the tightest, most dynamic and explosive bottom octave and a half I've heard from any amplifier I've auditioned in my house. On both pairs of my Alón speakers, the amps were causing the woofer cones to bottom out on "These Hands," from Janis Ian's Breaking Silence (Analogue Productions APP 027). So after the initial shock had worn off, I began mining for bass.

Grandmaster Flash and the Furious Five's The Message (Sugar Hill SH 584) had the requisite slam and room-shaking authority at 105dB. Naked City's Absinthe (Avant 004), John Zorn's take on electronic ambient music, has one track, "Artemisia Absinthium," most of whose musical information lies beneath 50Hz. After careful adjustment of the volume (this CD can easily cause speaker damage at too high a level), the effect was much like that of a number of subway trains running through my basement.

Aside from its midbass performance, the 218 THX had no particularly severe shortcomings. On all recordings I tried, soundstage delineation was realistic, with very good articulation of transients and good pitch definition. High-level dynamics were also fairly impressive. However, aside from its low-bass performance, there was no area of performance in which the NAD particularly excelled. Most important, its ability to resolve detail was acceptable but not especially noteworthy. This detracted from the amp's ability to unravel subtle microdynamic inflections and ambience cues. Moreover, during complex orchestral works like Messiaen's Turangalîla Symphony (LP, EMI 63-02 974), although the amp neither ran out of power nor congested, its ability to resolve low-level details diminished. Finally, during long-term listening sessions, the amp's articulation sounded a bit mechanical, particularly on rock and jazz recordings with significant transient information.

If I sound as if I'm being particularly hard on the 218 THX, it's because I addressed its absolute performance level using a much more revealing system than this amp is ever likely to be paired with. I do like the 218 THX very much; when its price and power rating are taken into account, it's an absolute bargain.

But when does the typical audiophile looking to spend $1100 on an amplifier really need 225Wpc? Wouldn't he or she be better off spending less money on a lower-powered NAD amplifier, and spending the savings elsewhere in the system?

NAD's Greg Stidsen doesn't think so. He believes the NAD 218 THX performs better sonically than its less expensive brethren partly because it remains in class-A mode up to 10Wpc, as compared with other NAD amps' lower thresholds. This makes sense; one of the reasons I like the high-powered Audio Research Reference 600 and Sonic Frontiers Power 3 amplifiers so much is because they never sound as if they're working very hard. A sense of ease will usually enhance the naturalness of sound reproduction.

Serious competition
I compared the NAD 218 THX to its direct competitor, the similarly priced and powered Rotel RB-991 amplifier that I review elsewhere in this issue, as well as to my reference Audio Research VT100 Mk.II amplifier. The Rotel made for an interesting comparison; it and the NAD are both extraordinarily competent audiophile components that represent good value, but they sound quite different.

The NAD was soft, rounded, almost tubelike, with extraordinary dimensionality and consonant euphonic flaws in its thick midbass and lack of high-frequency resolution. The Rotel was the more neutral and analytical of the two, with an extended and slightly prominent high-frequency response. Although the Rotel's bass was superb, it couldn't match the monster NAD in the bottom octave. However, the Rotel exceeded the NAD in its ability to unravel inner detail and subtle ambient cues.

Your choice will depend on your taste and system. The NAD was much easier to listen to over the long haul, but didn't go out of its way to impress. The Rotel, however, was quite impressive on first listen, but extended listening to source material with problematic high frequencies could become fatiguing. Neither was a match for the $5000 VT100 Mk.II, however; the ARC trounced both with its resolution of detail, neutrality, delicacy, ease, and lack of mechanical character—as it should at $5000.

Serious bread—not!!
The NAD isn't perfect, but it's an extraordinary performer for its price and power rating. In the right system with the proper matching equipment, it can provide long-term high-end listening enjoyment. But does the typical purchaser of an $1100 amplifier need 225Wpc? One should ignore the power rating and judge the product on its sonic merits. It's one of a handful of products that establishes a new benchmark for high-powered, low-cost audiophile performance, and could be the perfect amplifier for someone searching for a good amp in the $1500-$2000 range (the $1495 Classé CA-100 I reviewed in December 1997 also comes to mind) but is running short of cash. With the NAD 218 THX, such a purchaser can have his cake and eat it too.