Solid State Power Amp Reviews

The No.431's dual-mono design means that the amp has a separate power supply for each channel. Each power supply includes a low-noise, 660VA toroidal transformer and two triple-bypassed, low-equivalent-series-resistance 24,000µF, electrolytic capacitors. Heavy bus bars of oxygen-free copper and high-frequency power-supply bypass components are used to lower the No.431's power-supply impedance. The amplifier can draw 15 amperes at 120V from the mains when driving a 4 ohm load to its full power rating of 400Wpc.

A turn-on circuit prevents sudden thumps and damage to components from the inrush of current as the power supply's large filter capacitors charge, and extensive protection prevents internal or external component failure. The latter includes servos to block DC at the output, and a circuit that shuts down the amplifier if the temperature of its heatsinks or power-transformer cores exceeds 85ºC or if a sustained current draw exceeds 15 amperes. The voltage-gain stages are fully balanced, using independently regulated supplies, while each output stage uses five pairs of matched, complementary TO-3P bipolar output power transistors. These are clamped to the heatsinks with an aluminum bar. Soft-clip circuits prevent the output devices from saturating, so that the high-energy, high-frequency artifacts generated by hard-clipped output transistors don't damage the loudspeakers.

The No.431 enjoys the same fit'n'finish, tank-like internal construction, and superior component quality found in the Mark Levinson's reference monoblock amplifier, the No.33H. The No.431 comes with a five-year, nontransferable warranty, but it's built to last several lifetimes.

Setup
My lightly damped listening room is a rectangular space 26' long by 13' wide by 12' high. Behind my listening chair, the other end of the room opens onto a 25' by 15' kitchen through an 8' by 4' doorway. I set the No.431 between the speakers, which were 5' from the front wall and 3' from each sidewall.

I attached the spade lugs of my Pure Silver Cable speaker cables to the No.431's speaker binding posts, which are widely spaced to meet European CE regulations, and tightened the connections between speaker cable and amplifier using the large, curved, plastic wing nuts attached to the amplifier's speaker terminals. I plugged into the wall the amplifier's detachable power cord, pushed and released the Power button, then pressed and released the front-panel Standby button. Although the No.431 went into Standby mode, it then refused to turn on. After multiple attempts, I did what every red-blooded American does when faced with a technologically challenging device: I carefully but forcefully punched the top plate. Voil! I pushed the Standby button and the No.431 powered up. I e-mailed Andrew Clark of Mark Levinson, who rushed a second No.431 to my listening room. The new sample turned on immediately, and has continued to work without a hitch.

Sound
Driving my Quad ESL-989 loudspeakers, the No.431 sounded smooth and delicate, with open, extended highs. Just like the No.334, it had midbass punch and the ability to throw a wide, deep soundstage. It exerted tighter control over the Quads' bass response than had the No.334, but sounded more analytic driving my Revel Ultima Salons, with less bass extension. In contrast, the No.334 sounded fuller and warmer through the Revels, darker through the Quads.

Driving the Revel Ultima Salons, the No.431 proved fully capable of reproducing full-volume percussion without compression. During the opening of "Tito," from Arturo Sandoval's Hothouse (CD, N2K 10023), Tito Puente's timbales were reproduced with tremendous speed and definition, so that I could easily make out the tonalities of the separate drums in his kit when he struck two different drum heads simultaneously. Through the Salons, the No.431 matched the Bryston 14B-SST in playing this demanding drum solo without compression or distortion.

But even with the exemplary headroom the No.431 gave the Salons, the Quad ESL-989s proved a better match overall. When I hooked up the electrostatic screens and started playing music, it was amazing how the soundstage widened, the highs became more extended, and bass became fuller, deeper, and better defined. Whether it was Tom Fowler's subtle but firm electric bass backing B.B. King and Ray Charles' duet on "Sinner's Prayer," from Genius Loves Company (CD, Hear Music/Concord CCD-2248-2), or Michael Annope's tight, driving plucked bass and Ruben Alvarez's bongos, which open "Use Me," from Patricia Barber's Companion (SACD/CD, Premonition/Blue Note/Mobile Fidelity 5 22963 2), each bass note's pitch was better defined than ever before. I was easily able to distinguish the bass-drum and timpani overtones when I listened to tracks 21–24 of Eiji Oue and the Minnesota Orchestra's performance of Stravinsky's The Rite of Spring (CD, Reference RR-70CD).

The Quads' distinct tone and pitch enabled me to hear deep-bass notes without adding a subwoofer, including: the distant drum pulses that provide the dynamic backdrop of "Silk Road," from I Ching's Of the Marsh and Moon (CD, Chesky WO144); the deep pedal notes in Jean Guillou's transcription for pipe organ of Mussorgsky's Pictures at an Exhibition (CD, Dorian DOR-90117); the taut, well-damped, stepped bass notes that open Oregon's "The Silence of a Candle," from Beyond Words (CD, Chesky JD130); and the step-like progression of sustained organ-pedal chords that provide the underpinning of John Rutter's grand chorus "The Lord is My Light and My Salvation," from his Requiem (CD, Reference RR-57CD).

Similarly, organ-pedal notes rose distinctly above the bowed double basses in Uranus, the Magician, from Walter Susskind and the St. Louis Symphony's remastered recording of Holst's The Planets (SACD/CD, Mobile Fidelity USACD 4055). I was entranced by the ghostly soprano set against rumbling subterranean synthesizer chords in "The Hit," from the Patriot Games soundtrack (CD, RCA 66051-2). However, with their limited low bass, the Quad ESL-989s could only suggest the subterranean vibrations depicting the entrance of the ghosts in the Casper soundtrack (CD, MCA-11240).

The No.431's midrange reproduced the brilliant palettes of orchestral tonal colors heard in Susskind's Planets—in Mars, the Bringer of War, and the full, rich timbre of massed strings in Jupiter, the Bringer of Jollity—and brilliantly depicted the timbre of the bassoon in Herbert Owen Reed's La Fiesta Mexicana, from Howard Dunn and the Dallas Wind Symphony's Fiesta! (Reference RR-38CD).

Driving the Quads, the No.431 projected a huge, wide soundstage and pinpoint, three-dimensional imaging, as well as an intimacy during the call and response of tenor and chorus in "Mary had a Baby," from Cantus' Comfort and Joy: Volume One (CD, Cantus CTS-1204). During "Silent Night" from the same recording, I was able to make out the central singer, standing in his own space, as the chorus sang ascending and descending scales behind him. Mary Gauthier's voice, too, stood alone on "A Long Way to Fall," from her Filth and Fire (CD, Signature Sounds 1273), her central sonic image standing three-dimensionally between the Quads.

The amplifier and speakers allowed me to track the variations in Ray Charles' voice across the 12 duets of his Genius Loves Company. He harmonizes and blends so effectively with Norah Jones on "Here I Go Again" that the pitch of her voice drops into his range. He sounds hip and sophisticated singing "You Don't Know Me" with Diana Krall, then steps up the drive and pace in "Sinner's Prayer," with B.B. King. In contrast, the ambience generated by the Turtle Creek Men's Chorus' spacious-sounding and detailed voices on "Lord, Make me an Instrument of Thy Peace," from John Rutter's Requiem, helped delineate the recording venue. Similarly, the No.431 conveyed the ambience and soundstage width of the soft backstage female chorus that ends Neptune, the Mystic, from The Planets.

And the highs? The No.431 and Quad ESL-989s had an extended, translucent, sweet treble that just didn't stop. This combo brought out the transparency and speed of Etta Baker's guitar playing on "Railroad Bill," from Etta Baker with Taj Mahal (CD, Music Maker/Cello CD50), and conveyed the glistening transparency of the bells and xylophone in Mercury, the Winged Messenger, from The Planets. I was transfixed by the glowing timbre of the reverberating chimes that open Reed's La Fiesta Mexicana, and swept away by the blend of the Spyboy Band's voices in "Calling My Children Home," from Emmylou Harris' Spyboy (CD, Eminent 25001 2), Harris' ethereal soprano floating above, translucent and serene.

Conclusions
Mark Levinson Audio Systems may have moved its production facilities but it continues to build fine amplifiers, even after having shrunk those amps to fit into home-theater equipment racks. Compared with its predecessor, this newest and smallest Mark Levinson amplifier has gained smoothness, has an increased ability to transmit musical information, and continues to generate some of the best soundstage imaging I've heard. Sure, there was a slight reduction in bass solidity and punch when the slim No.431 was compared with the massive No.334 through the Revel Ultima Salons, but there were also improvements in midrange detail and treble extension through the Quads. Mark Levinson amplifiers, once proudly massive chassis fierce with rows of sharp heatsinks, are now configured for sonic excellence while being slim enough to fit into two-channel and home-theater systems alike.