Reviewer: Chip Stern

Source: Linn Unidisk 1.1 universal disc player [on review]; Upscale Audio Ah! Njoe Tjoeb 4000 vacuum tube CD player (in 24/192 Super Tjoeb configuration); California Audio Labs CL-20 DVD-CD Player; California Audio Labs Delta transport/Alpha 24-bit/96kHz vacuum tube DAC; Rega Planar 25 turntable with Rega RB600 tone-arm and Grado Statement Master cartridge); Marantz PMD430 portable cassette player/recorder
Preamp/Integrated: VTL 5.5 vacuum tube preamp; Rogue Audio Stealth phono preamp; Manley Massive Passive; Rogue Audio Magnum 99 vacuum tube preamp; Musical Fidelity Nu-Vista Pre-Amp; Sim Audio i-5; Mesa Tigris; Linn Classik
Amps: Musical Fidelity Nu-Vista 300, Mesa Baron
Speakers: Joseph Audio RM25si Signature Mk2 & RM7si Signature Mk2; Dynaudio Special 25 [on review]; Meadowlark Swallows [on review]; Epos ELS-3 [on review]
Cables: Acoustic Zen Silver Reference II interconnects; active-shielding equipped Synergistic Research Designer's Reference2 X-Series interconnects with mini-power couplers; active-shielding equipped SRDR2 Solid-State Reference speaker cables; Audioquest Panther interconnects and CV-6 speaker cables; Monster Cable Sigma Retro Gold interconnects and speaker cables; JPS Labs Superconductor II interconnects and speaker cable; JPS Labs Aluminata, JPS Labs Kaptovator Acoustic Zen Gargantua II and active-shielding equipped Synergistic Research Designer's Reference2 AC cords
Stands: Two PolyCrystal equipment racks, a PolyCrystal amp stand and PolyCrystal speaker stands
Power line conditioning: Equi=Tech Q650 and 2Q Balanced Power Systems; Monster Cable AVS 2000 automatic voltage stabilizer
Tweaks & Accessories: JPS Labs Kaptovator outlet center; Mondial Magic-Splitter; NEC CT-2070S monitor; Ringmat 330 and Signal Guard II isolation stand (turntable); Shakti Stones (electromagnetic stabilizers); PolyCrystal cones; Argent Room Lens; Echo Busters Bass Busters and absorptive and diffusive Panels.
Room size: 14' x 20' x 10', long-wall setup
Review Component Retail: $6,995

Consumer by Proxy
As a man of far too many words, it generally takes me a month of Sundays to prepare my approach to the runway. I clear my throat and gear up a garish array of metaphorical ordinance for a final full-Monty assault on your aural sensibilities. However, every now and then a piece of gear comes along which, from the outset, makes its presence felt in a most positive manner. It chugs along in a genuinely authoritative way sans glitches and complications. Thereafter, it proceeds to get nothing but better. You listen, you linger. You ponder and compare. You drive it non-stop for weeks on end, then let it ice down for equally extended periods of time. You wait for the other shoe to drop - something to mess up, something to reveal a kink in its armor. Then you eventually realize that you have no second thoughts, no major reservations, no compunctions about recommending it to friends and strangers alike. You linger some more just to revel. Finally one just kind of sighs, writes it down, packs it up and kisses her goodbye.

The McCormack DNA-500 power amplifier is just such a product - a total high-end slam dunk, an utterly authoritative performer with a warm, supple sense of detail and sufficient reserves of power to drive any set of loudspeakers to full live music scale with an inviting sense of ease and intimacy. And like Old Man River, it just keeps rolling along. Have we piqued your curiosity? Oh, but you're confused? Isn't 6moons that patron site of modestly empowered, lush-sounding single-ended triode amplifiers? Verily, don't Srajan Ebaen's initials simply scream SE? Ooooh, freaky. Coincidence? I don't think so. Aren't solid-state power amps politically incorrect, aesthetically wanting? Hardly - kindly refer to brother Ken Micallef's 6moons review of the Duevel Shuttle Integrated elsewhere on this site.

Hey, vive la différence. It ain't about the meat in the fleet but the motion in the ocean. It's about involvement with the music. It's about personal taste. It's about system synergy. Because audio reviewers often function as consumers by proxy, we're encouraged to obsess over individual pieces of gear, to delineate and describe every little nuance, to proclaim a hierarchy of performance parameters. But for any of us to simply impose our own tastes on readers seems rather narrow to me. We're supposed to set the stage for your own sonic investigations, your own audition process.

So, I'm not here to tell you that high-powered solid-state amps rule and SET amps are jive. That's poppycock. I am here to tell you that there are a lot more audio options available between heaven and earth than were imagined in your philosophy, Horatio. Remain open to a world of different possibilities. Don't get hung up on chat room snobbery or the received wisdom of others - myself included. Listen and learn. Contrast and compare. Develop your own reference points.

Anyway, end of rant.

As for the McCormack DNA-500 itself, its particulars and pedigree? Read on. If, however, you're too busy to rummage through a lengthy, unabridged Chip Stern audio review at this time, stop here. As a public service, we'll attempt to telescope our cumulative emotional responses, musical impressions and base conclusions into one single sentence: "Fuck me - what a terrific amplifier!" [While I'm not sure this will ever make it into the top-10 list of most-used quotes, it is rather conclusively descriptive. And do we intuit an innate sense of mischief already in Chip's earliest surviving mug above? Must be that New York air. It liberates the tongue - Ed.]
A Bridge To Tomorrow
In the process of simultaneously auditioning a number of different components, I devoted several months of listening time to the DNA-500 in a variety of systems. And while I had developed a very strong set of impressions, there was practically no technical information available on the amplifier save for a paltry sampling of specs on the website. Considering how well-engineered and cost-effective (by audiophile community standards) this amp is, I thought it important to give readers more in-depth information regarding the DNA-500's design.

So inspired, I had a very pleasant phone chat with the estimable Tor Sivertsen of Conrad-Johnson, the fabled high-end company that owns McCormack Audio Corporation of Virginia; and company namesake and chief designer Steve McCormack, speaking from his SMcAudio offices in Vista/California (about twenty miles outside of San Diego). Shortly thereafter, Steve was inspired to follow up with a brief white paper that touched upon some technical considerations we hadn't yet covered. As a result, I can now share some insights into the sonic goals and design considerations that informed the creative process during the development of this high value/high-performance solid-state power amplifier.

At a suggested retail price of $6995, the DNA-500 is conservatively rated at an imposing 500wpc into an 8-ohm load and 900 watts into 4 ohms. Based on my experience with some Japanese Godzilla amps over the years, I was charmed to discover that the relatively modest physical dimensions of the DNA-500 belie its muscle amp pedigree and powerhouse performance while reflecting the real-world aspirations of its designer.

My initial impressions of the DNA-500 were most serendipitous. In terms of pure practicality and while indeed hefty, it wasn't an utterly backbreaking hump. "Geez," I thought to myself, "I can actually lift this up and move about without having to abandon all thoughts of ever conceiving children again." At a shipping weight of only 81 pounds, I reckon it weighs in at roughly 75 pounds by its lonesome. That would constitute the heat sinks alone on some of those old dreadnought Krells. At only 19" x 6.75" x 20.5" WxHxD, the single-chassis DNA-500 should fit comfortably on the lower rack of most normal equipment racks. Better yet, because the amp outputs such a surprisingly modest degree of heat, you don't have to be quite as concerned about maximizing ventilation space (within reason, of course) as you might with some other amps.

"In the context of its power rating, how I can achieve this size and weight factor
while still delivering this type of power is because unlike previous DNA designs, the DNA-500 is a fully differential/balan- ced amplifier from input to output," McCormack explains. "Speaker drive is thus differential or push-pull as well. We combine two complete amplifier sections per channel, each of which is driven from an input phase-splitter. (The incoming signal is split into a pair of opposite-polarity waveforms, each of which drives one section of the amplifier pair.) In most conventional amplifiers, the speaker is connected to a single positive output and ground. In the DNA-500, the speaker is connected across a pair of positive outputs of opposite polarity, thus driving the speaker in push-pull mode. This arrange-ment delivers a degree of speaker control that is not possible otherwise.

Having experimented extensively with this design approach over the years, it has come to be my favorite method for producing high-performance amplifiers. It creates what is often referred to as a bridged amp. There are four independent amplifier channels, two per side, each channel pair in bridged/balanced configuration to double the voltage over a conventional amplifier. An ordinary 100-watt stereo amplifier in bridged mode will net you a 400-watt amplifier if the power supply can process the current. That's the principle of how the DNA-500 works."

"Many audiophiles feel that such a bridged-style amplifier design is a bad approach. Their prejudice is based on past experiences with stereo amplifiers that were switchable into bridged mono. These amps often had poorly designed input phase splitters and were not optimized to handle the reduced load impedance in bridged mode. The result was often compromised audible performance, instability, overheating, blown fuses and more than a few damaged amplifiers. It's no wonder that bridged amps have acquired such a bad reputation. However, the DNA-500 demonstrates that this need not be the case." [The Bel Canto Design eVo 4 in bridged mode operates likewise in differential fashion. The universally noted sonic improvement over non-bridged performance well beyond the raw power increase is due to exactly this bridged/balanced push-pull speaker drive - Ed.]

"The DNA-500 is a Class A/B amplifier that's biased fairly rich. Because I don't have to use extremely high voltages, it runs only warm at idle and I don't need a huge amount of heat sink surface area. If it were pure Class A, I would have had to use a huge heatsink to dissipate all that continuous heat. The heat sink in the DNA-500 is actually quite generous and can handle extreme operating conditions, including very low-impedance speaker loads."

Practical considerations notwithstanding, what really cements the DNA-500's bang-for-the-buck appeal is power. Lots of power. Smooth, clean, quiet and dynamic power with acres of headroom and the kind of transient speed and limitless reserves of current necessary to drive even the most demanding loads to realistic concert levels. And it does so not merely with the kind of visceral impact and physical immediacy we readily associate with big Rock venues and large-scale orchestral gestures. It does so also with a graceful sensation of elegance that allows the subtlest instrumental textures and acoustic details to glow in the dark as it were. Even without a subwoofer, the entire system seems to float.

"The 500-watt rating is rather conservative," asserts McCormack. "The DNA-500 actually delivers closer to 600 watts into 8 ohms, which will double into 4 ohms assuming you can provide enough electrical power from your wall outlets, something that is actually rather difficult to do at that point. The design follows the general circuit architecture I have preferred from the beginning: A JFET input stage feeding a MOSFET driver stage which controls a bipolar output stage. The bipolar outputs provide the sort of muscle and control I want while the FET driver circuit secures the smooth, liquid musicality we all desire. I also employ a small amount of global negative feedback, about 6dB worth, without which the amp takes on a kind of unruly quality."

"The overall topology is a fully symmetrical push-pull layout. And because bipolar transistors do not overload smoothly, my circuit design is arranged such that in the unlikely event of clipping, the MOSFET driver stage will overload before the output stage does, thus conferring a smooth overload characteristic to the amplifier. As you know, MOSFETS clip very gracefully and in a rounded way
very similar to a tube amplifier." "Bipolar power transistors in the output stage will also give you tighter bass," Sivertsen chimes in, "because the output impedance is lower and therefore the damping factor is higher. You initially boost the incoming voltages and convert them into current in the gain stage, then the driver stage takes that current and passes it along to the output stage - which is why Steve's use of J-FETS and MOSFETS in the gain and driver stages makes so much musical sense. J-FETS and MOSFETS display a more pleasant style of overload characteristics, with more even-order harmonics. That is a very good combination in an amplifier. It removes much of the edginess but produces fast, deep and controlled bass."