It’s said that a boy does not truly become a man until his father dies. I can’t confirm the truth of that adage -- my own father is alive and well -- but I’ve found that certain life-altering experiences have triggered new levels of responsibility, capability, and growth. I felt more a man after marrying my wife 15 years ago, and even more when my children were born. I suspect that when my parents shuffle off this mortal coil, another era of manhood will begin for me.
Having been imbued with a set of core characteristics by founder William Zane Johnson, Audio Research Corporation was raised well, and was ready to live on its own when its progenitor approached his end. Many hi-fi manufacturers -- even some industry stalwarts -- begin, thrive, and ultimately die while still riding on the shoulders of their founders. Not so ARC. Few companies in high-performance audio have a longer history or a greater pedigree. Johnson retired in 2008, handed over the reins, and set ARC free. He died in late 2011.
It’s my opinion that the changeover sparked a period of invigorating challenge and exploration that has borne exceptional fruit, the most impressive evidence of which was the Reference Anniversary Preamplifier, aka the Ref 40 ($25,000 USD, when available during the company’s 40th anniversary year of 2011). Special Editions of the Reference 5 preamplifier and Reference Phono 2 phono stage incorporated lessons learned from the Ref 40, and ARC’s earlier line of Reference 110, 210, and 610 power amplifiers have been replaced, respectively, by the Ref 150 stereo and the Ref 250 and Ref 750 monoblock models. Common to all are greatly enhanced power supplies, Teflon output capacitors, upgraded internal wiring, and other surgical changes. The improvements in the preamplifiers have been startling, taking class-leading sound to a new level, based on my firsthand experience with and daily enjoyment of the Ref 5 SE and Ref Phono 2 SE, which I bought for use in my large reference system. I was excited to see if the same would hold true for the power amplifiers. With my system’s need for monoblocks, a set of Reference 250 amplifiers ($25,990/pair) was the natural place to begin my explorations.
Two out of three
The Reference 250s arrived in two very large (about 25” square x 15”H), heavy (about 90 pounds each) boxes. As I’ve come to expect from ARC, the double-boxed packaging has a white outer skin emblazoned with the declarations “There Is Only One Reference” and “High Definition.” After 40-plus years, I guess ARC has earned such confidence. Between the inner and outer boxes is a six-sided cushion of Styrofoam; the inner box further protects its contents from damage with closed-cell foam supports and a heavy-duty poly bag.
What was unexpected was a somewhat smaller third box -- unexpected but not a surprise, given that each Ref 250 requires 11 tubes. In that one box, and for each of the two amplifiers, were three matched pairs of KT120 output power tubes, one matched pair of KT120 drivers, two 6H30 gain-stage and regulator drivers, and a 6550C regulator. The total 22 tubes were extremely well protected, and labeled for proper and unconfused installation.
After I’d unpacked each 77-pound amplifier, it was time to read through the succinct instruction manual and make repeated use of the included screwdriver. While the typical customer should expect the dealer to personally deliver these amps, install the tubes, and connect the works, reviewers must fend for themselves. This was more tedious than difficult -- about 20 screws secure each amp’s clamshell cover. Luckily, each clearly marked tube (thank you, Sharpie) corresponded exactly to its waiting socket, as illustrated in the guide.
One benefit of performing such an installation is the intriguing tour of the Ref 250’s interior it compels. Seeing the high-quality circuit-board material (a dark tan substance known throughout the industry for its superior mechanical and dielectric qualities, not the ubiquitous green fiberglass) and elegant circuit traces, the distinctive transformers that dominate the center line, the banks of large KT120 output tubes and similarly oversized Teflon output capacitors to the left, and the fields of power-supply devices at front right and hugging the back of the faceplate (to cram in some 900 joules of storage capacity), no one need ask, “Where’s the beef?”
After installing the tubes, replacing the covers, and schlepping the amps onto the HRS M3 platforms just vacated by my Ayre Acoustics MX-R monoblocks, it was time to size up the ARCs. The Ref 250 is large -- 19"W x 8.75"H x 19.5"D, plus another 1.5” for the handles -- especially compared to the very compact MX-Rs. The review pair came in the same black, brushed-aluminum finish of my Ref preamps. The twin handles on the faceplate are also black. The more common ARC combo of natural aluminum faceplate and handles is also available. Overall, the look is masculine, in an updated retro style I thought was cool. Nevertheless, and no matter how much my wife loved the sound, she repeatedly teased that the Ref 250s reminded her of the Hatch on Lost, and asked if she, like Desmond Hume, was expected to press a button every 108 minutes to avert catastrophe.
The front panel is dominated by a large analog power meter, which displays the Ref 250’s output in logarithmic fashion, in decimal-place increments from 0.0025W up to the fully rated 250W of power. Below this are indicators used in connection with biasing the output tubes, and below those is a row of five circular, contrasting silver buttons labeled (from left to right): Fan, Light, Power, Bias, and Meter. Because the Ref 250 is a tube design, it has no Standby button. The output tubes should last at least 2000 hours, but given the fact that two Ref 250s use a total of 22 fairly costly tubes, many in matched sets, and throw off a lot of heat -- each pulls 770W of 120V juice at rated output, 1000W at maximum -- I turned them on only when I was playing music; otherwise, they were shut down.
The Ref 250’s rear panel is relatively sparse. At lower left is a 20A IEC receptacle, ready to receive the included, heavy-duty power cord (its standard three-pin connector plugs into the wall or a power conditioner) or appropriate aftermarket cord, such as the excellent Shunyata Research Cobra CX I primarily used. To the immediate right are the fuse and two 12V triggers for remote turn-on. At top right is the single, balanced, XLR signal input. At bottom right sits an array of four binding posts for speaker cables terminated with spades, bare wire, or banana plugs, providing output taps for 4-, 8-, and 16-ohm speaker loads. With the Vandersteen Sevens in my main rig and the review pair of Magico Q1 speakers in my compact reference system, the 4-ohm tap was the proper choice. Between the XLR input and the binding posts, directly behind the bank of output tubes inside, is a two-speed whisper fan. I left this set to Low throughout my wintertime review period and never once heard it from my listening seat during music, regardless of volume level.
Knowing that ARC products require several hundred hours of active duty before revealing their full potential, I was pleased to see that each monoblock arrived with almost 300 hours of play under its belt. My practice was to bring the beasts to life about 15 minutes before getting down to business -- time enough to clean three or four LPs with Audio Desk Systeme’s remarkable Vinyl Cleaner, in preparation of an evening’s enjoyment. The Reference 250’s specifications read like a wish list: continuous power output of 250W from 20Hz to 20kHz; 1kHz total harmonic distortion typically 0.5% at 250W, and below 0.04% at 1W; power bandwidth of 5Hz-70kHz, -3dB; frequency response of 0.5Hz-110kHz, -3dB with 1W output; input sensitivity of 2.4V RMS balanced for rated output (25.5dB gain into 8 ohms); and input impedance of 200k ohms, balanced.
With such sterling specifications and only 8.8dB of negative feedback, I expected powerfully dynamic, wide-range sound. That is what I heard. A far cry from single-ended-triode or tube amps of yore, the Ref 250 put to rest the claim that tubes are all midrange, either too syrupy or too sunny and bucolic. Compared with the Ref 210 it replaces, not only does the Ref 250 employ a complement of the more authoritative KT120 tubes (with analog circuits optimized to match), but while their rated power output represents nearly a 20% increase over the Ref 210’s, the power supplies those tubes modulate have increased almost 50%. Perhaps that’s why the snap and authority on tap trounced every other tube amplifier with which I’ve had long-term experience. With these amps, my system captured all the glory of Louis Armstrong playing “St. James Infirmary,” from Satchmo Plays King Oliver (LP, Classic Collection/Classic Records ST-91058) -- from his chesty, inimitable voice to the explosiveness of his trumpet at full cry.
Dynamic, yes, but deftly controlled. When masters lay down live tracks in a tight ensemble, a smoldering tension exists as each musician’s individual abilities are reined in to benefit the whole. The phrase “magic in a bottle” is often used to describe the electricity captured in certain sparkling session recordings. It can similarly apply to the Ref 250s. With Lee Morgan’s Tom Cat (LP, Blue Note/Music Matters BST-1058), this effect was on constant display. Morgan’s sextet unites a veritable who’s who of the mid-1960s hard-bop scene. Side A is dedicated to “Exotique,” an original Morgan composition that showcases the caliber of each band member via breakout solos, the narrative baton passed from player to player in the middle portion of the track. Those moments of individualism underscore just how much collective creative power is toeing the knife’s edge of this music. It’s dynamite, but fully realizable only with superlative playback gear matched to perfection. With the Ref 250s commanding my Vandersteen Sevens, there was never a question that Tom Cat is one of Morgan’s crowning achievements -- made in 1964, when he was only 26. The control and authority of the Ref 250s amazed me.
Recognizing that, with their powered subwoofer systems, my Vandersteen Sevens don’t punish amplifiers in the current-sucking bass regions below 100Hz, I installed the Ref 250s in my compact reference system while the Magico Q1s were in the house. This was an explosive pairing. I pounded the system with low-frequency torture tracks, but it never gave up, even at ridiculous sound-pressure levels. Not only was the bass prodigious, but the lightning-like control of the Q1s’ sealed enclosures and pistonic, Nano-Tec drivers were upheld by the ARCs’ powers of definition, neutral tonal balance, and accurate timing. From the attack, swell, and decay of timpani in orchestral climaxes, to the explosion of fundamentals and harmonics of plucked double bass, to drum kits and synthesized dance beats, the Audio Research monoblocks always had the Magicos under full control and ready to boogie.
Solid-state vs. tubes
With a pair of Ayre MX-R monoblocks ($18,500/pair) in each of my reference systems, the tubes vs. solid-state cook-off should have been a snap. Yet in many heats, determining a victor was a matter of mere degrees. Each contender met the strengths typically ascribed to the other’s topology. As indicated above, the Ref 250s hit all the marks for attack, control, and pace for which the best of solid-state is known. On paper, and at 250W into 4 ohms, the Ref 250 is well shy of the MX-R’s 600W power output into the same load -- yet, apparently due to the robustness of their power supplies, the ARCs never left me wanting. With some densely layered, heavily produced studio fare, such as the discordant, unsettling score of The Girl with the Dragon Tattoo -- “composed, arranged, performed, programmed, and produced” by Trent Reznor and Atticus Ross (CD, The Null Corporation 002) -- the Ayres may have squeezed out a victory on points in terms of keeping everything sorted. Yet, if forced to choose, and wherever a recording captured whole a group of musicians actually playing together at the same time in the same room (not separately, or in bits and pieces), I routinely found the Ref 250s a skosh more pleasing. Additionally, both amplifiers provided a dead-silent background from which the music could flow or erupt, as needed, with none of the background noise or “tube rush” that causes apprehension in the tube curious.
The Ayre MX-Rs are, in my opinion, at the cutting edge of solid-state in re-creating a sense of spaciousness and offering an expansive yet defined soundstage, together with the full palette of tonal colors for which fine tube components are renowned. But as good as the Ayres are in those regards, the ARCs were distinctly if marginally better. Take, for example, the wonderful recording that comprises the Neil Young Archives Performance Series Volume 3: Live at Massey Hall 1971 (LP, Reprise 43328-1). On track after track, and during the between-song banter, both sets of amplifiers re-created a fine sense of space, clearly positioning Young and his acoustic guitar, harmonica, and voice onstage, at the center of an enveloping acoustic. However, through the ARC monoblocks, Young’s presence was slightly more palpable, the confines of Massey Hall more physically at hand. That presence from the 250s, especially with the human voice, was almost universally a positive -- yet with a few “hot” records whose engineers had presumably overcompensated in the midrange for the limitations of standard, consumer-grade systems, the balance sometimes slipped just into the “too much of a good thing” category.
Returning to Lee Morgan’s Tom Cat and listening to Art Blakey’s brushwork on the hi-hat was a revelation through the Ref 250s. So clear was the image cast by the system that I felt I could see through the decades and across the country, to Rudy Van Gelder’s studio in 1964. There, Blakey’s deft touch engaged the dozens of bristles on the cymbal in a momentary cascade, fundamental attacks radiating around the shimmering disc and releasing harmonics in perfect complementary form.
A final item worth noting applies to both the Ayre and ARC monoblocks: balance. Both were balanced through and through, and not just from input to output (each accepts only a balanced, XLR input). Rather than going for one or two obvious strengths, with perhaps a weakness or three thrown in, their respective design teams obviously followed the mantra of “a high tide raises all ships.” The level of execution across the board was extremely elevated, and the resulting musical satisfaction exemplary. Neither of these powerful amplifiers will induce listener fatigue, but will instead instill listener involvement.
Ultimately, and as good as I know the sound of my reference amplifiers to be, I must conclude that the sound of Audio Research’s Reference 250s is finer. If I had air-conditioning, and if my primary reference system were dedicated solely to me and my music, I would have been more than tempted to buy them. I would also have had to rearrange things -- while I was able to shoehorn these big tube amps into place temporarily, were they to take up permanent residence here, they and I would need a bit more breathing room.
The upside of reviewing world-class audio components is how much a reviewer can learn. How far can the envelope be pushed? How engaging can a domestic music playback system become? The downside is often the realization that ignorance can be bliss. Just as the Audio Research Reference 250 monoblock amplifiers have made me aware of even greater potentials of my system, I surmise that it was the Reference Anniversary preamplifier that shook things up in Plymouth, Minnesota. ARC may be walking the same evolutionary path originally charted by its founder, but the magnitude of the leap in performance embodied in the current crop of Reference models is testament to the growth of the company and those presently in command. I’m confident that William Zane Johnson would be thrilled by his progeny’s response to ever greater challenges, and would concur with my final thoughts following a splendid experience with the Reference 250s:
Seeking a Finer Pathway
. . . Peter Roth
- Speakers -- Vandersteen Seven, Magico Q1
- Digital sources -- Wavelength Crimson HS Balanced USB DAC, Ayre Acoustics DX-5 Universal A/V Engine, AudioQuest Diamond USB cables, Apple Mac Mini and MacBook Pro computers
- Analog sources -- Spiral Groove SG2 turntable and Centroid tonearm; Lyra Kleos MC cartridge; Audio Research Reference Phono 2 SE phono stage
- Preamplifiers -- Ayre Acoustics KX-R, Audio Research Reference 5 SE
- Amplifiers -- Ayre Acoustics MX-R monoblocks
- Interconnects -- AudioQuest Wild Blue Yonder, Cardas Clear Balanced
- Speaker cables -- AudioQuest WEL Signature, Cardas Clear Beyond
- Power cables -- AudioQuest NRG-Wild and NRG-100, Shunyata Research King Cobra CX
- Power conditioners -- Shunyata Research Hydra Triton, Ayre Acoustics L-5xe
- Supports -- Harmonic Resolution Systems MXR and SXR racks with M3X shelves
Audio Research Reference 250 Mono Amplifiers
Price: $25,990 USD per pair.
Warranty: Three years parts and labor; 90 days, tubes.
Audio Research Corporation
3900 Annapolis Lane N.
Plymouth, MN 55447-5447
Phone: (763) 577-9700