The Audio Beat - Jeff Rowland Design Group Model 825 Stereo Amplifier

Jeff Rowland Design Group • Model 825 Stereo Amplifier

by Marc Mickelson | December 11, 2015

© www.theaudiobeat.com

Thumb through issues of the magazines that comprised the underground audio press in the early 1980s (and now represent the mainstream audio press) and you'll see the name Jeff Rowland with some regularity. Rowland was one of the pioneers of today's high-end audio, and even after many product launches, he continues to produce consequential audio components here and now. His design approach is built on an embrace of innovation -- not merely keeping up with the times, but actually pushing product categories in important new directions. Some of what we consider de rigueur today were concepts and features that Jeff Rowland championed before they were commonplace. Exhibit one is remote control. I cannot say with complete certainty that Rowland's Consonance was the very first high-end preamp with remote control, but it was certainly among them. There is also battery power, which Rowland's preamps and amps of the early 2000s used. And does anyone remember Rowland's Complement phono cartridge, which was unusual for its lack of a cantilever? Yes, the cantileverless phono cartridge didn't exactly come to dominate the industry, but it was another example of Jeff Rowland's thinking outside -- far outside -- the proverbial box.

Even Rowland's use of established circuits occurs within a framework of innovation. There are six power amplifiers currently in the Jeff Rowland Design Group lineup. Four, including the subject of this review, were designed and built around class-D modules, while the other two have standard class-AB output. However, the class-D amps use three distinctly different base technologies -- ICEpower, Pascal and Ncore -- and the class-AB amps have some design wrinkles of their own.

When I initially considered writing about the Model 825, which, along with the Model 925 monoblocks, uses Ncore technology, I had some reservations. The very first class-D power amp I heard was Bel Canto's Evo 200.2, which was based on the Tripath module and a very fine-sounding amp indeed. All of the amps I've heard since then, including a few based on the ICEpower module that Jeff Rowland uses, were disappointing. However, I had never heard any Jeff Rowland electronics in my system, and that alone made the 825 intriguing. If nothing else, I could talk about how class-D technology had progressed -- or remained anchored in mediocrity -- over the past decade and a half.

While every audio manufacturer can recite a laundry list of fine points about its equipment, there are more similarities across any product category than differences. However, as you can probably guess from my preamble regarding innovation, the Model 825 is more exception than rule, and that stems from Jeff Rowland himself. I talked at length with him after I had written much of this review, and that conversation caused quite a bit of rewriting, mostly because of Rowland's refreshing approach to designing audio equipment. He calls himself "an integrator," not a designer in the contemporary sense. "You have to have a core philosophy," he concedes, "but I'm not someone who thinks my way is the only way." The idea is to use whatever technology is available to help reach the goal, which for Jeff Rowland is making products "that look good, perform well and last a long time." This gives him "the fulfillment and excitement that come from creating a product" in the first place.

This philosophy, more Eastern than Western, I would argue, manifests itself in the Model 825 in a number of ways, including a series of careful choices for its power technology, input stage and especially its 2500W switch-mode power supply, not to mention the choice of passive parts and the amplifier's mechanical design, which also help make the Model 825 what it is. The amp's Ncore class-D technology was designed by former Philips engineer Bruno Putzeys and used for his amps under the Mola-Mola brand name. Jeff Rowland admits that "class D is a hard road" because there are "lots of misconceptions about it." But "I am a class agnostic. I will use whatever is out there, based on performance advantages." For Rowland, these "performance advantages" begin with impeccable specs. The Model 825 has extremely low distortion (less than 0.004%) and output impedance (0.003 ohms) over the entire frequency range. The extremely low output impedance along with 400Wpc output (at 8 ohms, 750Wpc at 4 ohms) mean the Model 825 can drive any speaker extant without issue, no matter the load presented. "Ncore offered performance I would have had a hard time meeting with class AB," says Rowland.

Just as pertinent as Ncore in the Model 825's design brief is active power-factor correction (PFC), which performs three important functions. First, it ensures high efficiency of the amplification circuit, with nearly 100% of the input AC being converted to amplifier output, not heat. Second, PFC enables the Model 825 to pull AC power during the entire power cycle, instead of only a small fraction of it; voltage and current demands remain in phase with each other, eliminating out-of-phase, high-current pulses common to all amplifiers that don't employ PFC. Third, PFC prevents the circulation of a certain kind of noise -- harmonic currents -- into the AC line, reducing noise throughout the entire audio system.

As just about every audiophile knows, Jeff Rowland equipment looks like no other. Chassis parts are fashioned from billets of T6061 aircraft-grade aluminum by a high-tech supplier in Colorado Springs, where the Jeff Rowland Design Group is HQed. The look is even more intense for the 825, whose tall, wide, highly machined front panels look like a light source themselves. If you've ever seen one of those large, square LED light panels, you have a sense of what the 825 looks like in person. It shines, it gleams, it beams. The rest of the chassis, which is fashioned from a satiny black anodized aluminum, is machined with the same extreme care. Joints fit perfectly and precisely, and there are subtle facets that give the entire amplifier a considered, refined look. Lots of expensive audio equipment looks expensive, but even it doesn't look like -- and isn't built like -- Jeff Rowland equipment, which is a category unto itself.

As you can guess from all of the machined aluminum, the Model 825 is heavy, but exactly how heavy you will not understand until you try to lift just the top section. I did this, stupidly forgetting to use my legs and not my back, and I paid for it, crumpling to the ground in a heap after nearly tearing a muscle in my lower back. The Model 825 weighs 160 pounds, but all of that weight isn't for show. Jeff Rowland believes that mechanical integrity translates to better sound, and the Model 825's mass plays a part here, as does stacking the chassis, which you see in pictures. At first I thought this had to be done for convenience only -- and that I'd put the larger audio chassis beside the power supply. But the audio chassis has no feet of its own. Instead, Delrin spheres fit into recesses on the top of the power supply and the bottom of the audio chassis, locking the whole thing together, the weight of the audio chassis damping the power supply, and the radiated energy of the power supply, housed in a separate chassis, staying away from the audio circuitry.

The only feature that breaks the near-hypnotic look of the front panel is the on/off pushbutton, which may account for all that's around back. In addition to switchable pairs of RCA and XLR inputs (with an additional switch for XLR polarity), there are pairs of Cardas binding posts, the ones with the single easy-to-grip knob, making the Model 825 ready for biwired connection. There are also main and auxiliary connections between the audio chassis and power supply, and a very useful feature: a switch for choosing between 26 and 32dB of gain. If you use a tubed preamp with the Model 825, 32dB of gain may increase hiss from the preamp, which the lower setting will help alleviate.

More than just about anyone who designs -- er, integrates -- audio equipment today, Jeff Rowland has considered not only how his equipment sounds but also how it will be used -- with his own electronics or with those from other makers, with speakers that present no challenges to an amplifier or with those that can bring lesser amps to their knees. I've not had a power amplifier in my system that's as accommodating of the various and sundry circumstances in which it will be used as the Model 825.

What I first observed after turning on the Model 825 was literally nothing. While I'm not Roy Gregory, who, it seems, has heard every piece of audio equipment known to man, I have still had a lot of amplifiers through my system, and each one, to some degree or another, made mechanical or electrical noise on startup -- sometimes a slight hum from in-rushing AC, oftentimes a subtle but persistent hiss from the speakers -- and a series of metallic pings as the chassis warms up. Even their on/off switches make some sort of noise. But when I pushed the on/off button of the 825 and heard none of the expected sounds, I immediately thought something was wrong. I put my ear to one of the speakers and again was met with silence. It was only after turning up the preamp and music came faintly from the speakers that I believed the amp was actually working. This was a first for me -- and it's worth noting, lest you turn the preamp way up, then hit play and are blasted with music.

I mentioned all of this to Jeff Rowland, and he replied in his calm way, "I'm glad you noticed. You won't believe how difficult that is to accomplish." So it was no happy accident, but more important it does have influence on the Model 825's sound. This is one resolving amp, everything from the finest textural touches of the instruments to whatever is happening in the deepest recesses of the soundstage, all of which is made possible by that lack of noise, a deep, eerie blackness that is like life itself, a quality of live music and not an artifact of its reproduction.

But what's most endearing about this impossibly high resolution is the smoothness and liquidity that come along with it. So many lesser amps resolve to an extreme level by sounding hyped: bright, crisp, grainy or just plain aggressive, especially as volume levels climb. Not the Model 825, which reveals musical detail to a level I've not encountered from an amplifier, and does so without the electronic artifacts that are expected for such performance. It presents detail instead of thrusting it from the speakers, revealing it naturally. If you focus your attention on it, you notice it. Otherwise, the music simply flows.

Because I used the Model 825 with the Rowland Aeris DAC (see sidebar), I listened to more digital than analog while the amp was in my system, but it was analog's easy, unforced resolution that not only revealed the most about the amp but was also the best analog for the 825's sound. LPs I knew well were no more illustrative than ones I was listening to for the first time; both compelled me to listen, to relax into the disarming sound of the 825. And some of the best-sounding LPs, like those Mark Levinson recorded in the late 1970s, were immensely refined, or as Harry Pearson called them on his early Super Disc Lists, "Musically natural sound, as opposed to spectacular per se." I found the Art of the Fugue four-record 45rpm set [Mark Levinson MAL-5] at a garage sale, paying all of one dollar for it. A friend had told me about the sale, which I didn't get to until the second day, so it was clear that others had seen and decided not to buy the set, maybe because it had an area of water damage on the box, but more likely because they simply didn't know what it was.

This is not the sort of up-front, visceral organ blockbuster that was Telarc's specialty. It's much more difficult to reproduce well, because the recording is civilized, as much about the space in which the music emanates (Dwight Chapel on the campus of Yale University) as the organ itself, which is easily enveloped by noise, even very low levels, especially as you lean on the volume control. The Model 825 illuminated this music and, just as significantly, the deepest areas of the soundstage, capturing the copious air of the church and giving lift to the organ. The uber-quiet Model 825 simply revealed whatever it was given and absolutely nothing more. "Great soundstage lucidity, to the very reaches," I scribbled while listening. "No opacity, just clarity." I've praised Audio Research equipment for its portrayal of space, and the 825 does large-scale music just as well, but shines a light into the nooks and crannies of smaller, more intimate recordings even better.

There are moments of real power across The Art of the Fugue's four LPs, and they demonstrate that the Model 825 isn't all refinement and finesse. It can help locate the resonant frequency of your listening room when the recording and speakers oblige. The Model 825's bass has power without bloat, and the amp has dynamic vigor and immediacy -- the ability to convey startling suddenness, again without any electronic edge. So often really powerful amps sound, first and foremost, powerful, as though all of that power is their one big trick. As I've already described, the Model 825 definitely doesn't have a power-first sonic signature, but it is still a very powerful amp. It has serious reserves, and it can drive any speaker, I'm confident, to deafening levels with potent bass weight and punch.

Neutral is such an overused and misused term in audio reviews that it's meaningless -- more a matter of opinion now, even though it should be simply an observation, a reported fact. Well, I have to use it to describe the Model 825's tonality, which is unadorned, evenhanded, middle of the road, neutral. There's neither the honeyed color of some tube amps nor the emaciated grayness of some solid-state amps. There is an overwhelming sense of honesty, of the amplifier not editorializing to create an effect, whether it be midrange palpability or treble sweetness. The 825 reveals, presents. Images are neither wispy nor plump. Voices are chesty, breathy, nasally or crystalline depending on the recording, which I suppose is a way of using another overused term: transparent.

Suzanne Vega's great Close-Up Series [Amanuensis 2507] was a true revelation with the Model 825. Because I've used cuts from this six-CD set at shows, I've heard them on a huge array of systems. They've never sounded even remotely bad, but with my system and the Model 825 they sounded more authentic, akin to 30ips tape. The sense of hearing into not only the performance but the space in which it was captured was heightened, giving new insight into the small touches of the backing musicians, not to mention Vega's delicate vocals. I recommend this set often -- and not often enough. It cost $42 new -- again, for six CDs -- and has given me nearly endless pleasure, even as I've used it time and again as a reviewing tool. With all of the focus on file playback, I honestly wonder if in a decade CD will undergo a vinyl-like rebirth. After more than twenty years of CD's preeminence, so much music will still only be available in that format.

Such a peripheral line of reasoning underscores what is very best about the Model 825 -- and potentially any great piece of audio equipment: it makes you forget that you're listening to a complicated and expensive audio system. This is more than the ability to suspend disbelief; it's a disarming of critical faculties, even when you're trying to be critical and unravel what you're hearing. In my experience tubes do this more readily than solid state, and class D almost never does it. The Model 825 does it as a matter of course -- it can't not do it -- and it happens not because of one or two or three of the sonic traits I discuss above, but all of them, in their exact proportions. If the Model 825 were somehow more natural, bordering on romantic, or more round and rosy, especially through the mids, it would be a different amp and perhaps a very good one, but not a great one. And the Model 825 is a great amp -- in numerous ways, greater than any amp I've heard. It speaks not just in its own voice but in a voice I always wanted to hear, such is the pull, at least for me, of the utterly clear yet composed way it reveals all that's on each recording.

I often include comparisons to similar products in my reviews, because of the context they bring, not only to readers who have heard those products but also to my understanding of the one under review. Similarities and differences don't happen in a vacuum; pointing them out reveals more about the components that embody them. Here, however, there are in almost every way only differences. The Lamm M1.2 Reference monoblocks ($27,190/pair), for instance, sound fuller, darker and thus more colored than the Model 825, and their often-praised (by me) naturalness is of a different sort: more the result of those character traits than an encompassing quality of the amp top to bottom. The VTL Siegfried II monoblocks ($65,000/pair) also have a very strong character, one that's big and broad-shouldered, expert at conveying the presence and power of music. I admire the Siegfried IIs more than any other tube amp, but they also possess a level of personality that the Model 825 doesn't.

That's pretty much what I'd be writing about any amp I've heard compared to the Model 825: their overt character versus the Model 825's extreme retrieval of detail, purity and neutrality. I have described the Model 825's intrinsic sound, however, so it is there to be heard. But it's not as apparent as that of other amps, most of which don't possess anything close to the 825's spooky noiselessness. The Model 825 is about omission in the truest sense of the word. Its less is definitely more.

In many of the early reviews of Jeff Rowland's electronics, their tubelike qualities were observed and praised. Is that what's happening here, the so-often-cherished solid-state amp that sounds like tubes? The Model 825's sonic profile begins from a very deep well of musical detail that's free of accompanying noise. It is a model of directness -- of neutrality -- presenting the music the way it is on the recording with uncommon resolution and purity, and resolving space with singular acuity. And just when you've come to appreciate all of this, you realize how liquid and non-electronic it sounds, offering up its gobs of detail with abundant naturalness that at first seems out of place. It is a true connoisseur's product; beautiful and thoughtfully made, it does its proclaimed job, amplifying a signal, without even a minor issue. It hasn't just single-handedly redeemed class D for me, but made me take it seriously again, something I would never have imagined without experiencing it for myself.

So, no, the Model 825 doesn't have the sonic profile of so much solid state, but it doesn't really sound like tubes either. It is its own thing, and that thing is unique and special.

Price: $32,000.
Warranty: Five years parts and labor.

Jeff Rowland Design Group
2911 N. Prospect St.
Colorado Springs, CO 80907-6326
(719) 473-1181
www.jeffrowlandgroup.com

Adding Aeris

A few months into my lengthy listening time with the Model 825, Jeff Rowland made an offer I couldn't refuse: pairing his Aeris digital-to-analog converter ($9800) with his amp. The Aeris is physically configured like the Model 825: two precision-machined chassis, one for audio, one for power. Both are dense and stalwart; inch for inch, the Aeris is as heavy as the Model 825.

Just as with the Model 825, there really is nothing about the Aeris that's ordinary or derivative. In complete opposition to current fashion, the Aeris operates in adaptive-synchronous mode, not the asynchronous mode that so dominates the DAC field. Another unusual feature is the implementation of its volume control, which is handled through adjustment of the DAC chip's current to change output level. This avoids the sonic issues or added circuitry of the two prevailing ways to adjust the output of a digital-to-analog converter: in the digital domain or by use of an added volume control. Roy Gregory reviewed the Aeris over two years ago and he had much to say about it, so I will refer you to his very detailed review for a much deeper discussion of the Aeris and especially the rationale for Jeff Rowland's design choices.

In my system, the Aeris was connected to a preamp or directly to the 825. My Toshiba laptop and CEC TL1 CD transport -- a holdover from the early 1990s and, to my ears, still a uniquely musical piece of digital gear -- were sources. Using the Aeris with any of the preamps I had on hand, all very accomplished, meant accepting that their sonic signatures, slight though they might be, were injected into the signal path. With the preamp gone, the DAC-amp pairing was more like a multiplication of strengths, not a mere summing. Immediately and obviously, even the slightest remnants of noise absolutely vanished, leaving only the music behind. Transients were more sudden, textures more pure and varied, soundscapes were more spacious, and everything sounded more supple and liquid.

I spend a great deal of my listening time playing Blue Note LPs, even though I have so many of the CDs of the same music. I've found the RVG CD remasters of the Blue Note catalogue to sound lighter, brighter and more grainy than the LPs and even the earlier CD releases of the same music. The Aeris is one smooth-sounding DAC, but not to the point of homogenizing recordings. Instead, it gives the impression that the bits are somehow packed more tightly together, producing a more saturated, complete sound from even the RVG CDs.

I'm still not sold on file playback, because to my ears it does homogenize a little or a lot, depending on the source, "bits are bits" be damned. The Aeris didn't change this impression, pointing the finger once again at the method of delivering the bits to the DAC, but hearing the music without even the least bit of extraneous noise still made for some excitement with native high-rez material and ripped CD cuts alike.

If you accept the sonic outcome of the design choices made for the Model 825, you will find the Aeris to be an obvious and irresistible partner. Put another way, I think it would be wrongheaded to use the Aeris any way other than directly into the Model 825 (or any other amp for that matter), although one of Jeff Rowland's preamps may cause me to reconsider. The Aeris is every bit as innovative and consequential as the Model 825.

-Marc Mickelson

Associated Equipment

Analog: TW-Acustic Raven AC turntable; Graham B-44 Phantom Series II Supreme and Tri-Planar Ultimate U12 tonearms; Denon DL-103R and Dynavector XV-1s (stereo and mono) cartridges; Nordost Valhalla 2 and Odin 2 phono cables; Audio Research Reference Phono 2 SE and Lamm Industries LP2.1 phono stages.

Digital: Ayre Acoustics DX-5 "A/V Engine," CEC TL1 CD transport, Toshiba Satellite laptop.

Preamplifiers: Audio Research Reference 5 SE and Reference 10, Lamm Industries LL1 Signature, VTL TL7.5 Series III.

Loudspeakers: Paradigm Reference Signature S2 v2; Venture Audio Ultimate Reference; Wilson Audio Sasha W/P Series 2, Alexia and Sabrina.

Interconnects: AudioQuest William E. Low Signature, Nordost Valhalla 2 and Odin 2, Shunyata Research Zi-Tron Cobra and Anaconda.

Speaker cables: AudioQuest William E. Low Signature, Nordost Valhalla 2 and Odin 2, Shunyata Research Zi-Tron Cobra and Anaconda.

Digital cables: Nordost Valhalla 2 S/PDIF and AES/EBU cables.

Power conditioners: Essential Sound Products The Essence Reference, Quantum QB4 and QB8, Quantum Qx4, Shunyata Research Hydra Triton.

Power cords: Essential Sound Products The Essence Reference and MusicCord-Pro ES, Nordost Valhalla 2 and Odin 2, Shunyata Research Zi-Tron Cobra.

Equipment rack and platforms: Paradigm J-29 speaker stands, Silent Running Audio Craz² 8 equipment rack and Ohio Class XL Plus²platforms (under Lamm M1.2 amps), Harmonic Resolution Systems M3 isolation bases.