Jeff Rowland Design Group 725 Mono Amplifiers

by Roy Gregory | September 4, 2013

Several years ago, I caught my first glimpse of Jeff Rowland’s 625 power amp at the Munich show. A compact stereo chassis, it had all the gorgeous machined casework you’d expect from the marque, a higher rated output than its size would suggest and a total weight that definitely put it in the man-portable class. All that and a proper, class-AB output stage too -- what’s not to like?

Scenting something of a return to the company’s roots, I lost no time filing my review request, and when a factory-fresh unit finally appeared, it proved well worth the wait. At a time when power outputs and chassis size both seemed to be heading for the hills, closely accompanied by their associated price tags, the 625, at $14,500, seemed downright sensible in comparison. Manageable in every sense of the word, it combined easily accommodated dimensions, bombproof build with a genuinely useable power output. What’s more, its ability to step away from the music, to pass the signal without leaving its grubby fingerprints or DNA all over it, made for real long-term listening pleasure. It rapidly became a staple in the reviewing lineup, a go-to product that could be relied on to let its partners shine and show their true colors.

And so things might well have remained, except for the arrival of the KEF Blade. On paper, the 625 looks like the perfect match for the innovative, coherent-source loudspeaker design, its light-touch signature and open, unforced midband dovetailing perfectly with the seamless spatial presentation and natural weight, agility and tonality of the bottom end. But all was not quite as it seemed. At first things were just peachy, but the KEF’s low distortion combined with the amplifier’s sonic invisibility led to a less-than-restrained use of the volume control -- with the result that every time an orchestra hit a crescendo, the brass section ended up in my lap, a very nasty, glarey brass section too! Either there was something awry with the tweeter or the amp was running out of steam. This rather long and convoluted preamble serves to excuse, or at least to explain, my request for a pair of 725 monoblocks. Power-crazed megalomania had nothing to do with it -- honest.

The 725 is externally virtually indistinguishable from its stereo brother: the same beautifully finished but largely featureless chassis, the same illuminated standby switch on the front panel, the same suite of socketry on the back panel, just half as much of everything. Both the 625 and 725 offer balanced input only, so on the monoblocks you get one XLR socket, Cardas binding posts for speaker connection (one pair on either side of the chassis which is great for convenience and cable dressing) and a 20A IEC power connector, along with the main power switch. That’s your lot.

Now, the natural assumption might be that twice the chassis makes for twice the power, but that’s not the case. In fact, compare the specifications for the 625 and 725 and you could easily be forgiven for doing a double take ("Surely they’ve repeated the same figures by accident.") before concluding that Jeff Rowland Design Group (JRDG) have taken the familiar audio mantra of "less is more" well beyond the logical extreme. But fear not; dig a little deeper and all will become clear. The first clue lies in the rated output. The 625 claims a substantial 300Wpc output into the standard 8-ohm load, dropping 550Wpc into 4 ohms. For the 725 the corresponding numbers are 330 and 650 -- impressive for an amp that you can actually pick up and move about. That little bit of extra headroom is nice, but it’s the load tolerance that makes the difference -- that and the fancy ceramic circuit boards that grace the insides of the 725. They are not just lower loss in electrical terms; their increased rigidity stores less mechanical energy, passing it from the active devices into the massive one-piece milled-aluminum chassis. Finally, the 725 boasts a 40k-ohm input impedance, as compared to the 10k-ohm value for the 625, arguably making it less susceptible to the quality and character of the driving cables.

Other than that, the interior boasts all the JRDG norms: flawless surface-mount construction, fully differential topology, transformer-coupled input, and the company’s proprietary power-factor-correction technology to eliminate power-line noise and distortion. The circuit is highly regulated, overall-feedback-free and based on separate voltage and current gain blocks fed from massive, solid-copper buss bars, while the compact construction and solid chassis help ensure thermal stability. One other thing you’ll notice if you take a look -- and definitely if you pick the units up -- is the absence of the traditional massive AC transformer. Both the 625 and the 725 rely on Rowland’s sophisticated switch-mode power-supply technology. JRDG were early into the switch-mode game (1997!), and while it’s an approach that divides opinion and listeners alike, personally I’m more interested in results. Yes, I’ve heard plenty of poor-sounding amps with switch-mode supplies, but in audio it’s never a case of what you use, but how you use it that matters -- and in the case of the 725 I’ve no complaints at all.

The 725s are supplied with Rowland’s standard, minimalist feet: small Delrin balls and studs that screw directly into the underside of the chassis. Better than the rubber feet used by most manufacturers, they are a simple, elegant and pretty effective solution that recognizes that most serious listeners will substitute some sort of aftermarket foot or coupler, so money spent on fancy-looking standard feet is money wasted. In fact, the monolithic structure of the Rowland products makes mechanical grounding of their chassis particularly effective, and I’ve had excellent results using both Stillpoints Ultras and Nordost Sort Kones under both preamps and power amps. Putting a trio of titanium Sort Kones under each of the 725s was no exception, dropping the noise floor and improving focus, transparency, dynamic range and the sense of musical flow and presence. The standard balls do a fair job, but you really haven’t heard the 725s unless you’ve used them on superior supports.

So much for the material content; what about the musical performance? Back to the KEF Blades -- substituting the 725s for the 625 came as quite a shock. Not only did they completely banish the high-level aberration in the speakers’ upper mids, revealing it as a function of their impedance characteristic rather than a failing in the drivers, they totally transformed the clarity, stability and transparency of the sound. As good as the 625 is and as happy as I’d been with its musical attributes, the 725s were clearly in a different league. But best of all, they didn’t sacrifice any of the expressive and musical qualities that make the 625 so enjoyable. Instead they took them, extended them, and built a bigger and even better picture.

The thing that so endeared the 625 was its ability to stand away from the music, to remove any sense of it passing the signal. This unobstructive, light-touch quality allowed recordings and musicians to speak with their own voices, each disc, each performance having its own clearly identifiable character. Hold that thought for a moment while we consider what else the 725s add to the mix and the impact it has on the music.

The first and most obvious thing that strikes you when you first plug in the 725s is the sheer sense of clarity and separation. Compared to their stereo sibling, the monos deliver more space around and especially behind voices and instruments, as well as a greater sense of the overall acoustic. The space in which the performance happens (assuming there is one) now has a far more clearly defined volume and boundaries. Added to the impressive stereo spread and natural perspectives of the 625, that makes for a very impressive performance indeed.

Listen to "True Love Ways" from the Geffen CD Buddy Holly From The Original Master Tapes (a Japanese-pressed disc [Geffen UICY-6045]) and you hear the mics come up as usual, but there’s a wealth of additional spatial information. The control-room speaker, which so often sounds vaguely positioned, can now be placed precisely on a table stage right (the Japanese got the sound just right but managed to reverse the channels; either that or everybody else did!) and the arranger shushing the string section can now be clearly placed inside the studio. Even on the sparse opening, the floor and walls of the studio can be clearly heard, an actual defined space imposed on the listening room rather than superimposed on the existing boundaries. It adds significantly to the almost spooky "you are there" presence of this recording, the very quality that makes it such an audiophile favorite.

But the same sense of space and order applies to less celebrated recordings too. I’ve always loved Mravinsky’s work with the Leningrad Philharmonic Orchestra, including a box set of the last three Tchaikovsky symphonies [Deutsche Grammophon Gesellschaft 2721085]. He brings a tightly organized sense of drama and classical structure to works that are all too often swamped in a lush romanticism. On the emotive fourth movement of the 6th Symphony, his perfect pacing and control add poise and pathos to the almost call-and-response fragmentation of the orchestra, the sweep of the strings, the plaintive call of the woodwinds. But as great a performance as this is, I wouldn’t hold it up as a model recording. Despite that, each time the strings falter and the woodwinds enter, they do it from precisely the same point in space, fixed in depth and height. Each time the orchestra surges and dies, an effect so characteristic of this movement, the decay in the hall is consistent. Nothing moves, and nothing leaps forward or calls attention to itself. There is a complete absence of those sudden, startling interjections or spatial cues that disturb the listener: a stark halo around a harp or triangle, the sudden recognition of the wall behind the percussion section, intrusive details that serve only to remind you that this is a recording you are listening to, rather than a single, coherent event. Instead, the acoustic space is remarkably consistent, as is the orchestral perspective, allowing you to lose yourself in the piece rather than marvel at the reproduction. The 725s make Mravinsky’s talents clear, pushing the performance ahead of the system reproducing it.

What is less apparent, or at least, what only emerges over time, is the part that sheer stability plays in all this. An improved sense of acoustic space and intra-instrumental air almost always reflects greater low-frequency extension and transparency -- two qualities the 725s definitely bring to the party. But what they also add, and in many ways what really makes the difference in the credibility and presence of the performance, is the absolute stability of the space, the stage within that space and the musicians and instruments upon that stage. There is a sense of constancy, an unwavering consistency to the air and space of the acoustic that is at once familiar and wholly natural. In many systems the extent of the acoustic space only becomes apparent when a large low-frequency impulse, a drum beat or sudden crescendo, cannons across its expanse. When it happens it’s surprising -- a revelation, almost a reminder of the venue in which the event occurs. How often do we only hear that rear wall when the timps roll or the tuba trundles? In removing that sense of surprise, what the 725s do is allow the listener to relax. His antennae switch off and his warning systems shut down. By making the acoustic space and its boundaries a constant part of the equation, they also provide the all-important sense of context for the performers and their performance. These are not the only amps that perform this service, but they are amongst a very select few that do so without imposing some other intrusive artifact, character or coloration to distract the listener instead.

The other side of the low-frequency coin is the benefits that accrue in the treble range. Obviously, enhanced spatial definition and transparency will be reflected in the increased locational precision and air around high frequencies, but the actual effect is far from subtle -- in musical terms or in the sense of performers and their physical input. This is about input/output and the nature of musical energy -- the instrument that produces it and how the player uses it. Few genres use percussion with the abandon with which Latin jazz backfills its spaces with myriad knocks, bangs, clicks and scrapes. Play the Antonio Carlos Jobim album Stone Flower (CD, [Universal CTI 6002]) and the 725s integrate what can be the irritating busy-ness of the percussion perfectly into the musical whole. On the short track "Choro," the percussion balances the piano and bass lines, adding just the right degree of contrast, reinforcing and marking out the rhythms. But it is on the longer "Brazil" that it becomes apparent just how effortlessly the amps separate the different, overlapping sounds, isolating both their nature and their texture. The difference between hollow wood and metal chimes isn’t just clear, the contrast makes sense as the players weave the musical fabric behind the gentle insistence of Jobim’s electric piano. In the same way that the stability of the soundscape removes the need to question it, the ability to separate and so easily identify all those discrete, independent little percussive elements allows you to ignore the question of their identity and simply enjoy what they add to the mix, that infectious sense of motion that convinces even old white guys that they can dance.

Which should tell you that not only do the 725s display excellent high-frequency resolution and dynamic discrimination, their timing is pretty impressive too. Again, that sense of exactly what is happening, where it happens, precisely when and how much, is all built on the foundation of that low-frequency transparency, but the sheer clarity and precision, the effortlessly unforced way in which all that high-frequency information doesn’t just slot into place but makes sense when it gets there, is definitely way past unusual. Just how precise are these amps when it comes to tracking the signal? Hook them up to the Avantgarde Trios, with their 110dB sensitivity, and where most big amps would sound heavy, muscle-bound and sluggish, especially compared to Avantgarde’s own excellent XA electronics, the 725s sound delicate, agile and stop-on-a-dime authoritative. That’s impressive! It also demonstrates that the 725s don’t just get hold of the signal, they know when to let go too.

Talk of higher definition and greater transparency always sends a shiver down my spine. There are a lot of amps and particularly speakers that highlight treble information, spotlighting it above the mix in an impressive display of resolution and detail. "Just listen to me" they seem to be saying -- but the fireworks quickly become irritating simply because they are lifted out and separated from the music. Yes, they give a sense of heightened space and precision, of definition, detail and presence, but they do it at the expense of musical balance, disturbing the inner relationships that make up the whole. The Rowlands don’t just let you hear what is happening, by integrating it so seamlessly into that whole they let you understand why you're hearing it, in that same, almost subliminal way that we separate music from noise.

Which brings us back to the Rowlands’ exemplary record for hands-free communication. Take that ability to let the music speak for itself, to have and to use its own voice and combine it with the sheer stability, spatial and temporal integrity that the 725s graft on to the sound and what do get if it’s not music that’s been pulled apart? The answer is much greater insight and, as a result, greater engagement. The 725s do not sound as smooth as the 625. Their music has more corners and starker contrasts, but what those things provide is a clearer picture of the performance, its shape and structure. By letting you hear around and behind the notes, the instruments and the performers, the amps make the pattern and shape of the performance that much clearer, because everything has a place and that place is easier to understand. In Munich, I picked up an excellent Clearaudio repressing of Martha Argerich playing the Chopin preludes, Op.28 [Deutsche Grammophon Gesellschaft 2530 721]. The recording catches the young Argerich at her most instinctively spontaneous, the clarity and fluidity of the 725s revealing her verve and artistic response to pieces that so many play as disciplines rather than opportunities. The contrast here between one prelude and the next, the difference in weight, key and mood, is remarkable. Talk about the ability to give different recordings their own distinctive voices; here, the individual pieces each emerge as separate and distinct, the major-minor-major key progressions unmistakable, the shifts in manner and tempo, attack and weight beautifully traced and reproduced. The result is playing of fantastic sensitivity and delicacy one moment, vigorous, bright energy the next. Argerich’s performance is sure-footed, her hesitations and shifts in tempo unmistakable accents, her expressive range revealing the full compass and drama of the piano.

Solo piano is always an acid test of a system’s capabilities and the sheer brilliance of this performance, its elevation of expression over technique takes it to the logical extreme, yet the 725s remain unflustered, delivering the solid and considerable weight of the instrument without shackling the speed and brilliance of the rapid passages, or crushing the delightful poise and delicacy of the more contemplative ones. It’s a performance as deft, as elegant and as beautifully judged as Argerich’s and just as impressive.

Now look at (and listen to) an alternative take on Chopin’s virtuoso pianism: Rubenstein’s reading of the scherzos [LP, [RCA LSC-2368]). Not only is the piano sound completely different, but so to is the style of the playing. Rubenstein exhibits a honed, almost laser-like precision, with massive dynamic authority and a planted discipline that is totally different to Argerich’s intuitive and instinctive playing. Add a crisper, harder piano sound and the result is impressively brilliant and energetic, but lacking the sensitivity and impressionistic quality of Argerich’s performance of admittedly very different works. Rubenstein presents us with a serious and measured performance that leaves us in no doubt as to the technical demands of the pieces and the discipline required to play them. There’s little time for reflection or to absorb the deeper textures, but the mastery of the score and the clarity and confidence with which the rapid sprays of notes are produced and arranged are remarkable. Which sounds more like a piano in a recognizable space? The Argerich. Which tells you more about the piece and the player? Also the Argerich -- but here the gap is far narrower. The RCA recording might not match the quality of the DGG and its audiophile pressing, but the nature and the specific quality or style of the playing are clear, easily transcending the limitation of the pressing. Of course, I’m comparing what was one, if not the high point of Argerich’s recording career, with a Rubenstein recording and performance that’s not of equivalent prominence, but that’s not the point I’m making. It’s not about whether Argerich is better than -- or even preferred to -- Rubenstein. It’s about whether the system allows you to hear the qualities that each brings to his or her performance -- and that it does so with extraordinary clarity.

What you are hearing here is the ability of the Rowland amps to pull the message from within the medium, to free the performance of the constraints which physical bind it. The 625 is impressive in this regard; the 725s are simply better -- and significantly so. In separating message and medium, they don’t eliminate the recording, or obscure its quality, they place it in a different plane, rather like a really good cartridge that doesn’t hide surface noise on LPs but separates it from the music. So listening with the 725s, the limitations of a recording are certainly apparent, but they cease to be nearly as intrusive, while with really great recordings the performance takes on a life of its own.

Such sonic invisibility is not without its price and associated set of demands. You’ll need to pay considerable attention to setup and system infrastructure if the 725s are to deliver their full musical potential. If you open the window that wide, be aware that it will shine a pretty stark spotlight on your front-end components, be that the sources or the line stage that shuffles their signals. The 725s also sound at their best fed from fully complementary signal chains. I used them with a range of balanced and single-ended line stages and sources, but their full grace and authority really emerge on the end of a fully balanced system. But if you value what these amps don’t do to the signal -- the way they leave it and the musical performance unmolested and intact -- then getting the rest of the system working right is a small price to pay for the performances that will result.

When I reviewed the 625 (along with its matching Corus line stage), I summed it up as follows:

In a world where every review seems to be good and so many products exhibit so few specific, identifiable sonic flaws, these Rowlands represent a different level of achievement. They stand as examples of a select group of electronics and speakers that succeed in putting the music first, on placing the integrity of the whole above the hyper detail that, whilst it’s immediately impressive, ultimately fails to satisfy. For products that are so attractive and carefully crafted to step away from the limelight seems almost counter intuitive, but it’s precisely that attention to detail, that perfectionist insistence on the right over the easy, that has created them -- and recreated the musical performances they’ve played to such emphatic effect.

If you are feeling jaded and you are losing confidence in the promise and performance of high-end audio, the JRDG Corus/625 combination is just the antidote you need. Exquisitely constructed components with their feet planted firmly on the path to musical gratification -- they’ll plant yours there too.

The 725s take that already impressive achievement a whole stage further, revealing more music and more of the performance from the same recordings, the same material. I could reword that conclusion, but its sense is just as apposite, just as true of the 725s as it is of the stereo amp, yet they deliver even greater musical substance. What the mono amps do is the very same job as the 625, but they dig deeper, letting you hear further into the performance. Right about now is where most reviewers would start wheeling out the law of diminishing returns. After all, the 725s pretty much double the price of the 625 and add next to nothing to the numbers. In terms of quantity you get twice the box, but you can’t get twice the bandwidth, so who in his right mind would buy the 725s? The answer is, the listener who really understands that less is indeed more, that by imposing even less constraint on the passage of the fragile musical signal they deliver more of the message, more of the nuance, more of the drama and more of the human emotion that makes music so compelling.

I loved the 625 and, but for the unreasonable demands of the KEF Blade, I could have happily lived with it. But that KEF-shaped cloud had a gilt-edged lining. The 625 is a genuinely great amp, but if you have the money and the musical passion, the 725s are definitely worth the difference.

Price: $29,800 per pair.
Warranty: Five years parts and labor.

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

Associated Equipment

Analog: VPI Classic 4 turntable with JMW 12.7 tonearm, Lyra Titan i and Dorian Mono cartridges, Zu Audio Denon 103 cartridge, Nordost Blue Heaven tonearm lead and Tom Evans Audio Design The Groove+ phono stage, Nordost Odin tonearm lead and Connoisseur 4.2PLE phono stage.

Digital: Wadia S7i CD player; dCS Paganini transport, DAC and uClock; Wadax Pre 1 digital control unit, Krell Cypher CD/SACD player.

Preamps: Avantgarde XA Pre, Connoisseur 4.2, Siltech SAGA C1 Control Amplifier.

Power amps: Berning Quadrature Z monoblocks, Siltech SAGA V1 Voltage Amplifier/SAGA P1 Current Amplifier.

Speakers: Avantgarde Trio/Sub231, Crystal Cable Absolute Arabesque, KEF Blade, Wilson Benesch Cardinal.

Interconnects and speaker cables: Complete looms of Nordost Odin, Crystal Cable Absolute Dream or Ultra from AC socket to speaker terminals. Power distribution was via Quantum QRT QB8s or Crystal Cable Power Strip Diamonds, with a mix of Quantum Qx2 and Qx4 power purifiers and Qv2 AC harmonizers.

Acoustic treatments: As well as the broadband absorption placed behind the listening seat, I employ a combination of the LeadingEdge D Panel and Flat Panel microperforated acoustic devices. These remarkably simple yet incredibly effective acoustic panels have become absolutely indispensible when it comes to hearing what the system is actually doing.

Accessories: Essential accessories include the Feickert protractor, a USB microscope and Aesthetix cartridge demagnetizer, a precision spirit level and laser, a really long tape measure and plenty of masking tape. I also make extensive use of the Furutech anti-static and demagnetizing devices and the VPI Typhoon record-cleaning machine. The Dr Feikert PlatterSpeed app has to be the best ever case of digital aiding analog.