Soulution 711 Stereo Amplifier, 701 Monoblock Amplifier, and 725 Full-Function Preamplifier

Simply The Best

Equipment report
Solid-state power amplifiers,
Solid-state preamplifiers
Soulution 701,
Soulution 711,
Soulution 725
Soulution 711 Stereo Amplifier, 701 Monoblock Amplifier, and 725 Full-Function Preamplifier

Which brings us at long last (I warned you—remember?) to the Soulution 711 stereo amplifier and 725 preamplifier under review. Because the 711 and 725 sound so much alike, I’m going to concentrate on the amplifier—and comment on the preamplifier in a sidebar. You can safely assume, however, that when used together the 711 and the 725 (once broken in) have precisely the same sonic character.

Happily, it is easy to describe both of these products. On the outside, they are identical to their forebears; both are housed in the same gun-metal grey, Bauhaus-style chassis that Soulution used for the 710 amp and 720 preamp, with little rectangular windows inset in their faceplates for their LED readout screens that allow you, via the remote or control knobs on the units themselves, to select various options. Inside, they use the exact same high-speed, high-negative-feedback circuits found in their 7 Series predecessors. As far as the amplification stages are concerned, the 711 is identical to the 710, and the 725 to the 720.

As was the case with the 5 Series components, the big difference in both the amp and the preamp is their power supplies. Like the 501 monoblocks, the 711 dual-mono stereo amplifier uses two, fully regulated switched-mode power supplies (as well as several linear supplies for certain sub-systems), and it uses these SMPSes for the same reasons they were employed in the 501—to keep “the voltage to the amplifier channels perfectly constant irrespective of the music signals.”

As Cyrill Hammer says in the sidebar interview, the use of these SMPSes had certain beneficial side benefits beyond providing cleaner, nearly inexhaustible power. For instance, because an SMPS runs cooler (while permitting it to create higher voltage), Soulution was able to omit noisy cooling fans in the 711. In addition, since SMPSes allow for much more efficient power-factor correction (PFC), the supplies no longer polluted the mains with harmonics and current spikes, as linear supplies do, improving the performance of the amp itself and of ancillary electronics that are also plugged into the wall. Furthermore, the smaller size of the SMPSes allowed a more efficient arrangement of parts and boards inside the amp, reducing the lengths of cable that had to be used between and among them, thus making for shorter signal paths. Finally, when these much more stable and efficient, lower-noise, higher-output SMPSes were paired with 1,000,000 microfarads of custom-made ultra-low-ESR capacitors (as they are in the 711), current peaks, particularly in the bass, could be reproduced with greater ease and fidelity, and current delivery could be raised from 60A to 120A (although pulling that much current out of the wall may prove to be a problem in most homes).

What this translates to sonically is almost exactly the same thing that it translated to in the 501 monoblocks—an amplifier with simply unparalleled bass-range power, color, and impact (even better here than the 501, an amp that I thought couldn’t be bettered in the bottom octaves), a power range and midrange of exceptional warmth and tonal beauty (ditto), and a treble that is as liquid, edgeless, and delicately detailed as any I’ve heard from solid-state. The 711 stereo amplifier is every bit as gorgeous, thrilling dynamic, startlingly lifelike (given the right sources), and seemingly inexhaustible as the superb 501 mono. Indeed, it might be just a shade more inexhaustible (if that isn’t a solecism), in that it doesn’t ultimately give up the ghost and shut down, no matter how loudly you play it. In addition to its inexhaustibility, the 711 has much of the same marvelous (and extremely lifelike) sonic stability of the 5 Series monoblocks—sounding virtually (though perhaps not quite as completely) the same at very low levels as it does at ear-splittingly high ones.

So far I’m describing an amp that has the same virtues as a less expensive one. But the truth is that the 711 has a leg up on the 501 in every area in which the less-pricey amp excels; plus it does certain things more than a leg better that the 501. First, there is the sheer amount of information about performers and performance that the 711 delivers. While the 501 is an extremely detailed amplifier, it’s no Soulution 710 when it comes to low- and high-level resolution. The 711 very nearly is. To hear the effortless way this amp sorts out strings, winds, brass, and percussion (and individual players within each section) even on the most floor-shaking fortississimos of a terrifically busy and dynamic piece like the Feria of Ravel’s Rapsodie espagnol is to hear a huge symphony orchestra reproduced with so much of the limitless ease and air, dense and variegated tone color, and thrilling acoustical power of a real orchestra in a real hall that it will send chills down your spine and goosebumps up your arms. (The Soulution 711 is, if nothing else, a non-stop goosebump-raising machine, regardless of music.)

But the 711 doesn’t just turn this high-resolution trick with big music—be it classical, rock, or jazz. It also has the 710’s ineffable touch when it comes to very low-level textures—the way strings, for instance, are being plucked or brushed or picked, or singers are shepherding their breath or modulating their vibrato. Soulution’s new stereo amp will leave you in no doubt about how a performer is playing his instrument and the mechanism by which the instrument is producing sound. When, for instance, I told you in a previous review about being able to hear how pianist Gilbert Kalish was alternately using his fingernails and the pads of his fingertips to rub the thick coiled strings of his concert grand in the open-piano glissandos of George Crumb’s Four Nocturnes, I was also telling you about the incredibly fine resolution of colors, textures, and articulations that Soulution’s new amplifier and preamplifier are capable of. Of course, the 710 and 720 preamp were capable of this selfsame thing, the difference being that the 711/725 does it while also fully preserving the natural warmth and density of tone color of the instrument Kalish is playing. (The second thing the Soulution 711 is, if nothing else, is meltingly beautiful in timbre.)

Then there are its bass dynamics. As I’ve already noted, I thought the Soulution 501 was unbeatable in the low end. But in all my life I’ve never heard Fender bass lines, kickdrums, and toms reproduced by an amplifier with as much lifelike speed, color, power, authority, and effortless ease as they are through the 711. Listeners have literally come out of their chairs when they’ve heard the tremendous impact of Chris Frantz’s sledgehammer drumming at the end of “Life During Wartime” or Tina Weymouth’s fat, throbbing, incredibly powerful bass line intro to “Take Me To The River” from The Talking Head’s Stop Making Sense. And, as I’ve already noted, the 711 is just as incredibly lifelike on big moments with full orchestra, such as the massive crescendos of Rapsodie espagnol. Trust me here: Outside of an actual rock, big jazz band, or symphonic concert, you’ve never heard anything like this amp in the bottom octaves. Which leads me to the third thing that the Soulution 711 is; if nothing else, it is a benchmark in the bass and power range, capable of unrivaled slam, inexhaustible dynamic range, and ravishing tonal color.

So what doesn’t it do? Well, the 711 isn’t as colorlessly neutral as the 710. Like the 501, it has a big, dark, tremendously authoritative, bottom-up sound. Though not as beguilingly soft in the treble as the 501, it is still probably a bit softer than life in the top octaves (at least when it is driven by the phonostage in Soulution’s companion 725 preamp). While very high in resolution and superb on transients, it is not quite the sonic vacuum cleaner that the original 710 was or that the Technical Brain TBP-Zero/EX is. Though it has an astonishing measure of the three-dimensional bloom that I associate with tube amps (Soulution amps are almost unique among solid-state components in this regard), it doesn’t have quite the same lifelike midband presence of, say, the ARC Reference gear; nor does it have the pitch-perfect steady-state tone that ARC has in the midrange (although ARC simply doesn’t compete with the 711 on transients or at the frequency extremes). When it comes to soundstaging and imaging the 711 is also a bit reminiscent of ARC tube amps, in that the stage is wall-to-wall vast, while instrumental images within that stage are less razor-cut and more life-sized than they are through most other solid-state amplifiers. (Once again, this larger, more natural, more tube-like imaging is characteristic of Soulution.) Finally, because of its tremendous energy—it may sound like I’m exaggerating this quality, but I’m not—and dense, lifelike color from the bottom bass right through the power range, the 711 may drive your speakers and your room a little nuts on certain midbass notes in big tuttis (as I said in my review of the considerably more lightly balanced Odyssey Strati). But once you hear all that horripilating speed and slam and color, you’re not going to care.

As great as the Soulution 711 is, there are other amps out there that may equal or outdo it in this area or that. (The Constellation amps, for instance, are at least as quick and detailed, albeit leaner and less authoritative in the bass range and more top-down sounding; the fabulous Siltech SAGA system is also nearly as high in speed and resolution and at least as beautiful in tone color, although also somewhat top-down in balance and less visceral in impact, at least in comparison to the ultra-authoritative bass octaves of the Soulution; when it comes to vocal realism the ARC amps I mentioned a paragraph ago still rather own the midrange; and the Technical Brain TPB-Zero/EX remains the once and future king of transient speed, ultra-fine detail, and colorless neutrality—the perfect amp for “transparency-to-source” listeners.) Still, IMO, none of these very worthy competitors has quite the same universal appeal—the potential to please every kind of listener on every kind of music in virtually every kind of system (save perhaps for horns)—that I feel the Soulution 7 Series gear has. This is an amp (and preamp) with enough resolution to consistently delight a fidelity to sources listener like me, enough fool-ya realism (on realistic recordings) to make absolute sound listeners swoon, and more than enough beauty and dynamism to knock it out of the park for those of you for whom the power and passion of music come first. Trust me again, folks: Once you hear the 711 you’ll want to own it. If you can’t afford it (and how many of us can?) there is always the next-best 501/520 combo for less (albeit still a lot of) money, the high-res Constellation Performance Series at about the same price, the uniquely beguiling Siltech SAGA hybrid, the ultra-transparent Technical Brain, or, for a lot less dough, the phenomenal Odyssey Stratos monoblocks.

It goes without saying that the Soulution 711 gets my highest, warmest, and most enthusiastic recommendation, as does its companion preamplifier the 725 (for which see the sidebar). Once again, it is the most consistently beautiful, thrillingly dynamic, and persuasively lifelike amplifier I’ve heard in my system thus far, no matter the music or the source. It is also, in case you haven’t yet noticed, the winner of The Absolute Sound’s highest honor, our 2014 Overall Product of the Year Award (which it shares with its monoblock cousins and its companion-piece, the superb Soulution 725 preamplifier).


Soulution 711
Type: Stereo solid-state power amplifier
Power rating: 2 x 150W @ 8 ohms; 2 x 300W @ 4 ohms; 2 x 600W @ 2 ohms 
Output voltage max: 31V RMS
Output current max: 120A
Impulse power rating: >6000W
Sensitivity: 1.55V RMS
Gain: 26dB
Frequency response: DC–1MHz
Slew rate: 400V/ns
THD+N @ 1kHz: <0.001%
Signal to noise ratio: >108dB
Damping factor: >10,000
Input impedance: XLR, 4.7k ohms; RCA, 10k ohms
Output impedance: 0.001 ohms
Dimensions: 277mm x 480mm x 277mm
Weight: 143 lbs.
Price: $65,000

Soulution 725
Type: Full-function solid-state preamplifier 
Amplification: Balanced, +9.5–18.5dB; unbalanced, +3.5–12.5dB; phono, +54–60dB
Frequency response: DC–1MHz
Slew rate: 400V/ns
Distortion (THD): <0.0006%
Signal-to-noise ratio: 130dB
Crosstalk: 105dB
Input impedance: Balanced, 2k ohms; unbalanced, 47k ohms; phono, adjustable          
Output impedance: Balanced 2 ohms; unbalanced, 2 ohms; record, 100 ohms
Inputs: Two balanced (XLR); three unbalanced (RCA); one phono (RCA)
Outputs: One balanced (XLR); one unbalanced (RCA); two LINK-System (RJ45); one DC-Out (sub-D high current)
Dimensions: 480mm x 167mm x 450mm
Weight: 66 lbs.
Price: $50,000

JV’s Reference System
Loudspeakers: Raidho D-5, Raidho D-1, Avantgarde Zero 1, MartinLogan CLX, Magnepan 1.7, Magnepan 3.7, Magnepan 20.7
Linestage preamps: Soulution 725, Constellation Virgo, Audio Research Reference 10, Siltech SAGA System C1, Zanden 3100
Phonostage preamps: Audio Research Corporation Reference Phono 10, Constellation Audio Perseus, Innovative Cohesion Engineering Raptor, Soulution 725, Zanden 120
Power amplifiers: Soulution 711, Siltech SAGA System V1/P1, Constellation Centaur, Audio Research Reference 250, Lamm ML2.2, Zanden 8120, Odyssey Audio Stratos
Analog source: Walker Audio Proscenium Black Diamond Mk V, TW Acustic Black Knight, AMG Viella 12
Tape deck: United Home Audio UHA-Q Phase 11 OPS
Phono cartridges: Clearaudio Goldfinger Statement, Ortofon MC Anna, Ortofon MC A90, Benz LP S-MR
Digital source: Berkeley Alpha DAC 2
Cable and interconnect: Crystal Cable Absolute Dream, Synergistic Research Galileo LE, Ansuz Acoustics Diamond
Power cords: Crystal Cable Absolute Dream, Synergistic Research Galileo LE, Ansuz Acoustics Diamond
Power conditioner: Synergistic Research Galileo LE, Technical Brain
Accessories: Synergistic ART and HFT/FEQ system, Shakti Hallographs (6), Zanden room treatment, A/V Room Services Metu panels and traps, ASC Tube Traps, Critical Mass MAXXUM equipment and amp stands, Symposium Isis and Ultra equipment platforms, Symposium Rollerblocks and Fat Padz, Walker Prologue Reference equipment and amp stands, Walker Valid Points and Resonance Control discs, Clearaudio Double Matrix SE record cleaner, Synergistic Research RED Quantum fuses, HiFi-Tuning silver/gold fuses