Soulution 710 Stereo Amplifier, 700 Monoblock Amplifier, and 720 Preamplifier (TAS 199)

The Amp That Wasn’t There

I’ve listened to a lot of audio equipment over the years, but I can count on one hand (without using all my fingers) the number of times I’ve heard something that was fool-me realistic. The first time this happened—way back in the early seventies—was when I auditioned the Magneplanar I-U’s (still my all-time favorite Maggies) with Audio Research electronics and got tricked into thinking I was hearing an actual grand piano being played behind the “decorative screens” at the far end of the room. (The screens were the Maggies, of course, but back then I didn’t know they were loudspeakers.) The last time this happened to me was about a year ago when I listened to Steve Hoffman’s remastering of Joni Mitchell’s Blue [Warner] and heard the way her backup vocals had been potted into the mix with such clarity that I felt as if I were standing in the engineering booth alongside the mastering engineer, listening to him mix the multi-track mastertapes down to two-channel work parts. It wasn’t the same experience as the Maggie/ARC of years past. I wasn’t being fooled into thinking that an actual instrument was “there” in the room with me; instead I was being fooled into thinking that I was “there” at the mixing sessions, listening to recorded instruments being played back and mixed from separate tracks. In neither case was I aware that I was listening to speakers and electronics. All sense of hi-fi simply vanished.

If you’ve been following my other reviews in TAS or my blogs on our Web site, AVguide.com, you already know that the speakers I was listening to Blue on that day were the sensationally transparent MartinLogan CLXes and that the amp and preamp were two then-entirely-new-to-me solid-state wonders from an upstart Swiss company called Soulution.

I first heard about Soulution (the name is a Motown-like concatenation of “soul” and “solution”) from solid-state amp maven and loudspeaker-designer extraordinaire Alon Wolf. Soulution was not a company I was familiar with and when I looked it up on-line and discovered that it was a division of another Swiss company called Spemot that specialized in building electrical motors and refrigeration units for the automotive industry, I was not enthralled. Shades of Crown, I thought. Then I chanced upon a rave review of a Soulution product—the 120Wpc dual-mono Soulution 710 stereo amp—in the usually tough-minded German hi-fi magazine Stereo, and got more interested. You see, Stereo had pronounced the 710 a sonic and technological wunderkind. Indeed, the amp had tested so unprecedentedly low in distortion, so high in channel separation, so superbly well in S/N ratio that the magazine’s chief technician hung the test results in a gold frame above his bench.

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Sidebar: Design and Operation

Physically, all of the Soulution products share what I would call an austere Bauhaus aesthetic—kind of the anti-MBL/Burmester style. There is nothing fancy or gaudy about these simple, handsome, massive, beautifully machined boxes—each inset with its own glass window for readouts. They look like they’re ready to go to work. All three products give you an unusual amount of control over various functions—some operated by switches and some electronically. The electronic adjustments can be read out in the windows of each component. For instance, the 720 preamp allows you to set or adjust the starting volume level, the maximum volume level, the balance, the bandwidth of each input, the gain of each input, the gain of the phonostage, the highpass filtering of the phonostage, and the brightness of the display, among other things. Both amps and preamps have switches that allow you to lift grounds. The 700 has switches for selecting bi-amp or monoblock (bridged) modes and for fan level. All three products have XLR and RCA inputs and outputs. The EU-approved plastic-covered binding posts on the amps are a pain, but…what are you going to do? A chintzy but handy little plastic remote is included, which permits you to make all of the electronic adjustments from your listening seat. Form definitely follows function here—for the most part elegantly.

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Of course, some of us remember (at least some who go back that far) those Japanese solid-state amps from Sansui and others that also boasted record-low THD figures—but sounded like crap. The trouble was that to achieve such stellar specs the Japanese engineers had to ladle on so much negative feedback that the amps were virtual TIM generators. Feeding back the signal from the output in order to compare it to the signal at the input and eliminate any distortions that may have accrued as it made its way through the circuit works fine if that feedback process is instantaneous, but feedback is a disaster if the amp takes too long to make its corrections. After all, the musical signal coming into the amplifier doesn’t hold still for a portrait; it is constantly changing; and if too much time elapses (and we’re talking nanoseconds here), the signal that the feedback circuit is comparing the output to is no longer the same signal that was input. Think of it as a worst-case “jitter” scenario, albeit in the analog realm.