Solid State Power Amp Reviews

Threshold also makes a point of the fact that their STASIS designs maintain a constant (and high) damping factor over the full audio band. Contributing to this is the lack of overall feedback and the elimination of the ubiquitous output inductor (between the final output stage and the output terminal) required in most conventional designs.

Sound
OK, so we know that the big Thresholds are built like tanks compared with the go-cart construction of more real-world (pricewise) amplifiers. Two questions must be answered here. Are they among the best amplifiers in the world? (They better be, to justify the cost.) And are they really superior to considerably less expensive amplifiers?

After letting the big Thresholds "cook" in my listening room for a day or so, I was ready for a serious listen. First up was a recording that has had a lot of play around here lately: Fairy Tales (Odin CD-03). The image was precise and stable. High-frequency response was clean, with sibilants clearly audible (as they tend to be on this recording) yet totally free of spit or sizzle. Radka Toneff's voice was there, suspended in space between the loudspeakers. It was somewhat breathy in timbre (again, this seems to be a recording artifact), but convincingly real. The sound was open, with believable ambience. The analog-mastered cut (band 5) was clearly different in sound from the digital; both voice and piano were a bit sweeter, with a striking sense of space surrounding both. (footnote 6) Not a bad start.

And the positive first impressions held up. The most consistently recognizable qualities of the SA/12e were a gorgeously clean, natural high end with superb yet subtle detailing and an almost tactile midrange. Solo voice was consistently well-reproduced. The driving vocal and guitar rhythms on "Better Than Anything," from Tuck and Patti's Tears of Joy CD (Windham Hill Jazz WD-0111), were thrilling. Especially notable here were Patti Cathcart's terrific scat singing, tightly defined and detailed—totally devoid of harshness even at quite high playback levels. The real value of a good amplifier in a good system is not so much what it gives you as how well it lets you enjoy the music without being distracted by sonic flaws. The Thresholds passed this test with colors flying, on this and other recordings.

On "Stardust," from Rob Wasserman's Duets LP (MCA-42131), I found myself forgetting to take notes. Putting on my old, shopworn critic's hat became a chore. Definition was beautifully drawn yet never clinical—sweet but with no feeling of loss of detail. Voices in the mix were well differentiated. The midrange was strikingly clear. Natural sound is a complex mixture of the soft and rounded punctuated by transients of all descriptions; the Threshold rendered all of these subtle shadings in a musically rewarding fashion.

You'd expect a powerful amplifier with a high damping factor to produce a deep, solid, well-controlled low end, and you'd be right in the case of the Threshold. The bass drum on José Neto's Mountains and the Sea LP (Water Lily Acoustics WLA CS 02) was as punchy as I've ever heard it through the B&W 801s. The collapse of "The Beast" on Däfos (Reference Recordings RR-12CD) was thunderous, and the "Beam" in Psychopomp on the same recording was deep, growling, and downright eerie. The 801's bass tends to some warmth—especially in my current listening room, which is slightly smaller than the previous one and has a suspended floor—and the Thresholds were not able to make it as taut as I would like. But that's hardly the fault of the amplifiers. The low end was still very impressive.

My only reservation about the sound of the SA/12es came in the area of soundstaging. Lateral imaging was most precise—witness the drum set on "Brekkens Farm" from Flim & the BB's' Neon (DMP CD-458). The individual parts of the set could be precisely located from left to right—within inches. But on this and other recordings I didn't always get quite the same sensation of three-dimensional depth that I have obtained with other amplifiers. It was a sometime thing, however. I never felt a specific lack of depth when listening to the Thresholds by themselves. But the Thresholds do not have a laid-back sound. They are punchy and driving, and that up-front character tends to make depth less evident than it is with more retiring amplifiers. More on this shortly.

Listening to the SA/12es in isolation left no doubt about their quality. But how do they compare with other top-drawer units? Amplifiers of the price and power rating of the SA/12es are not exactly thick on the ground, even here at Stereophile Central. I decided on an end-run: the Mark Levinson No.23 (comparable in power) and a pair of Mark Levinson '20.5s (class-A monoblocks comparable in price (footnote 7), but at 100Wpc having considerably less oomph).

The results in both instances were intriguing. While I have to say that the Threshold came out on top, overall, in my judgment, the votes were decidedly mixed in many areas and the race was in no way a runaway. The No.23 was the first in the docket.

On the aforementioned Tears of Joy, the Threshold appeared the more coherent and dynamic. It actually seemed louder than the Levinson, though the relative levels had been closely matched by measurement. The Threshold reproduced Patti's voice in a more solid, gutsy manner—more "there." The Levinson was more laid-back, with highs that were a bit more prominent; sibilance was stronger, less smooth. But in no way was the Levinson over-etched. Score a close point for the SA/12e. On Jay Leonhardt's Salamander Pie (DMP CD-442, footnote 8), the Levinson's high end was crisper and more obvious, but in a highly attractive way. It sounded airier and more three-dimensional. But the double-bass was marginally more lively over the Threshold, and the latter continued to present a more live-sounding midrange. This one was a draw.

On the Astrée sampler CD (E7699) the baton was passed back and forth, the Levinson ultimately edging out the Threshold; the Levinson's slightly more prominent top end and laid-back quality gave it an airiness, depth, and "see-through" transparency which counted for more on most of the bands on this recording than did the Threshold's punch, drive, and, I feel, somewhat more accurate timbre and perspective. The opposite was true of Fantastic Journey, one of Telarc's (CD-80231) seemingly inexhaustible series of "theme" albums from Eric Kunzel and the Cincinnati Pops. Here the top end of the Levinson was overly crisp, the blat of the brass and shimmer of the cymbals taking on an edge that the Thresholds lacked. And the latter had the punchier bass, but only by a hair. The major difference in the low end between the Thresholds and the Levinson was in tautness (the Levinson being somewhat fuller and warmer), not in weight or extension.

Again, the race was a tight one. But the points started to add up in the SA/12es' favor. One particularly telling selection—though the CD set on the whole is far from reference quality sonically (I consider it dynamite in both music and performance, however (footnote 9)—was "What a Waste," from the original London cast recording of Miss Saigon (Geffen 9 24271-2). Early on a chorus enters, largely female in the center, largely male to the left and right. Through the Levinson the distinction between these groups was subtly smeared; the definition from the Thresholds was marginally but tellingly superior. And Jonathan Pryce's performance on the same piece seemed more "on" through the Thresholds, his vocal inflections more precise. I know—this doesn't seem like the sort of thing an amplifier can do. All I know is that I found this selection more of a knockout through the Thresholds: the difference between a superior performance and a show-stopper.

And what about the Thresholds in comparison with the Levinson No.20.5s? First of all, the 20.5s were closer in sound character to the No.23 than to the Thresholds. Clearly the Levinsons had a family sound. The 20.5s seemed a bit sweeter at the top than the 23, though both had quite similar timbres in this region. Both were less punchy and palpable than the Thresholds through the midband, and both gave a more obvious sense of depth. Compared with the Thresholds, I found myself strongly attracted to the airiness of the No.20.5s and their way with a three-dimensional soundspace. But the Thresholds seemed to have a timbre that was right. The Levinsons were more immediately impressive for their detailing, and while that detailing never seemed overt or etched, the more subtle top-end presentation of the SA/12es was a powerful draw, as was their midband vitality. And while we're on the subject of power, the Levinsons had a lot more sock than their 100W rating would lead you to expect, though they definitely ran out of steam—evinced by congestion of the sound and reduction of fore-aft depth and transparency—before the Thresholds. Not exactly an unpredictable outcome, considering the power difference. It must be noted that with all four of these current-happy monoblocks running at once, the line voltage dropped to between 106 and 109V. This put the Levinson at something of a disadvantage against the more powerful Threshold, though the former's power supply is heavily regulated. The Threshold's is not.

Conclusions
Before closing out my listening sessions with the Thresholds, I was able to audition them, briefly, in my listening room driving a different pair of loudspeakers: The Wilson Audio WATT/Puppies. This was clearly a loudspeaker with a different character from that of the B&W 801—more high-end energy, a leaner, tighter midbass, and a less extended extreme low end. But through these very different transducers the Threshold continued to display its open, lively midrange, detailed yet not overdone high end, and controlled bass. It is too early to judge if this is the best amplifier for these loudspeakers; a full review of the Wilsons is scheduled for a later issue. But I was not disappointed by the combination.

So do the Thresholds justify their lofty price? Is this trip really necessary? Yes and no. They provided, overall, the best performance I have ever obtained from my 801s. The latter, combined with the Levinson No.23, had been happy campers in the past, and that combination remains rewarding today. The Thresholds do not "blow it away" in any dramatic fashion. But they do differ from the No.23 in ways that will be significant to some listeners, subtle or unimportant to others. The same may be said of the Levinson No.20.5 comparison. The power output of the No.23, at least, is comparable to that of the Thresholds, but the price of the former is less than 40% of that of a pair of SA/12es (footnote 10). Threshold's own S/550e offers the same power (in a stereo, single-chassis, class-A/AB design) for less than half the price of a pair of SA/12es. And I intend to compare the two for an update when RH finishes his pending review of the S/550e.

The SA/12e is an imposing, stunningly good-sounding amplifier. Of that much I am absolutely certain. What is far less certain is the value of this amplifier to any given buyer. No one in his or her right mind, of course, would consider such a purchase without an extensive home audition—at this price, nothing less would be acceptable. For most of us, of course, amplifiers such as the SA/12e will remain pie in the sky. For those who might be barely able to afford the stretch in our audio budgets, the money might be better spent on one of the many excellent but less expensive amplifiers (Threshold's included) and a new pair of loudspeakers. Or a new turntable. Or acoustic treatment for the listening room. Or a trip around the world. But the SA/12e is worthy as a benchmark of state-of-the-art thinking in amplifier design. For those few readers who can genuinely afford and justify it, I can't imagine their being anything but ecstatic with the results.

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Footnote 6: This is not necessarily an analog vs digital issue, as this cut was recorded in a different studio under different conditions.

Footnote 7: Well, sort of. $12,000/pair (Levinson) vs $14,400/pair (Threshold).

Footnote 8: The lyrics of the title song alone are worth the price of admission.

Footnote 9: Though you should know that some of the lyrics are R-rated.

Footnote 10: As I write this, news has arrived of a new Levinson No.23.5, a substantial, and somewhat more expensive (early word: $5900 vs $5295) redesign of the No.23. Stay tuned.