Threshold Stasis SA/12e power amplifier Followup

Stereophile September 1991, Vol.14 No.9, Followup

When John Atkinson asked what I'd like to review for the September issue, I responded immediately that I had some unfinished business to attend to. When I reviewed the Threshold SA/12e monoblock (Vol.13 No.12) and Rowland Model One (Vol.14 No.4) stereo amplifiers, I left a few threads hanging. I'd promised a follow-up comparing the big Thresholds with one of that company's less pricey (though still far from cheap) stereo amplifiers, and I had yet to try a pair of Model Ones bridged as monoblocks. Hence this update.

Associated equipment used here included the Wadia WT-3200 transport and X-64-4 D/A converter (CD was used as the primary program source for these listening tests), Rowland Consonance preamplifier, and Apogee Stage and PSB Stratus Gold loudspeakers. Both pairs of loudspeakers were bi-wired using Symo cable. The CD processor-preamp link was via AudioQuest Lapis. The pre-power amplifier hookup was balanced Cardas Hexlink.

Threshold SA/12e vs the S/550e: After a period of listening to the SA/12es driving the Stages, my initial reaction on switching over to the S/550e (reviewed by RH in Vol.14 No.1) was one of familiarity. In no way was there any dramatic sonic change. But there were differences, which became clearer over time and in listening to the same program material over both amplifiers. The biggest difference was in the degree of focus and immediacy to the sound. What was perhaps surprising was that here the S/550e came out on top. It had the greater punch and "palpability," along with superb overall clarity. The S/12e was just a bit softer and sweeter—less incisively detailed and sparkling. On the Swingle Singers' new CD Around the World: A Folk Song Collection (Virgin Classics VC 7 91207-2), the interplay of the acapella voices was alive with energy and very much in-the-room with the stereo amp. Imaging was sharply defined, and the bass vocal solo on "Sakkijarven Polka" was striking. The more expensive monoblocks, in contrast, were just a shade less up-front and less tightly focused—a bit more relaxed, if you like it, or a bit less "there" if you don't. Both amplifiers were, again, still recognizable as members of the same sonic family.

On Leo Kottke's That's What (Private Music 2068-2-P) the sound of the S/550e was precise and pristine—detailed yet with a slight warmth. The perspective was still forward and present, yet not overdone. Percussion was sharply defined yet not clinically spotlighted. The 12es, on the other hand, were sweet and clean, yet perhaps because of this very sweetness they seemed to subtly soften the leading edges of transients and "slow" the subjective dynamics. The S/550e had more "startle-ability," a quality which extended down into the bass. Though the overall bass weight of both amplifiers was quite similar—I wouldn't choose one over the other on that basis in driving the Apogees—the generally more hair-trigger quality of the upper overtones of bass instruments through the S/550e made that amplifier seem to have the tighter low end.

To determine if the S/550e's more prominent top end would be a plus or a minus over a different loudspeaker, I set up the PSB Stratus Golds in the listening room. The PSBs were chosen for this audition not only for their overall high quality, but also because they have a rather different set of strengths and weaknesses from the Apogees. They are subjectively more extended at the top end than the Stages—on occasion a bit too much, as I said in my review in Vol.14 No.2—along with having a more extended (though not more powerful) low end. They lack the Stage's viselike midrange grip, but are otherwise open and relatively uncolored through that region.

The Threshold stereo amp was easily up to the challenge. Its midrange was vibrant and lively, its low end tight where required, explosive when called for. The soundstage, though definitely up-front, still exhibited a very effective sense of depth, and the lateral focus remained sharp. While I've rarely heard a true case where the loudspeakers "disappear" into the soundstage, this combination provided a reasonable approximation of that ideal.

The S/550e's incisive—though not, in my judgment, overdone—top end only ran into a bit of trouble over the PSBs with program material clearly recorded and mixed with too much sizzle on top. I suspect the moderately elevated response of the PSBs in the top octave, together with the Threshold's hang-ten response in the upper range (footnote 1) simply add up to a bit too much of a good thing on less than pristine program material. We're talking of a bit too much added zip here (which I do not credit to the amplifier), not major-league sizzle (unless you happen to be addicted to the early recordings of the Bubble Gums). But I'd advise caution in combining the S/550e with other equipment having a "hot" top octave. It is a superbly clean- and open-sounding amplifier, yet I would not describe its top end as "sweet" or in any way euphonic. The SA/12es, in contrast, do have a trace of sweetness, trading a bit of the excitement generated by the stereo amplifier for a slightly more refined, subtle quality, particularly in the treble.

Overall, then, a surprising result. Though I've used the SA/12es extensively to drive the Apogees, was certainly satisfied with them in that situation, and also used them as primary amplifiers in my reviewing of the PSB Stratus Golds, I have to say that I found myself marginally preferring the S/550e for driving both of these loudspeakers—with the reservations discussed above. If the S/550e lacks a trace of the SA/12es' subtle refinement, and it does, then it more than makes up for it with a more visceral, gutsy, tighter sound. I take back nothing that I said in my review of the big monoblocks, and they may very well win a face-off when driving loudspeakers in the stratospheric price category. But I would by no means assume that to be the case; no one in his or her right mind, in any event, should contemplate any amplifier in the price category of either of these Thresholds without first hearing them in the system in which they will be used.—Thomas J. Norton

Footnote 1: The surf board tied to a tree and visible over the back fence behind my office window, still waiting for Santa Fe's Monster Wave no doubt, is now largely hidden by the summer's foliage, but its presence must have somehow warped my subconscious.
Threshold Audio, Inc.
PO Box 41736
Houston, TX 77241
(713) 466-1411