The Threshold S/500 Stasis Power Amplifier  Solid-state stereo amplifier. 250 watts/channel, max. current 22 amp. Frequency response I to 100k Hz, +0/-3 dB. Damping factor 100 from 20 to 20kHz. Slew rate 80V/usec. Dimen-sions 19" W by 19" D by 9-1/2" H, overall. Weight 92 lbs. Price $2970. MANUFACTURER: Threshold Corp., 1832 Tribute Rd., Suite E, Sacramento, CA 95815

 Itís interesting how tubed and solid-state power amplifiers have been sounding more and more similar of late. Not too many years ago, you could identify the kind of amplifier you were listening to in about 30 seconds (often less). Solid-state amps were tight and controlled at the low end, slightly flat and grainy and rather withdrawn-sounding through the middle range, and more or less tipped-up and sizzly-crisp at the high end. Tubed amps were warm, mellow, fat through the midbass, deficient in deep bass, bright and forward in the middle range, and pleasantly, consonantly soft at the high end. I have tended for some years to assume that the ultimate correctness, if indeed there is any such thing, lay somewhere in between, but whether the tubes or the transistors were hewing closer to the mark was something about which I was not prepared to hazard a guess. Tubes sounded more "musical," but transis-tors had greater detail and better low end.

 With the arrival on the premises of two top-performing (and top-priced) representatives from the two campsó the solid-state S/500 Stasis and the tubed Conrad-Johnson Premier IóI have enjoyed the opportunity of comparing them side by side. No longer is there an immediate thatís-tube-and-thatís-solid-state difference. But the same differences remain, even though diminished in degree.

 The Conrad-Johnson does not have the glary middle-range brightness which, through the years, I have come to associate with tubes, but neither does the Threshold have that withdrawn, distant middle range that was for so long the trademark of the solid-state amplifier. By comparison, the C-J still has a softer high end than the Threshold, but the difference is no longer night-and-day dramatic. I will still hand the edge to the C-J for musicality through the most revealing speakers: electrostatics.

 But the Threshold is so close to it in this respect that the choice might now be made on the basis of personal taste rather than on what sounds good and what sounds awful. The C-J seems to reproduce depth and perspective better than the Stasis, but the Stasis seems to have more solidity and ease at comparable listening levelsóa difference I cannot attribute merely to a 25% difference in rated output. The C-J gets hot in normal use (of course it would, with all those tubes), while the Stasis just squats there with its cooling fins barely warmer than your fingers, practically daring you to blow out your speakers.

 But it is at the low end where the 5/500 stands out from the crowd. I have never, ever heard an amplifier that can control woofers the way this one does. Low-end detail from every speaker I fed it to was better than I had heard from those speakers before. It is also one amplifier that has the capability of wiping out a bad load instead of vice versa. I did not try the amplifier on the Quad 63s, but I have a strong suspicion that Quadís throw-a-crowbar-across-the-amplifier output-protection system would be splattered all over the map by this amplifier, simply because of its ability to throw overkill-type power at anything that stands in its way. (An accidental speaker-cable short caused a white flash that melted the offending wire strands.) I had the feeling this thing could cold-start a Mack truck.

 The S/500 is the second solid-state power amp I have found which does superbly on Acoustat speakers. It is slightly tighter and deeper at the low end, and perhaps a tad smoother at the top, than Acoustatís own amp. Differences are small though, and whether or not they are worth almost three times the price of Acoustatís TNT-200 is something only a prospec-tive buyer can decide for him or herself.

 Other observations: The S/500 has superb inner definition. Revealing individual voices in complex program material as well as any amp I have heard to date.* It is very quiet, and except for a momentary dimming of the house lights when first turned on, it just sits there and does its thing.At this point, I would rate this among the best amplifiers available, for use with the widest variety of speakers. C-Jís Premier I, I feel, is still slightly more agreeable-sounding with most electrostatic speakers, but I also think the S/500 is the closest an amplifier has ever come to being All Things To All People. If this does not become a Classic in its own time (i.e., before it is replaced by an s/500), I will be very surprised. JGH

* It is both amusing and chastening to recall that when I reviewed the Infinity HCA amplifier some four years ago, I declared that audio electronics had become about as good as they needed to. That was before the Berning TF-10 preamp, the Acoustat PNP and TNT-200, the Conrad-Johnson Premier I, the Threshold S/500, etc.,etc.I have since become more prudent.