Dynamic range, tonal neutrality, wide soundstage, can drive low-impedance and weird loads (read the Acoustat transformer interface) without problems. Build quality is outstanding; high-quality inputs/speaker terminals. Overall, the perceptively "sweetest" bipolar-output solid-state amplifier I've ever auditioned -- or owned. And -- it's a bargain even at retail. And -- it's fully dual-mono, right down to the dual toroidal transformers (this might in some part account for the extra-wide soundstaging characteristic).

Lack of "air" around individual instruments or performers, at least in relation to the best I've experienced as well as live performances. With some speaker systems, particularly those configured as line-sources, might exhibit a slight "hole" in the center while projecting a soundstage outside the speaker systems. Highs do not "bloom" as well as with the best (in my experience, MOSFET) solid-state or tubed amplifiers. And -- one thing -- the AC receptacle in back is a staggered 3-pin, like a standard IEC, but it is NOT a standard IEC unit (pin spacing is different) but rather a high-current industrial alternative, rendering aftermarket AC cords unusable unless their female socket is replaced with an appropriate connector (I've got an inquiry with a major Southern California supplier to see if a high-quality connector can be "grafted" onto one of my Tek Line power cords). The supplied cord is a molded-connector 12-gauge 3-wire type which seems to work fine -- but I just wonder if the slight drawbacks to this amp just might be ameliorated with a cord upgrade -- I could find out within a matter of weeks about this.

I'd known about the ATI stuff for some years; the co. principals are the same folks who started SAE back in the late `60's. I was doing some speaker design consulting for a local company; the head of that company knew one of the principals, and I had met the other some years previously when I worked for a now-defunct audio mfr (name withheld) who shared the same marketing/distribution firm. With a couple of phone calls and a little schmoozing I got the opportunity to try out an ATI amp. The most logical choice for me -- as well as the best perceived value -- was the 1800 series; particularly the 2-channel version (each product series can be configured for 2-7 channels!). I picked up the 1802, took it home, and set it up the following day. The product lit said it weighed in at 50 lbs; it actually tipped the scales at 61 (unpacked) -- a call to ATI revealed that they had "beefed up" their twin toroidal trannies with a more substantial core "donut"; this accounted for the additional weight. I was just glad they had included the optional front handles on my unit. Since it had been some years since I'd auditioned a unit from this design team, I thought I'd know what to expect -- the usual strengths of solid-state (this unit features bipolar output devices) with a lesser smattering of the drawbacks -- smaller than full-size spatial images, extended but non-dimensional highs, etc. -- the usual litany. And I was about to subject it to a real "acid test" -- my 1989 vintage Acoustat 2200 ES units, as well as a number of dynamic units (mostly of my own design). And it was being compared to an amp I had sold a year or so before and which I considered to be, overall, the finest I've owned to date -- the Belles 350A, which I had to sell for financial reasons due to health problems over a two-year stretch. In short, it had pretty big shoes to fill, so to speak! The upshot is: no, it's not, to my ears, quite as profoundly musical as the Belles. But, for a (relatively) high-powered amplifier, it comes surprisingly close. Its tonal balance, while falling ever so slightly on the side of lean, is the best I've experienced from a bipolar-powered unit. When used as a subwoofer amp, it reaches deeply into the lowest depths (when asked to pass a signal below 30Hz) without appreciable coloration. When used fullrange, it is perceptively neutral from top to bottom. In fact, neutrality could be the keyword to describe the tonal presentation of the AT-1802: it seems not to add a single characteristic of its own. However, that neutrality appears to come at a small price -- the sense of "air" around individual performers and/or instruments, so prominent with the Belles unit, is truncated with the ATI amp; the temporal and spatial cues that comprise this sense of "air" are slightly recessed in the sense that the primary tones are reproduced in a strightforward manner, with the sense of leading (attack) and lagging (decay) temporal ambience not there at the level of the best available amplification. This is not to say that it is absent -- just not particularly prominent. Dynamic range is excellent -- this thing responds quickly to such changes in the program material. When it comes to soundstaging, it is an unusual beast. With each of the speakers used, it projects a singularly wide soundstage, extending well beyond the speaker units to the edges of the listening room. With point-source dynamic speakers (particularly M-T-M - configured units) it extends this characteristic across the full stage -- but with line-source speakers (such as the Acoustat ES systems), the sense of center fill is lessened (not so with the Belles 350A). Front-to-back spatiality is above average, but not up to the standards experiences with tube or even MOSFET units, which, in my experience, excel at this. In summary, the ATI AT-1802 is a unit that, despite its few shortcomings, exhibits a sense of musical neutrality and overall "rightness"; at its $1K retail price, it is a steal. There's little it can't drive with panache. Having owned bipolar amps from the original SAE, Audire, Threshold, Electron Kinetics, PS Audio, and others along the way, I can state that the ATI is sonically the equal or better of them all; surpassed only in the solid-state realm by a couple of newer-design MOSFET units. Before I got the Belles 350A (back in those dark days right after 9/11) I had the opportunity to borrow a Odyssey Stratos for a week or so; luckily it had been burned in, so it sounded sweet -- up to this year, it was the best reasonably-powered-and-priced bipolar unit I've auditioned. The ATI is at least its equal. And -- most telling -- the 1802 is still sitting on its stand, driving the Acoustats; and the ATI factory rep has several hundred of my dollars in return. It's going to stay there for quite some time to come.

Similar Products Used:

Belles 350A (all-time solid-state reference), Musical Design D75 (nice-sounding unit but with limited dynamic range), Odyssey Stratos (extended audition).