Solid State Power Amp Reviews

I would frankly have been surprised if the low-end response of the Adcoms had been less than impressive, and no surprises were in store. In my listening room, the bottom end of most true-extension loudspeakers tends to be warm and full rather than tight and hair-trigger. The GFA-565s did not alter this situation—an amplifier cannot be expected to do so unless it is an amplifier problem to start with. But they did manage to flex the walls as impressively as any other amplifiers I have used there. I did note that low frequencies having significant upper-range overtones seemed a bit softened—more a function of the overtones than of the low-frequency response itself. But there were no problems with the low end of the Adcoms when it came to power and weight.

Through the midrange the GFA-565s had a convincingly real timbre and overall balance. I'm not the only reviewer here to use (overuse?) the term "palpable" to describe this quality. Readers may have been puzzled by that expression. What I mean by it is a feeling that the instrument or instruments (voices included) are fully formed and inherently three-dimensional. This is not the only component of realism and accuracy, but it is a significant one. This palpability provides a genuine feeling of immediacy, of communication with the performers. And it relates at a more technical level, to this reviewer at least, to a full-bodied (though not overblown) lower midrange.

This was a definite strength of the Adcoms. Solo voice was present, but not overdone. Instruments were weighty but not fattened. von Karajan's marvelous early-'60s London recording of Puccini's Tosca (CD, London 421 670-2) has always been one of my favorite recorded performances, largely for the magnificent sound of the Vienna Philharmonic, John Culshaw's spectacular production, and, most of all, the performance of Leontyne Price in the title role—fans of Callas in the same role notwithstanding (footnote 2). (Price occupies roughly the same position in my personal pantheon of singers that Elvis does in CG's.) I nearly listed this recording in my compilation for our "Records to Die For" feature in Vol.14 No.1, but its technical quality is not quite up to snuff (London's recordings of Wagner's Ring sound cleaner), nor are all the performances first-rate (footnote 3). But despite the recording's clearly audible overload in spots, intermittent glare on peaks, and its often less-than-liquid top end, the burnished glow of the VPO—particularity the sonority and sheer power of the brass section (listen to the opening chords of the last act, for example)—and Culshaw's striking staging were clearly audible through the Adcoms.

Through the high frequencies, the 565s remained totally clean and unflappable. They were entirely free of zip, tizziness, and any feeling of an analytical, "hi-fi" quality. I did note an occasional brightness in the lower treble, as if the amps were trying to harden up a bit but weren't really able to put much enthusiasm into it.

Although they certainly excel in delivery of clean power, dynamic punch, low-end weight, midrange timbre, and high-frequency ease and smoothness, the Adcom 565s are not entirely successful, in my opinion, in providing the ultimate in top-end detail, overall transparency, and soundstage depth. These limitations weren't immediately apparent—perhaps I was too taken with the Adcom's other, more positive traits. But I became gradually aware that the top end didn't sound totally open; the feeling of an unrestricted, unfettered treble extension was not there. Perhaps this is the back side of that clean, easy treble of which I spoke above. It also may relate to that sometime trace of lower-treble brightness (a subjective reduction in top-octave extension can, paradoxically, sometimes cause a corresponding sensation of emphasis on the region just below it).

Dorian's recording of Pictures at an Exhibition (DOR-90117) has been justly praised for its phenomenal low-frequency response. But it is also notable for its sense of space, air, and depth. The Adcoms certainly did justice to this recording at the low end. But its depth, while reasonably effective, was not totally convincing, and the sense of "air" surrounding the high pipes on this recording was less than fully developed. With this and other recordings, the focus and textures of the soundstage seemed slightly darkened. The effect was not dramatic, but was definitely noticed over time into a variety of loudspeaker loads. It was less of a concern (though still noticeable) with the Snell C/IVs than with the B&W 801s; the latter were just a bit warmer and fuller-sounding than the Snells in my listening room, which reduced midbass detail enough to further "darken" the overall sound with the Adcoms—something the latter did not need. The Adcoms also displayed a punchy, powerful quality, solid low end, and that same smooth (if slightly softened) extreme top end through the Apogee Stages.

But although I never felt any feeling of strain from those loudspeakers at the playback levels used, I did encounter some psychological misgivings: the Adcoms are able to push well over 500W into each of the (3 ohm) Stages. Since the latter can be overloaded with sharp, high-level, low-frequency transients (as can any panel loudspeaker of which I am aware), I'm not sure I feel entirely comfortable recommending this combination. The Stages are such embarrassingly good loudspeakers up to the point where they begin to beg for mercy that you may be tempted to overdo it in driving them with the Adcoms. If you do choose to try the combination, I'd at least advise caution until you explore its limits in your circumstances.

The Adcom GFA-565s turned in a fine performance with all of the test loudspeakers, though I continued to feel that their openness and transparency were a cut or two below the best, and a cut or two below their solid credentials in other respects.

Monoblocks or single-chassis: Sumo vs Adcom
In theory, separating the two channels of a stereo amplifier should yield dividends. Interchannel crosstalk will certainly be reduced. Heat buildup will be less due to a (usually) more open, less crowded architecture. Monoblocks can be (but aren't always) of a more practical size. And the amplifiers may be located closer to the loudspeakers. In practice, I have some doubts as to whether these advantages—except for the last—will always be significant. The only way to be certain, of course, is to compare two identically designed amplifiers—identical, that is, except for one being split into two monoblocks, the other being integrated as a one-chassis stereo amplifier. Even then, I suspect the results will differ depending on whether or not we compare modest, cost-efficient designs or all-out assaults on the state of the art. The monoblock configuration should, ironically, benefit lower-cost designs the most—the type of design in which it is least likely to be used.

Neither the GFA-565s nor the Sumo Andromeda II are exactly budget amplifiers. But neither are they all-out, price-no-object efforts. Both involve some degree of carefully balanced compromise—though I suspect that their makers will not agree that this compromises the results—to keep costs below the audio stratosphere.

They do not sound alike, as what I have written to this point should make clear. I found the Andromeda II to be, overall, the more involving performer. Though not without some reservations: the Adcoms displayed some pretty fancy footwork of their own. On the King's Singers' The Beatles Connection (EMI CDC 7 49556 2), the GFA-565s were hard to fault. The sound was very clean and sweet—certainly not analytical or in any way bright or artificial. The voices were up-front and very much "there." The Andromeda II was, in contrast, more laid-back through the midrange, less immediate. But the latter sounded more three-dimensional, with a more "see into" soundstage. Individual voices were easier to hear, massed voices had a more realistic texture and were less homogenized.

On Leo Kottke's That's What CD (Private Music 2068-2-P), the Adcoms came out ahead in more convincingly portraying the timbre of the lower midrange, in presenting properly weighted voices and instruments. Imaging was sharp, and on the two vocal cuts Kottke's, ah, rather strange voice (footnote 4) was realistically full-bodied and tactile. From the upper midrange and into the highs, however, the Sumo sounded, overall, "faster" and more detailed than the Adcoms, with a more layered, open, and transparent soundstage. The latter was the less "tube-like" of the two amps, though neither is likely to win over die-hard tube lovers. As to low-frequency response, I was rather surprised to find myself leaning, in the end, toward the less powerful, single-chassis Sumo.

On the Dorian Pictures, both amps will do a suitable magic-fingers treatment of your backside in the lowest frequencies. But the Sumo appeared to have just a bit more weight and gutsiness in its overall low-end performance. In part this was a function of its more open top end (definitely audible in the presentation of this recording's ambient space), its more evident overtone structure providing the harmonics which provide focus to even the lowest frequencies. This quality was also apparent on percussive bass. There's a sharp bass-drum impact near the end of "Pops Hoedown" on Telarc's Round-Up (CD-80141). With the Adcoms, the word "impressive" came quickly to mind as I heard it (over the Snell C/IVs in this case). With the Sumo, I bellowed out an involuntary and quite audible "Yeah!" following the same passage. The actual sonic difference was not that dramatic. My reaction was.

But the Sumo is, based on my experience, a bit touchier in the matching department than the Adcom. Though it was at its best through the Snell C/IVs and (in a briefer audition) the Nestorovics, I was never entirely happy with it through the Apogee Stages—especially when used (as already noted) with an analytical cartridge. And I found its low end to be a trace too full through the B&W 801s in my listening room, a fullness at least partially the fault of the loudspeaker/room match (I've obtained better results from the B&Ws in prior listening spaces). The Sumo's revealing, unforgiving, airy but somewhat crisp top end, combined with its slight leanness in the lower midrange, make it, to this listener, the more open, transparent window on the sound. But if you provide it with the wrong combination of associated equipment and program material, it can sound less than sweet; even, on occasion, overly analytic.

The Adcoms, on the other hand, except for that occasional tendency to brighten in the lower treble, never showed any rough spots which could not be attributed to the program material. And their sound was somewhat more consistent through the four pairs of loudspeakers used in the evaluation. But, at its best, the Andromeda II soared for me in a way that the Adcoms never quite managed.

Conclusions
I was favorably impressed by the Adcom. It is an attractive alternative to spending megabucks on system go-power, but it is not really a Krell (or whatever) in sheep's clothing. While I would certainly put the Adcom on my shopping list if I were looking in this price and power range, I would not make a decision until I had auditioned the Sumo Andromeda II. For this listener, the Sumo pushed the right buttons.—Thomas J. Norton

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Footnote 2: Letters. I'll get letters.

Footnote 3: Gary Galo asked me once how I could stand di Stefano's Cavaradossi in this recording. Frankly, he doesn't bother me much, and he moans convincingly in the Act II torture scene. Giuseppi Taddei's Scarpia has an occasional trace of wobble in his vibrato, but it's not a major negative—he's playing the prototypical Dirty Old Man anyway, and his characterization is marvelously oily.

Footnote 4: Described by Kottke himself as sounding "like goose farts on a foggy day."—Richard Lehnert