Adcom GFA-555 power amplifier J. Gordon Holt 1985
After reading AHC's very positive review of the Adcom amplifier (Vol.8 No.5), I just had to audition it. Not just any old GFA-55, but the GFA-55 reviewed by AHC.
I was initially impressed, but not terribly. A half hour's listening, however, revealed a significantly better sound (by now I should know better than to listen to any amp during the first half hour), so I left it to cook overnight. (The Eagle 2 cooked too, just to make things fair; since then, I've found this to be crucial for the Eagle.)
After cooking, the GFA-55 sounded like the first real competition for the Eagle 2 that I'd heard. Two hours listening on several speakers revealed the following differences: the Adcom was somewhat sweeter and more open at the extreme high end, comparable in detail throughout the middle range, and, for all intents and purposes, identical to the Eagle in low-end heft and tautness (control). This last finding was surprising; in low-end control, the Eagle 2 had surpassed every amplifier that's passed through here for a year, including its larger and much more expensive brother, the Eagle 7A.
The Adcom had a shade less mid- and upper-mid forwardness than the Eagle, putting it about halfway in this respect between the Eagle and the Rowland Research 7, BEL 2002, and B&K ST-140, all of which sound a little laidback. Since the Eagle is a bit forward-sounding (some think even more than a bit), the Adcom has possibly the most neutral middle range of any amp—at any price. But apparent listening distance (forwardness) depends more on the speakers than the amplifier, and the setup of your listening room is also crucial; the amplifier should be chosen to complement your situation, and your tastes, rather than on an absolute basis. For a reviewer, though, neutrality is extremely important.
The Adcom's soundstaging is a little deeper and wider than that of the Eagle 2, but front-to-back perspectives are rendered a bit better by the Eagle.
There may be further subtleties of difference between the two amps, but my comparison was foreshortened when one channel of the Adcom died. Further observations await a replacement GFA-555, and will be reported in a future "Followup." It's already clear, however, that the two amplifiers are directly comparable, though somewhat different, in sound quality. Which to buy? You could choose based on the differences in sound quality, which are relatively minor, but could be important in a particular setup. Or you could choose on the basis of price: the Eagle is $995, the Adcom only $595. The Adcom is also much more widely available, though I've heard that AHC's review has put it in short supply—that's why we don't have a replacement yet!—J. Gordon Holt