Adcom GFA-7805 five-channel power amplifier

For me, the iconic Adcom power amplifier was the GFA-555. As an aspiring audiophile, I was deeply impressed with Tony Cordesman's review in Stereophile in 1985 (Vol.8 No.4). That did it! After years of kit-building and doing it myself, the '555 was the first factory-built amp that I wanted and could afford. Over the years, I changed speakers several times, and even added a fully regulated power supply to the '555, but it never balked. At the end of its tenure at my house, it had been demoted to my third-string backup; today it's making someone else tap his toes.

That typifies my view of Adcom amps and preamps: well-designed, well-constructed, and well-priced. For many, they're the first step from an integrated system to separate components, and Adcom's reliability and simplicity serve well in that role. Today, Adcom's line includes everything from a DVD player to multichannel controllers and amps. Still, it was easy for me to decide on their top-of-the-line five-channel powerhouse, the GFA-7805, because it embodies the same spirit that the GFA-555 did in its time: lots of power, no frills, good value.

The GFA-7805 is an 88-lb block of solid amp. Aside from the AC socket, fuse post, and trigger input on the right, the rear panel is arranged in five vertical segments corresponding to the five channels. From the top down, each segment has an RCA input, an RCA/XLR switch, an XLR input, and a pair of multiway binding posts. No heatsinks are visible on the GFA-7805's rear or sides; the ridged panels on the top and bottom of the front panel seem more of a design motif harking back to the GFA-555 II than functional heat dissipaters.

The central portion of the GFA-7805's front panel bears an illuminated power switch and two rows of LEDs, two for each channel. The upper LED lights when its channel approaches 1% THD, as informed by a circuit that monitors nonlinear distortion and clipping. These LEDs may flicker briefly at very high levels; a steady glow indicates that the amp is being overdriven. Given the GFA-7805's power capability, this will probably mean that you're deaf or soon will be. The lower LED indicates when the internal heatsink of that channel's amplifier has exceeded 85 degrees C and the thermal protection circuit has shut it down. That LED will extinguish, and the sound will return, when the temperature drops to within normal range. One should never (well, hardly ever) see any of these LEDs lit longer than briefly. (But I did. See Sidebar, "Cable Issues.")

All five channels at work
In my multichannel room, the GFA-7805's power was overkill for both my Magnepan Home Theater and Paradigm Reference Studio speaker systems. No matter the signal's level or dynamic range, the Adcom drove the speakers with aplomb. There was a general feeling of smoothness and balance, with no particular part of the spectrum out of place. That was of great value with older reissue material and FM broadcasts. Newer, more dynamic material, such as Romero's Un Segundo Una Vida (SACD, 333 Entertainment 333ESA001), was conveyed with tremendous power and weight, as well as great delicacy when appropriate. I heard no veiling or grain in my multichannel system, although I often found that, in an effort to hear some details, I was listening at somewhat louder levels than I had with other amps. Imaging depth and breadth were equally good with two- and five-channel material. Overall, I had the impression that the GFA-7805 was more sophisticated and liquid-sounding than its '555 ancestors.

It was clear that the GFA-7805 was a smooth, clean, powerful performer, but also that it complemented the Maggies somewhat better than the Paradigms. Because deep bass in the multichannel system was handled by the Paradigm Servo-15, it was not so much the quantity of bass as its quality and balance that were at issue. The Maggie-Adcom combo sounded relaxed, with transparent mids and highs and more than adequate midbass. The GFA-7805 lacked some brilliance in comparison to my Bel Canto eVo6 power amplifier, but that was consistent with the Adcom's more distant perspective. Overall, the Maggies sounded most balanced from top to (almost) bottom with the Adcom, while both the eVo6 and my Bryston 9B-SST made the Maggies seem smaller and closer. The Skrowaczewski-Minnesota recording of Ravel's orchestral works (SACD, Mobile Fidelity UDSACD 4002) made the distinction clear. The Adcom let the Maggies open up a wide, deep soundspace, and kept the intra-orchestra positions very well; nothing, not even brass or wind solos, jumped out. The other amps moved the soundstage closer, spread it wider, and made it more intense, but with some loss of stability in instrument spacing.

When I switched to the Paradigms, the tables turned. I loved the weight and power of the Adcom with the full-range Studio/60s. The GFA-7805's forgivingly soft rendition of the upper part of the spectrum complemented the '60s, but perhaps a bit too much. With Eric Clapton and B.B. King's "Riding with the King" (DVD-A, Reprise 47612-9), I kept wanting the guitar licks on "Help the Poor" to come out and grab me. With such solo-oriented discs as the SACD remastering of James Taylor's Dad Loves His Work (Columbia CH 90750), JT was not in front of the band but in it. There was clarity and detail to spare, but a bit too much velvet glove covering the steel fist.

Pick any two!
After a sojourn on John Atkinson's test bench, the GFA-7805 (serial no. FCS0000) was put back to work in my stereo system in New York City. Instead of the single-ended inputs, I used the XLR inputs and only two channels. Arbitrarily, I chose the two on the extreme left and right. The GFA-7805 has no bridging facilities, so the other channels sat idle. I encountered no stability problems with the Revel Ultima Studios using AudioQuest, Straight Wire, or Harmonic Technology speaker cables.

In this system, due to the dynamic capabilities of the speakers and a well-damped room (to say nothing of accommodating neighbors), I was able to run the Adcom quite a bit harder. No matter what I asked of it, and without flickering its LEDs or turning on its cooling fan, the GFA-7805 delivered full, extended, defined bass, a balanced midbass and midrange, and silky highs. In addition, its performance quality was consistent at all power levels, from easy-listening to shake-the-walls. One might think that two-fifths of a $2400 power amp might be out of its weight class in a high-end system, but the Adcom was a pleasure to listen to for extended periods.

That said, the GFA-7805 was not without character. It seemed rolled-off in the highs, which made it slightly distant and tended to soften high-frequency dynamics, even though changes in volume, per se, was easily accomplished. Some of this had to have been the smoothness and effortlessness with which the GFA-7805 handled wide dynamic change. Perhaps it made those changes seem less imposing than if they were announced with a shout. The soundstage was as wide and deep as I have ever experienced with this system, but the central images lacked some of the etched specificity I've come to expect from the Revels. The Rosalyra String Quartet's performance of Shostakovich's Quartet 8 (SACD, Artegra ART1002), via Theta Digital's Generation VIII DAC-controller, was particularly intense—especially the exquisite intimacy of the slow movements. In switching from the Classé CAM-350s ($7000/pair) or the Sonic Frontiers Power-3s ($10,000/pair) to the Adcom, I sensed no loss of resolution or music, but here and there I missed little frissons of delight that I'd experienced with the other amps. The experience was too relaxed to be as shattering.

Big stuff or jazz, such as the 24-bit/96kHz rendering of Ray Brown's Soular Energy (DVD-A, Hi-Res Music HRM 2011), had excellent presence and detail. But Wayne Horvitz's Forever (DVD-A, Hi-Res Music HRM 2001) sounded a bit "hooded" and dull. The latter is decidedly not an open, airy recording, so the Adcom was not itself creating this effect, but rather emphasizing what was already on the disc.

That, I suppose, is the bottom line. Every amp I've used has had some signature. The Adcom's was a reticence in the upper midrange and treble that I perceived not as dimness or murk but as a lack of assertiveness. That's not necessarily bad. In the right context, all the detail and resolution were apparent. In my own fairly warm setup, the problem was quite minor. Given the variations among systems and sound rooms, the GFA-7805 will be out of step only in highly damped rooms.

What? 300Wpc ain't enough for you?
They say that power corrupts. They're right...but I just had to try biamping the Ultima Studios with pairs of the Adcom's 300W channels. Because the Sonic Frontiers Line-3 has multiple line outputs, I just ran two pairs of AudioQuest balanced cable into four of the GFA-7805's channels, sparing the central segment. Such a setup invites megalomania, so I hauled out the appropriate blockbusters.

My favorite was Pierre Boulez's new recording of Mahler's Symphony 3 (CD, Deutsche Grammophon 474 298-2). Glorious! Played at levels that drove the less committed from the room but strangely evoked no reprisals from the neighbors, the Adcom and Revels performed masterfully. From the powerful, martial opening (oh, those drum whacks!), the charming posthorn serenades, the lighter-than-air "Bimm bamm!" of the chorus, and on through the hopeful and expansive exaltations of the finale, it was a thrilling experience filled with piquant detail and emotive power. I had to close my eyes—what I saw of my modest room was in violent contrast to the spaciousness of the ensemble at full cry. As did many other DDD recordings from DG, this one benefited from the Adcom's smoothness and lack of edginess. While it's likely that using only two 300W channels of the Adcom would have handled this, the thrill of ultimate power probably added to my excitement.

Conclusions
It is very hard to fault the Adcom GFA-7805. It certainly doesn't lack power, with five channels of 300 clean watts each. It certainly doesn't lack clarity or transparency, or extended, powerful, and controlled bass. If anything, the Adcom GFA-7805 was somewhat softer and more forgiving in the highs than other premium amps, but this very fault might be an asset in a brighter room and/or with a brighter system. For a two-channel system, it can be recommended to anyone looking for gobs of well-behaved power. For a multichannel system, it's hard to pass up. Like the two-channel GFA-555 in its day, the five-channel GFA-7805 offers great sound and all the power most systems can use, at a price that's remarkably low.

COMPANY INFO
Adcom
8551 East Anderson Drive, Suite 105
Scottsdale, AZ 85255
(480) 607-2277
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