Solid State Power Amp Reviews

Okay, here you are: You're a Real World music lover trying to sling together a Real World hi-fi rig. You gotcha budget-king NAD/Rotel/JVC/Pioneer CD player, your SOTA Comet/Sumiko Blue Point analog rig, and your cool-man NHT/PSB/Definitive Technology entry-level speakers. Hell, you've even gone out and bought a few pairs of Kimber PBJ interconnects to hook it all up. This ain't no dog and pony show—you want that High-End High, not just some cheap'n'cheerful, low-rez rig to stick in the rumpus room so the kids can listen to that weak-ass, faux-grunge, watered-down Hendrix-howl that modern-day wimp-boys like Pearl Jam dish out to anyone under 30 who doesn't know any better.

But what are you gonna drive this Real World rig with? A Japanese surround-sound receiver with 1000 buttons and a power supply the size of Tattoo's gallbladder? Forget about it—you need a real high-end power amplifier to get your money's worth out of all that cool-man, entry-level gear you've slung together. You want clean, steady power, and enough of it to do the job—60W a side can drive most loudspeakers to minimum Rock-Approved levels in all but the most cavernous rooms. You want something that'll give you 90% of the sound of the best amps out there—and you want all this for under 400 clams! Me, I'd throw in fat-free hotdogs that tasted as good as Nathan's, but then I always dream big.

Which brings me to a sub–$400 power amplifier that also dreams big: Adcom's GFA-535 II. It's rated at 60Wpc, it's from a company that has achieved good a track record over the years for reliable, good-value gear, it's made in Taiwan, and it's been fired up in my Real World system now for many months. Does it kill Krells, thrash Thresholds, vivisect VTLs, and bum-rush Boulders?

Press on and ye shall know!

Adcom GFA-535 II
I'll get the techno-jizz out of the way so you can enjoy the rest of the review in comfort. The Adcom's circuit features a discrete-transistor front-end and voltage-gain stage, both class-A biased, and a high-current triple-Darlington-follower output stage. The signal path is AC-coupled before the input stage, a small series polycarbonate capacitor and a shunt resistor providing high-pass filter action down 3dB at 1.9Hz. There's a single op-amp in the circuit per channel, used in a servo circuit to correct for DC at the speaker outputs. No series output inductor is employed, causing long lines at the inductor unemployment office.

Internally, the GFA-535 II's build quality is up to Adcom's usual high level. Low-noise, metal-film resistors and precision film caps populate the printed circuit board, while the pcb layout minimizes long wiring runs throughout. The two-transformer dual-mono power supply is quite a bit beefier than normally seen in this price range, with each transformer's 50VDC supply rails smoothed with a 6800µF/63V electrolytic cap bypassed with a 0.22µF film cap.

Okay, so Extreme Dual-Mono fetishists will bitch that the Adcom's supply isn't truly dual-mono 'cuz of the single AC power cord, but do me a favor, guys—a little deodorant now and then, hey?

Surprisingly for such a budget-minded design, the Adcom's input RCA jacks are high-quality, Tiffany-style, gold-plated types, but the output posts are a bit lower in outlook—raised plastic ridges at their bases preclude the use of spade lugs, and the round knurled plastic nuts mean that you can't use a hexdriver to tighten them down. You'll have to use bare wire stuck through the post's hole, or perhaps speaker cables terminated with either banana plugs or Deltrons.

The front panel features three LEDs: one to indicate that the thermal-protection circuit has been tripped, and two to indicate "instantaneous distortion alert"—in all my headbanging with the Adcom, I never saw any of these lights come on, and I drove this amp hard!

Sound
The littlest Adcom was a pretty forward-sounding amplifier, with a brightish balance that always called immediate attention to itself in my two systems. The Adcom's low treble had a persistent edge which produced a fairly piercing sound that made Rock-Approved listening levels a bit hard to take. Unfortunately, this type of tonal balance does not tend to flatter the kind of budget gear you're likely to mate with an amp in this price range. When you get down into the Lower Reaches with hi-fi gear, the first thing to go is usually a clean midrange and high end. The most common characteristic I keep hearing while reviewing budget gear is a gritty coarseness through the mids and highs that tends to make music sound more synthetic than with the higher-end gear. And unfortunately for the Adcom GFA-535 II, it seemed to accentuate this hardness, adding a bit of bite and roughness of its own to the overall sound.

The Adcom did have a pretty good bottom end—a little light and restrained in absolute terms, but tight and well-defined. Music with strong bass lines, like the Masters of Reality's Sunrise on the Sufferbus CD and DCC's (the label, not the data-compressed format) reissue of Cream's Wheels of Fire, came across as less balls-out slammin' with the Adcom in the chain than with the Acurus DIA-100—but then the Acurus does cost almost three times as much moolah. I found the Adcom's bass to be better suited to slower pieces that throb, like Masters of Reality's "V.H.V. (Blues for Eartha)," rather than 4-2-the-floor blasters like MOR's "She Got Me" from the same disc. The Adcom just didn't have the speed and attack of the Acurus in the low end, or, for that matter, Adcom's own GFA-555 II. It was also slightly bettered in this regard by the Rotel RB-960BX, though the Rotel's low end wasn't really anything to get jazzed about, either.

I don't think you can expect Bass O'The Gods from a li'l $350 amplifier, and I certainly didn't get it from either the Adcom or the Rotel: Tickets to the Big Bass Ball just cost more than $350, that's all. With budget designs like these, corners have to be cut, and it's the smart designer who can best hide his compromises when trying to deliver high-end sound for a few hundred clams.

But it was that ever-pervasive sense of hardness and grain that kept me from getting too worked up over the Adcom's sound. In my opinion, if budget gear can't achieve the same level of cleanliness and clarity that even most mid-priced gear seems to possess these days, it's better that it err toward softness rather than hardness. (I have to assume that most listeners fishing around in this low-dollar pond would rather listen to somewhat softened, rounded-off sounds than ones whose coarseness keeps calling attention to their inexpensive origins. I know I do.)

Replacing the Adcom GFA-535 II with a good mid-priced amplifier such as the $1200 Muse Model One Hundred or the $600 Rotel RB-980BX (footnote 1) pretty much banished this midrange congestion, transforming the sound of the Real World system into something much more akin to a true high-end rig.

Here's what I'm talking about: When I played the Fairfield Four's Standing in the Safety Zone CD with the Adcom in the chain, I heard a raspier, grainier sound from this gospel quartet than the kind of stunning clarity and openness I regularly experience when I plop this amazing CD into my He-Man rig. The music's clean-headed vibe is normally stuff you want to sit back and drink in like fresh-squeezed orange juice, but the Adcom's congestion through the midrange made the sound much less satisfying, with a trace of hash surrounding the whole ensemble. I found the $995 Conrad-Johnson PV10A tube preamp to go a long way toward smoothing the Adcom's rough edges, but a thousand-buck preamp is a bit out of place in a Real World budget rig. Using the excellent, passive McCormack Line Drive wasn't a good choice, either, because this unit's extreme transparency didn't balance the Adcom's bite in the way that the PV10A did.

I'd have to rate the Adcom GFA-535 II as average in terms of re-creating a believable sense of space on well-recorded program material. My Real World system isn't really a champ at throwing up a wide, palpable soundstage, but the sense of 3D space was much better when the system was driven by the Rotel RB-960BX. The 535 II tended to flatten the depth of images and the soundstage, making for a shallower presentation overall than the RB-960BX. The Adcom did seem to have sharper image focus, but I'm not sure that this wasn't mostly due to its much brighter and more forward signature. The Rotel, with its softer-focus rendering, nonetheless had a bigger, more accessible sound. I think that pinpoint imaging and that nth degree of soundstage width are thangs that the Real World music lover needs to forget when trying to assemble a system like this. At these prices you just can't have it all, and I'll trade Ultimate Space Trippin' for a more relaxed and less hashy sound.

Perhaps the most telling moments came for the Adcom when I had it and the Rotel running in the He-Man room, alternating them to drive the big NHT 3.3 loudspeakers. When friends came by, it was always the Rotel that I'd hook up to show my pals what a good el-cheapo amplifier could do. When it was time to lay it on the line, the Adcom just wasn't up to the challenge. It's a decent little amp, but it didn't really juice my lizard the way Adcom's bigger GFA-555 II or the similarly priced Rotel RB-960BX did.

Conclusions
The Adcom GFA-535 II will appeal more to listeners looking for a forward-sounding amp to give an otherwise wimpy system a sharper character. The Adcom's high end has a fair amount of bite to it, so careful system-matching is needed in the case of shrill-sounding speakers and/or rough-sounding budget CD players and preamps. The Adcom tries hard to be a He-Man full-range amplifier, but it winds up sounding hard, too.—Corey Greenberg