Rotel RB-960BX power amplifier By Corey Greenberg   •   October, 1993 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 couple of sub–$400 power amplifiers that also dream big: Adcom's GFA-535 II and Rotel's RB-960BX. Both are rated at 60Wpc, both are from companies who've achieved good track records over the years for reliable, good-value gear, both are made in Taiwan, and both have been fired up in my Real World system now for many months. Do they kill Krells, thrash Thresholds, vivisect VTLs, and bum-rush Boulders?

Press on and ye shall know!

Rotel RB-960BX
Circuit-wise, the Rotel RB-960BX is similar to the Adcom GFA-535 II. There are differences in parts values, layout, etc., but these are not two radically different designs.

What is pretty radical, though, is the difference in build quality. While the Adcom is built to a standard that suggests higher-priced components, the Rotel is built more like...well, an amp that only costs $369. The input RCAs, for example, appear to be lower-grade than the Adcom's, though the speaker posts appear to be identical—you can't use speaker cables terminated with spade lugs with this amp, either. And overall, the board work is fairly sloppy, with some parts that were apparently assigned to the board after the design had been finished. While none of this somewhat "relaxed" workmanship is cause for real concern—the Rotel ran strongly, with no problems whatsoever—its build quality wasn't as high as the Adcom's.

Like the Adcom, the Rotel is an AC-coupled design. But where the Adcom uses a small-value polycarbonate film cap in series with the signal, the Rotel uses a 10µF/50V electrolytic cap, this a Modkateer-Approved "Black Gate" type from Rubycon. Shunted to ground by a 27.4k resistor, the Rotel's DC-blocking filter has a response of –3dB at around half a hertz. There is no additional DC-servo circuit as with the Adcom.

The RB-960BX is also similar to the Adcom in having dual-mono power supplies, with each channel having its own beefy power transformer and two 10,000µF/50V reservoir caps, one for each 47VDC power-supply rail.

The Rotel sports a triple-Darlington push-pull output stage, with two pairs of bipolar output devices per channel. And, again like the Adcom, the Rotel employs no output inductors—so if you see an output inductor on the side of the road with a "will isolate capacitive loads for food" sign, help the poor guy out, okay? Times is tough.

Unlike the Adcom, the Rotel is bridgeable to mono configuration by flicking a switch on the back panel, in which case it's rated at 180W into 8 ohms. Because the Rotel is capable of bridged-mono operation, I also tried two of 'em as monoblocks.

Sound
If you've read my description of the Adcom GFA-535 II's sound, then you know I preferred the Rotel RB-960BX's. The Rotel isn't a perfect amplifier, but I found it much more forgiving of the typical budget gear it's likely to be matched with.

For starters, the Rotel had a much softer and easier character. Voices were clearer and less congested, and the system sounded much more musical and pleasant overall with the RB-960BX. While the Adcom sounded very forward and aggressive, the Rotel was more laid-back and relaxed. Yes, there were slight traces of grain and bite through the mids and highs, but the Rotel had much less of this than the Adcom, and was much easier to listen to and live with in the long term.