Integrated Amp Reviews

The 4-CD set of Ligeti's complete Deutsche Grammophon, Decca, and Philips recordings entitled Clear or Cloudy (Deutsche Grammophon 00289 447 6443) held my attention for two long nights. The sound from the Rotel DT-6000 sourcing the RA-6000 was moderately shy on reverb and atmosphere but fully alive and dramatic. Like most avant-garde music, Ligeti's art directs listeners' attention to dramatic contrasts of volume, force, and tone—and, more dominantly, the passage of time. The Rotel excelled at the volume, force, and time-passage parts but fell a breath short on recovering a full harmonic spectrum of tone.

Listening to LPs
Just as the sound quality of Rotel's CD player forced me to binge-play CDs, the solid sonics of the 6000's phono input impelled me to do the same with LPs. It applied extra torque and a well-tempered demeanor to every disc I played. The RA-6000 liked every moving magnet cartridge I tried, but it mated exceptionally well with the taut rhythms and crystalline detail that emerge from Goldring's $899 high-output (2.5mV) Eroica HX moving coil. The Eroica HX steered by Music Hall's Stealth turntable exposed the best part of the RA-6000's personality: its ability to let recordings sound like themselves, open and clear with no issues to distract listeners. It was a joy.

The album the Rotel integrated played best is one of the best-sounding, best performance blues albums ever set to vinyl: Skip James's Devil Got My Woman (Vanguard LP VSD 79273). James's singing is famously otherworldly, and this impeccable 1968 recording shows us his ethereal high-pitched vocals, the delicate elegance of his guitar picking, and his Fats Waller–level piano accompaniments. The RA-6000 played the devil out of this recording: not missing a microbeat, while putting nothing but clean sound-charged air between Skip and his microphone. Tiny rhythmic accents, atom-scaled tonal nuance, and the goosebump tactility of Skip's voice came through easily via the Falcons.

With Ortofon's 2M Black moving magnet cartridge ($695), the sound from the Rotel's phono stage got richer, darker, and quieter. The top tones of Skip James's voice came down a few hertz—perceptually—and the space behind James got deeper, more real and reverberant. The bottom strings on his guitar sounded thicker and fuller of tone. Ortofon's 2M Black sounded deep, smooth, and creamy through the Rotel.

In my system, the RA-6000 played LPs even better than CDs—and that's saying a lot.

But what about the DAC?
Once my hot romance with Rotel's DAC Transport cooled, and my phono stage impressions were complete, I started switching between the RA-6000's internal DAC, the DT-6000's DAC, the $3098 HoloAudio Spring3 DAC, and the $17,000 dCS Bartók DAC.

Generally speaking, recordings played through the RA-6000's DAC (based on the Texas Instruments PCM5242 chip) were no less awake and dynamic than they were through the DT-6000's ESS ES9028PRO-based DAC. However, with the former, recordings sounded much dryer (atmospherically) and pared down (information-wise), with a slight blunt, brittle quality. On stringed instruments, the beauties of texture and harmonics were presented less richly. Nevertheless, performances moved along and presented themselves in a bright, lively way that kept me listening contentedly.

I like to compare every DAC, no matter what its price, to the dCS Bartók. It's a benchmark. Comparing less-expensive DACs to the dCS helps me better understand what happens to sound quality when we spend more (or less) money. You know, is butter really better than margarine? Of course, the outcome is usually the same as it was here: Recordings through the Bartók seem more structured, display more and subtler gradations of tone, and are more atmospheric and transparent than they are with the RA-6000's DAC.

What I noticed also during this comparison was how, compared to my reference amplification, the RA-6000's line-level input blurred and slightly hardened data it received from the dCS Bartók.

Rotel vs Rogue
Switching from Rotel's $4499 RA-6000 to Rogue Audio's $1295 hybrid (tube-class-D) Sphinx V3 integrated amplifier and playing Robert Nighthawk's "Take It Easy Baby" off And This Is Maxwell Street (Studio IT CD R2641), the first thing I noticed was how the sound through my Falcon Gold Badges and the Klipsch RP600M IIs sounded distinctly darker and thicker. The class-D Rogue was fuller and more textured but less clearly spoken than the class-AB Rotel. With the Sphinx V3, the leading edges of Nighthawk's guitar strumming were slightly rounded. On every And This Is Maxwell Street track, the sonic presentation seemed more blended, more shadowy, and less particularized than it had been with the Rotel. Fortunately, neither amp suppressed that Maxwell Street trance-dance boogie power.

Rotel vs Pass Labs
The $7250, class-A Pass Labs INT-25 integrated amplifier is rated at 25Wpc into 8 ohms or 50Wpc into 4 ohms, weighs 51lb, and has no DAC or phono stage, just three unbalanced line-level inputs, and only five buttons on its front panel. It is my reference for how invisible solid state amplification can be.

Using the dCS Bartók into the INT-25 to play single-miked Nagra III field recordings from the soundtrack to Mike Shea's 1965 documentary And This Is Free: The Life and Times of Chicago's Legendary Maxwell Street (16/44.1 FLAC, Shanachie/Qobuz), I realized that the notions I hold regarding audio transparency are influenced by my endless attraction to raw, unprocessed field recordings. These documentary recordings are typically mono; they capture a distinct area of sound in the space around the microphone and performer.

Driving the Falcon Gold Badge speakers, Rotel's class-AB RA-6000 integrated did not equal the Pass Labs class-A–level detail or its you-are-there-and-can-feel-the-air clarity, but it had no trouble establishing a sense of space, place, and time and an avalanche of lively audio vérité intangibles. The RA-6000 integrated amplifier did not reduce the feelings of energy or authenticity of these valuable cultural documents. And that is all that really matters.

Driving the GoldenEar BRX
I've saved the best for almost last. Rotel's RA-6000 did its best work, made its most music magic, made its cleanest bass and most transparent treble, sourced by the dCS Bartók driving the hard-to-drive GoldenEar BRX loudspeakers ($1599/pair). And I can't guess why.

On my latest favorite streaming album, Debussy's Corner: Works for Flute, Viola, and Harp (16/44.1 FLAC Cypres/Qobuz), it presented Bernard Pierreuse's flute with goosebump-level texture and much fuller tone and harmonics than it did with my 15 ohm Falcons.

I played this recording several times, and each time I enjoyed it more. Each time I thought, Wow, this is a great amp-speaker combo. According to John Atkinson's measurements, the BRX has minimum EPDRs of 2.15 ohms at 59Hz and 1.53 ohms at 135Hz. The EPDR remains below 4 ohms in the midrange. Consequently, "This loudspeaker will work best with amplifiers that are comfortable driving loads below 4 ohms," John wrote. Rotel's RA-6000 seemed to breathe comfortably, and it looked beautiful, as it played this endearing Debussy recording.

Listening to György Kurtág: Kafka-Fragmente (24/96 FLAC, Harmonia Mundi/Qobuz), the top reaches of Anna Prohaska's soprano voice came through with chilling, undistorted clarity. Isabelle Faust made quick, loud, knife-sharp electrifying sounds with her violin, and the Rotel-BRX pairing made reproducing them seem easy—and Kafka-level frightening.

The headphone output
Neither Rotel's website nor the RA-6000 owner's manual give any specifications (power, gain, and output impedance for example) for their 1/8" front-panel headphone output. So I asked Coates for more information. "The headphone output on the RA-6000 is designed to be used with most lower-impedance headphone designs. 32 ohms is the design reference, but there's plenty of drive for headphones of slightly higher impedances as well," he wrote in an email. "600 ohm, low sensitivity monsters need not apply, though! The rated output is 120mW into 32 ohms full bandwidth at less than 0.02% THD. Distortion rises quickly beyond that point, with a maximum rated output of 140mW [also into 32 ohms]. Output impedance of the headphone amplifier circuit is rated at 680 ohms." (footnote 1) The specified gain at the headphone output is 14.8dB.

Those specifications caused me to wonder: What headphones might a typical RA-6000 owner use? I didn't have a ¼" to 1/8" adapter, so I reached for my use-it-all-the-time, works-with-every-amp Sony MDR-Z1R headphones, which employ dynamic drivers, cost $1798, and come stock with a 1/8" plug. Their 100dB/ mW sensitivity and 64 ohm impedance classifies them as easy to drive, and their style suggests something a Brooklyn hipster might use if they owned a Rotel integrated.

And guess what? I used the Z1Rs to play that chilling, spectacular-sounding György Kurtág: Kafka-Fragmente album, and it sounded considerably less transparent than I hoped it would. Still, through the Sony headphones, all octaves of Anna Prohaska's voice were almost as chilling as they were coming out of the GoldenEar BRXs. Skip James's voice was mesmerizing enough. Robert Nighthawk's guitar was nasty enough. Easy-to-drive headphones should sound nice enough for casual listening.

Conclusion
In his 1993 review, Stereophile reviewer Corey Greenberg concluded that the Rotel RB-960BX was a good, solid little amplifier. Maybe so, but Rotel's new Diamond Series 60th Anniversary RA-6000 integrated amplifier is much more. It is a well-built, timeless-looking, solid-sounding tour-de-force that should serve its users very well for decades. Bravo, Rotel! Here's to 60 more years as a family-owned business!

---

Footnote 1: That output impedance is quite high, which means that low-impedance 'phones could have some trouble, too.