Integrated Amp Reviews

Before this month, I'd never experienced Rotel amplification in one of my own systems, but I have memories of how their amplifiers sounded back in the early 1990s. In those days, at audio shows, I would audition every Rotel amp I could find; I was especially interested in their $369, 60Wpc RB-960BX. I was curious about that model because it was the number-one competitor to the 60Wpc darling of the audiophile proletariat: Adcom's GFA 535 II. My friend Corey Greenberg compared these two popular amps in Stereophile and concluded, "The Rotel is for the budget-minded music lover who wants a good, solid little amplifier that's not going to make listening to music a trying experience."

I trusted Corey's judgment, but the RB-960BX fascinated me because it was a plain-clothed, black-boxed budget amplifier that used ultra-premium, Japanese-made, "Modkateer-Approved" Black Gate capacitors by Rubycon, for which I was the US importer. I had more than an academic interest in the Rotel sounding better than the Adcom.

The Rotel amplifier I remember best is the hip, radical-looking RB-991, which Robert J. Reina reviewed and Thomas J. Norton measured in the August 1999 Stereophile. When I read that review, I thought, Damn! Rotel put the heatsinks on the front! How cool is that? So ha!

When I first saw Rotel's new Diamond Series 60th Anniversary RA-6000 integrated amplifier and the matching DT-6000 DAC Transport, at a preview demonstration at Café Kitsuné in Brooklyn, I recognized those fin sections that bookended their brushed aluminum faceplates as an aesthetic nod to the RB-991's cool-factor styling.

It was happy hour at Café Kitsuné, and after some relaxed listening, I set my drink on the bar, picked up my reporter's notebook, and asked Rotel's super-cool PR crew, "When I write about this, what would you like Stereophile's readers to most understand about these new products?"

Almost in unison, Julia Lescarbeau (global PR & communications manager for the McIntosh Group) and Ricky Miranda (Rotel's marketing manager) responded, "Tell readers that the Diamond Series RA-6000 integrated amplifier and its matching DT-6000 DAC Transport are now Rotel's flagship integrated and CD player, designed to commemorate 60 years of continuous family ownership." I raised my glass in a toast.

Later, in an email, Jeff Coates (marketing director for Fine Sounds, Rotel's US distributor) answered the question further. "The Diamond Series truly represents the culmination of our 60+ years designing, improving on, and building audio gear. We think of this as an iterative process, and the RA-6000 is the latest iteration of who/what Rotel is. It is a big and loud, yet articulate and controlled, work of engineering that we know will bring decades of joy to our fans."

Thus began this month's listening adventure with new products from an old Japanese manufacturer, one I always wanted to know better.

My review samples of the RA-6000 integrated amplifier and DT-6000 DAC Transport arrived a few weeks after my Café Kitsuné auditions. A week after that, curiosity forced me to install the CD player in my everyday reference system. I fell into a maelstrom of intense excitement, listening to the first CDs I've played in years.

I describe those CD-playing excitements in this month's Gramophone Dreams column, but I am impelled to say, here and now, that when, later, I mated Rotel's $2300 DT-6000 CD player to their $4500 RA-6000 integrated amplifier, I was instantly smitten by the dynamic, super-engaging sounds coming out of my Falcon Gold Badge loudspeakers. These Diamond Series components appeared to enhance each other sonically, each sounding better with the other than they did alone.

Consequently, during the bulk of this review period, I kept the Diamond Series integrated connected to its matching DAC-CD player, with my Roon Nucleus+ streamer-server connected via USB to the DT-6000's ESS ES9028PRO DAC. I fed the RA-6000's 47k ohm phono input from a high-output (2.5mV) Goldring Eroica HX moving coil cartridge mounted on Music Hall's Stealth turntable. This real-life system was such a blast—so innately compelling—that I found it almost impossible to audition the RA-6000's internal DAC or to stop listening and make a few sensible comparisons for this review. I forced myself.

Description
When I looked at the RA-6000's spec sheet, I saw that it was rated at 200Wpc (continuous) into 8 ohms and 350Wpc (maximum) into 4 ohms. The abovementioned RB-991 was rated at 200Wpc into 8 ohms and 300Wpc into 4 ohms, but coincidently, Tom Norton measured 349.1Wpc (max) into 4 ohms. Then I noticed how Rotel's $3200 RA-1592MKII integrated was also specified at 200Wpc into 8 ohms and 350Wpc (max) into 4 ohms. I asked Jeff Coates how is the RA-6000 different from the RA-1592MKII? He explained: "The main difference is in the power section, which is more closely related to the one in the Michi X3. The RA-6000, while not a 1:1 copy, is comparable to the front end of the 1592MKII and the power section of an X3."

Rotel's website specifies the RA-6000's total harmonic distortion as <0.0075%, so I asked Coates to define "maximum" and "continuous" power.

"Maximum power output is the measured output power under the stated conditions still within the rated THD specification. Power output at 4 ohms at 1.0% THD is 390 watts. However, the unit cannot sustain this output level continuously, as the thermal sensor would engage and put the unit into protection. ... The continuous power rating specifies the power output the unit can provide at the rated distortion continuously, without overheating."

Because readers want to know, I then asked Jeff where this amp was assembled. "Everything that has ever had the Rotel or Michi names on them has been built in a wholly owned and run Rotel factory. Our current factory was built from the ground up and been in operation for close to 18 years just outside of Zhuhai, China. The toroidal transformers used in these and almost every other product we build are built on site from scratch. About 25% of our factory staff builds transformers."

After bragging about Rotel's power transformers, Jeff answered proudly when I inquired if the RA-6000's power supplies were all linear. "One hundred percent linear! It's one of the things we feel that sets Rotel apart. We wind our own toroidal power transformers and use them at the heart of a very carefully regulated linear power supply, with separate secondary windings for things like the DAC section, analog audio circuits, separate windings for each power amplifier channel, and even a separate secondary winding for the housekeeping portion of the products: front panel displays, IR receiver, etc."

The power section of the RA-6000 uses Sanken transistors operating in class-AB. Its phono input sports 37.5dB gain and acepts high-output cartridges into 47k ohms with a specified 52mV input overload level. Its four line-level inputs deliver 14.9dB of maximum gain and are labeled CD, Tuner, Auxiliary, and XLR. Bypassable analog Balance and Tone controls are included.

On its front panel, below the RA-6000's unobtrusive 1.25" × 5.25" display, lies a drill formation of 14 Source Selector buttons, which struck me as the military half of Rotel's button fetish, the other half being the marching-band plastic remote, with 54 blue-lit buttons in six formations with 10 different shapes.

Two front-panel buttons select speaker outputs A, B, or both, while four more buttons assist navigation of the simple menu shown on the display. The display dims while not in use; all I see at night are Rotel's signature blue ring lights around the Power button and Volume controls.

Like many of today's integrated amps, the RA-6000 includes a DAC. For the 6000, Rotel's engineers chose a Texas Instruments PCM5242 chip, which allows conversion of PCM data at sample rates up to 192kHz but no DSD conversion. For digital inputs, the RA-6000 provides aptX and AAC Bluetooth; RCA and TosLink S/PDIF; and PC-USB with MQA; plus an Ethernet port. There is also a trigger port and an RS232 port for custom integration.

The RA-6000's dimensions are an ordinary 17" wide × 5 7/8" high × 16" deep. It weighs 44.5lb, substantial but easy to handle.

Listening to CDs
I tend to buy CDs in boxed sets representing artists I want to study over time. So now, having a CD player allowed me to pick up my explorations where I left off when the drawer stopped working on my last one. After the Maxwell Street CDs discussed in Gramophone Dreams #69, I continued to examine the music of Hungarian composer György Ligeti. My deep reverence for Hungarian filmmaker Béla Tarr, as well as my close long-term relationships with the music of Frans Liszt, Zoltán Kodály, and Béla Bartók, led me to discover Ligeti, who had a talent for parlaying the odd and unexpected into the marvelous. His compositions present music as phenomenological/metaphorical representations of thought. But György Ligeti's art is not about inner thoughts or sentimental musings; it is about force of mind. It needs a strong, clear-speaking hi-fi to reproduce it properly.