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- Created on Saturday, 15 February 2014 00:00 15 February 2014
- Written by Erich Wetzel Erich Wetzel
Rotel has been building audio gear for more than 50 years -- a longevity impressive in any business, and especially in audio. Continued ownership by the founding family since inception is an even greater accomplishment. The company originated in Japan, and design is generally done in the UK. Rotel now designs and manufactures models for just about every product category of consumer audio -- their components are distributed by the B&W Group, which owns and distributes Bowers & Wilkins and Classé.
My subject here is what Rotel calls a “classic stereo power amplifier,” the Rotel RB-1582 MkII ($1599 USD). It measures 17”W x 5.5”H x 16”D, and the review sample had traditional black audio-amp styling with some industrial flair added for visual appeal. The center third of the thick metal faceplate is taken up by 15 vertical slots, backed by a textured-plastic panel and surmounted by the company’s deeply engraved name. The finish and feel of the faceplate are very good, and quarter-round corner columns of painted aluminum provide a nice contrast with the metal face. The only control is the Power button at the top left: a large round pushbutton surrounded by a brightly illuminated blue ring. Though at first this was interesting, I found the lighting effect harsh and somewhat bothersome in a dim room. A "dimming ring" is included to fix this.
The top and side panels are typical fare for the price: a single piece of perforated and folded black metal that’s secured to the chassis on each side with two large, nicely black-chromed screws. Five large feet (four corners and center) support the RB-1582 MkII’s roughly 40 pounds. Being somewhat old school, I find the mass of an amplifier -- or any other complicated device -- reassuring. Obviously, newer designs, especially the increasingly high-quality sound from class-D circuits from Rotel and others, don’t demand the parts or power overhead and their resultant mass. Change is afoot, but today was happily a class-AB day.
On the rear panel are both single-ended RCA and balanced inputs, separated by a switch for choosing between them, and two pairs of binding posts per channel. (The original RB-1582 had only RCAs.) The five-way binding posts are easy to screw down tightly without tools. However, the lower two posts were too close to the bottom of the chassis for my less flexible speaker cables. Fortunately, I usually place amplifiers on an MDF platform that sits on my carpeted floor, which raised the Rotel enough that I could connect my speakers without putting strain on the cables or connectors. The proximity of the top set of posts to the bottoms made it hard to connect to them from the bottom, and the balanced connector is in the way when trying to connect to them from the top. If you have reasonably flexible speaker cables, you’ll be in good shape. The single-ended connectors are sufficiently far outboard of the binding posts that they have no impact on other connections. Also on the rear panel are a replaceable fuse, a standard AC connector, and a set of handy in/out trigger ports, grouped with an on/off switch of their own.
Rotel specifies the RB-1582 MkII as a class-AB amplifier providing 200Wpc into 8 ohms. Its output power will vary with the load your speakers present to the amplifier, as usual. Total harmonic distortion (THD) is specified as less than 0.03%, and the frequency response as 15Hz-100kHz, +/-1dB, which should cover everything within the audioband with plenty of treble headroom. The signal/noise ratio is a claimed 116dB, the power consumption 550W. The RB-1582 MkII never got excessively warm to the touch in its time here.
Details of the RB-1582 MkII’s circuit design include a low-magnetic-field, “extremely large toroidal transformer” and “monoblock design” thereafter. The supply side of the audio circuit includes 60,000µF of storage in “slit-foil” capacitors feeding “ten discrete high-current transistors per channel” on the output side. I wasn’t able to push the RB-1582 into clipping during brief high-volume tests, and heard no distortion throughout its time here.
Setup and use were as elementary as for most amplifiers, and the owner’s manual proved typical: pages of required nanny-state warnings in several languages, followed by diagrams of installation suggestions for joining the RB-1582 to a Rotel preamplifier. Attach your speaker cables, interconnects, add the included power and trigger cables, set appropriate switches according to needs, and power it up. Rotel had sent along their RC-1570 preamplifier (review forthcoming), which matched up well with the amplifier and installation diagrams.
Once the trigger wire is connected, the RB-1582 MkII is plugged into the wall, and its Power button is pressed, the amp can be switched into and out of standby with the preamp’s remote control. There wasn’t the slightest bit of exercise involved with this review: I could control everything from a comfy chair -- no precarious bending over to turn this amp on!
General listening involved feeding the system digital signals of various resolutions wirelessly from iMac to AirPort, and from there to the Rotel preamp’s optical digital input. Critical listening involved the iMac optically feeding data directly to the preamp.
The Rotel RB-1582 MkII played well with my Bowers & Wilkins 801 Series 2 speakers, which support its partially English heritage. Its sound was warm, but without sounding as if it contained a phalanx of tubes. With 200Wpc, the RB-1582 MkII certainly had the power to run the B&Ws’ 12” woofers and allow the bottom end to have significant impact. This amplifier handled most of the relevant frequency range uniformly -- it was neither too bright and harsh, nor boomy. It was, however, sensitive to the source equipment providing the signal. This last point is an important one. An amplifier’s job is, essentially, to greatly and without prejudice increase the level of whatever signal it is provided while injecting no sound or character of its own. Of course, that’s the ideal -- every audio product, to however small a degree, modifies the sound. However, if the final sound changes with each new source component, the amplifier is doing its job satisfactorily. The RB-1582 MkII did well in that regard.
I began with some nuanced music: Joaquin Rodrigo’s Concierto de Aranjuez, recorded in 1980 by guitarist Carlos Bonell with Charles Dutoit conducting the Montreal Symphony (16-bit/44.1kHz AIFF, Decca). It’s a challenge for a system to balance the grace and intimacy of a solo acoustic guitar with the size and power of a full orchestra, but the RB-1582 MkII was up to it. The soundstage was anchored between the speakers, the guitar forward in the mix. The farther apart you can place your speakers with the RB-1582 MkII, the wider your soundstage will be. This recording doesn’t include a great deal of heavy bass, which allows the details to flow nicely. Big string attacks were large and a bit bright, but had the impact massed strings do in concert. Bonell’s guitar was nicely rendered, and the subtleties of a picked and plucked instrument closely miked were evident, lending credibility to the sound.
I then played the title track of Jean Michel Jarre’s 2004 remix (with a couple of new tracks) of Aero (16/44.1 AIFF, WEA). Most if not all of this track was created electronically, so its synthetic “soundstage” should be relatively easy to re-create, and the Rotel did a good job of reproducing the sounds the composer moves around. The tracking of midrange sounds from left to right and from back to front were not smeared and were easy to follow, while static sounds remained so, but were not quite as isolated as they may have been designed to be when played through more resolving systems. There is a modest illusion of depth in this bit of electronica, and the Rotel handled it well. The track is a bit bass heavy, and so it sounded through the RB-1582 MkII.
Amazing progress has been made in studio processing for lower-resolution recordings distributed by most of today’s big music retailers, and many of us have recordings at these resolution levels that we love to listen to. An example is Iameve’s “To Feel Alive,” found at iTunes on the soundtrack of the 2013 film Percy Jackson: Sea of Monsters (16-bit/320kbps AAC, Sony Classical/iTunes). If it were 2004, this track would be lifeless, without depth or width. The Rotel helped to demonstrate that even lo-rez but recent MP3s can be played through good audio gear and still be enjoyed. The ethereal sound of the song filled the soundstage’s width and was relatively deep. Eve Ami’s voice has a slightly raspy sound that came through nicely with the Rotel.
The big Rotel could move with a beat and rhythm, too. Moby’s “Bodyrock,” from his 1999 album Play (16/44.1 AIFF, V2), can still bring it with a techno and traditional club feel. The electric guitar leading the rhythm of the track has the nice fat sound you get when a guitarist sets up a rig with some modest distortion and a wah-wah pedal at a club or other small setting in which you’re hearing only the musicians’ own equipment, not some battered PA. The RB-1582 MkII helped keep the boogie going by retaining that fat sound, and even emphasizing it a bit. A more analytical amplifier might lose some of this effect, along with the desire to move to the beat.
“Too Close,” from Alex Clare’s The Lateness of the Hour (16/44.1 AIFF, Island), is a complicated track that includes unusual combinations of busy electronic sounds along with nicely rendered woodblock and other supporting percussion. The percussion instruments with higher frequencies had a nice sense of space around them, and a sharpness in the beginnings and endings of their sounds that felt lifelike. Clare’s voice is very forward in the mix, as is the guitar in the Rodrigo, and the Rotel put it front and center, well in front of the rest of the performers. This placement left it sounding somewhat disconnected from the rest of the music, but that is an artifact of the mix rather than the RB-1582 MkII doing something unusual. This amplifier slightly accentuated any built-in forwardness in my recordings.
Throughout all of my listening, I did hear one unusual trait from the RB-1582 MkII. At high volumes, the system hit the resonant frequencies of my room much more often than with any amplifier I’ve had here recently. The Rotel clearly had the power to drive the 12” woofers in the big B&W 801s, but it got a little loose in the lows, possibly allowing for several room modes to be excited at once. Speakers with smaller drivers will probably show less of this behavior compared to my 801s.
I had on hand a Parasound Halo A 23 amplifier ($950, review forthcoming), which is lower in price than the Rotel but puts out only 125Wpc into 8 ohms. I inserted the A 23 between the Rotel preamplifier and the B&Ws and replayed several musical selections back to back, including those above. In general, the Rotel sounded warmer, the Parasound more precise and smooth. Through the Parasound, the Jarre track had a smoother blending of sounds than the Rotel. Alex Clare’s voice was less forward of the music, and, like the Jarre, blended more smoothly into the backing instruments.
Both amps did well for their prices. I didn’t find that the difference in power output made any difference in sound, but I also found that their sounds are very, very different. Take this analogy with a grain of salt, but the Rotel sounded more like a conceptualized tube device, warm and comfortable; the Parasound sounded more solid-state: accurate and analytic. All I can conclude from the comparison is that there are a lot of choices to be made in maximizing sound quality. Those choices can lead designers and manufacturers down many paths of sound. I now have two distinct sonic signatures on hand.
Rotel’s RB-1582 MkII is a reasonably priced, attractive power amplifier with a warm sound. Its marked difference in sound from that of, say, the Parasound Halo A 23 is worth exploring for yourself, especially if your taste tends a bit toward warmth. The RB-1582 MkII could soften an overly analytic front end or be the powerhouse of an already comfortable-sounding system. Not surprisingly, it blended well with its preamplifier mate, Rotel’s RC-1570. If all of that sounds appealing -- and I could see it being just that for a lot of audiophiles -- this Rotel should be on your shortlist for audition.
. . . Erich Wetzel
Rotel RB-1582 MkII Stereo Power Amplifier
Price: $1599 USD.
Warranty: Five years, moving parts excepted.
Rotel of America
54 Concord Street
North Reading, MA 01864-2699
Phone: (978) 664-3820
Fax: (978) 664-4109