Product Review - Rotel RMB-1075 THX-Ultra Five-Channel Power Amplifier - July, 2001
John E. Johnson, Jr.
Power: 120 Watts RMS X 5 into 8 Ohms
MFR: 15 Hz -100 kHz (-0.5 dB/-3 dB)
Size: 7 1/2
" H x 17" W x 15 1/2" D
Weight: 39 Pounds
Rotel of America, 54 Concord Street, North Reading, Massachusetts 01864; Phone 978-664-3820; Fax 978-664-4109; Web http://www.rotel.com
Rotel has long been a respected name in European hi-fi components, and they have made significant inroads to North America because of their fine, and very competitive products. The RMB-1075 is a follow-up to the successful RB-985 and RB-985 MK-II, which sold for $1,000. The 1075 adds a beefier power supply and ups the power output from 100 watts per channel, to 120 watts per channel.
As you can see from the photo above, there are heat sinks on the front panel. This is very distinctive of Rotel's latest amplifiers, and I really like the look. However, the design is more than just cosmetic. The inside of the chassis (photo below) has heat sinks too, on both sides. The large toroidal transformer powers eight 10,000 µF capacitors ± 63 Volts (total of 159 Joules of energy storage) which feed the various channels. Two channels are on each side, and one is in the front. Thus, the three arrays of heat sinks. Four output transistors drive each channel. The front panel has a push-button on/off switch and LEDs which turn on if the amplifier is driven into protection mode (indicating shutdown of the channel that is overdriven).
The rear of the 1075 (photo below) has RCA jacks for each channel, along with a DB-25 jack for use with processors that have DB-25 output jacks (all the Rotel processors and some other brands), and color-coded five-way speaker binding posts. The detachable AC connection is non-grounded, but fits a standard grounded AC cable.
I tested the RMB-1075 with our Toshiba SD-6200 DVD Player, Theta Casablanca II Processor, Krix Esoterix I Mk II Speakers, Threshold ES-500 Full-Range Electrostatic Speakers (ESLs) , and Nordost Cables. A PS Audio P1200 served for clean AC supply. Although the manual says to use speakers with no lower than 4 Ohm impedance, I still like to use the ESLs just to see what a product can do under stress.
I have to say that I was delighted with how the 1075 performed, because it is so great to have affordable home theater amplifiers to choose from when you can't afford the big Krells, Cinepros, and others of that caliber. The Rotel RMB-1095 that we reviewed a while ago had a laid back high end, and the 1075 continues in that mold. This is probably because Rotel is thinking of all those harsh DVD sound tracks, and it means you can listen at higher volume levels without grimacing. Indeed, I, like most fellows, really enjoy action films, and lots of watts are required to do the job right. For example, Stallone's "Daylight", although a lousy movie, is great for demonstrating amplifiers and subwoofers to friends (chapter 8, the tunnel scene). Of course, "The Matrix" is not only a wonderful movie, but several chapters make fantastic demo material. Chapter 29, where Neo (Keanu Reeves) and Trinity (Carrie-Ann Moss) shoot up the lobby, just blows me away every time I watch it. My neighbor uses that scene whenever he feels depressed, just to get his juices flowing again. Chapters 4 and 11 of "True Lies" are also very demanding, with action going on in every channel. The 1075 took all this stuff in stride with tons of easy-to-listen-to sound.
The 1075 did just fine with my two ESLs as well, so it might just be a good match with some of the surround sound sets of ESLs that are coming on the market, such as the Final 0.2s that have just been released. I used the DTS Sampler with Tchaikovski's 1812 Overture, Alan Parsons, and other such amplifier busters, but the 1075 maintained its composure.
The 1075 has an inductor on the output connection of each channel (yellow arrows in photo below, left) which makes the amplifier more stable with capacitive loads (I guess they figured someone like me would come along and connect it to some ESLs). However, this does not appear to limit the bandwidth very much, because I measured the - 3 dB down level at 153 kHz. The 10 kHz ± 10 Volt square wave (photo below, right) is very good too. More and more amplifier designs are incorporating the output inductor. Having such things in the signal path is loathed by purists, but as we get more and more powerful amplifiers, and crank the volume higher and higher, the inductors form a safety net, so they are not likely to go away.
Rotel has done it again with the superlative RMB-1075. I think this product represents one of the best values in home theater amplification on the market right now, and recommend that you put it on your short list when shopping for upgrades. It would be a fabulous addition to the pre-outs of any surround sound receiver, bypassing the often less-than-adequate power amplifiers they have, and especially when you migrate your system to DVD-A and SACD. But, also, it would be wonderful to pair it with any dedicated processor out there. I have been working on this review for quite a while, but I have had so much fun showing it to friends, and enjoying it here in the lab, I put off publication because I did not want to send it back.
- John E. Johnson, Jr. -
© Copyright 2001 Secrets of Home Theater & High Fidelity
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