|Rotel RMB-1077 Multi-channel Power Amplifier|
|Home Theater Power Amplifiers Multi-Channel Amplifiers|
|Written by Matthew Evert|
|Saturday, 01 April 2006|
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Rotel’s illustrious history was started in Japan over 40 years ago by a family whose obsession with music inspired them to manufacture truly high fidelity stereo components of their own unique design. Today, Rotel engineers are known for their tendency to select only the finest capacitors, resistors and other parts from all around the globe. The goal of these searches for the best audio components is to create audio equipment that is musical and reliable, yet affordable. If a component has not met the engineer’s desired standards, Rotel is not afraid to make the actual part itself. This was the case for Rotel’s decision to make its own toroidal transformers. One of Rotel’s latest contributions to the home theater market is the RMB-1077 a seven-channel amplifier that retails for $2,500.
Now, you ask, what is so great about this amplifier? Amplifiers have been around for years and much of the technology has not changed significantly. One thing in particular has changed with the introduction of the RMB-1077 amplifier is that it no longer uses the massive toroidal transformers that Rotel once prided itself in manufacturing. This amplifier doesn’t employ the traditional large heat sinks that are needed to dissipate the heat generated by a traditional amplifier’s transistors. Instead, more efficient “Class D” amplifiers with lighter switch-mode power supplies replace the large capacitors and coils of wire. There are two types of Class D amplifiers. One type is digitally controlled and the other is analog controlled. The Rotel RMB 1077 is an analog controlled Class D amplifer. It has an analog input signal with a digital switching power supply.
Amazingly, the above changes allow the RMB-1077 to reduce its footprint to just two-and-seven-eighths inches high and its weight down to a little over 17 pounds. My Parasound HCA-1000A amp is twice that weight and height and is only a two-channel 100-watt amp.
The black steel chassis of the RMB-1077 is 17-and-one-eighth inches wide and 16-and-three-eighths inches deep. The chassis has tabs on the front for easy rack mounting capabilities. The front faceplate has a platinum finish to it and features the Rotel name imprinted on the top. Rubber spacers on the bottom of the amplifier allow it to be stacked if rack-mounting is not desired. A protection LED will signal to the user that the amp is overheating due to improper ventilation or if there is a shorted speaker wire. The amp will also turn itself off if the condition continues uncorrected by the user for an extended period of time. When the power switch is in the on position and the 12-volt trigger switch is enabled on the back of the unit, the amp can be remotely powered on by a preamp or other control device.
The back panel of the RMB-1077 provides a RCA connection for each of the seven input speaker channels from your preamp. Seven pairs of color-coded four-way terminal posts are provided for connection to your speakers. Lastly, a detachable IEC-standard power cord provides easy removal of the amp from a rack system and offers the possibility of using an upgraded power cable or longer power cord at a future date.
This new amplifier design, one that Rotel and ICE engineers worked cooperatively to achieve, features seven channels (100 watts each) of amplification that is a fraction of the size and weight of other traditional amplifiers. By using ICR’s patented ICEpower® technology, the RMB-1077 can deliver full bandwidth sound with ample power output while generating very little heat and distortion. Rotel uses two other ICE technologies to aid in the intelligent power processing of this digital amplifier: Controlled Oscillation Modulation (COM) and Multivariable Enhanced Cascade Control (MECC).
COM technology obtains higher efficiency, better stability and more effectiveness from a switching-type digital power supply that will support all seven ICE power amplifier modules. The MECC system is a circuit topology that creates an intelligent amplifier. This intelligent amplifier is one in which the power supply and the amplifying circuits work together. These technologies allow for high power output with over 90 percent efficiency, thus minimizing heat and therefore the need for bulky heat sinks. High efficiency at high power levels also means lower distortion, less interference and better control over its frequency response from earlier class D digital amplifier designs. As a result, the RMB-1077 behaves more like a conventional class A/B amplifier in power capabilities and frequency response, but retains the benefits of a smaller size and weight class D amplifier. The RMB-1077, like all Rotel amplifiers, doubles it's power as the impedance drops but unlike conventional designs this one can run into 1 ohm loads safely while still pushing out 400 watts. It makes it ideal for low impedance speaker loads.
Indeed, this amplifier is light and easy to move around. You will still need about a four-inch clearance for heat venting on the top, back and sides of the amp. I was amazed how cool this amp ran and, even after several hours of going at 75 percent power, the amp felt room temperature. My Anthem A5 could hatch a baby chick after two hours of running at the same volume. That said, better to be safe than sorry, so I would stick to the recommended guidelines for venting. The 12-volt trigger is a nice feature for integration to preamps like my Anthem AVM30. This trigger will automatically power on the RMB-1077 when the AVM30 is powered on. The output trigger of the RMB is useful if you need to power-on yet another amplifier downstream from the RMB.
The RMB-1077 delivers wall-rattling sound with little hardness or strain to speak of. Rotel’s amp was able to drive my large Paradigm S-8 and C-5 center channel loudspeakers over 35 feet of AudioQuest speaker cable. The rest of my test system included my Anthem AVM30 preamp/processor, a Marantz DV9500 Universal DVD player and a Monster HTPS7000 power conditioner.