Power Amplifiers

Rotel RMB-1085 Class D (Switching) Five-Channel Power Amplifier

ARTICLE INDEX

Rotel RMB-1085 Design

The overall package is very slim and discrete; the back panel has RCA inputs only, standard five-way binding posts and 12volt input/outputs. The front is very clean with only a power button and protection light, and comes with either a silver or black faceplate.

The big advantage to using class D is efficiency. The potential downside is sound quality and dynamics. Fortunately the Rotel design team has created a small five channel amplifier that does not sacrifice either, to achieve great efficiency. The Rotel Class D amplifiers utilize Controlled Oscillation Modulation which is an analog circuit that drives the switching output stage. Other Class D designs use a digitally generated control that switches the output stage which can sometimes lead to increased noise and distortion.

Specifications

  • Design: Class D - Switching
  • Power Output: 5 x 100 Watts RMS into 8 Ohms, 160 Watts into 4 Ohms
  • Dimensions: 2.8" H x 17.1" W x 15" D
  • Weight: 15 Pounds
  • MSRP: $1199 USA
  • Rotel

Another feature found in the Rotel amplifiers is the Enhanced Cascade Control. This circuit gives the amplifiers very low output impedance (high damping factor) across the entire operating range. All this translates to an amplifier that has flat frequency response no matter what sort of speaker impedance is presented.

Rotel RMB-1085 Setup

Setup of the unit is rather simple. Connect five analog cables from the processor to the amplifier and run five cables to the speakers. I then connected a 12v trigger from the processor and finally the detachable power cord. All connectors on the Rotel are solid and tighten easily. After that I ran a speaker calibration setup using the internal test tones in the RSP-1069 processor and my Radio Shack SPL meter.

rotel-rmb-1085-multichannel-amplifier-fig-2-large.jpg

For critical listening I used a Rotel RSP-1069 processor (review to follow), being fed by my Oppo 981HD DVD player. For speakers I am using Raw Acoustics OB3 open baffle speakers (in the front) and Paradigm ADP surround/center speakers. To put this amplifier through its paces I used Pink Floyd's Dark Side of the Moon (SACD), Frank Zappa's Halloween (DVD-Audio), The Melvin's A Senile Animal (Redbook CD) and Kung Fu Hustle (SD-DVD).