Rotel RB-1552 MkII Combines Brawn and Beauty: 130Wpc Power Amplifier Features XLR Inputs, Efficient Operation, In-House Made Toroidal Transformer, and More

High-end values don't come much better than this. The Rotel RB-1552 MkII power amplifier is designed, engineered, and constructed to drive most speakers with proper timing, poise, control, and authority. Able to provide the brawn needed for complex passages as well as the grace for delicate nuances, RB-1552 MkII is resolved and refined, dynamic and detailed, fast and confident. Its high-current 130Wpc output, efficient operation, balanced XLR inputs, independent left-right power rectification stages, and left-right channel monoblock design attest to its sonic prowess.

Purpose-built in an in-house factory, the 27-pound RB-1552 MkII's large toroidal transformer combines with special "slit foil" capacitors to provide completely stable power to the output stage. The capacitors also have the ability to rapidly charge and discharge, ensuring signal fidelity during orchestral crescendos or repetitive kick-drum impacts, for example. All grounding gets terminated in a star pattern on a copper grounding plate for ultra-low signal-to-noise ratios. Moreover, the discrete output stage consists of 10 high-current bipolar transistors per channel. The Class AB RB-1552 MkII also includes a pair of unbalanced RCA inputs in addition to two sets of speaker terminals.

Supplied with ears for optional rack mounting, RB-1552 MkII has a 3U high front panel and sleek, utilitarian look that can enhance your listening space. The implementation of Rotel's Balanced Design Concept (read more below) and our 100% Music Direct Satisfaction Guarantee invite you to experience the difference RB-1552 MkII can make for your music in your own home.

"[It] boasts the sort of holistic design and careful parts-selection that have distinguished Rotel's best amps through the ages."
—Alan Taffel, The Absolute Sound

Circuit Topology

It's not enough to simply use good parts. Where you put them is equally if not more important. Which is why Rotel keeps circuit paths as short as possible. That's also why it often uses more expensive "onboard" relay source switching rather than routing a signal from a rear panel input to a front panel control. Rotel also relies heavily on Symmetrical Signal Trace design. This keeps each channel's signal path identical to the others to preserve the imaging and soundstage. In addition, the company employs electrically superior "star" grounding techniques to improve performance because star grounding routes all ground connections to a single point to reduce potential loops that might introduce noise or produce hum. Further, Rotel Class A/B amplifiers don't use output inductors because they decrease control and, consequently, sound quality.

In-House-Built Power Supplies

The heart of any audio component is the power supply, of which the type, size, and material plays a major part. Refusing to leave something so important to anyone else, Rotel invested the money and developed the knowledge to build its own toroidal transformers. Without a good power supply, the rest of the design can never deliver the desired performance. Rotel engineers carefully evaluate the power requirements of each new model. This information is conveyed to the transformer engineering team, which calculates the requirements including voltage, current, physical size, and product type. These engineers then design the exact specification for the transformers and begin the process of designing the transformer and winding a sample for testing. Each transformer is custom built to exacting standards using materials conforming to the strictest of standards. The metal winding material of the transformer is rigorously checked to confirm no impurities exist in the steel. The wire used for Rotel transformers is sourced from trusted suppliers that produce certified documentation of the copper materials. Each transformer core is built, baked, wound, and stress-tested to ensure power supply delivers all the clean, undistorted power each component requires for optimum audio performance.

Critical Evaluation

Rotel has found that critical listening is as important, if not more so, than even the most sophisticated instruments in the hands of experienced engineers. That's why its development team places such importance on critical listening sessions. Electronic and acoustic engineers, both in the U.K. and Asia, have honed their aural acuity over the course of decades of collective experience to evaluate each stage of product development from working samples, through pre-production and, finally, to verify that final production is the same as the pre-production units. Some sessions evaluate different circuit elements: capacitors, resistors, and active devices such as transistors or operational amplifiers. Others focus on differences in circuit layouts or differences caused by power-supply elements.