Rotel RB-1552 Mkii Stereo Power Amplifier

Rotel RB-1552 MkII Stereo Power Amplifier – 130W Class AB Stereo Power Amplifier

The Rotel RB-1552 MkII is a dedicated stereo power amplifier: it does one job, driving a pair of loudspeakers, and leaves source selection and volume control to a separate pre-amplifier. Rotel rates it at 130 watts per channel into 8 ohms with all channels driven across 20Hz to 20kHz at under 0.03 percent THD. It shares its platform with the larger RB-1582 MkII, with a slightly smaller output capability, and is built using Rotel’s Balanced Design Concept, in which the power supply, circuit layout and parts selection are engineered together rather than in isolation.

The construction details explain the performance. A custom toroidal transformer with low magnetic field radiation feeds independent left and right rectification stages, the layout is essentially dual mono block in approach, and the power supply uses British-made slit-foil capacitors chosen for their ability to deliver and replenish reserve energy quickly during demanding passages. High-current bipolar output transistors complete a Class AB design intended to sound composed at any level.

Key features

• 130W per channel into 8 ohms, all channels driven, under 0.03 percent THD
• Class AB design with high-current bipolar output transistors
• Balanced XLR and unbalanced RCA inputs
• Custom toroidal transformer with slit-foil capacitors
• Damping factor of 450 for firm loudspeaker control
• Signal-to-noise ratio of 120dB, IHF A-weighted

Power supply and output stage

Power amplifiers live or die by their power supplies, because the supply is what the speakers ultimately draw from. The RB-1552 MkII’s oversized toroidal transformer and slit-foil capacitors hold a deep reserve for dynamic peaks, so a sudden orchestral crescendo or a kick drum transient does not sag the rails and compress the sound. Independent rectification for each channel reduces interaction between channels, preserving stereo separation when one channel is working harder than the other. Thermal and over-current protection circuits guard the amplifier and the connected speakers if a fault condition arises.

Connections and system matching

Inputs are balanced XLR, with a sensitivity of 2.5V and 100k ohm impedance, or unbalanced RCA at 1.5V and 12k ohms, with gain of 22.5dB and 26.5dB respectively. Balanced connection is worth using when the pre-amplifier offers it, particularly over longer cable runs. Two pairs of speaker binding posts per channel allow bi-wiring, the amplifier is stable into loads down to 4 ohms, and a 12V trigger input and output with a mode selector lets it wake and sleep with the rest of the system. Rack ears are included, and the 3U front panel suits cabinet or rack installation in a 431mm-wide chassis weighing 12.4kg.

Where a separate power amplifier earns its place

Adding a power amplifier of this quality is the classic upgrade path for a system built around an integrated amplifier with pre-outs, an AV receiver whose front channels need more authority, or a pre-amplifier and streamer combination. The RB-1552 MkII also serves as a front-channel amplifier in a home theatre, where its headroom takes the load off a receiver, or in a dedicated two-channel separates system. Frequency response extends from 10Hz to 100kHz within 0.5dB, and intermodulation distortion is held under 0.03 percent, figures that reflect design headroom well beyond the audible band.

Ownership details

Power consumption is 400W in operation and under 0.5W in standby, with a heat rating of 905 BTU per hour at one-eighth power into 4 ohms, so allow ventilation space around the chassis in a closed cabinet. The amplifier is a straightforward, serviceable component with no firmware, no streaming platform and no format obsolescence to worry about.

For listeners who want honest, generously engineered stereo power that will outlast several generations of sources and pre-amplifiers, the RB-1552 MkII is Rotel’s long-standing answer, and its specification shows why the model has endured.