Power amplifiers mono — Vitus Audio SM-103 MK.II

The SM-103 Mk.II is a monaural amplifier in the Vitus Audio Signature range, made by a Danish company that builds its products in its own facility in Denmark. It is based on the SS-103 stereo model, and its layout draws on work done for the MP-M201, where Vitus used a four-chassis system to keep power circuitry apart from audio circuitry. At its launch at High End 2023 in Munich a pair was priced at EUR 70,000.

Key specs that matter

Rated output is 100 W into 8 ohm and 200 W into 4 ohm, and Vitus gives the same wattage whether the amplifier runs in class AB or in pure class A, so the choice of mode does not reduce the available power. Connections per unit are a balanced XLR socket and a single-ended RCA socket, each with 2 V RMS sensitivity and 10 kohm input impedance. Output impedance is 0.075 ohm. Every channel carries two pairs of loudspeaker binding posts, so bi-wiring is possible. Vitus quotes bandwidth past 800 kHz, noise at more than 100 dB below signal when measured at 1 kHz and THD plus noise below 0.01 percent. The chassis measures 310 mm high, 435 mm wide and 601 mm deep, and each unit weighs 75 kg.

Engineering and use context

Vitus uses a true balanced circuit, fed by a local shunt-regulated power supply, which the maker links to a low noise floor. Only matched transistors and super-precision resistors are used, selected to keep each stage of every module in its intended operating window. Because the internal structure is built from modules, an existing unit can take new boards as Vitus releases them, instead of being replaced. The bias switch changes heat and energy use rather than rated power - in class A the amplifier runs much hotter and draws roughly double the mains energy it needs in class AB. White, black and silver are standard colours, while titanium orange, titanium grey and a dark champagne tone cost extra, and custom colours can be ordered through the bespoke service. Registered owners receive a six-year warranty.

Pairing

Each chassis handles one channel only, which means two of them are required for stereo, and each of them weighs as much as a complete large amplifier. With balanced and single-ended connections on each unit, the amplifier accepts balanced or single-ended line stages, and since the power doubles as impedance halves, loudspeakers of low impedance suit it. The twin terminal sets serve speakers with split crossovers wired by separate cable runs.

Alternatives

The Vitus Audio MP-M201 Mk.II is the monaural power amplifier of the Masterpiece Series, the range above the Signature line.