Nagra AMP II-S – Stereo Power Amplifier with Class AB Output Stages

Swiss manufacturer Nagra has expanded its Series II range of audio components with the introduction of the AMP II-S stereo power amplifier, designed, among other applications, to work alongside the PREAMP II-S preamplifier. The new model replaces the Classic AMP, introduced in 2015, retaining the fundamental principles of its circuit design while incorporating substantial structural improvements. In developing the Nagra AMP II-S, the company's engineers adapted several technical solutions previously implemented in the more expensive HD and Reference series. Particular attention was paid to increasing dynamic capabilities, improving spatial precision, and preserving the natural sonic character for which the Swiss manufacturer's amplifiers are renowned.

The Nagra AMP II-S employs a Class AB amplifier design delivering 120 watts RMS per channel into an 8-ohm load. The first 10 watts, however, are delivered in pure Class A operation. Each channel features just one complementary pair of MOSFET transistors, allowing the signal path to be simplified and the number of electronic components to be reduced. The power supply has also undergone a major upgrade, now incorporating a powerful linear design with a custom-built 800 VA transformer housed in a sealed enclosure. The increased power reserve enables the amplifier to handle short-term peak loads more confidently and maintain stable performance when reproducing music with demanding dynamic passages.

Significant improvements have also been made to the input circuitry of the Nagra AMP II-S, drawing on engineering solutions developed for the flagship Reference AMP. The new input board is designed to improve stereo channel separation, increase resolution, and provide more precise positioning of individual sound sources within the soundstage. At the same time, the manufacturer has revised the printed circuit board layout, optimized internal wiring, and introduced optical isolation for the control circuits to minimize the influence of electrical interference on the audio signal path. The mechanical construction has also been upgraded: a massive CNC-machined heatsink provides efficient cooling while increasing structural rigidity. To reduce vibration, the power transformer is mounted on a dedicated suspension system that prevents mechanical vibrations from being transmitted to the chassis. The front panel features Nagra's traditional MODULOMETER analog meter, highlighting the amplifier's heritage and its connection to the company's professional recording equipment.

According to Nagra, these comprehensive improvements have resulted in more articulate microdynamics, greater midrange transparency, and improved bass control. Particular emphasis has been placed on creating a stable, deep soundstage and preserving subtle tonal nuances when reproducing complex musical recordings. Despite the numerous design changes, the Nagra AMP II-S remains an evolution of the Classic AMP concept, combining a relatively straightforward amplifier architecture with technologies borrowed from the brand's higher-end models. The amplifier is intended for high-end stereo systems and can be paired with other Series II components as well as compatible equipment from other manufacturers. The recommended retail price of the Nagra AMP II-S is $27,900 in the United States or €24,500 in Europe.