Arcam A25+ Integrated Amplifier

The A25+ is the flagship of Arcam's Radia+ integrated amplifier range — 100 watts per channel of Class G amplification, an ESS DAC with Time Domain Jitter Elimination, USB-C for direct computer audio, HDMI eARC for television integration, and 0.002% THD. It is the amplifier in the range for listeners who want Class G efficiency and dynamic reserves rather than the Class AB architecture of the A5+ and A15+.

The Flagship of the Radia+ Range

The Radia+ range covers three integrated amplifiers. The A5+ delivers 50W Class AB with a phono stage. The A15+ steps up to 80W Class AB and adds HDMI eARC. The A25+ at the top of the range moves to 100W Class G amplification and adds USB-C for direct computer audio — features that are exclusive to this model.

Class G is what separates the A25+ from the rest of the range. Where the A5+ and A15+ run Class AB throughout, the A25+ operates its core circuit at a lower voltage during normal listening — where most music sits — and switches to a higher voltage rail only when transients demand it. The amplifier runs cooler and draws less power under typical conditions, while retaining the dynamic headroom of a larger Class AB design. It is the topology Arcam chose for their reference integrated amplifier.

USB-C is the other A25+ exclusive. Unlike the optical and coaxial inputs shared across the range, USB-C accepts 32-bit/384kHz and allows direct connection from a computer or compatible device without an external DAC. For listeners whose primary source is a laptop or desktop, this matters.

Sound Performance

The A25+ presents a soundstage that is wide, stable and precisely layered. Instruments occupy specific positions rather than spreading vaguely across the stereo image — the kind of imaging that rewards careful speaker placement and shows whether your room setup is working. Voices are anchored with solidity. The tonal balance is neutral without being cold.

Dynamics are where the Class G topology shows its value most clearly. The shift from a quiet passage to a loud one is handled with greater ease than a Class AB amplifier at the same power rating, because the A25+ has voltage reserves available instantly rather than having to drive a single rail harder. At low volumes the character of the amplifier does not thin out: late-night listening at modest levels sounds like music, not a reduced version of it.

THD at 80% power into 8Ω measures 0.002%. The ESS DAC handles all digital conversion on a Time Domain Jitter Elimination platform — a circuit that reduces timing errors in the digital signal before conversion. Both figures reflect engineering quality rather than marketing numbers.

Build Quality and Design

The A25+ shares the 431mm width and aluminium front panel of the rest of the Radia+ range. At 83mm height and 9kg it is fractionally lighter than the A15+, a reflection of the Class G design running more efficiently rather than any reduction in build quality. The chassis is solid, the terminals are well-made, and the front panel carries only the controls that are actually needed.

Built in Cambridge to standards Arcam have maintained across nearly fifty years of amplifier design. If you are building a matched Radia+ system, the A25+ sits visually consistent alongside the ST25 streamer or Radia CD5 CD player.

Connectivity and System Matching

The rear panel carries three RCA line inputs, MM phono stage, optical and coaxial digital inputs (up to 192kHz/24-bit), USB-C (up to 384kHz/32-bit), HDMI eARC, and Bluetooth 5.4 with aptX Lossless and Auracast. A headphone output and pre-out complete the specification. This is a genuine one-box solution for a modern listening setup.

For sources, the A25+ pairs naturally with the Arcam ST25 network music streamer — shared Cambridge engineering and consistent presentation across analogue and digital. For physical media, the Arcam Radia CD5 connects via coaxial. On speakers, the A25+ handles bookshelf and floorstanding designs from 86dB sensitivity upward — KEF LS50 Meta, Bowers & Wilkins 606 S3 and Fyne Audio F500 series all pair well.

For a dedicated multichannel home cinema system, the Arcam AV range is the better choice. For a two-channel setup that also handles TV audio through HDMI eARC and direct computer audio through USB-C, the A25+ covers everything in one box.

Technical Specifications

Who Is the A25+ For?

The A25+ is for the listener who wants the best the Radia+ range offers: Class G efficiency, USB-C for direct digital connection, and the dynamic reserves to drive demanding speakers in larger rooms without compromise. If your room is modest and your speakers are efficient, the A15+ does everything most listeners need. If you have no need for HDMI eARC or USB-C, the A5+ is the more honest recommendation. The A25+ is for the listener who knows exactly what they want and is not willing to settle for less.

Buying from Martins Hi-Fi

Martins Hi-Fi has been in Norwich since 1968. Elizabeth Gould runs the business today, and we stock only brands we have heard properly and stand behind. Arcam have been a core part of our range for many years — Dave and Chris can talk you through whether the A5+, A15+ or A25+ is the right fit for your room and your speakers, and have it set up in our Norwich showroom for you to hear.

Contact us at info@martinshifi.co.uk, call 01603 627010, or WhatsApp on 07554 687137. You can read more about how we work on our Why Martins Hi-Fi page. We are at 85–91 Ber Street, Norwich, NR1 3EY.