Vitus SIA-025 MK II Integrated Amplifier

The SIA-025 Mk.II is Vitus Audio's Signature Series integrated amplifier — a single-chassis design of extraordinary ambition that combines the preamplifier topology of the SS-010 with fully integrated amplification, and that demonstrates with complete conviction that Signature Series engineering principles can be achieved within one chassis without concession of any kind.

The SIA-025 Mk.II delivers approximately 25W per channel in pure Class A into 8Ω — covering the vast majority of real-world listening levels with any loudspeaker of reasonable sensitivity — before transitioning seamlessly into Class AB, delivering approximately 150W per channel into 8Ω and approximately 300W per channel into 4Ω. This combination of Class A intimacy and Class AB authority defines the SIA-025 Mk.II as one of the most complete integrated amplifiers available at any price.

The 25% Rule

Every component within the SIA-025 Mk.II operates at no more than 25% of its rated capability under normal conditions — a Vitus Audio engineering discipline applied without exception across every Signature and Masterpiece Series product. The result is an amplifier of extraordinary longevity and consistency, one that eliminates thermal stress, reduces long-term component degradation, and ensures every element of the circuit operates in its most linear and musically accurate region at all times.

Fully Balanced Architecture

The SIA-025 Mk.II is fully balanced throughout — three XLR balanced inputs and two RCA single-ended inputs, balanced speaker outputs, and a preamplifier output via XLR for bi-amplification with a dedicated power amplifier such as the Vitus SS-025. Signal-to-noise ratio exceeds 100dB, rendering the noise floor effectively inaudible and allowing low-level detail to emerge with a precision and naturalness that single-ended designs cannot replicate.

Full Bypass Function

The SIA-025 Mk.II incorporates a full bypass function for complete compatibility with external surround processors — allowing it to serve as the high-quality stereo amplification foundation of a wider AV installation while retaining its full two-channel musical authority without compromise.

Relay-Controlled Volume

Volume is controlled via a relay-controlled fixed resistor network, operating across -81dB to +11dB in precise 1dB steps — eliminating the tracking errors and channel imbalance of conventional potentiometers, and preserving the SIA-025 Mk.II's extraordinary low-level resolution at every point on the volume range.

Technical Specifications

Finishes

Available as standard in Pure White, Jet Black, and Warm Silver. Titanium Orange, Dark Champagne, and Titanium Grey are available to order — speak to us for the full range of options.

Who Is It For?

The SIA-025 Mk.II is for the listener who wants the full authority of the Vitus Audio Signature Series in a single integrated chassis — Class A operation at realistic listening levels, full bypass and bi-amplification flexibility, and a one-box solution that sacrifices nothing musically. It partners naturally with the Vitus SD 025 MK2 as a digital source, and with the Vitus SP-103 Phonostage for vinyl. For those considering the next step, the Vitus SIA-030 makes a compelling comparison at our Norwich showroom.

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. The SIA-025 Mk.II is available to audition at our Norwich showroom — speak to Dave or Chris, who can demonstrate it in the context of a complete Signature Series system and guide you through finish options and system matching.

Contact us at [email protected], 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.