Quad QII-Forty

The Quad QII-Forty is a valve power amplifier that occupies a unique position in the history of high-fidelity audio — a design that draws its fundamental inspiration from Peter Walker's original Quad II, refines and develops it with five decades of subsequent engineering knowledge, and produces an amplifier of extraordinary power, resolution and musical authority that the original, for all its greatness, could never have achieved. The QII-Forty is not a replica, nor a tribute — it is the logical and inevitable evolution of one of the most celebrated circuit topologies in audio engineering, brought fully into the modern era without compromising the valve character and musical integrity that made the original Quad II a legend.

The output stage of the QII-Forty employs KT88 valves operating in a push-pull configuration — a topology that doubles the output power available from the valve complement while preserving the even-order harmonic structure and musical naturalness that characterises the finest valve amplification. Push-pull operation in the QII-Forty is executed with a precision and circuit refinement that extracts the full potential of the KT88 — a valve celebrated for its combination of power, bandwidth and tonal authority — delivering an output of 40 watts per channel that transforms the QII-Forty's ability to drive the full range of contemporary loudspeakers with complete composure and dynamic authority. A choice of 4 ohm and 8 ohm output taps further extends the QII-Forty's compatibility, ensuring an optimum electrical match with the widest possible range of loudspeaker designs — including Quad's own legendary electrostatic loudspeakers.

The output transformer design of the QII-Forty draws directly on the engineering heritage of Peter Walker's original Quad II transformer — a component whose design philosophy has been extensively studied, reverentially preserved and refined with the benefit of modern materials and manufacturing techniques. The new transformer design engineered for the QII-Forty achieves a bandwidth, linearity and dynamic performance that exceeds what was possible in the 1950s, while maintaining the fundamental circuit relationships that give the original Quad II its distinctive and celebrated tonal character. Significantly better components throughout — from the output valves to the passive components in the signal path — ensure that the QII-Forty delivers a fast, crisp and detailed sound that is delicately balanced between the warmth of the valve tradition and the resolution demanded by modern high-fidelity listening.

The QII-Forty's 40 watts per channel equips it to drive a genuinely wide range of contemporary loudspeakers with authority and control — a significant advance over the 15 watts of the Quad QII-Classic, and one that opens the QII-Forty's extraordinary musical character to listeners whose loudspeaker choice demands more power than a pure Class A single-ended or small push-pull design can provide. For those whose system demands the ultimate in valve power delivery, the Quad QII-Eighty extends the same engineering philosophy to 80 watts per channel — a level of output that eliminates any remaining question of loudspeaker compatibility or dynamic headroom.

The QII-Forty is the ideal centrepiece of a complete Quad valve system. Paired with the Quad QC 24 Pre-Amp valve preamplifier, it forms a pre/power combination of the highest musical authority — one that draws directly on Quad's unbroken engineering lineage and delivers a listening experience of extraordinary coherence and emotional engagement. Those building a complete Quad digital front end will find the Quad Artera Play+ an ideal source component, its high-resolution DAC and preamplifier output stage providing the QII-Forty with a signal of the finest quality. The Quad Revela 1 loudspeaker represents a natural and musically coherent partner — its ribbon tweeter and carefully engineered crossover ideally suited to the QII-Forty's valve output stage character.

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 Quad QII-Forty is available to hear in our Norwich showroom — speak to Dave or Chris to arrange a demonstration with the QC 24 preamplifier and a carefully chosen pair of loudspeakers.

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.