Quad QII-Eighty

The Quad QII-Eighty is the pinnacle of Quad's valve power amplifier engineering — an 80-watt monoblock of extraordinary authority and musical refinement that represents the fullest and most uncompromising expression of the design philosophy Peter Walker established with the original Quad II in 1953. Designed by the late Tim de Paravicini — one of the most celebrated valve amplifier engineers of the modern era, whose understanding of transformer-coupled valve circuit design is without parallel — the QII-Eighty takes the fundamental topology and engineering principles of the original Quad II and develops them to a level of performance that the original could never have approached, producing an amplifier whose combination of power, resolution and tonal authority sets a new standard for valve amplification at any price.

Output Stage & KT88 Valve Configuration

The output stage of the QII-Eighty employs four KT88 valves operating as two matched pairs in push-pull — a configuration that delivers 80 watts of output power from a valve complement whose individual characteristics are selected and matched with the precision that this circuit demands. Push-pull operation in the QII-Eighty is executed with Tim de Paravicini's hallmark rigour — a circuit architecture that preserves the even-order harmonic structure and musical naturalness of the finest valve amplification while delivering the dynamic authority and loudspeaker control that 80 watts of carefully engineered valve output power provides.

Partial Cathode Loading & Output Transformer Design

The output transformer — always the critical component in any valve power amplifier, and the element whose design most directly determines the amplifier's sonic character — incorporates Quad's hallmark topology of partial cathode loading, a circuit refinement that maintains the output transformer's operating conditions within an optimally linear region across the full dynamic range, minimising distortion and preserving the tonal integrity of every musical nuance from the quietest pianissimo to the most demanding fortissimo. The partial cathode loading topology employed in the QII-Eighty's output transformer is the direct descendant of Peter Walker's original circuit insight — the engineering principle that gave the first Quad II its celebrated tonal character and that has been studied, analysed and reverentially preserved by every Quad valve amplifier designer since. In the QII-Eighty, Tim de Paravicini's application of this topology to an 80-watt KT88 push-pull circuit represents a feat of transformer and circuit design of the highest order.

Dynamic Authority & Loudspeaker Compatibility

Eighty watts per channel from a monoblock of this circuit refinement transforms the QII-Eighty's ability to drive the full range of contemporary loudspeakers — including the most demanding multi-way floorstanding designs and the lowest-impedance electrostatics — with complete composure, dynamic authority and the musical coherence that is the exclusive province of the finest valve amplification. Where lesser valve amplifiers retreat into compression, hardness or tonal thinning under dynamic demand, the QII-Eighty maintains its composure with the quiet confidence of an amplifier that has enormous reserves of power and the circuit intelligence to deploy them precisely when and where the music demands.

Who Is It For?

The QII-Eighty is for the serious valve enthusiast who demands the full authority of 80 watts of monoblock power without sacrificing the tonal purity, harmonic integrity and musical naturalness that only the finest valve circuit design can provide. It is an amplifier for those who have heard the best valve amplification available and understand precisely what they are looking for — and who recognise in the QII-Eighty a component of the very highest order.

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-Eighty is available to hear in our Norwich showroom — speak to Dave or Chris to arrange a demonstration with the QC 24 preamplifier and your chosen loudspeakers.

The QII-Eighty is the natural partner for the Quad QC 24 Pre-Amp valve preamplifier — together forming a complete valve amplification system of the highest order. Those building a complete Quad valve system may also wish to consider the Quad QII-Classic and Quad QII-Forty — the QII-Eighty's stablemates in Quad's valve power amplifier range. The Quad Revela 1 loudspeaker represents an outstanding partner, its ribbon tweeter and carefully engineered crossover ideally suited to the tonal character and dynamic authority of the QII-Eighty's output stage.

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.