QII-Forty

The QII-Forty is a stereo-style valve power amplifier based on the classic QUAD II concept. The circuit topology differs slightly from the original, and the components are of a higher grade. A newly engineered transformer is fitted. The aim is a fast, crisp and detailed sound while keeping the balanced character of the original, with enough output current to drive modern loudspeakers, including QUAD's own ESL models.

The output stage uses two KT88 valves in a push-pull configuration. The input stage uses two 6SH7 valves and a 5U4G valve handles rectification. Rated output is 40 W RMS, with total harmonic distortion of 0.3% at full power and 0.03% at 1 W.

Speaker connection is through 4 Ohm and 8 Ohm taps, which allows a range of loudspeaker configurations. Input sensitivity is 1 V RMS, and maximum power consumption is 180 VA.