II

About the II

The Quad II monoblock valve amplifier, originally released in 1953, is a highly regarded class-A push-pull monophonic amplifier designed by Peter Walker. It uses a minimal two-stage circuit with two EF86 input tubes, two KT66 output tetrodes in a cathode-coupled arrangement, and a GZ32 or GZ34 rectifier tube. The amplifier delivers 15 watts into 8 ohms with very low distortion and a frequency response spanning 10Hz to 20kHz. Its design features a legendary output transformer that contributes to its refined sound quality and stability. The Quad II is noted for its low distortion, high signal-to-noise ratio, and a damping factor of about 11.75 at 700Hz. It is supplied as a monoblock pair, typically finished in stoved steel grey, weighing approximately 18.25 lbs (8.3 kg) each, with dimensions around 13 x 4.75 x 6.5 inches (335 x 121 x 171 mm). The amplifier requires an input sensitivity of about 570mV to 1.4V for rated power and is designed for speaker loads between 7 and 15 ohms. Vintage units remain highly collectible and are still appreciated for their musicality and engineering excellence.