❱1949 – QA/12P Integrated amplifier
Peter Walker’s first commercial, domestic amplifier was a development of the Public Address amplifier that he had been building and selling in pre-war years. With superior sound quality to its competition, it was adopted by the BBC for studio use.
❱1949 – Acoustical Corner Ribbon loudspeaker
Although not Walker’s first speaker design, the Corner Ribbon was the first of note using the company’s unique design and manufacture of a ribbon diaphragm to cover the midrange and treble output.
❱1951 – Q.U.A.D. 1 Control Unit and Power Amplifier
Although the power amplifier was, again, a development of the QA/12P, the associated Control Unit or preamplifier saw the birth of the distinctive fascia design and innovative filter and tone controls as well as the acronym QUAD or Quality Unit Amplifier Domestic.
❱1953 – QUAD QCII and II Power Amplifier introduced
The significance of the QUAD II Power Amplifier has been, perhaps, underplayed in a history of valve amplifiers otherwise devoted to Ultra Linear operation of the output stage. But the Cathode coupled output stage of the QUAD II offers the best balance of phase linearity and low distortion coupled to high efficiency.
❱1957 – QUAD Electrostatic Loudspeaker
The world’s first full range, ultra-low distortion electrostatic loudspeaker set standards for accuracy and fidelity in loudspeakers that remains unsurpassed to this day. A labour of love for Peter Walker, the ESL-57, as it came later to be known, is still revered by audiophiles all over the world.
With the advent of stereo in 1958, this stereo version of the QCII drove two QUAD II power amplifiers and created a matched stereo system with a pair of ESLs.
❱1967 – QUAD 33/303 preamp/power amplifier combination
At this point in time, transistor amplifiers generally sounded far worse than their valve counterparts but QUAD showed what could be done with carefully researched and advanced design. The ‘output triples’ configuration of the 303 power amplifier was a major breakthrough in current drive capability.
❱1975 – QUAD 405 Power Amplifier
With loudspeakers generally becoming smaller and less sensitive, there was a clear need for more powerful amplifiers. Peter Walker’s answer was to marry a pure Class A ‘clean’ power amplifier to a Class B ‘Current Dumping’ feed forward stage that provided the grunt when needed. A brilliant design which heralded another QUAD classic.
❱1981 – ESL-63 Electrostatic Loudspeaker
Acknowledging the slight limitations of the ESL-57 in terms of treble ‘beaming’ and low power handling, the ESL-63 was designed to achieve the ultimate electrostatic speaker. Featuring a time aligned midrange/treble set of annular rings, this design emulates a true ‘point source’ with added bass panels for improved power handling and sensitivity.
❱1996 – QUAD 77 system
QUAD’s first system to be conceived as an interlinking whole, with CD player, tuner, preamplifier and power amplifier all controlled by an innovative remote handset, the 77 system was actually most notable for its unusual ‘pure Class B’ integrated amplifier, designed by Jan Ertner, which solved all the problems of crossover distortion. Jan is still designing amplifiers for IAG today.
❱2000 - QUAD QC-24 Control Unit
Not an update of the QC-22 but a completely new design from valve guru designer Tim de Paravicini. In combination with the 11-Eighty Power amplifiers, this is by far the best system to match to Electrostatic loudspeakers.
❱2006 - ESL-2805 and ESL-2905
Still using Peter Walker’s innovative ‘point source’ panel design, these versions of the ESL-63 featured improved structural rigidity and power handling, the larger ESL-2905 being particularly suitable for bigger rooms and high listening levels.