VACUUM TUBE AMPLIFIER SYSTEMS
the closest approach to the original sound.
C l a s s i c s e r i e s
The Quad
II-forty
The Quad II-forty valve amplifier is not only one of the finest sounding valve power amplifiers available in the market place today, it is an aesthetic and engineering masterpiece.
An understated elegance lies beneath the smooth curves and lustrous finish, for the power amplifiers use a circuit dating back over fifty years to the time when vacuum tubes ruled the electronics industry and Peter Walker considered by many to be the master of audiophile design.
He often shunned traditional thinking, preferring to go his own way, relying on excellence in circuit design. Circuits that are still admired today by the finest minds in electronics for their stunning performance and, by today’s standards, simplicity.
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“Factor out nostalgia. Forget the miracle of Quad making valve amps in the 21st century. Look
at the Quads in terms of a current pre/power tube combination. Then look at the opposition. Now factor in gorgeous styling, superb build quality, perfect ergonomics, ample grunt, genuine heritage and the kind of sound which allows valve enthusiasts to show two fingers to transistor users.”
– Ken Kessler, Hi-Fi News
The Quad II-forty power amplifiers are much more than a tribute to one of the most famous designs in audio - they are both refined and powerful in the modern sense of the terms.
Although the circuit topology has changed little from the original, significantly better components and a brand new transformer design - still delicatelybalanced-meansthattheyarefast,crisp and detailed, whilst producing an output current, more than capable of driving modern loudspeaker loads, even our very own ESL loudspeakers are well within their capabilities.
The champagne finished chassis is strong and heavy, internally wired with solder tags - not PCBs. TheKT-88outputvalvesinpush-pullconfiguration
are visually stunning, sitting safely within a cage to protect them. Gold-plated phono connectors replace the ‘Jones’ plugs of the original - with a choice of 4ohm or 8ohm taps, allowing for the widest possible choice of loudspeakers.
Everyproductwemakeishand-builtbycraftsmen for a lifetime of duty. Quad products rarely, if ever, need replacing and we regularly service and maintain products over fifty years old.
This means many of the original Quad II amplifiers have been passed down, into the hands of the children - and even grandchildren - of the original owners, something that is uniquely Quad in essence. A product that is relevant today and will remain so for generations to come.
Quad products have always been amongst the finest audio products in the world. When
Peter Walker started making commercial PA systems in 1936, few could have predicted the revolution in hi-fi that many of his products were to cause, the lon-
gevity they would have and the esteem with which they would be held.
In the early 1950s, he and Gilbert Briggs, founder of Wharfedale, embarked upon a series of now famous concerts demonstrating how real high-fidelity music should be virtually indistinguishable from a live performance. In order to prove this they toured such venues as the Royal Festival Hall in London and Carnegie Hall in NewYork. Audiences were amazed at the similarity the Quad amplifiers were able to reproduce relative to the live performance.
Since these early demonstrations of true high-fidel- ity, our product philosophy has remained constant, to produce a sound which as closely as possible replicates the experience of the live performance. For many other manufacturers, the term hi-fi may mean ‘exciting’ or ‘dramatic’ and this can be easily produced without regard to what the music sounded like in the concert hall for the listener and may sound ‘impressive’ to the uneducated ear, but in reality is no substitute for the sound produced by ‘real’ hi-fi.
“Musicians and recording artists all over the world have long recognised the outstanding quality of Quad products – exquisite engineering, build-quality, finesse and refinement.”
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The Quad
II-eighty
The Latest addition to the Quad Valve Power amplifier series is the long-awaited Quad II-eighty amplifier. The perfect partner to our latest ESL speakers, the II-eighty is not merely a nod in the direction of retro styling, it’s a modern high-performance amplifier designed by one of the most famous tube-amplifier designers in the world (Tim De Paravicini) using more than a little inspiration from the original Quad II amplifier.
The Quad ll-80 is an 80 watt mono power amplifier following in the tradition and philosophies of PeterWalker. The output section consists of 4 KT88 valves running as two pairs in push pull with the hallmark Quad topology of partial cathode loading in the output transformer.
This method reduces distortion when compared to the usual Ultra Linear or triode methods, however, it does require a greater grid driving voltage. This is achieved, again in true Quad fashion, using a balanced pair input stage.
The output transformer has been designed to improve high frequency performance and accurately balance the two push pull halves. Also the transformer has been designed to make sure that full output is realised at the bass frequencies down to 20 Hz.
Each output valve has its own cathode resistors to provide reliability and self-matching. The screen grids of the KT88 valves are run from a lower voltage, again for good reliability. The whole amplifier has a total of only 16 dB of feed-back providing good stability into virtually any known loudspeaker and especially the famed Quad electrostatic loudspeakers.
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