Quad II-Eighty Power Amplifier


Reference Quality Valve Power Amplifiers

The Natural Match With Quad Electrostatic Speakers, Will Drive Normal Box Speakers Perfectly

Designed By Valve Maestro Tim de Paravicini

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The Quad II-Eighty Mono Valve Power Amplifiers are some of the most richly rewarding audio components you will ever lay ears on. From the company that bought you the electrostatic speaker, Quad continues it's tradition of 'The Closest Approach To The Original Sound'.


The range topper of the Quad Valve power amplifier series is the Quad II-Eighty amplifier. The perfect partner to Quad’s electrostatic 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 using more than a little inspiration from the original Quad II amplifier.

The new Quad II Series circuit design is the work of Tim de Paravicini, a man widely acknowledged to be the UK's foremost valve amp designer. His design is faithful to Peter Walker's philosophy of cathode loading onto the same output stage and fundamental simplicity of design, ensuring the new amp delivers the same wealth of detail and exquisite tone as its famous predecessor.

Yesterday’s Inspiration, Today’s Technology

The Quad ll-Eighty is an 80 watt mono power amplifier following in the tradition and philosophies of Quad founder, Peter Walker. The output section consists of four 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 20Hz.

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.

In The News

The Quad II-eighty embodies all of what aficionados have come to expect and love from these classic valve designs. Let’s start at what I rate as the biggest strength at hand here; the sublime midrange. Valve amplification, at its archetypal best, has been treasured for its palpable and life-like presentation of vocals and instruments that live within the midrange of the frequency spectrum. Well, the Quad II-Eighty manages to retain this cherished quality in spades.

Sonic excellence continues up higher in the frequency range, with the Quads’ refined sound making all treble information come across cleanly and without a trace of hardness or grain.

I have always maintained that two of the most important elements that help create a more believable facsimile of reality are dynamic contrast and accuracy in instrumental and vocal tonality. From top to bottom, the Quad amplifiers’ delivery of timbre is spot on. Instruments sound like the ‘real thing’. What’s more, be it guitar, piano or percussion, the sound is lush and vividly textured.

Here is a revamped and re-engineered version of an amplifier with an enviable heritage; the Quad II. Tim de Paravicini has taken the classic Peter Walker design, modernised the assembly and cosmetics, elevated the power output and updated its sonic qualities. Effectively, de Paravicini has retained the legacy midrange magic and has improved the overall sonic and physical package to an extent that would make Peter Walker proud. With the Quad II-eighty, excellence has become truly immortal.

Our Take

"The Closest Approach To The Original Sound" has been Quad’s goal since the company was founded by Peter Walker way back in 1936. One owner suggested they should update the wording to "The Original Approach To The Closest Sound" because the custodians of Quad have created these new valve amplifiers, based on the circuit topology of the past, but using modern components and high quality wiring.

The Quad valve amplifiers of the past were limited by available components and the thinking of the time. The new series II range, especially the II-Forty & II-Eighty retain the charm and magical midrange these amplifiers are famous for but add startling dynamics and deep tuneful bass to mix, allowing these amplifiers to be used with a wide range of speakers and sound absolutely magnificent. Of course they work brilliantly with the Quad electrostatic speakers, allowing you to approach the original sound as close as possible.

The price is not insubstantial, but we think it completely fair for the quality on offer. And remember, unlike many other hobbies, whatever the weather you can also sit down and listen to some beautiful music through you stereo system. It will let you escape from the world of trouble and strife to a place of calm and relaxation. Live life to the full because second chances are hard to get.

Main Features & Specifications

  • Design: Mono Valve Power Amplifier
  • Input Sensitivity (nominal): 1V RMS for full output
  • Power Output: 80W RMS
  • Output Impedance: 4 Ohms or 8 Ohms, selectable
  • THD @ 80 Watts:
    • 0.5% - 30Hz - 15kHz
    • 1.0% - 20 - 20kHz
  • Residual Hum and Noise: Better than -94dB
  • Frequency Response:
    • 10Hz - 30kHz (+0dB, -0.5dB)
    • 3Hz - 50kHz (-3dB)
  • Damping Factor: 16 @ 1kHz (referred to 8 Ohms)
  • Power Consumption: 180VA maximum
  • Valves:
    • 2 x 6SL7
    • 1 x 6SN7
    • 4 x KT88
  • Size (WxHxD): 430 x 220 x 190mm each
  • Weight: 20.3kg each
  • Finish: Lancaster Grey
  • Manufacturer's Warranty: 2 Years

Note: Features & Specifications Subject To Change Without Notice. E&OE. All other equipment in illustrations is sold separately.

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