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Quad II-Eighty Power Amplifier 80 Watt Mono Valve Power Amplifiers (Pair)

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Item: Quad II-Eighty Power Amplifier - 80 Watt Mono Valve Power Amplifiers (Pair)
Location: Ringwood
Price: $9,500 was $14,999
Item Condition: Demonstration Model
Reason for selling: It is the last model and needs to be moved.
Payment Method: Pickup - Cash, Paypal, COD Only
Extra Info: 

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.


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.


  • 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

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