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Quad 520

Stereo Rack Mount Power Amplifier

Designed for professional applications

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Quad 520


The Quad 520 is a two channel 100 to 150 watt amplifier for 19 inch 2U rack mounting.

Intended to drive loudspeaker loads the amplifier will deliver up to 100 watts into 8 ohm or 150 watts into 4 ohm with very low distortion.

Input sensitivity is 0.5 Vrms for full output with a lockable gain control.

Balance inputs can be provided to special order.

The standard of quality of the amplifier is of the highest order, and with any complex input distortion falling within the useful part of the audio range will not exceed a small fraction of one percent.

Overloading with any load will not significantly affect long time constants, ensuring immediate recovery and minimum distortion resulting from such overload.


Power output: 100 watts per channel into 8Ω (stereo)

Frequency response: 20Hz to 20kHz

Total harmonic distortion: 0.1%

Input sensitivity: 0.5V

Signal to noise ratio: 115dB

Dimensions: 482.6 x 88 x 310mm

Weight: 12.5kg



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Reviewed Jun 14th, 2017 by chazola

Still the best amp I've heard, tons of power and clean, uncoloured sound. Getting old now so greatly benefit from re-capping- the power supply caps are a little tricky but can be done by the competent home-solderer.
Industrial look and XLR in/outs on most models which can put home users off- but making up cables is easy enough.



NMarshall's picture

Quad 520

The 520 is physically well engineered but, sonically, it is let down by poor (cheap) component choice and it has significant upgrade potential. The starting point is to replace the low grade caps with Nichicon and Elna substitutes, the op amps with Burr-Brown OPA227s and to fit decent RCA connectors. The effect is marked - greater transparency, improved soundstage and slam.

There are several firms who provide advice, upgrade kits and a complete re-build service for Quad amps. Have a look at the Quad Spot blog from Brussels based Dada Electronics. DC-Daylight Ltd's, Bernd Ludwig's and Net Audio's thoughts on Quad 405 modifications are also worth a read.

quad 520f

is this a better amp then the 520

This website is not affiliated with or sponsored by Quad. To purchase 520 spares or accessories, please contact the company via their website or visit an authorised retailer.