Quad 303 Power Amplifier

About the Quad 303 Power Amplifier

Through an overhaul of the QUAD 33 and Quad 303 power amplifier components, Quad Audio demonstrates its authenticity, pedigree and excellence as a powerhouse in the British hi-fi world – both past and present.

When listing the names involved in the development of this beautiful iteration of an icon, you will find a calculation of almost 200 years of engineering experience and over 100 years of QUAD-exclusive design and service.

A dream team of Rob Flain & Paul McConville (the most experienced QUAD service engineers in the world), Jan Ertner (30 years experience in QUAD design), Peter Comeau (the acoustic director behind some of QUAD's most successful loudspeakers).

And David McNeill (the industrial designer responsible for two decades of QUAD innovations) were all part of this love project, where no compromises were made when it came to a product that could bear the name of 33 and 303.

The QUAD 303 power amplifier was intended for normal domestic use with moderate efficiency loudspeakers! But it was also used by broadcast and recording studios worldwide, who appreciated its excellent performance and reliability. The ethos has not changed.

Functionality QUAD 303

The outstanding performance of the QUAD 303 is still celebrated to this day. This is largely due to the unique output circuit developed by QUAD.

In re-releasing the concept of the QUAD 303 power amplifier. Just as with the accompanying 33 preamplifier, QUAD’s incomparably experienced service team was matched with the equally skilled engineering team to recreate the design, romance and performance in a thoroughly modern version of a hi-fi legend.

Like the new QUAD 33, every aspect of design and performance has been analyzed and rethought, going far beyond simply updating components and refreshing specifications.

The QUAD 303 power amplifier was intended for normal domestic use with reasonably efficient loudspeakers. But it was also used by radio and recording studios all over the world, who appreciated its excellent performance and reliability.

The ethos has not strayed. The original 33 and its partner 303 were awarded the Council of Industrial Design Award in 1969. Even today the original design is celebrated and acknowledged by its presence in the Museum of Modern Art in New York. The new 33 and 303 are industrially designed to exceed those original standards! With a truly modern look and feel.

Circuit QUAD 303

However, just like the original, the new QUAD 303 stays true to the original by using the famous QUAD 'symmetrical triples'. These are used to provide a fully symmetrical output stage. This significantly reduces distortion and makes the quiescent current independent of the temperature of the output transistor.

This development enables the designers to reduce distortion to remarkably low levels without sacrificing stability and maintain this excellent level under all dynamic conditions.

To put this into perspective, the lowest possible theoretical distortion present on the source material will still be about a hundred times greater than that of the QUAD 303!

Such a level is of course completely inaudible, no matter how refined the test.

The use of 'triples' allows simple and effective control of the output current. And since the voltage is also controlled, the output transistors are fully protected and must operate within their specifications at all times. With the obvious advantage of significantly improved reliability under all conditions, without the use of complicated and expensive circuitry.

Due to the lack of complementary transistors (NPN and PNP power transistors) in the past, the older QUAD 303 used a quasi-complementary output stage. The new version of the QUAD 303 now uses a fully complementary output stage.

Providing better linearity, more stable static bias, and improved stability under high voltage and high current conditions. By using high quality power transistors, the 303 provides excellent gain linearity for accurate reproduction of the input signal with a wider dynamic range.

The amplifier cannot be upset even if it is overloaded by an unbalanced signal or if the speakers are short-circuited or disconnected.

Transformer

A brand new 200VA, custom made, low noise toroidal transformer has been developed by Quad Audio for the new 303.

The output stage of the discrete power amplifier circuit uses an advanced feedback topology! To ensure superior linearity and exceptional thermal stability. The Class AB design maintains the ideal current regardless of the temperature of the output transistors.

The result is a compact, cool-running power amplifier capable of delivering dynamic power and a firm grip on the music while delivering rich sonic detail.

Always respected for its conservative but consistent power delivery, the classic QUAD audio 303 was officially rated at 45W @ 8 ohms. A modest but honest output! The 303's respectability lies in the finesse of its performance, not just in its raw power. The new model is exactly the same.

With some tweaks and improvements the 303 is loaded with a bit of extra power. With 50W @ 8 ohms (70W @ 4 ohms) and a maximum current delivery of 10A into difficult loads. The original 303 was known for its problems with lower impedances, the new 303 has no problems at all.

Perfectly suited to the more demanding requirements of the modern audiophile, the 303 ensures that any loudspeaker – even QUAD’s electrostatic designs – can be driven with ease.

Quad Audio Connections

Connectivity includes single-ended RCA and balanced XLR inputs, a 12V trigger input and high-quality speaker terminals. Simple, solid and thoroughly authentic, inside and out. Power output for 'bridged mode' (for use as a monoblock amplifier) ​​reaches 140W @ 8 ohms. Or 170W @ 4 ohms (bridged mono).

 

• Check out the accompanying Quad 33 preamplifier https://mister-hifi.nl/product/versterkers/voor-versterker/quad-33/

 

More information can be found on the manufacturer's website https://quad-hifi.co.uk/ or also take a look at our collection page about Quad https://mister-hifi.nl/beste-versterker-luidsprekers-quad-hifi/