QUAD 303 amplifier

The QUAD 303, with its QUAD 33 preamplifier, are among the rare emblematic high-fidelity products. They have left their mark on several generations of music lovers and audiophiles over the last fifty years.

They still remain one of the most popular models in history and from Quad, one of the best-known Hi-Fi brands in the world. The first QUAD 303 left the manufacturer's factories in 1967 and, throughout all these years, it has symbolised a benchmark in terms of performance and reliability.

By revisiting the QUAD 303, the brand demonstrates its wish to reconnect with authenticity and history!

QUAD 303: Enclosure

You find the lines and codes of the Quad 33, but this one receives a slight makeover that gives it both a vintage and very contemporary touch. This "industrial" design of the new version is immediately recognisable. The anodised chassis is fitted with heatsinks machined with a CNC machine. The assembly of the housing provides a very robust and inert structure that resists interference and vibrations, both internal and external.

QUAD 303: Connections

On the back of the unit, you find a pair of unbalanced inputs in RCA format and a balanced one in XLR. A small push-button allows you to choose between these two inputs.

Another one allows you to set the amplifier to bridged (Mono) mode.

The connection to the speakers is made via a very nice and high-performance terminal block accepting banana plugs and spades.

The power cable is in IEC format and can therefore be upgraded if necessary.

QUAD 303: Technology

The exceptional performance of the QUAD 303 is still relevant today, and is largely due to the output circuit developed by QUAD and Peter Walker in 1967.

As in the original, the new QUAD 303 remains faithful to the original circuit by employing the famous "triple balanced" scheme of the historic QUAD.

These are used to provide a completely balanced output stage, considerably reducing distortion and making the quiescent current independent of the thermal drift of the output transistors.

Due to the lack of complementary transistors (NPN and PNP power transistors) in the past, the old QUAD 303 used a "quasi" complementary output stage. The new version of the QUAD 303 now uses a fully complementary output stage, thus offering better linearity, a more stable static bias and improved stability under high-voltage and high-current conditions. This development allows designers to reduce distortion to extremely low levels without sacrificing stability, and to maintain this excellence under all dynamic conditions. As the voltage is also controlled, the output transistors are completely protected and always operate within the limits of their rated values. This offers obvious advantages in reliability.

Every stage of development and every innovation was thoroughly tested and fully agreed with QUAD's technical design and service team.

The Quad 303 can be used alone, and therefore in stereo mode, offering a stereo power of 50 w into 8 ohms. By using 2 Quad 303 bridged in mono, you get a mono power into 8 ohms of 140 w, and into 4 ohms, 170 w per channel!

QUAD 303: Test and listening

When launching this project, it was decided at Quad that the new 33 and 303 combination would only see the light of day if performance was improved over the original.

58 years after the release of the original 33 and 303, innovations and developments have been exponential, but only some were used, and each one rightly so.

The Quad 303 is an admirable amplifier. It can be used with its long-standing partner, the Quad 33, but also with the majority of balanced preamplifiers on the market.

This amplifier brings a refinement that is rare in this price range. It reproduces music with a lot of space and breadth. The timbres are rich and full. You sometimes get the impression of listening to a tube amplifier. It remains transparent, precise and dynamic whatever the style of music. The Quad 33 clearly favours musicality and naturalness, so much so that you can listen to it for hours (even at a high volume) without asking yourself any questions. The high frequencies are precise enough to bring out all the ambiance and atmosphere of the recordings. And this extends down to the bass, which is both powerful when needed and capable of revealing all the snap and resonance of a bass drum or an electric bass.

The Quad 303 is very different from what you generally find in this segment in terms of reproduction. This new version goes much further in terms of definition and subtlety than its ancestor, without making any sacrifice in terms of musical enjoyment. This amplifier is a real success and a bargain at this price!

Being able to bridge it in mono, and therefore use a second Quad 33, is an additional asset.

Our favourite!

FAQ: Everything you need to know before buying the Quad 303 amplifier

Can I use the Quad 303 on its own or do I need the Quad 33?

The Quad 303 can be used perfectly well on its own, in stereo mode. It pairs ideally with its historic partner, the Quad 33, but remains compatible with most balanced preamplifiers on the market thanks to its unbalanced RCA and balanced XLR inputs, selectable via a push button.

 How much power does it deliver and how can I get more?

In stereo it delivers 50 W per channel into 8 ohms. It also offers a bridged (mono) mode: using two bridged Quad 303 units, you get 140 W into 8 ohms and 170 W per channel into 4 ohms. Switching to bridged mode is done with a simple push button.

 How does it connect to my speakers and sources?

On the back panel there is a pair of unbalanced RCA inputs and a pair of balanced XLR inputs. Speakers connect via a fine binding post accepting banana plugs and spades. The power cable uses the IEC format and can therefore be swapped for a more refined model if you wish.

 What kind of sound does the Quad 303 deliver?

This Quad power amplifier brings a refinement that is rare in its price range. It reproduces music with plenty of space and scale, rich and full timbres that sometimes recall a tube amplifier, while staying transparent, precise and dynamic whatever the style. This new version goes much further in definition and subtlety than its ancestor, without sacrificing musical enjoyment.