Quad 33 Preamplifier and 303 Power Amplifier (2024 Edition)

Very few Hi-Fi components are as instantly recognisable as the QUAD 33 and 303, and for that we make no apologies!

Still one of the most popular models in the history of one of the world’s most poignant Hi-Fi brands, the QUAD 33 and 303 are benchmarks in almost every angle of desirable audio equipment – performance, reliability, industrial design, value and musical romance.

By revisiting the QUAD 33 and 303 components, QUAD demonstrates its authenticity, pedigree and excellence as a juggernaut of the British hi-fi world - past and present.

In listing the names involved in the development of this stunning iteration of an icon, you’ll find a calculation of close to 200 years of engineering experience and 100+ years of QUAD-exclusive design and service.

A dream team of Rob Flain & Paul McConville (the world’s most experienced QUAD service engineers), Jan Ertner (30 years of 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 a part of this labour of love, making no compromise in the demand for a product that could bear the name of 33 and 303.

The external design is specifically intended to continue the QUAD tradition of practical simplicity. Yet, it would be foolish to ignore the implementation of modern-day capabilities, such as an informative backlit display, delicate LED illumination and remote control functionality. And just like the original, the overall appearance is unmistakably QUAD, albeit now with a premium machined and anodised front panel and all-metal chassis.

Quad 33 preamplifier
The external design of the QUAD 33 Pre-Amplifier retains the brand’s characteristic simplicity, but now integrates modern features such as a backlit display, LED illumination, and remote control functionality. The premium machined and anodised front panel, along with an all-metal chassis, enhances its modern look while remaining unmistakably QUAD. Despite its updated digital control system, the QUAD 33 stays true to its analogue roots, reflecting a balance between tradition and technological advancements.

MM/MC Cartridge Compatibility
The QUAD 33 offers improved connectivity with fully balanced XLR inputs and outputs, setting it apart from its predecessors. The new phono stage is compatible with both Moving Magnet and Moving Coil cartridges, allowing seamless switching between the two. The input stage is designed for ultra-low noise performance, using advanced audio op-amps, and includes a high-performance RIAA processing circuit for exceptional sound quality, even during demanding output swings.

Control
The controls of the new QUAD 33 echo the simplicity of the original, with logically grouped functions that are easy to navigate. A backlit LCD screen displays settings and input selections, while motorised volume controls offer both tactile precision and remote adjustment. The addition of bass, tilt, and balance controls allows for fine-tuning of sound without compromising the integrity of the audio. The unique Tilt control, developed by QUAD’s founder Peter Walker, enables precise tonal adjustments by modifying both ends of the frequency spectrum in unison.

Quad 303 Power Amplifier
Evolution of the QUAD 303
Every aspect of the QUAD 303 Power Amplifier has been re-engineered beyond a simple update of components. Originally designed for domestic use, it also became a favourite in broadcasting and recording studios for its reliability. The new model surpasses the original’s standards while maintaining its ethos, with modern design and functionality that reflect its enduring appeal, even earning a place at the Museum of Modern Art.

Technological Advancements
The QUAD 303 stays faithful to its roots with QUAD’s ‘symmetrical triples’, ensuring low distortion and stable performance under dynamic conditions. This advancement means distortion levels are now almost negligible, far below what is detectable by the human ear. The ‘triples’ design also protects the output transistors, enhancing reliability without complex circuitry.

Complementary Output Stage
Unlike the original’s quasi-complementary stage, the new QUAD 303 employs a fully complementary output stage, using premium transistors for better linearity and stability under challenging conditions. With this, the amplifier handles overdriven or disconnected speaker scenarios effortlessly, maintaining excellent sound quality and reliability.

Modern Features and Power Output
The new QUAD 303 incorporates a custom low-noise toroidal transformer and the amplifier’s design remains iconic, with durable materials and rugged construction that offer both style and substance. However, with some tweaking and enhancements, the 303 is loaded with a little extra power – offering 50W @ 8 ohms (70W @ 4 ohms) with a maximum current delivery of 10A into difficult loads. The original 303 was known to have issues with lower impedance loads, the new 303 has no such trouble. Perfectly suited to the more demanding requirements of the modern audiophile, it ensures any speakers – even including QUAD’s electrostatic designs – can be driven with ease. Connectivity options comprise single-ended RCA and balanced XLR inputs, a 12V trigger input and high-quality speaker binding posts. Simple, solid and thoroughly authentic, inside and out. The power output for 'bridged mode' (for use as a mono-block power amplifier) reaches 140W @ 8 ohms or 170W @ 4 ohms (bridged mono).

Specifications
33 Preamplifier
Physical characteristics
Weight - 4kg
Dimensions (HxWxD) - 258mm x 165mm x 82.9mm
Technical specifications
THD+N - <0.001% 1W, 1kHz, 4 ohms
Frequency response - 20Hz - 20kHz (+/-0.2dB)
Input sensitivity - 695mV (Line / XLR) 3.2mV (Phono MM) 460uV (Phono MC)
Input impedance - 10k (Line / XLR) 47k/100pF (Phono MM) 100R/1.7nF (Phono MC)
Output Impedance - 120 ohms
Inputs/Outputs
Inputs - 3 x RCA, 1 x Balanced XLR (pair), 1 x Phono (MM/MC switchable)
Outputs - 1 x RCA (AUX), 1 x XLR, 1 x RCA (Pre Out), 1 x Headphone, 2 x 12V Trigger Out

303 Power Amplifier
Physical characteristics
Weight - 8.4kg
Dimensions (HxWxD) - 325mm X 176mm X 120mm
Technical specifications
THD - <0.002% (1kHz)
Frequency response - 20Hz - 20kHz (+/-0.3dB)
Input sensitivity - 700mVrms (Line) 1.5Vrms (XLR)
Input impedance - 10k ohms
Gain - +29dB
Inputs/Outputs
Inputs - 1 x Line, 1 x XLR
Outputs - 1 x 12V Trigger 1 x Stereo Speaker, 1 x 12V Trigger (Link)