Quad 33 Pre Amplifier - 2024 Edition

Icons of British audio

Born in the Swinging Sixties, QUAD’s famous 33 preamp and 303 power amp return in fresh, revitalised form to delight a new generation of music lovers seeking a modern-retro twist One of the most celebrated amplifiers of all time – the 33/303 two-box pre/power amp system from QUAD, Britain’s original high-end hi-fi brand – makes a triumphant return 57 years after it first recalibrated expectations for transistor-based sound. Teased in prototype form at the High End audio show in Munich in May 2024, the reimagined QUAD 33 preamplifier and QUAD 303 stereo power amplifier are already among the most hotly anticipated hi-fi launches of 2024.

This reflects not only the appeal of modern-retro design in audio, but also the high esteem in which the original amps are held – the 33 and 303 remain among the most sought-after ‘vintage’ amplifiers on the second-hand market. Upon their launch in 1967, their innovative circuit design elevated transistor-based amplification to new heights. The new 33/303 contain highly evolved versions of the same signature technologies, wrapped in an industrial design that echoes the past and embraces the future.

Design evolution

QUAD’s decision to revisit the 33 and 303 was in no small part due to the continuing demand for these amps on the second-hand market some four decades after they were discontinued in the 1980s. What Left Launched in 1967, QUAD’s original 33 preamp and 303 power amp were innovative inside and out 3 a tempting proposition, to take such an iconic design and update it inside and out, creating a new amp pairing that is unmistakably a QUAD 33/303 yet benefitting from the advances in design, engineering and manufacturing in the 57 years since the original was first realised…

To achieve this vision, QUAD assembled a formidable in-house team at its HQ in Huntingdon, Cambridgeshire. The new 33 preamplifier’s compact size and shape is faithful to the original, but the detailing has been enhanced and the casework’s grey colour is a little less ‘taupe’ and more ‘matt silver’. The distinctive control layout is similar, with a volume knob to the left and a trio of flush-mounted rotary controls to the right (although the functionality of these controls is now somewhat different).

Crucially, the original 33’s orange accents remain, albeit cleverly updated. The buttons beneath the rotary controls are now all orange (no white), with the addition of LEDs to illuminate them. And the orange strip containing labelling for the three flush-mounted rotaries now includes an LCD display with orange backlighting. Such things were not possible in the 1960s, yet the ingenious way these visual updates have been applied to the new 33 feels entirely in keeping with the classic aesthetic. The backlit buttons and LCD display – which can be dimmed or switched off entirely – are not the only nods to modern expectations.

Between the 33’s two rows of orange buttons are a 6.35mm headphone socket and an IR receiver for the supplied remote control – more ‘mod-cons’ added to the original’s specification. Further differences in the facilities offered by the original 33 and the new 2024 edition are highlighted in the ‘Technology’ section below. Like the 33, the new 303 stereo power amplifier is instantly recognisable yet smartly updated. The original’s vertical orientation remains, together with the distinctive heatsink fins at the front – albeit there are now ten fins rather than eight, and these have been neatly squared off.

Technology

The new QUAD 33 The original 33 preamplifier was launched at a time when vinyl was king and digital audio was still some 15 years away from entering the domestic scene in the form of CD. It offered several vinyl-oriented facilities for users to tailor the sound, including 5k, 7k and 10k filters, accessed via the buttons beneath the rotary controls for bass, treble and slope adjustment. These filters were intended to remove record surface noise and high frequency distortion when used in concert with the slope dial.

The new 33 remains a staunchly ‘analogue’ preamplifier, with no built-in DAC for digital sources, but its facilities have been adapted to better suit contemporary requirements. For a start, the filters for vinyl have gone and the bass, treble and slope dials have been replaced by bass, tilt and balance. The ‘Tilt’ control was created by QUAD’s founder Peter Walker as a more sophisticated form of tone control. It was introduced in 1982 on the QUAD 34 preamp, which succeeded the 33; although not contemporary to the original 33, it is considered a classic QUAD feature that remains highly useful and so has been added to the new 33. Walker believed that traditional bass and treble controls were a rather ham-fisted way of adjusting tonal balance. The tilt control differs by adjusting both ends of the frequency spectrum together, either attenuating the bass and lifting the treble or lifting the bass and attenuating the treble in 1dB steps. Essentially, it rotates – or tilts – the audible frequency range on a 700Hz axis, thereby adjusting the overall sound balance with 'warm' or 'cool' hints without altering volume or adding colour to the sound.

The tilt control works in tandem with independent bass adjustment, accurately applied from -3dB to +3dB. These subtle, precise and consistent methods of tailoring tonal performance are tremendously useful given the varying quality of the music sources we listen to today, from streaming services to vinyl Left New versions of classic QUAD features ensure the 33 preamp is a faithful evolution 5 to hi-res digital files. They also help to tune the sound to suit different acoustic environments and, of course, personal taste.

Connectivity has also evolved.

The original 33 used DIN sockets for its inputs and outputs; these have been swapped for a mix of single-ended RCA and balanced XLR sockets, opening up a much wider range of cable options. The original’s four source inputs – labelled ‘disc’ (for vinyl), ‘radio 1’, ‘radio 2’ and ‘tape’ – have been replaced by four line-level inputs (3x RCA and 1x XLR) and a phono input, and there is also a choice of RCA and XLR outputs to connect the 303. Other modern conveniences include two 12V trigger outputs and a USB data input for firmware updates.

While the latter input shows that the new 33’s user interface is microprocessor controlled, the audio signal path is entirely analogue. A high-quality motorised Alps potentiometer adjusts volume, while the three rotary encoders for bass, tilt and balance provide the precision of digital control but act entirely in the analogue domain – classic QUAD features updated for 2024 and beyond

The new 33’s audio circuitry is faithful to the intention of the original – a groundbreaking design of its day – whilst acknowledging that the quality of today’s electronic components is vastly better than those available in the 1960s. The design team has created an entirely new circuit design, including a low- noise, custom-specified toroidal transformer, numerous reservoir/smoothing capacitors and five regulated supply rails, remaining true to the original’s ethos whilst improving on its sonic performance. The new 33’s low-noise phono stage is also a significant advance on the original’s, with adjustable gain for MM and MC cartridges, precise RIAA equalisation, precision input filtering and an upgraded power supply, delivering every drop of detail dug from a vinyl record’s grooves. As for the dedicated headphone amp – an entirely new addition – its current-feedback design and high slew rate ensures a dynamic and detailed performance with all manner of headphones.

QUAD 33 PREAMPLIFIER (2024 EDITION) – SPECIFICATIONS SUMMARY
Inputs 1x stereo XLR; 3x stereo RCA line level; 1x stereo RCA phono (MM/MC)
Outputs 1x stereo XLR; 1x stereo RCA; 1x stereo RCA AUX; 1x headphone; 2x 12V trigger
Other facilities Bass and Tilt tone controls; balance control; remote control
Dimensions (WxHxD) 258x82.9x165mm