Quad 33 Preamplifier

Together, the new 33 preamp and 303 power amp offer a compact and cool-running analogue pre/power pairing that is both faithful to the iconic originals yet thoroughly updated inside and out. The fact that vintage 33/303 units made in the 1960s and ’70s are still in use today, and their sound still much admired, is testament to the original design.

The new editions maintain and elevate these core attributes in every respect. They capture the originals’ silky sonic delivery that set them apart from transistor-based amps of the time, adding greater clarity, detail, bandwidth and dynamic impact. This pre/power amp brings back the romance of the original but over 50 years of innovation and improvements, making it a joy to behold regardless of source; track after track, symphony after symphony, the 33 and 303 are thoroughly engaging the listener whether the volume is set low or high!

Function

The new QUAD 33 is supported by digital microprocessor control but is otherwise faithful to a classic analogue design.

The 33 feeds the loudspeakers via the power amplifier using dedicated stereo pre-outputs, with an RCA line-level and balanced XLR pre-out option. For additional versatility and functionality, there’s also an AUX output.

Now equipped with fully balanced XLR inputs and outputs, the 33 is set apart from other preamplifiers and even its forefather model.

The brand new phono stage is Moving Magnet and Moving Coil compatible with the ability to simply switch between the two options – no mods or board upgrades necessary. With a gain of 46dB for the MM and 63.5dB for the MC, the input stage uses ultra-low noise audio op-amps. This ultra-low noise performance is combined with high slew rates and very low distortion specifications. The RIAA processing circuit has its own dual Bipolar/JFET Audio Operational Amplifier. The JFET portion of the input stage enables high slew rates to keep distortion low, even when large output swings are required.

Controls

The controls are comprehensive but simple. Again, this echoes the original design concept. Logically grouped to facilitate selection and control of the programme, a backlit LCD screen relays settings, adjustments and values. The same backlighting principle is applied to each of the push buttons, further enhancing the intuitive design with a visual indication of input selection and mode. Illumination settings for buttons and the LCD screen allow for brightness adjustment, contrast adjustment, and a simple on/off setting to suit the user’s preference.

The master volume control is a fully analogue, precision motorised ALPS potentiometer offering long-life and low-noise performance. The volume control is not only tactile and precise; its motorised operation will automatically rotate when adjustments are made via the remote control. A further row of three endless rotary encoders offer intuitive and immediate control over the QUAD-specific fine-tuning settings.

The original QUAD 33, as with many previous and subsequent QUAD preamplifier components, offered filters considered essential for ‘modern good quality speakers’ (as was stated at that time). Such controls are no longer required; therefore, in applying modern-day logic and suitability to today's technology, the new QUAD 33 presents bass adjustment, tilt control and balance control to allow tuning to a fine degree without intruding unnecessarily into the harmonic range essential for realistic reproduction.

The bass control allows adjustment from-3dB to +3dB. Perfect for subtle adjustments in the low-end, as a solution to adding body to thinner source material. Or conversely, reducing bass tones in the event of room-affected 'boominess'. In comparison to the time of launch of the original QUAD 33, loudspeakers and source materials have evolved mainly for the better. This evolution saw the adoption of ‘Tilt’ control in the QUAD 33’ssuccessor, the QUAD 34 (1982).

Developed by QUAD founder, the legendary Peter Walker, the Tilt control is an audiophile-quality solution for adjusting tone. Its design stems from the belief that traditional tone and EQ controls are inadequate and clumsy when adjusting tonal balance.

The Tilt control differs in that it adjusts 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. This feature is unique to QUAD and offers a subtle, precise, and consistent way to adjust your system's performance and compensate for recordings or environments.

The Tilt control, Bass control, and Balance controls are all composed of low-noise op-amps, electronic switches, and MELF low-temperature coefficient metal film resistors, forming a negative feedback adjustment circuit.

Performance

No one knows more about the QUAD 33 than the immensely experienced QUAD service department – still based at QUAD HQ in Huntingdon, Cambridgeshire, England.

Upon initiating this project of passion, it was determined that the new 33 and 303 combination will only see the light of day if the performance stands true and improves on the original.

In over 50 years since the release of the original 33 and 303, innovations and developments have been exponential, but only some have been employed and each with good reason. Each stage of the development and every innovation was subject to thorough testing and complete agreement with the QUAD technical design AND service team.

It is bold but fair to claim that the low-noise, custom-specified toroidal transformer, numerous reservoir/smoothing capacitors, and an impressive number of regulators put the new QUAD 33 technically ahead of the original. The power supply incorporates five regulated supply rails, including multiple ultra-low-noise regulators with extensive measures employed to prevent contamination and cross-coupling. Following traditional QUAD practices, the core signal path is short and direct to preserve signal purity, and volume is adjusted purely in the analogue domain under microprocessor control. No one will champion the virtues of the original QUAD 33 more than QUAD, ourselves. However, side-by-side, technical innovations and improvements in signal processing cannot be denied.

Fit and Finish

The QUAD 33 has a crisp and clean aesthetic that evokes QUAD’s past yet sits in the modern-day with a futuristic accent. The housing is rigid and oozes quality. The end-finish is precise, just like the audio signal path. The anodised and custom-tooled fascia demonstrate the quality and level at which the new QUAD 33 will be recognised. No longer subject to cracks, fading or other issues associated with classic front panels, the QUAD 33 is ready for a lifetime of performance.

Ultimately, the new QUAD 33 considers every angle and aspect to underline the faithful evolution of the ‘33’ concept. With each step in transitioning from concept to reality, the commitment to ‘the closest approach to the original sound’ is evident.

A new classic is born, and the 33 emerges in the modern era. The past is not forgotten, but the future is undeniably here.

Learn more about this product in our detailed video review: