Quad Quad 303 Power Amplifier

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.

INPUT SENSITIVITY

- 1.5Vrms (XLR)
- 700mVrms (Line)

OUTPUTS

1 x 12V Trigger
1 x Stereo Speaker, 1 x 12V Trigger (Link)

POWER REQUIREMENTS (DEPENDING ON REGION)
 
- 220 - 240V - 50 / 60Hz
- 100 - 120V - 50 / 60Hz

DIMENSIONS 2 (CARTON SIZE)

- Width : 226 mm
- Height : 312 mm
- Depth : 462 mm

RATED POWER OUTPUT 

- Stereo : 2 x 50W (8 ohms, THD<1%)
- Stereo : 2 x 70W (4 ohms, THD<1%)
- Bridged : 140W (8 ohms, THD<1%)
- Bridged : 170W (4 ohms, THD<1%)

CIRCUITRY 

However, much like the original, the new quad 303 maintains its faithfulness to the original by employing the famous quad ‘symmetrical triples’. Employed to provide a completely symmetrical output stage, greatly reducing distortion and rendering the resting current independent of output transistor temperature.

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

To put this in perspective, the lowest theoretical distortion present on the very source material will still be some hundred times greater than that the quad 303!

OUTPUT STAGE FOR ENHANCED AUDIO PERFORMANCE

Due to the lack of complementary transistors (npn and pnp power transistors) in earlier times, 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 large current conditions. Using premium power transistors, the 303 offers excellent gain linearity for accurate reproduction of the input signal with greater dynamic range.

VERSATILE CONNECTIVITY & HIGH-LOAD PERFORMANCE

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).

FUNCTION

- The outstanding performance of the quad 303 is still celebrated to this day, and is largely due to the unique output circuit developed by quad.

- In reissuing the quad 303 power amplifier concept, exactly like the matching 33 preamplifer, quad’s incomparably experienced service team was matched with the equally adept engineering team to reinvoke the design, romance and performance in a thoroughly modern iteration of a hi-fi legend.
- As with the new quad 33, every aspect of design and performance has been analysed and re-engineered way beyond simply modernising components and refreshing of specifications.

- The quad 303 power amplifier was intended for normal domestic use with moderately efficient loudspeakers, but it was also used by broadcasting and recording studios worldwide, who appreciated its excellent performance and dependability.
- The ethos hasn’t deviated. The original 33 and its partnering 303 were awarded with a ‘Council ofIndustrial Design Award in 1969’. Even today, the original design is celebrated and confirmed by its presence at the Museum of Modern Art in New York. The new 33 and 303 have been industrially engineered to surpass those original standards, with a truly modern appearance and functionality.