After IAG released a new edition of the 60s classic, the LEAK Stereo 30 amplifier, and another famous British audio manufacturer, Musical Fidelity (Audio Tuning), introduced a replica of its 1980s A1 cult amplifier a couple of years ago, it was only a matter of time, I guess, before IAG would release a new edition of one of the QUAD’s classic amplifiers.
Retro is fashionable. Nostalgia sells. Nothing wrong with that. Would QUAD have joined the trend if Peter or Ross Walker had still been at the helm of QUAD? We don’t know. Peter Walker retired in the late 1980s, in 1995 QUAD was sold to Verity Group, and to its current Chinese owner IAG (International Audio Group), it ended in 1997.
To avoid any misunderstanding, QUAD/IAG tells it has assembled a dream team around the 33/303 revival project including two experienced QUAD service engineers, Rob Flain and Paul McConville, Jan Ertner, who designed Audiolabs and QUADs for IAG, and a speaker maestro and IAG director Peter Comeau (Heybrook, Mission, JPW) plus industrial designer David McNeill. If this group cannot create British Hi-Fi, who can.
WHY 33/303?
But why the 33/303 pre/power amp combination? QUAD, or Quality Unit Amplifier Domestic as it goes, would have had plenty to choose from. Why not the QUAD 44 (1979-89) & 405/405-2 (1975-93)? The 44 measured better than the 33, and the 405 was the first power amplifier in which QUAD introduced its famous current damping technology (a small Class A voltage amplifier controlling the output current of the power transistors). The combination sold almost as many (about 200,000) as the 33/303 combo.
Three reasons. First, the 33/303 was QUAD’s first transistor amplifier, and although Peter Walker reportedly did not warm to it (an amplifier is just a piece of wire between the source and the speakers no matter how it is realized), when QUAD, in 1967, announced its own vision of a quality transistor amplifier – the 33/303 – it became perhaps the most important milestone in its entire history. 120,000/94,000 units were sold, many of which are still in high demand on the second-hand market.
Two. The innovative circuit design of the 303 with its triple output stage became a beacon for the entire British Hi-Fi, and amplifier manufacturing industry more generally. The innovative stable, low-distortion, and good-sounding transistor amplifier was even considered to be one of the best in the world.
RETROMODERNISM
The third – and the most obvious – reason is retromodernism: the art of designing a product that is suitably anachronistic, but at the same time signals modernity. With the new 33/303, QUAD has done just that, and has also succeeded, if not completely, reasonably well anyway.
The 33/303 combo has retained its easily recognizable appearance: the preamplifier and power amplifier isolated in their own small housings, the cooling fins brought to the front of the 303, the 33’s colorful front panel with all kinds of controls. The 33/303 combo soon became not just a pictorial symbol of its manufacturer, but also a design icon for the collections of several design museums.
There is no doubt that IAG has wanted to capitalize on the looks and reputation associated with the 33/303’s technology and appearance, do what it beautifully stated on another occasion (QUAD II Classics) : “offer audiophiles the opportunity to recreate the spirit and atmosphere created by one of the most famous amplifiers in Hi-Fi history in their own home”.
But will the new 33/303 be able to convince younger generations who lack a touchpoint with a 60-year-old model? Those who’re immune to retro? To this end, QUAD has changed the dimensions e.g. of the 303 a little to make it look more dynamic, and fresher. The brighter light modern gray gives the amp almost a plastic impression.
The new 33 operates strongly with buttons and displays with an orange backlight in a way that would not have been possible in the 1960s. At the same time, the front panel is more two-dimensional, less colorful and less eventful than the original. Nevertheless, the new 33 is a sympathetic acquaintance, nice to look at in the darkening evening. And if the backlight starts to look too bling-bling, it can be dimmed or turned off completely from the armchair with a handy remote control.
ANALOG TECHNOLOGY
The new 33/303 is 100 % analog amplifier. The 33 doesn’t sport a DAC or a streamer, and the 303 trusts on well proven Class AB technology. Class D would have been not only a label error, but a cardinal one. The volume control (ALPS) is microprocessor-controlled, as is the display, but the volume, like other adjustments, are handled purely on the analog side.
The guiding principle in the technical restoration seems to have been not to touch the original connections and audio circuits (the so-called brand design integrity), but to update the components to modern standards and redesign the power supplies. To what extent this is true is not always easy to assess. At least the power supplies have been renewed. Both now sport a customized toroidal transformer, more caps for filtering and more efficient regulation. The 33 has five regulated supply rails instead of one.
The RIAA stage is implemented with two transistors and a feedback circuit, but the transistors are now said to be low-noise and low-distortion BJT/JFET op amps. The MC cartridges now have their own 63.5 dB input. No input impedance selection, but 100 ohms/1.7nF is a pretty good starting point for many MC carts.
The former DIN inputs are now RCA line inputs (3), plus there are symmetrical XLR line inputs/outputs. At the same time, the preamplifier seems to have become a mere buffer (0 dB, RCA/XLR), while the original 33 had 13.6 dB of voltage gain. Also new is a current-feedback headphone amplifier, and a 6.3 mm jack for 20 – 600 ohm headphones.
FINE TONE ADJUSTMENT
QUAD 33 wouldn’t be QUAD without tone controls, but the adjustments have been implemented in a different way. The bass has a gentle +/-3 dB adjustment between 20 and 40 Hz instead of more usual +/- 10 dB at 100 Hz. The range is not enough for large room corrections, but the control works surprisingly well for minor tonal purposes.
The treble control has been replaced by a tilt control developed by Peter Walker in the 1970s, and which QUAD introduced in the QUAD 33’s successor, the QUAD 34, in 1982. The tilt control corrects both ends of the frequency spectrum (20 Hz and 10 kHz) simultaneously, either by attenuating the bass and raising the treble, or vice versa, in 1 dB steps (-3dB … +3dB) with a lever frequency of about 700 Hz. The tilt changes the tonal balance slightly warmer or cooler without actually changing the volume or coloring the sound. A wideband tilt control acts like an ear, always relating a single frequency change to the entire frequency balance. That’s the way to do it!
LESS WATTS, MORE CURRENT
In the early 1960s, practically all transistor amplifiers were biased in Class B. When one output transistor was conducting, the other was completely cut off, meaning that each transistor only conducted for one half of the signal. However, due to transient distortion, it was practically necessary to add a small quiescent bias, which often then varied with the temperature of the output transistors (depending on thermal properties of the transistors and the amount of output power).
Peter Walker solved the thermal problem with his triple output stage: a feedback topology of three transistors in the output stage. The topology did not require a large amount of feedback, but made the amplifier thermally stable so that the output current was almost immune to temperature variations in the output transistors. The circuit made the 303 power amplifier so linear that QUAD advertised it as “the world’s first low-distortion transistor amplifier.”
QUAD says the output circuit of the new 303 has retained the triplet structure of the old 303. The fully symmetrical and complementary output stage is realized with high-quality NPN and PNP transistors. The result is a compact, cool-running power amplifier that delivers about 50 watts into 8 ohms in Class AB with less than 1% total distortion. 50 watts is only 5 watts more than the original 303, but into 4 ohms (thd <1%) the new 303 delivers 70 watts, while the original 303 delivered less than 30 watts into 4 ohms. More importantly, the output current is now hefty 10 Amps, which should be enough for even more demanding speakers, including, perhaps, QUAD’s own electrostatics.
ALL COLORS TOGETHER
I listened to the 33/303 package with a variety of speakers (Dynaudio, QUADs etc.) from 86 dB/6 ohm up, including floorstanders, although I think a compact standmount speaker would be a likely choice for an amplifier combo like the 33/303, which itself is more comfortable on a bookshelf or on top of sideboard than hidden in a Hi-Fi rack.
Generally speaking there were no power adequacy problems or problems with transient reproduction. The loudest music samples I simply skipped. If the 303 feels underpowered, one can always buy another 303, and bridge them (a small button on the back) to form a 140 W mono amplifier (170 W into 4 ohms).
But how did the new 33/303 sound? The sound? According to Peter Walker, people in QUAD never listened to music when designing their amplifiers, only distortions, noise or other obscure sounds that could potentially interfere with music listening, never Beethoven, Bach or anything like that. In the spirit of Walker, I loaded music into my CD player, disc after disc, this time almost exclusively modern, post-modern and contemporary art music, in the style of Schonberg, Webern, Berio, Ives, Stockhousen, Hindemith, Poulenc, Lutoslawski, Ligeti, Landowski, Elliot Carter, Kirschner, Zimmermann, Schnittke, Gubaidulina, Saariaho, Lindberg, Takemitsu, Pärt and the like, and in the end didn’t really understand why should I have drawn any other conclusion than that the music in question sounded largely as it was supposed to: fast-moving, multi-tonal and multi-structured, dynamic. What a joy to hear again these CDs!
Of course, counterfactually, had, for example, the bass instruments been clearly over-represented, the music in question might have sounded veiled and even a bit boring. But no. Muted treble would have compromised the sonic subtleties that are so important to this music, extra brightness would have made listening fatiguing, and so on. But no. And I’m not really surprised, as such anomalies are more characteristic of loudspeakers than the amplifier. A quick listen with worn-out test records did not change the impression.
The recordings naturally differ from each other with respect to the way they are recorded and the tonal balance, and that’s where the genius of the tilt adjustment came to the fore. It changed, just rightly, the unnecessarily aggressiveness, if any, to be more gracious, and the fainter sounds to be more brightly radiant. Music-friendly tone control at its best!
A short experiment with a Lenco 75/Ortofon/Denon DL-103 produced a distortion-free, wide-band and tonally neutral MC sound with a good rhythmic grip. The 100 ohm load impedance was almost right on target in this case, although connoisseurs may disagree.
Compared to Cary Audio’s 8,000 euro SLI-100 tube amp, I would say that the QUAD 33/303 did not quite possess the same level of transparency and immaterialism, attunement, even though it created a large soundstage in front of the listener, extending from a speaker to a speaker. Compared to a similarly priced Class D amplifier, the 33/303 combination exudes more of a calm whiteness, where all the colors of the spectrum are equally represented, and the grasp of the music is more holistic, instead of being excessively clean or artificial.
QUAD’s new 33/303 is a small, elegant amplifier combination, implemented with a good taste and proven technology, given the state of the markets nowadays, at a quite reasonable price of 3 000 euro. I’m not saying there are no competitive amps in this, and in particular the 5 000 – 6 000 euro range, but none of them have the same story, the same history, and best of all, the same immortal appearance!
QUAD 33
Voltage gain: 0 dB (line/xlr)
Frequency response: 20Hz – 20kHz (+/-0.2dB)
Thd+n: 0.0005% (1kHz)
Input/output impedance: 10 kilo-ohms / 120 ohms
Sensitivity: 695 mV
SNR: > 108dB (A-weighted)
Analog inputs: 3 x rca, 1 x xlr, 1 x phono (mm/mc)
Digital inputs: –
Outputs: 1 x rca, 1 x xlr, 1 x pre out, 1 x headphone, 2 x 12V Trigger
Phono input:
Voltage gain: 46dB (mm), 63.5dB (mc)
Input impedance: 47 kilo-ohms/100 pF (mm), 100 ohms /1.7nF (mc)
Thd+n: 0.002% (1kHz, mm/mc)
SNR: > 82dB/> 74dB (A-weighted, mm/mc)
Headphone amplifier:
Thd+n: 0.01% (1kHz, 50mW)
Output impedance: 2.35 ohms
Load impedance: 20 – 600 ohms
Dimensions (W x D x H): 258 x 165 x 82.5 mm
Weight: 4 kg
QUAD 303
Output power (stereo, thd <1%): 2 x 50W into 8 ohms, 2 x 70W into 4 ohms Output power (mono, thd <1%): 1 x 140W into 8 ohms, 1 x 170W into 4 ohms Thd: < 0.002% (1kHz) Frequency response: 20Hz – 20kHz (+/-0.3dB) Input impedance: 10 kilo-ohms Sensitivity: 700 mV (line)/1.5 Vrms (xlr) SNR: > 108dB (A-weighted, 8 ohm, 1 kHz)
Max. Output current: 10A
Analog inputs: 1 x rca, 1 x xlr
Dimensions (W x D x H): 120 x 325 x 176 mm
Weight: 8.4 kg
