Solid State Preamp Reviews

Launched in 1967, Quad's highly original, elegantly styled 33 preamplifier and 303 power amplifier were Quad's first all–solid state designs and among the first solid state separates. The 303 may have been one of the first "vertical" amplifiers. Together with the 405 stereo amplifier, which came out in 1975, and the FM2 and FM3 tuners, these products proved to be enduring, widely feted successes from their launch until they were discontinued, the 33 in 1982, the 303 in 1985. Meanwhile, they enjoyed massive production runs, were marketed worldwide, and were much admired for their modern industrial design. It's said that Quad sold 120,000 33 preamps and 100,000 303 amplifiers. Across two versions, the 405 sold even more.

Quad introduced new versions of the 33 and 303 (each component $1599) in 2024, apparently moved to do so by the continuing hot market for originals. The 2024 components are not identical to them, but at least conceptually, they share much with the originals. In appearance, the new 33 control unit has distinct echoes of the original, which in its time won many design awards—as did the 303. The 33 retains the compact, chunky, weighty form.

It is finished in a muted, low-key orange/tan, not so different from the original. It has streamlined, low-profile controls and now a matching LCD display, backlit in orange, with user-variable brightness. That LCD panel is small and not high contrast, so it's not easy to read at a distance, especially the smaller, secondary legends.

Conveniently, the tone controls can be bypassed with the remote control, which is important for assessing the value of more subtle adjustments. Considering the generous feature list, the 33 is quite compact, allowing the slender 303 power amp to sit beside it if you so wish. Build quality is excellent for both products, with precision machined metal-alloy panels and camera-quality fixings. The components themselves are let down a little by a remote control handset in molded polymer. The remote requires a little practice to operate, but familiarity comes with use.

The electronics found inside the new pre/power units result from the creative input of Quad group engineers, headed by the highly experienced Peter Comeau, the head of engineering for parent company IAG. Peter has enjoyed a run of wins with his creative updates of legacy products including the Mission 770, which I reviewed in HIFICRITIC (footnote 1) and John Atkinson reviewed for Stereophile.

One key feature of the new 303 that the original version lacked is bridge mode. If you need extra power, each 303 can be bridged to serve a single channel. (They can also be used for biamping.) I think it makes sense to think of the Quad proposition as two separate offerings, a pre-power stereo set with 50Wpc at $3200 and a pre-power set with a pair of 140W monoblocks at $4800. That extra $1600 expenditure seems quite reasonable for nearly three times the power and, who knows, maybe better sound. You could of course buy one 303 now and another later. Incidentally, the old 405 was rated at 100W; it is easily supplanted by the new 303 in bridge mode.

Those original Quad preamplifiers are famous for a distinctive feature that allows control of timbre and, to some degree, stereo image perspective, achieved by controlling the tilt or slope of the frequency response. The usual 0dB flat response may be gently tilted up or down about a perceptually chosen middle frequency, here 700Hz. In place of conventional tone controls, with all their limitations, the seamless tilt adjustment can bring the performance closer if it sounds too distant. Conversely, if a recording is rather bright and too closely miked, a counterclockwise rotation imparts depth, weight, and perspective. The effect is subtle and worthwhile. With the new 33, you can control this feature from your listening seat, which after all is where this perceptual action happens. Many vintage recordings will benefit from a gentle blowing away of their dusty acoustic cobwebs with a gentle uptilt. Conversely, a downward tilt may happily tame some modern rock, in which an overloud steely or brittle sound dominates. A touch of down-tilt adds perspective and allows greater power to be exercised, for example on The White Room by The KLF, specifically the tracks "Last Train to Transcentral" and "Justified and Ancient."

The legendary Cello Palette boasted an advanced multi-frequency control that could be configured for similar duty, though it was certainly more awkward to program. I bought one some years ago for its effective timbre optimization and lovely sound but eventually lost patience with that before-listening, time-consuming precalibration. Conversely, Quad's own convenient broad-brush "timbre-tilt" facility on the 33 may be a primary reason to commit to purchase. "Tone" settings may be quickly compared via that vital "bypass."

On the back panel, you will find one of the most densely packed sets of facilities that I have yet experienced yet beautifully laid out and eminently usable. The LP input phono sockets have a local ground/earth terminal. Gain and loading may be conveniently set remotely at the listening seat, either for MC or MM cartridges. There is a silent internal toroidal power transformer feeding five low-noise regulated supplies, and there is not a scrap of audible hum anywhere, electrical or mechanical. This whole 33/303 affair is impressively thought out and well executed.

On the densely packed rear panel of the 33, from the left we find the rocker switch for power and the IEC 3-pin socket with adjacent 0.5A fuse (1A USA): Access to the voltage selector is via a cover plate, while the adjacent USB socket is for software updates, as in this design system control is by a microprocessor. Two 12V trigger outputs are for synchronizing power-up for one or two power amplifiers, as needed (cables not included). Preamp outputs are in both RCA, balanced XLR, plus a fixed-gain "aux" output. There are four aux/line inputs, three in RCA format, one in XLR balanced. The final pair of phono sockets are for LP disc with a ground terminal, here gain switchable between MM (47k ohm) and MC (100 ohm) via the versatile remote control or the front-panel buttons. There is a ¼" headphone jack socket powered by a dedicated, wideband current feedback amplifier, and it sounded just fine.

The brand-new phono stage is both moving magnet and moving coil compatible with the facility to switch between the two options on the fly; no mods or board upgrades necessary. With a gain of 46dB for the MM and 63.5dB for the MC input, the input stage uses very quiet, low-distortion audio-dedicated op-amps. For RIAA processing, the circuit has a separate wide bandwidth dual bipolar/JFET op-amp with a generous dynamic range.

A low-noise toroidal power transformer feeds oversized reservoir capacitors connected to five regulators. The motorized ALPS volume control is a high-resolution analog type, here a selected version with position-sensed data driving the numeric volume readout.

The Quad 303 stereo/mono power amplifier has a tidy, minimalist front panel featuring elegant vertical fins in cast alloy; these are quite shallow and this efficient and versatile design runs cool.

However, the rear panel (below) is as busy with sockets and switches as that jam-packed 33 control unit. For the 303, the upper section carries four generous shrouded 4mm binders/sockets for left and right speaker connection, while the two locking XLR input sockets for left and right channels are complemented by an array of phono sockets in gold plate. Pushbutton switches select between the XLR or RCA inputs and also set the alternative single-channel, higher power "bridge mode." Mini-jack sockets facilitate cabled synchronization of the power amplifiers with preamp power-up, including that second channel when operating in bridge mode. The required leads were not provided but are easy to procure. Power input is via an IEC 3-pin facility with the power switch adjacent. After a period of inactivity, the 303 powers down automatically, as per EU-legislated grounds of economy. Thankfully, warmup is quite rapid, usually unnoticed after a few minutes of music play.

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Footnote 1: See HiFi Critic Vol.16 No.4 (2022).