Stereo Amplifier

Review: Quad 34 Preamplifier

The Quad 34 has four inputs, Radio, Disc, Auxiliary and Tape and they are selected by a vertical row of push-switches at the extreme left of the diecast metal panel; each has an associated green LED which remains alight after the input has been selected. Silent solid-state switches are used and, as there is complete isolation between all inputs, no breakthrough is audible. The second row of LED-indicated switches select monophonic operation and engage the four treble filter characteristics. To their right are the two lever knobs of the tone control switches, not the usual Bass and Treble but Bass and Tilt. The large knob is the stepped volume control and the small lever to its left swings the balance from left to right with an obvious notch at the central position. The sole remaining control is the mains switch knob at the extreme bottom right.

If we look in a little more detail at the arrangement and circuit layout it will help us to realize how much this model has to offer. The Radio input is straightforward, requiring 100mV of signal for full output and loading it with 100k. The auxiliary input is the same, being intended for Compact Disc players. However, like Radio and Tape, connection is via a 5-pin DIN socket (which Quad consider to have superior mechanical and electrical properties) and so the tape recording feed can also be brought to this socket, enabling a second tape machine to be wired in if desired. Tape monitoring (using a three-head machine) can be performed only on the real Tape input and it is interesting to note that, although a DIN socket is used, the signal levels are chosen to match the standard Line Input and Line Output more common on modern tape machinery; it is acknowledged that the true DIN standard levels, which are rather odd, have proved unsatisfactory with high-quality equipment. As a further measure of flexibility the Quad 34 can provide tape input and output levels of either 100mV or 300mV by plugging a couple of resistors into spring-loaded contacts provided on the printed circuit board. Source impedances are 2.2k and loads 120k and the record outlets are buffered so that the signal path cannot be interfered with.

The Disc input is even more flexible, for here a plug-in module is fitted which the user can easily change without in any way dismantling the equipment. Two are norm ally provided, one to suit most moving-magnet cartridges has 3mV sensitivity and a 47k/220pf load. The other for low impedance (usually moving-coil) cartridges offers 0.1 mV sensitivity and 100ω/22nf load. Others are becoming available. The disc input board incorporates the only discrete transistors to be found in the direct signal paths, all the rest of the amplification being provided by quantities of Bifet ICs. A form of single-ended push-pull arrangement has been chosen with the supplies carefully stabilized and with a part of the feedback loop on the module used to set the gain. RIAA compensation is active at all audio frequencies changing to passive at ultrasonic frequencies.

The tone and volume controls are true stepped attenuators made for Quad by ALPS in Japan; they incorporate contacts and resistive material deposited on a common base material and matched between channels by an etching process which enables Quad to claim balance errors of less than 0.5dB over a 60dB range - and the one I checked was rather better than that. The unique tone control arrangements brought in with the Model 44 are developed in the 34. The major control is descriptively labelled 'Tilt' and it does just that, see-sawing the bass and treble about a hinge at 950Hz. It is quite gradual and thus adds no coloration or loss of naturalness in the resultant sound, whilst quite accurately compensating for the differing behavior of rooms and their furnishings. The Bass control on the other hand is concerned with loudspeakers and their position in the room. Small, bass light, loudspeakers benefit from the Lift positions, which deliberately fall away at the lowest frequencies to avoid pushing them beyond a sensible limit, whilst the Step mode reduces bass output by a fixed amount at three frequencies as a palliative for unfortunate, but domestically necessary, loudspeaker placement, e.g. too near a corner. The balance control is straightforward, swinging the signal completely from left to right and thus acting as a mixing control between channel inputs if the Mono mode is engaged. It is in the filtering arrangements that a major departure from Quad practice can be seen. This is the first control unit of theirs not to incorporate a continuously variable slope filter-perhaps an acknowledgement that distortion in the source is less of a problem these days. However, I am already given cause to wonder if some or the peaky sounds being put on to the Compact Disc and being accurately reproduced by it might not require its return. Time and experience will tell. In the present case, Quad have elected to provide two fixed slopes or about 6 and 12dB per octave occurring at roughly 6 and 10kHz.

How it performed

Internally the construction is a pleasure to behold, as was the case with the FM4 tuner. A single printed-circuit board covers the entire area with all the major components on it. Once again all those parts or the power supply which could constitute a shock hazard are safely isolated in a screened-off corner and there is a corresponding insulated area on the underside or the board.

Satellite boards are connected via ribbon cables and every component is identified. I think it is safe to say that no audio equipment produced elsewhere is better made, and none of a comparable price gets anywhere near it. After which high praise one is justified in asking '"How does it perform?'"-and once again the answer can only be expressed in high marks. On measurements alone it is exemplary, although it should be pointed out that unlike the Model 44 it will only drive Quad or other 0.5V-input power amplifiers; it s quite gentle overload, if asked to provide higher levels, having been deliberately engineered, perhaps with some foresight. Subjectively too it is a very gentle-sounding control unit with a smooth creamy character which, on first acquaintance, has fooled many people into suspecting a railing frequency response. Direct comparisons with a couple of formidably expensive designs showed that everything seemed to be there, although one appeared to hear slight differences, noticeable perhaps in the appreciation or the surroundings in which the players were performing. Of course slight differences in choice of pickup loading can produce such subtle effects or maybe-I say maybe-there are differences in amplifiers which cannot be explained by the most scrupulous scientific tests.

The tone controls are meant to be used and do exactly what is intended without any loss or information. I proved to my own satisfaction that use or small loudspeakers was most definitely enhanced by the bass lift, and a deliberately - induced room honk was somewhat ameliorated with the step function. In the past I have tended to ignore the usual bass and treble controls for they often disturb the naturalness or reproduced music. I own one control unit which has none and on another they have remained switched to Cancel for many moons: not, may I add, that I am one of those poseurs who recoil in horror at the very thought or tone controlling whilst listening to record s that have been through every form of electronic cooking known to man. What I am saying is that I pleasantly listened for long periods with some degree or tilt either way, when I happened to disagree with the programme producer's choice or environment.

Quad's 34 control unit can be thoroughly recommended and, in view or what it offers at such a truly modest price, there is every l likelihood of it remaining a popular choice for many years to come.