Review: Musical Fidelity The Preamp and Typhoon Power AmplifierReview: Musical Fidelity The Preamp and Typhoon Power Amplifier

 

Despite their comparatively small number of years in business — the company was started in 1983 — Musical Fidelity have managed to build an impressive catalogue of products, driven ever forward by the indefatigable force at the helm, founder Antony Michaelson. The core products have always been amplifiers, but there have been important contributions in other key areas such as CD players, digital-to-analogue Converters, tuners, loudspeakers and so on, so that followers have been able to choose from a selection of units in order to assemble a complete single brand hi-fi system at a given price break. Some of the more esoteric models are deliberate 'statements', what one might call 'overkill' products—physically imposing power amplifiers and so on which respond to the challenge of imported 'super-fl' units, answering them not only in terms of performance but also in build quality, presentation and, not least, price. These top-end units remain expensive but they nevertheless aspire to the stated company principle of "extraordinary value for money".

The greater part of Musical Fidelity's success has been built upon their eminently affordable integrated amplifiers, notably the Class A model Al (reviewed by John Borwick in April 1987) and the Class AB model B1 which I looked at in July 1990. Although rated at a modest 32 watts per channel rating, the B I has the ability to deliver a very high instantaneous current, which with normal music signals is what really matters— in that sense the B 1 really is a wolf in sheep's clothing. It was this ability of the circuit, built around a simple yet novel output stage which uses paralleled high current output devices, which became the starting point for the new Typhoon reviewed here, the power amplifier half of a £500 pre/power combination which is well able to 'see off' many competitors costing very much more and bows to none in its price range.

Basically the B1 has been split into a separate preamplifier and power amplifier, the extra space available in what is now just the power amplifier cabinet occupied by twice as many output transistors-16 in all, eight per channel. Together with an up-rated power supply these give it a continuous power output rating of 45 watts per channel into 8 ohms and, more significantly, a remarkable 60 amps instantaneous peak current ability.

This latest version of The Preamp, as it is called (it was the name of Musical Fidelity's first ever product and has been given to several others since), is a line-level only device with six inputs labelled CD, Tuner, CDV (sound channels only), Aux, Tape 1 and Tape 2. There are just five front panel controls: a mains power on/off rocker switch with a built-in red indicator plus four to decide the signal routing and level. The main input selector is a six-position rotary switch which is complemented by a simple two-position pushbutton to provide a true monitor for Tape 1. A second six-way switch determines which of the input signals will be sent out to Tape 2; thus for example one could choose to listen to a Compact Disc whilst recording a radio programme on to a cassette recorder connected to the Tape 2 terminals. The remaining control is for Volume. There are no tone or balance controls or filters of any kind, and no headphones socket.

The biggest novelty is the balanced output stage which is brought Out to a pair of three-pin XLR sockets at the rear. In audio, balanced lines have been largely the province of the professional studio world where long cable runs are prevalent and immunity to noise a prerequisite. Whereas the normal unbalanced signal routing of domestic audio uses a just two connectors—a 'hot' signal wire screened by its own return—a balanced line uses three: two wires for the signal plus a quite independent overall screen which is connected to ground only at one end. The signal is fed in opposite phase to the two wires and recovered at the far end of the cable by an active circuit or transformer which recognises only difference (i.e. out-of-phase) signals. Because the two wires are in close proximity, any external noise components will be common to both and thus in-phase, so will be rejected. Normal unbalanced feeds are perfectly acceptable for short domestic runs (and indeed are used for all inputs and the tape output of The Preamp) but there is no gainsaying the effectiveness of a properly realised balanced configuration, particularly when long cable runs may be involved.

Inside, The Preamp is remarkably bare with a large and very thinly populated single-sided glass-fibre printed circuit board occupying most of the floor area. To the left is a large toroidal mains transformer, its primary feed protected by a socket-mounted fuse on the rear panel. There are just a handful of active components: four operational amplifiers and three transistors plus a pair of IC voltage regulators. The passive components are all high quality types. The signal routing is managed by switches located immediately behind the gold-plated phono socket array and controlled by extension rods from the front panel knobs, thus keeping the signal paths very short. The same arrangement also applies to the volume control which is an Alps device. All signal sockets are directly mounted on the pcb. The Output is muted by a relay to eliminate switch-on thumps.

The case, which is essentially common to several items in this range, is made up of an L-shaped chassis which forms the base and rear panel, a high quality custom alloy extrusion forming the fascia, a second removable steel sheet forming the top (lipped at its rear edge and screwed through to the chassis) and two plastics end plates. The legends are in a light blue with the company name in white. It is a very simple yet very well thought Out and realised arrangement and it looks very neat and unobtrusive.

The case for the Typhoon is all but identical except that its chassis and top are perforated to allow the free passage of air and of course the fascia carries only a power on/off switch. The rear panel has two XLR input sockets and four 4min socket/binding posts for the loudspeaker outputs. Both The Preamp and the Typhoon are fitted with captive mains leads which terminate in a moulded two-pin wall plug (which, as we've noted before, is best removed by UK users and replaced with a proper household three-pin plug).

Internally, the Typhoon is dominated by the 16 power output transistors, each of which is mounted directly on to the pcb through its own finned heatsink. The two stereo channels are completely independent— separate bridged rectifiers and reservoir capacitors and so on — only the mains transformer being common to both, and even on that there are separate secondary windings so to all intents and purposes, this is two mono amplifiers in a common case. Operational amplifiers are used again to process the balanced input signal but discreet transistors are employed beyond that in the gain and pre-driver stages.

One by-product of balanced operation is the ease with which bridged operation can be established. In this mode the two channels of a stereo amplifier are driven anti-phase with respect to one another to form a composite mono device of very much greater power; the loudspeaker is connected across the two 'hot' (usually red) terminals. A bridged Typhoon is rated at 150 watts into 4 ohms. For stereo one would purchase a second Typhoon and a pair of special 'Y' adaptor leads, bringing the total cost (preamplifier and two power amplifiers) to around £800, which is still very modest for a combination of this ability.

Performance

Connecting up the system is very straightforward for normal operation and only a little more complicated for a bridged set-up. Being a line-level only unit The Preamp has no provision for a pickup cartridge, which is becoming something of a trend as the LP heads towards extinction. Many listeners have substantial vinyl collections of course, in which case an alternative control unit, recently released (it was not yet available when I collected this review set) called the Rainbow can be substituted at the same price of £299. Otherwise identical it simply substitutes an RIAA input for one of the line-level set and has a switch to select MM or MC gain. Although I have not heard it I have every expectation that the quality via this MM/MC input will be high, the circuit based on a tried and trusted configuration that MF have refined through several amplifiers over the years.

As to the performance of these two combinations, I must say that I can think of no good reason for anyone to spend more on an amplifier in order to obtain the highest quality sound from a domestic system, almost regardless of the loudspeakers used. The straight Preamp/single Typhoon combination will give very fine results, conceding little or nothing to any of the various similarly rated units that I have tried in recent years; it provides a clear, focused sound, quite free of any hardness or sibilant emphasis, a very musical result with which one feels at once comfortable.

Bridging offers substantially greater headroom of course but more significantly an enhanced sense of bass weight and control. In practice this manifests itself as a still greater feeling of authority, with superbly delineated stereo imaging and a corresponding finesse in detail. Two contrasting discs that I happened to use at the time—.-Stanford's Sixth Symphony (Ulster Orchestra under Vernon Handley on Chandos KD CHAN8627, 9/88) and Telemann's Water Music in C (Musica Antiqua Cologne/Reinhard Goebel on DG D 413 788-2AH)demonstrated these effects well, the luxurious Chandos recording extremely convincing and literally brought to life in front of me, the arguably too close DG conveyed so cleanly as to seem now far more musically engaging than simply analytical, which is how I had remembered it.

There is a small caveat regarding bridged operation: the effective gain of the composite power amplifier is 6dB greater than the normal stereo mode and this means an increase in whatever background noise emanates from the preamplifier and also that one will have less 'use' Out of the volume control's rotational arc for a given loudness. Using Quad ESL-63s this was pretty well irrelevant, but with KEF 103/4s, with their much greater sensitivity of 91dB/watt/metre. I did notice an increase in background hiss which was enough to trouble me. I should add that with most loudspeakers this will not be a problem at all but it would be as well to check.

Well conceived and well made, The Preamp and Typhoon will certainly find favour with the many enthusiasts whose first priority is sound quality. This is a 'big' amplifier hiding behind a modest facade; there is no 'statement' about its presentation, no thick brushed aluminium fascia or gold-plated screws. The money has been spent wisely where it matters; a concept which deserves to do well.

Specification

The Preamp

Frequency response: 10-60,000Hz ±1 dB

Input sensitivity for 775snV output: all inputs 250mV Output: balanced tine via XLR connectors

Output impedance: 700 Dimensions (W x H x D): 440 x 45 x 165mm

Weight: 5kg

UK retail price: £299

Manufacturer: Musical Fidelity Ltd., 15/16 Olympic Trading Estate, Fulton Road, Wembley, Middlesex HA9 OTF. Tel: 081-900 2866 

Ivor Humphries

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