Sugden Bijou
Sugden has a three-piece mini-system, tested here with the Totem Acoustic Sttaf Loudspeaker.
Cleckheaton: a small Yorkshire town whose name became something of a byword for hi-fi three decades ago. Jim Sugden started his original company, Research Electronics, in 1960, specialising in scientific instrumentation and then audio test equipment.
The company that bears his name was established a few years later to manufacture the domestic audio amplifiers with which he had caused a stir, both in public demonstration and in a series of articles for HFN . Appearing in 1969, Sugden's A21 was one of the first really excellent-sounding transistorised designs. It had a Class A output stage and was thus free of the odd-order distortion artefacts which led many Class B circuits to disappoint at the time. At just 12 watts per channel, though, it found itself underpowered, with the trends towards lower sensitivity loudspeakers that the transistor had encouraged, so in 1974 Sugden produced the 40W/ch A48, his most famous design. In a textured Nextel finish with a choice of two-tone brown/beige or black/grey, this was tremendously successful. It was uprated to 50W/ch with a series II suffix in 1976, receiving a Design Council Award in 1979. |
 |
The company continues to make the A21 today under the dedicated eye of it's present-day MD and chief designer, Tony Miller, but the company has also moved with the times of course, producing an unhurried, considered flow of new designs. Currently the catalogue lists the Audition Series and the high-end Masterclass Series. The most recent release, causing something of a stir at The Hi-Fi Show 2000, is the uniquely styled, mini-sized Bijou system, which compromises the HeadMaster headphone/pre-amplifier (£519), AmpMaster power amplifier (£629) and CDMaster CD Player (£1250) plus, soon, a stereo tuner, the FMMaster. The HeadMaster has been available for just over a year now, and has sold well around the world. Capable of driving most moving-coil headphones, its current-controlled Class A driver stage is also ideally suited to serve as a pre-amplifier output, capable of driving long pre-/power interconnects. Minimalist in facilities it has just three unbalanced line-level inputs plus a tape record output, all on Teflon-insulated gold-plated RCA phono sockets. There are no balance or tone controls and no filters. At the front is a single 6.35mm (1/4in) headphones socket, a small red LED power-on indicator and two rotary controls: a three-position input selector and a volume control. The circuit is built on a single PCB, including the plastics encapsulated mains transformer. Signals from the rear panel array are taken via short lengths of high-quality shielded cable to the nearby edge of the board and thence to three adjacent gold contact, bifurcated crossbar relays which handle the switching. The fascia control simply routes control voltages to these relays; it carries no audio signals. Inserting a headphones jack mutes the pre-amplifier output. With the exception of a single LM317 voltage regulator, the circuit employs only discrete components, of exceptional quality and close tolerance. The volume control is an Alps device.
 |
The casework is altogether special, made in-house from six precision engineered aluminium pieces each 6mm thick, except for the rear panel which is 3mm to accommodate the phono socket thread depth. The front, side and rear panels locate in slots in tubular corner posts. these eight items sandwiched between the top and bottom plates and held together by bolts which pass through the corner posts and whose retaining nuts are hidden by rubber-cushioned machined aluminium feet. The two control knobs are also turned from solid aluminium. This is all beautifully done and visually very striking - a sort of domestic instrumentation look. All the panels are chemically dyed in what Sugden terms 'black chrome': a sophisticated silky finish which gives a two-tone effect as the light strikes it. |
The only legending is screen-printed in a special black etching ink on the top plate, along with the banner 'Handcrafted Audio Products', the make, model name and line drawing of its function. At once macho and cute, it smacks of class.
AmpMaster is a modestly rated 34W/ch stereo amplifier in an almost identical cabinet. There's little room here for the large, heavyweight components routinely employed in power amplifiers these days, and the dissipation required for Class A output stage is too great for a cabinet this small. Instead, Miller uses a trans-impedance, or current feedback circuit of the sort more commonly seen in HF applications. Inherently stable, it requires no frequency compensating capacitor, its bandwidth limited only by a passive 6dB/octave filter at the input.
A single 100 watt toroidal mains transformer is employed, feeding a pair of 10,000uF reservoir capacitors via a four-diode bridge. The supply is common to both channels, with each protected by fuses in its DC supply rails. The loudspeaker outputs are protected by a muting relay. Mains input is on a fused IEC socket again with the power switch now a latching push button on the fascia accompanied by a red LED. Just one set of output terminals is fitted - of the sort which will accept bare wire ends or 4mm plugs - and the (unbalanced) input on high quality phonos as before. Case construction is almost identical to the HeadMaster, except that rectangular holes are cut in the base to allow air to pass across the vanes of the internally mounted heatsinks, the warmed air venting over the top of the rear panel via a groove cut into the underside of the top plate.
The modular design of the Bijou case makes it easy to produce a dual-height case and Sugden has used this for the CDMaster. The transport and digital/analogue output stages reside in the lower compartment, the lid of which forms the base of the upper one, where the power supply, control/display cicuitry and DAC reside. The transport is a substantially modified Philips CDM12.1 short-loading model; but all digital filtering, noise shaping and conversion in undertaken on Sugden's own circuit boards. Digital-to-analogue conversion is based around a DAC7 18-bit, four-times oversampling hybrid IC. The output stage is a low-impedance cascode current circuit with zero feedback. This board employs the very high quality OP27 op-amps. A substantial toroidal mains transformer provides the energy for no fewer than seven regulated power supplies. The rear panel sports a fused IEC mains input socket with adjacent rocker switch. Analogue stereo and coaxial digital outputs are provided, again on gold-plated Teflon-insulated phono sockets.
There are just six fascia controls: Standby (the unit is normally left powered), Next and Previous track, Open/Close, Stop and Play. True to its name, the Previous track button takes you to the start of the preceding track rather than back to the beginning of the one in play; to restart the current track simply press Play. Sugden's 27-button CD/preamp/tuner system handset is supplied, which offers direct track access via numeric buttons plus fast forward/reverse searching, random track play, track programming, pause, repeat (of track or disc) and tray open/close. Its mute button doesn't function with this player, though, and there is no time display button, even though the player is capable of showing disc elapsed and disc remaining time, in addition to the default of elapsed track time. These are standard RC5 commands, so the function is available if you have a suitably endowed handset. |
TECHNOLOGY
In Class A circuits the output devices are fully conducting the whole time, irrespectively of the demands of the signal, with energy not required for the load dissipated as heat. This rules out Class A operation in all but a few power amplifiers. This gross inefficiency is not a concern, though, in low power devices such as a pre-amplifiers, headphones amplifiers or the early stages of a power amplifier, where Class A's predominantly linear behaviour and absence of crossover distortion are of particular benefit. Class B or AB circuits routinely employ voltage feedback working into a high-impedance return input to set gain and minimise distortion, but there are potential penalties in terms of high frequency instability and so-called Transistent Intermodulation Distortion (TIM). A transimpedance circuit has a low impedance feedback path, keeping the voltage difference and input current small. The significant benefits are that the slew rate can be higher and that stray capacitance won't greatly affect bandwidth or stability.
For all its benefits, Class A is not immune to irregularities in supply voltage. Cascode circuits address this limitation by employing an additional active device, be it a transistor, FET or valve, to maintain a constant voltage across the amplifiying device irrespective of variations in supply. The configuration also facilitates reduced distortion and increased bandwidth by minimising the device's internal capacitance, which is why it is often found in ultra high frequency (UHF) circuits.
KEY FEATURES
-
Very solid, machined casework
-
Class A pre-amplifier/headphone amplifier
-
34 watt power amplifier
|
|
Totem Sttaf
Audio Synergy, the company behind Sugden, also handles UK distribution for the Canadian loudspeaker manufacturer Totem Acoustic, whose floor-standing design Sttaf was supplied for review with the Bijou units. This slim, two-way design employs a 127mm (5in) plastics-coned bass midrange unit and a 25mm (1in)woven fabric dome tweeter, both flush-mounted high up on the baffle and retained with Torx screws. The cabinet is made of 14mm thick balanced veneered Medrite, its joints 'lock-mitred' with the front and rear panel edges gently bevelled, exposing the MDF, which is stained to match the veneer - a surprisingly elegant effect. The appearance is conservative, almost retiring had the units been covered (no grille is supplied) but the high quality materials and care taken in the construction are evident throughout.
It is on the inside where this intriguing design hides its credentials. Rather than line the cabinet with bitumen and/or stuff it with absorptive wadding or foam, Totem has painted all internal surfaces with a NASA-developed damping material, borosilicate, a titanium-rich suspension which is claimed to be unequalled for micro-energy dissipation. The cabinet is braced by a heavily perforated MDF panel set at an angle just below the LF driver, and by a sloping partition a little way up from the base. The latter divides the cabinet to form a lower compartment which can optionally be filled with ballast such as lead shot or sand to add physical stability (although Totem and Audio Synergy prefer the sound with the compartment unfilled). The cabinet sits on small spiked plinths which increase its footprint and hence stability, particularly on carpeted floors. The recommended medium for fixing plinth to cabinet is that stalwart audio assistant, Blu-Tack. Bass loading is defined by a 45mm diameter rear-firing reflex port. This plastics tube is cut at some 45 degrees on its internal end, presumably to smooth the air flow's transition. A tiny foam-covered hole at the top of the input terminal panel apparently relieves back pressure on the LF driver cone, increasing its dynamic capability (though I fail to see how).
The bi-wirable crossover is hard-wired on two fibreglass modelling boards mounted on the reverse of the input panel. A simple second-order circuit centred on 2.2kHz, it uses very high quality components including an air-cored inductor and an oil-filled metallised polypropylene capacitor in the low-pass pole. Point-to-point wiring is made with Teflon-coated silvered OFC copper. The gold-plated terminals cater for bare wire ends or 4mm plugs.
So to the sound, and first of all how the units behaved individually. I was in the middle of a CD mastering session when the kit arrived, so quickly unpacked the HeadMaster to try in with the Sony MDR-CD2000 headphones I'm using for editing. These present a low impedance load (32 ohms) so need a good, 'solid' feed. The HeadMaster was something of a revelation here in its effortless control, silky smooth top end and transparency. I hadn't anticipated so much of an improvement over the simple home-built circuit I have been using for some years. The immediacy of headphones can quickly tire unless the balance is smooth, well articulated and clean, and this is without doubt the best driver I have used. It came up trumps, too, substituted for the pre-amplifier in my regular system: transparency and control again evident regardless of the source material. This is an extremely good device and I have no hesitation in recommending it, provided its ultraminimal facilities are enough for your needs.
The next step was to substitute the AmpMaster for my regular monoblocks, somewhat ambitiously driving ELS-63s, but again I was struck by the effortless control: tight, clean and open with excellent imaging, the only obvious limitation being its modest wattage. In a smaller room or with high efficiency loudspeakers it would perform marvels. Like the HeadMaster it convinces the ear by ensuring that the signal's harmonic content remains coherent, something by no means all amplifiers achieve.
TECHNOLOGY
Borosiliate is a glass made from silica and boric oxide. Commonly employed for resistance to chemical corrosion and/or thermal shock (eg, Pyrex ovenware) it is also used where glass has to be bonded to metal. The titanium-based formulation used by Totem is highly efficient in dissipating molecular hot spots and was originally developed by NASA for use in conjunction with the ceramic heat-shield tiles on the space shuttle.
KEY FEATURES
-
Sophisticated internal cross-bracing and damping
-
Floorstanding design with capacity of additional ballast
-
High quality crossover with metallised polypropylene oil-filled capacitors
|
|
CDMaster presented more of a challenge compared to my Meridian 508.24, since it was hard to tell any difference. Again this is very high praise. Identical discs were used for A/B testing, cued together with the levels and polarity carefully matched. The 508 yields a fractionally more transparent sound stage, perhaps, with the space around musicians just a little more clearly defined, but in all other respects the Sugden is its equal, which is a remarkable achievement at less than two-thirds the cost. It would certainly see off most competitors in and beyond its price range. What impressed me most was its relaxed, natural musical presentation, every strand coherent and in perspective.
Finally to the Sttaf. It takes but a few moments of listening to appreciate that this highly musical performer belies its rather unassuming appearance. Few moving-coil loudspeakers compare with open panel electrostatics in terms of detail and transparency but the Sttaf comes close and, remarkably, exhibits none of the 'lag' which typifies so many reflex designs, blurring the image and subjectively slowing the pace. No this is a highly articulate sound with a crisp, fast, dynamic response. With its surprisingly capable bass extension
(-3dB point at 39HZ) it replays careful siting - it can sound a little bloated if placed too near the room boundaries. Get that right, and the tonal balance becomes remarkably even. A degree of warmth at around 230Hz was about the only box loudspeaker characteristic that I could detect. Imaging is needle sharp with a plausible depth to the sound stage. Delicate and fast, with an impedance which never sinks below 5 ohms, it presents a straightforward load well suited to modestly-powered amplifiers such as the AmpMaster. |
Each of these components deserves high praise in its own right. When used together they have an obvious rapport, creating a first-rate system which will have its owners rediscovering neglected corners of the CD collection long into the night.
|