WWW.HIFICRITIC.COM ISSN 1759-7919 HIFICRITIC AUDIO REVIEW MAGAZINE £15 Vol8/No4 OCT - DEC 2014

KAOS RULES REVIVING THE LS5/9 Paul Messenger tries out the extraordinary With assistance from ex-Spendor Derek Hughes, Soundkaos Wave 40, an Anglo-Swiss confection Graham Audio has reincarnated the BBC LS5/9, that redefines the full-range driver loudspeaker a compact stand-mount with an illustrious monitoring pedigree MUSIC WITHOUT WIRES (OR STANDARDS) It’s getting easier to stream music wirelessly, but CHEAP BUT VERY CHEERFUL there’s no shortage of competing standards to Dali’s Zensor 1 is probably the cheapest speaker confuse consumers, says Andrew Everard HIFICRITIC has ever reviewed, It’s also rumoured to be a serious bargain. Paul Messenger checks out I’M SPARTACUS the rumour mill The Thrax Spartacus valve monoblock is the finest amplifier Chris Bryant has ever heard SANDWICH ANYBODY? 60 years on, Martin Colloms re-assesses Leak’s NAIM NDS PLUS 2x 555PS famous Sandwich loudspeaker, with surprising results Martin Colloms tries out Naim’s flagship NDS streamer/DAC with twin 555PS power supplies. Does MUSIC & MORE streamed audio replay get any better than this?

REVIEWED THIS ISSUE: SOUNDKAOS WAVE 40, GRAHAM AUDIO BBC LS5/9, DALI ZENSOR 1, NVA BALANCED MAINS UNIT, HENRY AUDIO USB DAC 128 MKII, NDS + 2X555PS, THRAX SPARTACUS, VALVE AUDIO DEVICES DAC-12 DSD, SONUS FABER OLYMPICA II, NEAT MOTIVE SX2, LEAK SANDWICH, VALVE AMPLIFICATION COMPANY SIGNATURE MK IIA, APPLE EARPOD, SENNHEISER HDVA 600, SENNHEISER HDVD 800, TRILOGY 933/900, VERTEX AQ HIREZ SOLFONN, PHILIPS FIDELIO X2, RUSSELL K RED 50 HIFICRITIC OCT | NOV | DEC 2014 1

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Spartacus Rules THRAX’S VALVE-BASED MONOBLOCK POWER AMPLIFIER IS CALLED SPARTACUS, AND IT HAS REALLY GOT CHRIS BRYANT GOING

wo years ago I encountered an expensive machined from solid aircraft grade billets, with Orpheus phono stage from a Bulgarian a moondust type finish. Since there’s no cover operation called Thrax (seeHIFICRITIC Vol6 underneath it’s possible to see the two large circular TNo4), and was somewhat surprised to find it was the fans part concealing the mains transformer and best sounding amp of the type I’d thus far experienced. choke that hang centrally from a mid-mounted I’ve since been eagerly awaiting another product dividing plate. This brings the centre of gravity from the brand, and in September a pair of Spartacus down, so the smaller signal transformers can be monoblocks arrived. After unpacking, inserting the mounted on the top panel while still maintaining valves and connecting it to my system, it was left to stable equilibrium (and away from any mains settle down for a few minutes, but after only the first transformer or choke flux leakage). The sensitive few bars of music it was obvious that it was something electronics are housed in another cavity below the rather special and demanded to be heard. valves. The case outside is totally clean, and looks There is no secret to the performance of Thrax like a solid block – and at 35kg it feels like one when equipment: it’s clearly explained in the literature. moving it around. One small criticism is that the A preferred technology is chosen, such as a simple panels have sharp edges, and with no base it’s not the short signal path with zero feedback. The best bits most comfortable lift. Our early sample had no valve currently available are painstakingly selected and guard, but I gather one is normally available (for EU put together very carefully, while careful design then safety standards). A large round silver ‘on’ button sits ensures everything continues to run with optimum in the middle of a elegantly sculpted front panel. operating parameters. The front has only an on off switch: first a red Thrax describes its approach as ‘engineering LED flashes, turning to green three or four minutes overkill’ and isn’t prepared to stop development until when the amp is biased and ready for use. A built it sounds just right. Add the elegantly understated in timer tracks the valve operating time, a speaker styling and excellent build quality to create a impedance switch selects 4 or 8ohm operation, and component that at first sight appears anachronistic another switch selects low, medium or high input until its design is fully appreciated. gain. The output stage is a matched pair of costly Spartacus is a two stage, shunt regulated, 520D B3 directly heated triodes – a state of the art monoblock power amplifier, using directly heated product based on the 300B tube but more efficient, triodes and with a claimed output of up to 70W with higher gain and better bass control. The input into 4 or 8ohms. Two rectifier choke input power driver is a highly regarded PX25 triode with an supplies feed film reservoir capacitors, so there are SV811-10 used in the shunt regulator, two 6D22C no electrolytics to age and need replacing every few rectifier valves and an SG13P glow discharge voltage years, and sound quality should be improved too. reference. Costly Furutech Torque Guard speaker Each stage has its own shunt regulators, each with a binding posts have pre-set torque settings to prevent constant current feed. The input signal goes straight over tightening. Inputs include one unbalanced into a high quality transformer which leads into a RCA/phono socket and one balanced XLR with a driver stage that uses a single directly heated triode illuminated switch for selection. operating with grounded cathode and fixed bias. This The heart of the amplifier is the PX25 direct is loaded with a special Japanese transformer that heated triode, which is a rather pessimistic mark couples via independent windings into the grids of the of the lack of progress made over the years in the output valves. The output stage uses a pair of directly art of sound amplification. Originally a British heated triodes driving a costly Japanese permalloy- design first introduced in 1932, it sounds beautiful core transformer. Automatic biasing uses innovative but has limited power (only a few Watts), and it is thermal circuitry, and the heater filaments are powered still used by triode-enthusiastic audiophiles. The by low noise voltage controlled current sources. massive 520B output valves are a development Each amp weighs around 35kg, the casework of the famous Western Electric 300B which first made from different thickness aluminium panels appeared in 1938. The valve designs have therefore

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CHRIS BRYANT been around for a few years, though the ones used in this design, sourced from Emission Labs, are thought to be the best currently available. A servo circuit keeps the anode current in both output valves constant, so they continue working perfectly as they age, and balance the DC component in the output transformer. Heater supplies come from a separate transformer winding, feeding a rectifier and capacitors; a matching voltage regulator and gyrator ensure a stable, low noise heater current. One key to formalising this design is the use of advanced modern magnetic materials and the latest transformer fabrication techniques, but attention to detail is also an important factor.

Lab Report I thoroughly tested this object just in case some technical anomaly was fooling me about the sound, and managed to get 55W into 8ohms and 42W into 4ohms at 1kHz using the preferred 8ohm output tap. At 20kHz, 25W was measured for 8ohms and and subtle, and produces such an exceptionally “The observation that 32W into 4ohms, while it was less successful at interesting sound is almost intoxicating. Everything it’s so sweet and subtle, 20Hz, producing only 11W for visual oscilloscope you thought you knew well now sounds better, easier distortion into 8ohms,and I got no reliable figure to listen to, and with less listening fatigue. Textures and produces such an for 4ohms at 20Hz. These figures are actually quite are lusher, the stage is more realistically portrayed, exceptionally interesting reasonable for a low feedback valve amplifier of this and every phrase has more meaning. Voices sound sound is almost type, while the dominant midrange power output is more natural and are substantially more articulate. intoxicating. Everything particularly encouraging. The output impedance of It doesn’t matter whether it’s jazz, a string quartet, 2.5ohms in the bass and midrange then rose slightly solo violin, massed orchestra, choral or modern you thought you knew to 2.8ohms at 20kHz, which is much as expected, synthesised pop and rock – all are rendered more well now sounds better, and may well introduce some audible change in enjoyable and exciting than I’ve been used to, and easier to listen to, and timbre with some loudspeakers (potential purchasers old recordings sound revived. with less listening fatigue” please note). Spartacus invariably seems able to extract more At 1W, midrange harmonic distortion is low at information from sources than was previously -68dB (roughly 0.03%), and HF intermodulation thought possible, and improving the source distortion was an equally encouraging -53dB (about produces better sound quality. But the ability to 0.2%), and a very good signal-to-noise ratio was extract more from what is fed into it also seems an recorded 84dB (A-weighted at 1W). On ‘high gain’ almost unreal skill for a power amplifier. Its micro- the 168mV input sensitivity will suit a wide range dynamic reproduction is exceptional, and extra of pre-amplifiers. Although the frequency response audible nuances are now a delightful experience. For rises by almost 2dB at 20kHz, and below 200Hz falls example, backing vocals that were previously masked to -1.8dB at 20Hz, it’s essentially flat through the are now revealed. It has you going back to listen important midrange region. This behaviour is not again and again, and leaves you wondering why the unusual with this type of amplifier, and I consider many other amplifiers I’ve experienced had managed it has little impact on the listening experience. to obscure so much information. These amplifiers do get quite hot, consuming (and Surprisingly and delightfully, midrange percussion therefore radiating) about 400W each. Local cooling has real power and natural dynamics, bringing is down to a commendably quiet fan, and while such greater realism to hi-fi reproduction. Percussion also heat might be fine in winter, it can be a little too sounds startlingly realistic in the upper bass. Focus is much for comfort on a warm summer day. top class, with great stage depth, image stability and precision. The treble is detailed and coherent, with Sound Quality excellent ‘shimmer’ that’s as natural and complete as The Spartacus is capable of more musically realistic the silky smooth and very coherent midrange. reproduction than any commercial amplifier I’ve True, the bass doesn’t have the thump and sheer heard to date. The observation that it’s so sweet power of the best transistor amplifiers, but it has

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plenty of detail and an impressive ability to reveal bit of extra ring at the top of the scale, and music pitch and structure. Timing is not quite as up beat doesn’t seem to flow in the same mellifluous way. AUDIO EXCELLENCE as the fastest solid state designs either, but it still It just sounds less immediate, losing some of the has rhythm in spades due to the plentiful detail almost magical ability shown on the 8ohm tap and and wonderful dynamic contrasts. Its presentation that middle gain setting. I tried various speakers, MC Comments is thoroughly beguiling and its musical phrasing including Magico S5s and my own familiar full After a warm up, and just draws you in. It also has a wonderful start/ range 8ohm system, and this amplifier never failed to playing through Magico stop quality, so the listener doesn’t have to guess produce that extra fidelity. S5s that were still running exactly where a note starts and finishes. It simply It even managed to enhance the entertainment in, I was entranced by this explains just how each sound and nuance is carefully quotient of TV sound, the Thrax simply improving power amplifer’s sheer structured in great recordings, allowing real artistry the diction and intelligibility of everything I musicality. Its outstandingly to be revealed in the most unlikely places. All the watched. It might not transform the indifferent TV natural acoustic sounds, recordings I tried, both new and old, digital and sound quality that the BBC, for example, seems to excellent resolution, great analogue, had their story retold, making it essential think is good enough for its audience these days, but communication skills, and for me to try and re-visit my entire music collection, it makes the most of a bad situation. (I tried to watch driving sense of performance, in order to discover exactly what had been previously one of the Proms broadcasts but the sound was so was very seductive. Familiar left unexpressed. undynamic and bland I gave up after about five Radio material was rendered in Trying the three gain settings, the highest gave a minutes. Yes I know I should have listened on 3 a more complete manner, slightly looser sound: less incisive, but sweet and still but I really expected they would try to provide and one instinctively knew clear, though not quite as beguiling. Low gain was decent sound quality for what is, after all, a flagship that this sound was simply tighter but not quite as interesting, sounding less music programme.) more correct. It somehow rich and generous. The middle setting proved the Conclusions amalgamated many separate best in my setup. Furthermore, the 4ohm speaker strands of known detail tap sounds less transparent than the 8ohm example, I only had these amps for a limited period, but kept and quality into a superior and not as dynamically interesting in either a gross hold of them for as long as possible simply to revel whole. Musically it delivered or micro-dynamic way, whatever the actual speaker in their amazing abilities, and even managed to get more natural timbres, greater load. Piano doesn’t sound as natural, showing a them back for a second visit to consolidate my early expression, and a deep, opinion. I don’t take the word amazing lightly in the glowing soundstage, and the POWER AMPLFIER TEST RESULTS context of hi-fi (or anything else for that matter), but Spartacus certainly had a startling effect on me. familiar limitations found with ______Make Thrax less stratospherically priced ______Model Spartacus Ser. No. 312302 I certainly want a pair, but at £32,000/pair it’s not a POWER OUTPUT 20Hz 1kHz 20kHz power amplifiers were clearly ______purchase that can be taken lightly. ______Continuous 8 ohm 1channel 11 W 55 W 25 W Since these monoblocks are typically only capable absent. ______Continuous 4 ohm 1 channel W 42 W 32 W ______Output impedance (ohms) 2.5 ohms 2.4 ohms 2.8 ohms of 50W, they may not go loud enough for owners of ______Distortion, THD inc. noise -38 dB -68 dB -55 dB modern low efficiency speakers. But anybody who ______Frequency response -1.5 dB 0 dB 1.8 dB wants really convincing music in the home should Intermodulation Distortion 19.5kHz/20.5kHz ______1:1 rated power, 8 ohms dB either get hold of some live performers, or choose Intermodulation Distortion 19.5kHz/20.5kHz 1:1 1W, a compatible loudspeaker, sacrifice the ultimate ______8 ohms -53 dB 22Hz – 22kHz ______CCIR A weighted in sound level, and try some Thrax gear. Certain Signal to noise ratio ref. even lower power purist triode amplifiers might ______1W 8ohms 73 dB 85 dB 84 dB conceivably sound even better in specific systems, ______Signal to noise ratio ref. rated power 91 dB 103 dB 102 db DC offset Left 0 mV Right 0 mV but will never drive the wide range of loudspeakers ______as effectively as Spartacus. (An alternative might be to Input Data Socket Sensitivity Loading ______use a home cinema system for the loud stuff and set ______Input single ended phono 168 mV ohms nF ______Absolute Phase correct up a purist hi-fi system for exquisite personal musical ______Size WxHxD 210 mm 420 mm 440 mm experiences.) Price £32000.00 The Thrax Spartacus amplifier is not perfect Thrax Spartacus Frequency Response 1W (Red) and – nothing is. It could be slightly more up beat and Distortion (Green) 8 ohms load have better bass impact in the lower octaves, but the rest of the sound is so amazing, these small shortcomings can be easily forgiven. Scoring is difficult, but it has an array of attributes that are comparatively lacking in the others I’ve heard, so on balance 250 points seems appropriate, and I find it very easy to place it in the Audio Excellence class.

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