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THE METAXAS CHARISMA II PREAMPLIFIER AND IRAKLIS II POWER AMPLIFIER:
Reviewed by GEOFFREY HORN, GRAMOPHONE, England
CHARISMA II PREAMPLIFIER AND IRAKLIS II POWER AMPLIFIER
MAS, Metaxas Audio Systems, although becoming well known a a source of up-market audio products in Europe is relatively new to the UK. Originated By Kostas Metaxas, a third generation Australian of Greek origin, it emanates from Melbourne where it has earned a number of native awards. The trio of products supplied for this report are of unusual appearance and, in their extensive use of mirror finished stainless steel sheet, more in the fashion favoured in continental Europe where domestic products of like appearance often feature, particularly in France, Germany and Italy. To us it looks rather home made, though not in any derogatory sense, for I have come across remarkably impressive pieces of equipment which had their source in an enthusiast's workshop. Interestingly, the Metaxas literature lays stress on the hand-crafted approach, which is clearly indicated by the case and chassis construction from individual folded members bolted together with black, domed hexagon-headed screws engaging shank bushes. However, make no mistake, this is a technically advanced product, extremely well though out and containing a number of refreshing features which result in a very high standard of performance. Its major appeal is likely to be to the enthusiast with a 'willingness to investigate the less stilted designs and I shall deal with it as such.
The Charisma preamplifier comes with a separate power supply unit, also housed in a ventilated stainless steel box containing a fair sized toroidal transformer, rectifiers and four 4,700mF electrolytic capacitors, two on each positive and negative 30V supply. There is an IEC mains connector (lead supplied) and a locking three-pin connector and cable to the preamplifier itself. Inside the latter there is further smoothing and unique regulation circuits using discrete components to give a final +- 20 volts. No on/off switching is provided.
The control amplifier itself has a contrasting 3mm thick black anodised aluminium panel engraved and filled with white legends. There are three large polished chrome knobs for the three-position line-level input selector switch, balance and volume controls. Three small toggle switches bring in phono (cutting out the main selector), tape monitoring and defeat. In addition there are two red LED's, one indicating power on and the other a warning of DC at the output, due perhaps to an offset in a connected input source, which, because the Charisma is direct-coupled and therefore devoid of capacitors in the signal path, will be progressively amplified as the volume control is advanced. As the Iraklis power amplifier is also direct coupled a potential disaster would threaten one's loudspeakers if this warning were ignored. However, the avoidance of capacitors wherever possible is an essential part of the design philosophy - Metaxas calls them "a necessary evil which store energy at various frequencies and release this energy over a period of finite time to smear, add grain or texture and a form of hardness to the overall sound". I well remember this same cause being preached (?) in the 1930s letters to Wireless World from a Reverend Noel Bonavia-Hunt. Strangely, both gentlemen seem able to forget that the final smoothing capacitor in the power supply is also in the signal path, for where else does the energy come from? However, supposing they are right it may help the sound if we avoid the blighters (correct use of the word!) wherever possible.
Two other design facets are important to Kostas Metaxas. The first we have touched on in relation to power supplies, which must be very sturdy and, where regulation is called for, some rather unusual circuit arrangements have been brought in. The second is using component layouts which yield extremely short interconnections on the printed circuit board and off where he regards the unshielded signal path, which is of uncommonly wide bandwidth, as vulnerable to possible contamination.
All the amplifying stages in this Metaxas equipment use matched complementary PNP/NPN pairs of selected transistors in a differential arrangement. In the case of the preamplifier four pairs are deployed in the phono stages with an unusual and highly accurate correction for the RIAA recording characteristic. Multiple internal miniature switches provide a wide choice of cartridge loading from 47k ohms down to 100 ohms plus an optional 270pF of capacity. Although the Charisma arrives set to a basic sensitivity suitable for most modern moving-coil cartridges, instructions are given to raise or lower it by changing a few resistors.
A further four pairs of transistors take up the output of the phono stage or the line inputs after switching and the 50k ohms volume control. Balance is set by an ingenious feedback circuit and an isolating tape buffer stage ensures that it causes no corruption of the main signal path. Construction is absolutely first class with a generous sprinkling of quality components on a single large ground plane printed circuit board. Individual gold-plated phono sockets are lined up on the rear panel opposite their board connections. The left hand section of the board houses the phono stages and that on the right the line and output section, with the power regulators in between.
Similar circuit ideas permeate the twin power amplifiers, which are dominated by the case of the enormous power transformer - the only component common to both channels - and the black 'butterfly wings' of the two projecting heatsinks. This is quite the heaviest amplifier in relation to its output power that I have handled. The discrete dual-differential early stages have local feedback paths and the four fast parallel pairs of power output devices are arranged in a type of Darlington circuit with their drivers and have a small amount of overall feedback derived directly from the output terminals. These are large and solid with 4mm centre holes and are joined on the rear panel by two gold-plated phono sockets and an IEC mains connector. The front panel is again of 3mm thick black anodised aluminium, engraved with "IRAKLIS II" and the MAS logo. The only control is a red illuminated on/off rocker switch.
Performance
Like a number of up market British makers Kostas Metaxas only provides a very minimal specification and during the course of an amusing conversation at the recent Heathrow show he told me that he recommended potential customers "to buy it with their ears". Well, that is not a bad idea but before commenting on the sound - or lack of it, for this is a freewheeling neutral performer, I will fill in a few gaps as measured on my sample.
The power amplifier requires an input of 630mV to provide the stated output of 50 watts into 8 ohms loads, both channels driven, and some 56 watts were observed before clipping with the supply standing at a below-normal 230V. Into 4 ohms loads 72 watts was available. Total distortion is average for a low feedback design at around 0.05% but the signal-to-noise ratio is excellent at almost 110dB. The Charisma required 45mV at its line inputs to drive the Iraklis fully at a similar distortion and S/N ratio of 94dB. As described, the phono input is capable of considerable variation but set for a sensitivity of approximately 200mV it yielded a signal to noise ratio in the 75dB area. In both cases overload margins were adequate. (Note the quoting S/N ratios with input shorted, as Metaxas does, can often give inferior figures as induced alien current in input circuits can rise above those present with a normal source).
I have been running this system for several weeks now with a wide variety of sources and several differing pairs of loudspeakers. After an initial 'so-so' period while it was settling down it developed that easy confidence which is the signature of a thoroughbred, only marred by rather too much mechanical hum from that oversize power transformer. I had chosen decent interconnect and loudspeaker cabling - no leads apart from IEC mains supply came with it - and, because of the stress laid on it in the literature, spent some time listening via the phono input to several alternative pickup cartridges, thus renewing acquaintance with a number of long-forgotten LP's to which it did full justice. However, recording exercises over the last few years have many times provided me with the unrivalled experience of directly comparing live feed from e microphones to the digital master tape and later that master tape to the completed CD. There can be no doubt where accuracy lies and so most of my listening has been to the latter. You may have read some of the resulting comments in December's "Sounds in Retrospect" and I have been indulging in repeat performances of some of my top choices via this Metaxas system. This has served to confirm my opinion that although one might describe its appearance as business-like rather than pretty, its sound is fully capable of bringing on the elated feeling that often follows a good live concert performance; quite the opposite, a musician friend points out, of the equally enjoyable soporific contentment which follows a good meal!
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