Croft Charisma X preamplifier and Redshift amplifier

Glenn Croft has been busily building beautiful sounding amplifiers in the Black Country for longer than I can remember, though I'm sure he won't mind me adding that marketing skills are very low down the list of his talents and accomplishments.

That the company has survived for so long despite indifferent marketing says plenty about the quality of its equipment, while the relatively recent decision to team up with Eminent Audio has added that missing marketing dimension. The result of this alliance seems to be entirely positive from every perspective, especially style.

Although the power amp is attractively and unusually slim and neat for a valve-driven device, no one could accuse earlier Crofts of being particularly stylish. What with wooden fascias and brass trim, old fashioned tended to be the first world that sprang to mind, even though the components do possess a certain understated nostalgic charm to these eyes.

This new-look Croft still retains much of the familiar, but puts it into a much more modern context, with thick 'n' chunky alloy fascias, shiny polished steel casework and rather cute illuminated badges, all of which adds considerably to the visual appeal (as well as putting some £300 on the price). The only criticism is that said fascias do have decidedly sharp corners, and stand well proud of the casework proper.

Croft's 'hair shirt' traditionalism remains, however, in the selection of features and facilities provided on the £2,050 charisma X stereo pre-amp. It's very purist, to which I've no objection whatsoever, as it makes plenty of sense from a performance perspective. But it's also rather as though the last thirty years hadn't really happened, the feature set reflecting the somewhat old fashioned mindset. There's no remote control, and only three(!) line level stereo phono inputs. A 'record-out' pair is labelled tape (probably with reel-to-reel in mind!).

A fourth input is provided for moving magnet (high level) vinyl pickup cartridges, which again brought a nostalgic twinge. I know there are those who profess to prefer moving magnet cartridges, but I'm not amongst them, and as a long time user of low-output moving-coil cartridges, I queried whether there was any intention to provide matching low-output cartridges. In fact plans are well advanced to provide a higher gain phono stage to handle low output m-cs, based on J-FETs in order to keep noise low, though unfortunately this was not quite ready in time for this review.

Another Croft tradition is to use separate volume controls for each channel. This minimises the number of potentiometers needed and helps keep the channels well separate. But it also makes achieving correct channel balance more than a little tricky, while actually adjusting the volume becomes a pain in the butt, because of the need to reset the balance by ear every time you want to make a change in level. Purist it may be, and practice might well make perfect, but over the short term I found it difficult to set this right, and can fully understand why the approach has never really caught on. The preamp is available in zero and high (+12dB) gain versions, the latter (which inverts phase) being supplied for this review. In fact the zero gain version is considered superior, and would made a sensible choice here (given the super-high sensitivity of the Loth X speakers which arrived at the same time from the same distributor). Simply for reasons of availability, however, we ended up with the higher gain option. Accordingly, the speaker connections from the £2,950 Red Shift power amp - itself a feature-free zone - should be re-inverted by reversing the polarity at either its or the speakers' terminals (but not both).

This Red Shift power amp, rated at 10W/ channel into 8 Ohms, is based around two type 6080 double-triode output valves per channel, in single-ended triode push-pull operation. Paper-in-oil coupling capacitors are again used throughout, along with non-inductive wire-wound resistors, tuned bypass caps and full frequency copper wiring. Incidentally, those interested in Croft's CTC© Transformerless valve amps, but for whom a 10W rating is insufficient should note that there's a significantly larger 50W Dakshini, which uses six valves per channel in a much larger open-chassis layout and is priced from £3,300.

One point that might or might not be relevant is that even this quite modest power amp chucks out quite a lot of waste heat. This might or might not matter, though it can become a pain in high summer for those without air conditioning, and it does make ventilation provision important under all circumstances.

A year or so ago, I got to try one of Croft's less expensive pre-/power amp combos - a Vitale SC/Series VC, priced at around half the cost of this Charisma X/Red Shift combo. My abiding memory was of a delightful transparency, dynamic tension and great timing, but also that the sound was somewhat marred by a bright 'shiny' quality which was a trifle wearing over the longer haul, and a definite disincentive to playing the system at high volume levels. The joy of this Chairsma X Red Shift combo is that it has all the sweetness and delicacy and more - that I recall from the Vitale SC/ Series VC pairing, but without the shiny forwardness that tended to undermine that less costly combo. Indeed, after a few days enjoying this output-transformerless valve device, I found it very difficult to go back to my regular (and considerably more expensive) solid-state amplification, which sounded somehow thick and congested by comparison.

What impressed me most about this Croft combo was the way it seems to have all the delightful mid/top end sweetness and delicacy one has come to associate with high class thermionic devices, yet with the sort of overall neutrality that it normally part of the solid state experience.

A lot of people seem to like valve amps because of the warmth and romanticism they seem to bring to the party. That is not my personal preference - no I gather where Glenn Croft is coming from either if the sound of this amp is anything to go by. Perhaps it's the absence of output transformers, and the consequent closer coupling between the output valves and the loudspeakers, but there seems to be much less of the 'coloratura' effect here than I normally associate with valves, and the sound is all the better for that, to these ears anyway.

"What impressed me most about this Croft combo was the way it seems to have all the delightful mid/top end sweetness and delicacy one has come to associate with high class thermionic devices, yet with the sort of overall neutrality that it normally part of the solid state experience." 

Ultimately, there's a slight tendency to favour the top end over the bass, and a very mild loss of low end and authority is apparent on weighty material. It even passed the KLF test without a qualm, rendering complex and subtle bass textures without apparent difficulty or distortions. Indeed, the reproduction of a church organ during on of Radio 3's (excellent) Choral Evensong programmes recently was quite stunning in its exceptional and convincing realism.

Indeed, provided one keeps within the (modest) power envelope, this amplifier sounds reassuringly clean right across the audio band, with notable clarity and accurate tonality throughout its dynamic range. It's particularly good with the delicate fine musical detail and the texture of acoustic instruments, where solid state amps tend to sound clogged and thickened by comparison.

The major practical limiting factor with this amplifier is likely to be its low power output; depending to a considerable extent upon the loudspeakers it's used with. Obviously super-sensitivity horns like the Loth X Polaris (or indeed the Beauhorn Virtuoso I reviewed two years ago for this journal), which combine sensitivity ratings of 100+ dB/W with 'easy' 8 Ohm loads, will not stress a 10W/8 Ohm amp such as this, and will deliver ample loudness too.

But the majority of speakers are likely to have around 10dB less sensitivity, as well as quite probably a load that drops to a 4 Ohm minimum (where essentially just 5W maximum power is available, see Box). Here the loudness capability becomes altogether more marginal - the more so because this amp sounds so good that you really want to start winding up the volume, and wind it up some more, especially with rock or dance material. Naturally this is much less of a problem with acoustic sources, though a full scale orchestra is a potential source of stress.

It's tricky to try and predict the exact interaction between this power amplifier and any given loudspeaker type. For some of the time I used the very transparent and revealing B&W Nautilus 800, which is certainly a difficult load (dipping to just 3 Ohms through the power-hungry mid-bass), but which also has a very generous sensitivity of around 93dB. This combination worked very satisfactorily up to a point (i.e. qualitatively speaking), but the inability to play decently loud was certainly also in evidence. I could get levels measuring up to 95dB peaks in the listening zone, which I found adequate enough for most purposes, but it could get a mite frustrating with some material.

I spent most of the time focusing on the pre-amp's line level inputs, using my regular sources which include a Magnum Dynalab MD102 tuner, Naim CDSII and Rega Jupiter CD players, plus a hybrid Linn/Rega/Naim vinyl spinner which delivers a post-EQ line level output from a low-output Linn Arkiv B moving-coil cartridge. I also checked out the Croft's moving-magnet phono stage, which seemed to work perfectly satisfactorily, though it did nothing to change my long-term personal preference for the low-output m-c approach. To sum up, there's something about Glenn Croft's amplifiers, which is both exciting and enervating, yet also irritating. These are the hi-fi equivalents of extreme machines, making no concessions to either mainstream ergonomics or audiophile fashion. Yet for all that they deliver a revelatory high standard of sound quality, at the sort of prices that must leave most 'high end' brands squirming with embarrassment.

That's certainly true of this Charisma X/Red Shift combination, which seems exceptional value in a 'high end' audiophile context. The only down sides I've been able to find are the limited power delivery and idiosyncratic ergonomics. Over twenty something years Croft has been one of Hi-Fi's better kept secrets, supplying sparklingly superior sound quality at surprisingly realistic prices. Its quirky individuality should ensure it remains a small specialist/enthusiast brand, but in truth I wouldn't really want it any other way (and I don't think Glenn would either).

The heart of the power delivery limitation here is that, over the years, speaker makers have tended to evolve their design to suit the typical transistor amplifier, which is essentially a voltage source with a low source impedance. Halve the speaker's impedance from 8 to 4 Ohms, and the speaker draws twice the current and hence power from the amplifier. This extra power gives an increase in apparent (though mythical) sensitivity, so once on e manufacturer adopts the stratagem; others are effectively obliged to follow.

Unlike transistors, valves have a high source impedance and behave as current sources. In order to transfer power to a loudspeaker they are normally coupled via matching transformers. However, a direct-coupled valve system, such that as used by this Croft amp, inevitably finds it that much harder to transfer the power. Instead of doubling power as impedance is halved (a la transistor amp), because maximum current is the limiting factor, the power deliver capability is actually halved. The 10W available into 8 Ohms therefore becomes just 5W into the (increasingly widespread) 4 Ohm load.

Hi-Fi +

 


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