CLASSICAL GLASS

Ken Kesler auditions a 125 - valve pre-amplifier from Croft

GOOD THINGS DO COME IN threes, or that's the way it's gone this past month. Just as I finished reviewing a magnificent budget Class-A amplifier (Musical Fidelity's A1, October) and Audio innovation's sub 1000 value offerings (Series 800, also October), I learn that the entry level for valve preamplifier purchase has dropped a whopping 50% or more, down to 125. Yes, 1 did say 125. And it comes from a UK company best known for a pre/power combination that tops the 5000 mark.

Croft Acoustics, for it is they, are a tiny company devoted to the manufacture of ultra-purist designs. They eschew such things as circuit boards and output transformers and transistors, but they're wise enough to know that the market for hi-fi products the price of cars is not that big. By making available a truly affordable valve preamp, Croft not only give themselves a 'bread-and-butter' product, they also catch first-time buyers who are ripe for pro-valve influence. This is, though, but part of Croft's reasoning, to satisfy the beginner with limited funds; Croft also recognise the need for a preamp to satisfy hi-fi users with Golden Age preamps needing replacement, as c. 1960 valve preamps often do not match the performance of their partnering amplifiers (e.g., Quad's pre vs. power).

But Croft has overlooked one other needy breed of audiophile. The Croft Micro Valve Preamplifier is the perfect preamp for the impoverished DIY type, exactly the same sort of audiophile who, 20 years ago, would have supercharged his Dynaco PAS-3. The standards are the same, up to a point, for both are simple and straightforward and intrinsically fine-sounding, though the Dynaco did contain enough extra facilities to make it of wider appeal. (The equally straightforward, suitable-for-tweaking Counterpoint SA7 does not qualify as a latter-day Dynaco because it is priced further up the scale.)

The Micro is as tiny as its name implies, measuring 10x6.5x3.5in. (WDH), and one look at its off-the-shelf housing tells you just where some of the costs were cut. If this sold for 500 or so, I'd call it inexcusably ugly; as it costs so little, it earns the same forgiveness as a Citroen 2CV: hi-fi for the masses. Ironically, the hood effect over the controls gives this item a lovely scent of nostalgia, for those with long memories will recall such equally sheltered designs as the Tannoy Hi-Gain and the Pamphonic 1004. But they had jam-packed fascias: the Micro I tested offers only a small on/off toggle switch, a volume control, and a source selector. The back houses phono sockets and a binding post.

The Micro is available in a few different versions, starting with an m-m-phono-only version for 1 25 inc VAT. The unit shown here adds one line input and tape in/out, and sells for 150 inc VAT; this is about to reappear with a second line input due to customer demand. Either model can be ordered with an m-c phono section providing four times as much gain to suit most m-cs for an additional 10.

Inside, there's not much to look at and plenty of space in which to play around - just the kind of atmosphere to inspire some creative tweaking. The valve complement consists of an ECC81 and a pair of ECC83s, 1% metal film resistors, and polypropylene capacitors. As with Croft's other products, it's hardwired throughout, again making it easier to Modify. As far as cost-cutting within the Micro is concerned, this is restricted to a basic power supply and adequate, rather than exceptional, pots.

The design is basic, but Croft reckon that it loses out to their 399 preamplifier in terms of facilities rather than in overall sonics. The Micro lacks the dearer model's standard m-c stage, dual mono volume controls (thank God), mute control, flashy cabinet, and beefy power supply, with only the latter causing any real sonic inferiority. The Micro's phono section consists of two triode stages, the second having high impedance, shunt-feedback RIAA equalisation. The line inputs and the phono output pass through the single selector switch via the volume control to the low impedance output stage. Both the heater and HT supplies are fully regulated. The HT regulation is common to both channels, so it's this area, which could benefit from some creative input on the part of the DIY'er; the caps, resistors, and valves are of sufficiently high quality in standard form.

Though Glen Croft probably did not expect this product to be used with high-end systems, I inserted it in the Oracle/Zeta/Decca, Beard power amplifiers, and Apogee Scintilla set-up, just to isolate it in a system I know. Additionally, I tried it with a Radford STA25, the type of amplifier - both vintage or in new MKIV form ~ which it will most .likeley serve. The Micro showed that simplicity is a virtue.

Absolutely straightforward in set-up, the little Croft needs no more attention than any other like-priced component. Fit a mains plug, connect the leads, and switch on. Warm-up was around an hour for best performance, and I did place it on a Mission Isoplat with a Flux Dumper over the power supply. Ironically, this unit needed these two tweaks much less than some far costlier designs, like the Counterpoint SA-7, but they do 'fine-tune' the unit and serve as sensible upgrades for those who buy the Croft with little money to spare. Though the unit is disarmingly quiet, the isolation and damping process provides an audible - if ridiculously subtle - improvement. The sound was leaner than 1 expected it to be, for my initial expectation (inspired by the ancient styling?) was to hear a vintage sound. I anticipated slightly dulled transients and a fat, loose lower register- in other words, all visual signs pointed to the romantic, overly kind sound typical of vintage gear. Croft, however, was right when he said that the Micro lost little to its decidedly modern bigger brother. I seem recall that the bigger Croft preamp sat nicely between the pure vintage candy floss of, say, a Quad valve preamp, and the superanalytical leanings of today's most advanced tube designs. If the line was drawn with Gold Oldies to the left and the Audio Research SP-10 or conrad-johnson Premier 3 at the right, the big Croft would be dead-centre and the new Micro would be just left of centre.What the latter lacks, or more accurately, what it needs to push it further to the right, is not more detail but greater capabilities in handling dynamic contrasts. The overall sound is 'wide range', but demanding material with extreme level changes, like Telarc's Time Warp CD, could sound slightly compressed.

Coloration was surprisingly low, much better than any other sub-200 preamplifier I've tried, though it sounded slightly grainy in comparison with clearer units like the PS Audio PSIV or the Beard P505 MkII. It was joyously free of colorations on vocals - no nasality or chestiness, and never a trace of spit on sibilants - but deep bass could sound thick. What it lost in the lowest register was 'speed' readily apparent through the Apogees - and the result on some plucked bass, particularly as found on 12in. singles, is a touch of sogginess.

This became academic, though, when used with systems more in keeping with its price tag, and I'd expect the Croft to find a home in a system with speakers far less revealing of bass anomalies than the Scintillas. When used with the Radford amp and the LS3/5As, the effect was diminished to a point of insignificance.

Whether used in a costly system or a 'real world' package, the Micro showed soundstage capabilities well beyond any preamp I've tried up to twice its price. Depth, while not astounding, was acceptable even with the deeper-than-thou portrayal of the Scintillas; Stage width was wide enough to guarantee that the Micro will not a limiting factor in this area.

The Micro is a mid-band performer, handling the all-important meat of the music with aplomb. It's only when you subject it to the most wide-ranging of systems that you're reminded of its price tag. There's no telling what it's going to sound like after a knowledgeable tweaker gets his hands on it, but straight out of the box, I'd prefer to hear it in systems using other components of its ilk. Paired with the Radford or the new Audio Innovations power amplifiers, it worked like a dream, and it means that all-valve sound is now yours for as little as 125 plus 575 for the non-Signature Radford MKIV. 1 simply cannot think of another 700 package that will beat this on musicality, though lovers of ultra-tight bass may prefer a solid-state alternative in place of valve openness.

Reliability hasn't proved questionable - it's too simple to be troublesome, it would appear- and it has no glaring faults. The price is too low to be true, and the sound is worth twice the sticker value I'd say that the only problem this unit will present will be one for Croft in keeping up with demand. Maybe now our less wealthy readers will feel they're better served?
 
 
Manufacturer's specification

Input sensitivity
3mV RMS @ 1kHz (m-m)
650mV RMS (line)
 
Input impedance
47k-ohms/50pF (m-m)

Overload
210mV RMS @ 1kHz (m-m)
45V RMS (line)
 
Output
650mV RMS rated sensitivity

Max output
45V RMS @ 1kHz into 22k-ohm, 5000pF

Output impedence
200 ohms

Manufacturer
Croft Acoustics

Price
150 inc VAT

Croft Micro Amplifier

~  H1-FI NEWS & RECORD REVIEW NOVEMBER 1985

 


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