It's no secret that we have been consistently highly impressed with all the Pro-Amp products we've looked at so far. Judging by the superb Venom Mos-Fet combo (winner of a MUSIC U.K. STAR BUY Award) and the fine Demon practice combo, they are in the very first rank of British manufacturers and that means (happy to say) in the world's first rank, too.

Anyway, this was my first chance to have a crack at their Viper dual concentric model, and I borrowed a 100 watt 2x12 version from Roger Haines and his team, to subject to the usual Cooper thrash.

The Viper is heavy - all valve amps are, of course — coming out at about 70lbs. — hernia sufferers beware! The weight is partly an indication of the structural integrity of the amp, though. It has a well constructed frame with a 19mm chipboard case and 19mm Finnish birch ply baffles. The corners have metal protectors fitted, there are sturdy rubber feet, a top-mounted carrying strap and the covering is a glossy black vinyl leather look kind. Overall the Pro-Amp looks as tough as a tank — and I don't mean the one you have in your loft!

The rear view of the Viper reveals an open-backed design, with a captive mains lead and, sensibly, a footswitch which is also permanently wired-in. This way, of course, there's no chance of turning up to a gig and finding that you've left your footswitch behind, which, on a channel switching amp like this, could be most embarrassing.

The back panel features a fuse holder, line out socket, a jack socket for extension speakers and another for the on-board pair of Celestion 12"-ers. There's also a switch for 4 or 8 ohm output impedance selection, with a clear marking to show that it should be set to 4 ohms for extension speaker use and 8 for internal speakers on their own.

"ALTHOUGH THERE APPEARS TO BE JUST ONE SET OF TONE POTS THEY ARE, IN FACT, DUAL CONCENTRIC..."

The front panel demonstrates the extent of Pro-Amp's originality — this, I believe, was the first amp on the market with double tone pots, i.e. one set for each of the twin channels. It's obviously an excellent move as it means that, virtually uniquely, you don't have two channels (one for lead, one for rhythm) with the channel volume controls alone to play with. Much more usefully, the Pro-Amp gives you tone controls on each channel, as well as each having pre and post gains. It even has separate reverb controls per channel too, so that you could set a light level of reverb for your rhythm sound, say, and a heavier reverb on Channel 2, for lead guitar.

To explain this more clearly, I'll run through how you set the amp up. To begin with you've a pair of inputs (high and low gain). Having selected whichever suits your pickup power, you then set the volume level you require for the clean channel. This is adjusted by two clearly marked black pots, one for your pre-amp gain, the other for the main output volume. As usual, this allows you to set a variety of rhythm sounds — mainly on the clean side (especially when I tested the amp with a Strat, which only had just enough power in it to add a hint of rasp to chords — my Gibson drove it harder, of course, into a suitably dirty chord sound). Tone on Channel One is set by the centre section of the pots, from a choice of three active types (treble, middle and bass). You can then wind on what reverb you want via the central part of the reverb pot. You also have a rocker switch for a bright setting, positioned back down by the inputs.

Having now set your first channel, you can also make use of the front panel mounted effects send and return jacks, plus an unusual feature, a standby switch which operates as a normal valve standby in the central position and a high power output setting when up, low power set down. Completing the fun is a plastic mains switch and an on/off light.

Having got what you want for rhythm, you next set your lead sound. To achieve this you click the footswitch over (a red light shows that you are on Channel 2) and then repeat the process of setting your volumes via the next two, red-rimmed, pots. The gain here is far greater, but more of that later. Being able to adjust tone separately for the lead channel (not to mention having a separate reverb level) is a luxury which someone should have thought of twenty years ago. Although there appears to be just one set of tone pots they are, in fact, dual concentric; in other words the centre protruding section governs one channel, the outer rim handles the other. The rims are colour coded red, as are all the second channel's controls. Thus the range of sounds you can get from the lead channel can be totally different from those on the rhythm one — as I say, luxury!

So — waffle time over — how about the sounds? As usual I ran the test amp hard, but didn't manage to blow it up. I used it with a variety of guitars, mainly a Tokai 'vintage Strat' and a Gibson 335-S.

"THERE ARE PLAYERS WHO DON'T WANT DISTORTION, OF COURSE, AND, YES, THERE IS PLENTY OF CLEAN ATTACK ON THIS AMP TOO..."

Kicking off with the single coil Tokai, the Pro-Amp sounded remarkable on its clean settings. With the rhythm I couldn't get quite the distortion I'd have liked - but this is a common single coil problem, and one that I may tackle soon with a set of Seymour Duncan 'vintage Strat' pickups which I'm shortly to be testing. Either way the clean sound was like crystal glass — the tonal range fine and, with the bright switch on, it sounded perfect for a country or funky chord sound. My size ten planted on the footswitch, however, made the Viper shriek out a battle cry that would seduce a Valkyrie! Here it was — that 'right, mate — cop this for starters' sound which shrilled out through my windows and probably did much for next door's crystal glass collection — treble? Oh yes, and a wrenching, shattering, overpowering Strat attack too! There are players who don't want distortion, of course, and, yes, there is plenty of clean attack on this amp too — but, with a single coil pickup the amp produces such a lusciously shrill (yet, curiously, somehow warm) distortion that it would be a crime not to use it.

My Gibson took a fancy to the Viper too. The far higher output from the humbuckers drove Channel One into plenty of raunch and roll, with big fat chords and chugging rhythms ragged enough to satisfy the devoted Gibson hard-rock player. The Lead channel, though (again) was a revelation. There are few (very few) amps that I've ever got anything near that archetypal Jeff Beck sound from, but the Viper was certainly one of them. With the bridge pickup set on twin coil, the Gibson produced a sweeter, woodier sound, more like cream than blood (that was the Tokai's forte!), I'm grasping for the right words to describe the sound of the Viper with a Gibson on full hoot — soulful? emotional? they're not quite right, but it was that sound which (especially when given a tweak of the Pro-Amp's noteworthy application of the Accutronics spring-line reverb) could bring tears to your eyes — I certainly don't sound anywhere near as good as I did with this combination normally. This is one of those few amps whose sound makes you appear better than you are by both inspiring your playing and rounding your style out with its tone.

The Viper 2x12 is horrendously loud, too. Pro-Amp have recently started fitting the latest Celestion speakers (G 12 K85's) as opposed to the older G 12 60's. These are a far better speaker (not that the old types were anything other than great for a perfect distorted lead sound). These speakers are rated at a sensitivity of 100dB at 1 watt per metre, and the use of two probably gives around a 3 dB lift in sound pressure level (effectively, twice as loud as using just one of them!) Remember, dB ratings are logarithmic in their progressions, hence the apparent doubling effect. Not only are the Celestions superbly loud (this amp could cut you off at the knees if you stood too close!) but they retain that characteristic Celestion warmth of distortion/overload with a clean, smooth sound. Congratulations, equally, to Celestion for making them and Pro-Amp for choosing them!

"PRO-AMP HAVE RECENTLY STARTED FITTING THE LATEST CELESTION SPEAKERS (G 12 K85's) AS OPPOSED TO THE OLDER G 12 60's."

Ecstasy aside for a moment, could I find any flaws with the Pro-Amp? Well, in absolute terms I would have to admit that I could still detect a slight presence of transistorisation in the pre-amp. This is because the Viper uses MOS FET's here, instead of valves. The power amp (which is what does the main work of the overdrive effect) runs a pair of American 6L6GC valves (a la Fender, Music Man, Peavey, etc.). Someone who was a total neurotic about valves, or who could detect the miniscule rasp of a non-valve pre-amp might detect it. For myself the giveaway was a slight lack of the sensitivity to picking attack, which sets apart the 100% bottle-powered amp from the transistorised type. The principle, however, has proved good enough for countless players far better than I am to use it — after all, Clapton finds his tranny pre-amp/tube power amp Music Man good enough, doesn't he? Try it for yourself and see what you think — I doubt if it will bother more than a tiny percentage of players.

Anyway, that aside, I can only rate the Pro-Amp dual concentric Viper as a superlative modern amp, offering a tonal range and convenience, a quality of construction and components, and, above all, a definitive lead sound. Now for the really good news! Just as we went to Press, Pro-Amp told us that their amps were now selling so well that they were stepping-up production considerably and, as that will lead to a lower unit cost, this will mean that the price of this fantastically good amp will actually drop — down from the previous £399 to £375 inc. VAT.

At the price the Pro-Amp Viper is excellent value for the player who wants one of the best combos around. Yet another winner from this outstanding team!

PRO-AMP Viper Dual Concentric 100 Watt 2x12 Combo RRP: £375 inc Vat.