Audiovalve Baldur 70 Amplifier Reviewed

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Wherever and however the 'radar' is focussed, too many worthy brands suffer in near-anonymity below its sweep. Some deserve to, some don't. Germany's AudioValve is one of the latter. Aside from questionable aesthetics, their products are hard to fault for performance, build quality, reliability or - most remarkably - value for money despite being made entirely on the Continent; there are no off-shore cost benefits here. So far, I've reviewed a couple of their more affordable integrated products and their under-priced Eklipse pre-amp, and loved each one of 'em. Now (he said, rubbing his hands in anticipation), it's time to play with the big stuff.

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No, not the rather scary Baldur 200+, but what a few observers have already deemed to be amongst the best-value, all-tube, high-end monoblocks on the market today. According to AudioValve's charming Frau Heike Becker, who handles sales, customer relations and technical queries (sexist pigs, take note: she's an electronics engineer), 'During the 2003 CES show in Las Vegas, it was obvious that there was a need for a smaller version of the Baldur 200+. Everyone loved it, but it was too much for some. According to the dealers and distributors, size and price were the main reasons we needed to develop an alternative, entry-level Baldur.' So her husband Helmut, the designer of all of the AudioValve products, set to work.

Only a few months later, at the 'High-End-Show' in Frankfurt, they unveiled the Baldur 70 Class-A triode monoblock, which was immediately dubbed the Baby Baldur. It even looks like a 3/4 scale model of the original Baldur. And like every other one of AudioValve's larger power amps, it features the novel circuitry that Helmut has perfected over a decade. As Heike (whose English is fluent, while Helmut's is about as good as my German) explained, 'AudioValve has absolutely no interest in the "exotic valve game" that forces customers to spend a fortune of so-called, "selected" valves. Helmut designed a circuit that takes automatic biasing to another level, eliminating concerns for minor variations from valve-to-valve. The circuit even allows the user to mix tube types within the same channel, like 6550s and KT88s.'

Called the 'automatic bias regulator', or ABR for short, it endows the amplifier with a number of benefits, including instant warning if a tube has 'gone bad' while ensuring that nothing nasty reaches the outputs. The circuit matches the tubes, continually adjusts the bias and acts like an on-board, real-time tube tester. Because the comprehensive capabilities of the ABR circuit obviates the need for over-priced, matched valves, it's reflected in the price. Frau Becker notes that, 'Some companies charge up to 100 euros each for the valves we use. We charge less than that to replace the output valves for the whole amplifier.' And as one observer noted, there are amplifiers out there that cost more to re-valve than you'd pay for a pair of Baby Baldurs.

Along with an extremely reliable output stage, the 'Baby Baldur' includes other familiar details (to Baldur owners, that is), such as balanced or single-ended operation and the cluster of red LEDs that indicates when the unit is in stand-by or if a valve needs replacing. The valves line-up, per amplifier, consists of a quartet of 6AS7G power triodes while the Baldur 200+ uses eight per side. The input and driver complement includes one ECC83, one ECC82 and two 6N6Ps - none of which will break the bank at re-valving time. With half the output tubes, the Baby Baldur delivers half the power of the Big Baldur, circa 75-80W...though it seems like a lot more.

As is favoured by Helmut Becker, all of the electronics of the Baldur 70 are on one enormous printed circuit board, viewed through the clear Perspex top-plate. The valves peek through it and are protected by a cage. [Note that the curved rods that form the cage on the review sample have been replaced in certain markets - including Europe - with a new cage that won't permit fingers to poke through the gaps.] Helmut prefers well-made, well-filled, top-grade circuit boards to hard-wiring because, 'The advantage is that all the production models of whichever AudioValve model you try are exactly like the reference sample, in contrast to "hardwired" components, where the outcome varies with the soldering abilities of the constructing technician. All too often, unfortunately, the case with hard-wiring is that one amplifier is hardly like the other. At AudioValve, we compare every amplifier we produce to the reference sample.'

Helmut adds, however, that sample-to-sample consistency is certainly not the only reason for using a single PCB. 'Dynamic inter-relations can occur between the various components, in the context of the total construction. Only the use of a well thought-out and carefully-calculated printed circuit board will stabilise or eliminate these conditions.'

Helmut found with the power triode 6AS7G, which he first tried in 1982 in the original Baldur 100, that there are a number of demands that must be met before this valve will perform to its maximum ability. 'For one, there has to be a stable electrical environment to sustain this highly-demanding tube if you expect to achieve maximum musicality during its entire lifetime. The intricacies and traps with the 6AS7G are such that they cannot perform this task without an automated bias circuit and simply cannot be done without AudioValve's ABR. ABR forces all the tubes effectively to act in a "common mode", fundamental for any multiple tube design.

'Traditionally, this task is performed with a screwdriver, to adjust the bias current, but that is only a momentary fix, if at all. Even selected tubes cannot deliver their potential in the long term, because tubes age and change, and a matched pair or quad grouping will be "matched" only for so long. ABR regulates each of the two triodes in one glass bulb and so on with the other tubes. Whenever you see this tube in use, accompanied by only a half-dozen components around it, scepticism will be your best response.'

If you need to change an output valve in the Baldur 70, the related ABR circuit will indicate its terminal status or pending demise via the aforementioned LED, and you have to change only that valve for another, either new or even used. You just plug it in and off you go. The ABR circuit will compensate for, say, ageing in a valve you found in your 'spares' box. Helmut argues, too, that the Baldur 70 is more or less indestructible, even if you short circuit the output, or inadvertently, leave it running without a load. He adds, 'That, by the way, applies to all of our amplifiers!'

Read more about the Audiovalve Baldur 70 on Page 2.

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