Audiovalve Baldur 70 Amplifier Reviewed

Published On: January 4, 2009
Last Updated on: March 9, 2022
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Audiovalve Baldur 70 Amplifier Reviewed

You know what you need? That's right, large format German tube amps. Packing 70 Watts per channel, the Audiovalve Baldur are the pinnacle of audiophile esoterica. God knows what this stuff sells for on but its sure is cool looking. Check out the full Ken Kessler review here.

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.

Given the power rating and the option of balanced operation, the Baby Baldurs were drop-in replacements in my main system: SME 30 Mk II turntable with Series V arm and Decca Reference cartridge, EAR 324 phono stage, Marantz CD-12/DA-12 CD player. McIntosh C2200 preamp and Wilson WATT Puppy 7, all wired with Transparent Reference. Thus, the main comparison was with the amplifier for which I substituted the AudioValves: the McIntosh MC2102. More powerful, more expensive and easily as advanced - maybe it was unfair to the AudioValve, but the results proved otherwise. I also wired in the Nu-Vista 300s and the McIntosh 275 reissue, and had other amps like the PrimaLuna Prologue One in use during the same period.

As luck would have it, the amplifiers were completely burned in, the pair having made the rounds of the UK for nine months. Yes, this review is running almost a year late, but far be it for me to berate distributors; let the retailers and suppliers beat 'em up. Suffice it to say, I'd almost forgotten I was supposed to review it. Anyway, it was worth the wait, because - instantaneously - the Baby Baldurs delivered performance so far beyond what I had expected that I found myself undergoing the exact same shock revelation I experienced a few months ago with the ProLogue One, but at a higher price point.

Installation was a breeze as the inputs and speaker terminals (sets for 4 and 8 ohms) are widely-spaced and of top quality. Switch on is but a brief ritual: First, you flick the main power rocker, followed a few seconds later by the stand-by switch. The LEDs extinguish when the amplifier is ready to use. After five minutes or so, the units were warmed-up to optimal running temperature, but some valve fusspots may prefer a half-hour.

Regular readers know that, although they're sensitive, WATT Puppies are not an easy load, and they are so revealing that they can easily embarrass most amplifiers. At the risk of alienating 75 percent (or more) of you, they also show in spades why solid-state amplifiers are NOT the preferred mode of amplification for some of us. So, while the Baby Baldurs are hardly the sort of behemoths most WATT Puppy owners will use, they are, at least, sonically sympathetic to the Wilson speakers, and the immediately-perceived synergy was flagged by a deliriously sweet top end simply unavailable from the WATT Puppies when driven by transistor amps. (Let me qualify that with an 'In my experience...'.)

Confirming this initial response were smiles all around with every listener who visited during the review period. But however much I expected them to comment on the glistening, silky treble region, the most oft-elicited response was a real shocker, especially when you consider we're talking about a valve amplifier with output only in double figures. To a man, each and every visitor commented first on the sublime bass: controlled, deep and, above all, natural.

Let's examine this a bit more closely. Despite the compact dimensions of my room - 12x18feet - it acts almost like a quarter-scale version of the SME room because of its solidity. As such, within its confines, it is able to deliver smooth, controlled and rattle-free bass. [Interestingly, when the gents from PMC arrived and we ran a test sweep, the only crud we found at low frequencies turned out to be buzzing caused by some loose CD jewel boxes sitting near the speakers.] It managed to exploit the sheer power of the Puppy bass module with the efficacy of a big solid-state amplifier, but without applying most tranny amps' unnatural overdamping.

Even with a bottom octave foundation that substantial and solid, and upper frequencies as honeyed as those from a Dynaco Stereo 70 or Radford STA-15, the best was still to come. Hands down, this pair of monoblocks creates a soundstage as wide, deep, open and airy as any I've experienced from amplifiers under 5000. It is thoroughbred soundstage recreation as beloved of American audiophiles with massive panel speakers and a cherished Denon 103D. I whacked up the volume for the stereo mix of the Beach Boys' 'Surfin' USA' off the newly-released Best of and marvelled at the smooth lateral spread, from a recording that can sound ping-pongy at worst. The cheesy organ break, Brian's chunyk bass playing and uncluttered, but perfectly blended harmonies - Charlie may not surf, but Fritz clearly does.

When it came to the new Wilson Phillips CD, definitely the 'sleeper' of the year because of pop snobbery, the Baldur 70s showed how they could handle a trio of ultra-sweet voices backed by the slickest of studio sessioneers: clarity, detail and a way with layering that will baffle those who simply refuse to believe in front-to-back depth, especially listeners still stuck in a 1980s UK solid-state rut.

But it was something entirely unexpected, unwarranted and unreasonable that made me fall head-over-heels in love with the Baby Baldurs: 1950s
mono recordings of the Capitol variety. Sick puppy that I am, I fed the Baldurs track after track of Mickey Katz - vinyl and CD - to hear my fave Yiddish klezmer comic, with Benny Goodman-grade clarinet, vocals recorded with the finesse of the best Frank/Dino/Nat classics, percussion just waiting to be sampled by the hip-hop thieves. Through the Baldurs, the sound was palpable and room-filling - kosher, even. Within seconds, listeners forgot that they were listening to a single-channel recording, the sound plunked straight in the middle of the speakers, in the room. Why the recidivism? Because it was so fat, rich and, above all, lifelike that satisfaction was guaranteed. The readily-available layering of a stereo recording was evident here with unmistakeable lucidity. You could taste the soured cream and blintzes. Expect Mickey Katz LPs to shoot up on eBay.

Consistent from source to source, recording to recording, was an effortlessness that belied the power rating, though a headbanger could reach its limits if the speakers were too hungry. And the amplifiers are, despite Frau Becker's insistence, sensitive to clean mains, if insensitive to cable selection. Overall, though, they behaved impeccably, and I wouldn't imagine that any owners would fail to pay attention to positioning, ventilation or, indeed, choice of AC cables.

And in the back of your mind, all the while you savour the sound, there lurks a crucial specification that should make the Baby Baldur the hit of the season: a pair will set you back around 3195 depending on finish.

Let's put this into context. Here's Kessler, with no great love for the Fatherland, raving feverishly about another Teutonic tube amp, and in under a year. While it is completely unlike the T+A, which is ultra-modern and 'lifestyle' and sexy, it represents the same sort of value - real and perceived. It will not replace the McIntosh, which edges it out in absolute dynamic contrasts, absolute quietness and sheer grunt, as well as looks. And I still have dreams of the Marantz Project T-1, the Nagras and one or two others requiring a lottery win. But, damn, the Baldur 70 is one miracle of an amplifier. 'Today Kessler, tomorrow....'

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• Find an AV receiver to pair with the amplifier.

Audio Reference 01252 702705

Amplifier type Push-Pull - Class A
Max Output/ch 80W@8ohm load, 1% distortion
THD at rated output 0.3% 
Power bandwidth 10Hz-50KHz (8ohms)
Finishes Black as standard, silver on request
Dimensions 325x385x300mm (WDH)
Weight 16kg

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