BALDUR 70 Mono Power

Audio Valve Baldur 70 Mono Power Amp
During the CES show in Las Vegas 2003, the need for a smaller version of Baldur 200+ became apparent. Size and price were main cause for the search for an alternative consumers entrance into the ‘world of BALDURS’ !
Thus said and done, AudioValve can offer you, as shown in the accompanying illustrations, the final developments and esthetics of BALDUR 70 (“baby-baldur”). World premier performance was at the ‘High-End-Show’ in Frankfurt-Germany, Summer of 2003. 
Like in all AudioValve’s larger model power-amps, our proven fully automatic bias regulator –short ABR- at the powertubes, also appears here in the power stages of BALDUR 70. This is world wide unique and this feature is a ‘must’ for relevant tasks to stabilize the bias of the power valves and actually belongs standard into 21fst century tube-technology - at least with AudioValve ! - 
Safety, reliability and durability are synonym for our tubeamps for over a decade! Apart from the high reliability of the outputstage, the ‘baby-Baldur’ unites further interesting, typical AudioValve’s refinements on the part of the concept. As for the powertubes, BALDUR 70 utilizes only four 6AS7G’s / ch. where BALDUR 200-plus uses eight 6AS7G’s per channel. (And in doing so, it’s the only world-wide power stage, using 8 tubes coupling a clean 150Watts power-output to a dampingsfactor of 100!!) 
The baby-Baldur cannot compete completely with the extreme standard of Baldur 200, but gives a real run for its money, and makes a quiet worthy and certainly more inexpensive entrance possible to a true triode Poweramp. And with this masterpiece one immediately recognizes the incomparable quality of a correct trimmed set of 6AS7G’s !! (75W/ch)
But what makes this outputstage something special? It is the sum of all consistently architected thoughts and accomplished development-steps. All electronics of the BALDUR 70 are on one enormous printed circuit board accommodated -a masterpiece of a special kind- evenly typically AudioValve, with the advantage that all the production models of whichever AudioValve model is exactly like its reference sample! In contrast to “hardwired” components , where the outcome varies with the construction technician…, as to often, unfortunately, the case is. With free wiring one amplifier is hardly like the other. 
But that is certainly not the only reason for this one PCB; dynamic interrelations can settle in between elements in context of the total construction. Only the use of a well thought out and calculated printed circuit board, will stabilize these conditions.
If using the power triode 6AS7G, first tried in 1982 in the original Baldur 100, there are a number of demands to meet before this tube 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 maximum musicality during its entire lifetime.
hold there promise in the long term, because tubes run their own life, and a matched pair or quad will be matched only for so long!! 
The ABR of the BALDUR 70 will regulate each of the two triodes in one glass bulb and so on with the other tubes. All together the 6AS7 G is still protected by reversible devices. Whenever you see this tube in use, accompanied with only half a dozen components around this tube,skepticism will be your best advisor. 
If you should have to change a powertube in the BALDUR 70, the respectively related ABR circuit will indicate so, and you exchange only that one to another, for ex. a new one. BALDUR 70 is more or less indestructible, even if you shortcircuit the output, or inadvertently, leave it running without load. That, by the way, applies to all our amps!
BALDUR 70 reaches with a dampingfactor of 20 not the dream-value of its big brother, nevertheless in comparison with its competition it plays absolutely in the upper league; while generally dampingfactor of tubeamplifiers is not their strongest feature.
In particular OTL designs with a damping factor of 1 or 2 will make you believe that they’re wonderfully musical. Well, maybe in exceptional cases, certainly not generally, simply because without control over the speaker from the amp, there is no such thing as musicality!
The intricacies and traps with the 6AS7G are too many to perform this task without an automated bias circuit and simply cannot be done without AudioValve’s ABR! Besides that will ABR forces all tubes effectively in a “common mode”, fundamental for any multiple tube design.
Traditionally this task is performed with a screwdriver, to adjust the biascurrent, but that is only momentarily, if at all. Even selected tubes cannot The damping realized in BALDUR 70 means strong, clean, dry, thumpy and sharply outlined bass; accompanied of the soundstage and velvet high’s only known from real triodes.
BALDUR 70 will not only drive ‘tube-friendly’ speakers, a wide range of dynamic speakers are well within the limits of its power; even magnetostatic speakers can easily be driven! Thereby, the BALDUR 70 will drive excellently a multiplicity of usual loudspeakers.
Naturally BALDUR 70 has also a driver stage before output stage. AudioValve hasn’t let that pass unnoticed! It consists of four (!) double triodes/ch, responsible for tension-amplification and current-amplification, splitting of the complementary wave to feed the parallel-mirror-symmetrical coupling to powertubes.
Filament voltage as well as plate voltage of the driver section are stabilized, and provide a solid, rock steady operation conditions. The r0emaining characteristics of BALDUR 70 resemble otherwise those of BALDUR 200-plus.
Power supply:
100-245 Volt
Power consumption / ch:
250 Watt
4* 6AS7G, 1*ECC83, 2*ECC82, 1*6N6P or 6 CG 7
Push-Pull ?class A
Max Output / ch:
70 Watt (8 ohm load, 1% dist.)
THD at rated output:
0.3% ( 50Watt/100Hz - 1KHz ?10KHz)
Power bandwidth:
10Hz ?50KHz (8Ohm load)
20 (output Z= 0.4 Ohm)
Input sensitivity:
0 dBm ( 775 mV)
Automatic Bias Regulation:
Yes, unique full automatic biasing for all powertube-triodes
Black or silver colored case and chrom or gold terminals
Width 32.5 cm; Depth 38.5 cm; High 30 cm
16 Kg
Dimensions with package:
W: 45cm; D: 52.5 cm; H: 50cm
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!'
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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