::: highest accurate class A mono tube triode power amplifier :::
minus 94 dB S/N ratio – 0,25 % distortion by 50 watt and damping 20 !!!
Three statements – that make the difference and I will now explain why.
1.) The SNR with -94 dB notes the ratio of the amplifier’s own noise to its useful signal. In our case, with the BALDUR 70 (and Baldur 300 also), this value is a whopping 94 dB – or in other words, the remaining noise voltage that the amplifier itself produces is not noticeable in the loudspeaker. A phenomenon that is rather the exception for tube amplifiers and Baldur 70 is this exception. Ultimately, this also proves how well the power supply is screened and how exactly even the quiescent currents on the left and real bank of the circuit board are. Only then does the hum in the transformer cancel out and go to zero. In the case of older third-party products, this fact leads to the despair of the users because the quiescent current cannot be kept constant. There are too many variables that are constantly changing, such as Tube aging etc. All things that you can easily forget at Baldur, because our ABR ensure that the quiescent currents remain exactly the same until the end of our days. So very important – the amplifier that buzzes in the speaker is simply badly made and should be disposed of.
2.) This very low distortion factor is already unusual for small triode monoblocks and cannot be realized in SE Topology. This small distortion factor is achieved by pure Class A operation – generated by auto-biasing – the tailpipes on which the circuit concept is based. These end tubes require less than 250 VDC operating voltage and can therefore tolerate an anode current that is all the higher. The overall construction thus becomes very low-resistance and this always has ONLY advantages. In conclusion, when listening, this means that even at high volumes, the full signal control is retained until shortly before the output stage clips and the entire musical presence is available up to this level – and 50 watts are a lot on the right speakers!
3.) Damping – do I have to have that? The answer is simple – YES. The attenuation describes how low-impedance an amplifier is at its loudspeaker terminals. In principle, transistor output stages are generally low-resistance, which means they have a high damping factor. That we achieve through measures such as operating mode and negative feedback, etc. But the decisive factor is that only low impedance at the amplifier output can ensure that the loudspeaker is controlled. Loudspeakers have a design-related “life of their own”, and the less the amplifier is able to counteract its life, the more pronounced it becomes. Of course, this has an enormous effect on the sound and discolors the musical image. Example, take a low-frequency chassis and press on the membrane, that is still relatively easy, now short-circuit the pole terminals of the chassis and you find that there is now considerable resistance when pressing. The coil of the chassis wants to generate voltage at the terminals from the movement – but if you short it now, you feel a considerable resistance because the short circuit at the terminals prevents the build-up of the voltage and thus a high short circuit current in the coil of the Cause chassis. The example should show how the membrane is deflected due to external influences. The lower the impedance, the better the control of the membrane. With good control, the basses are short, dry and crispy, very different for power amplifiers with low attenuation, because the speaker does what it wants and swells e.g. the bass, there are some who like that, but it’s not right. Our triode power amplifiers have exactly these properties of high insulation with a factor of 20 – and this is rare for tube power amplifiers. The internal resistance of the power amplifier is the 20th part of the loudspeaker – and you can hear that. Conclusion for the user – damping is important and should never be less than 5.
During the CES show in Las Vegas 2003 with our importer Mr. Goldstein from FANFARE Intl. NY, 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.
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 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 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.
one reason for the excellent musical playback quality of the audioValve amplifiers is the fact that the output transformer is based on near perfect transmission characteristics. Audiovalve power amplifiers reproduce rectangles at 10 khz, which otherwise are only known from the theoretical ideal treatise on textbooks. Anyone attentively studying the American audio press has probably already found many of these images that are not nearly close to the theoretical ideal – just as audiovalve amplifiers do, so the success of the musical reproduction of audiovalve amplifiers is unstoppable and will prevail, everything only a matter of time.
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.
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!’
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.
and the winner is ……. HEATHROW – SHOW , London 2004 – AudioValve win the international title
“INDUSTRY AWARD 2004” in the categorie “best tube amplifier”
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 8000,- 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….’
It’s a long and rocky road from the idea of an amplifier to the finished product. Our BALDUREN are an example of this and at this point we want to give you a little insight into the construction secrets. The diagram below shows a so-called SPICE simulation on the computer of the drivers of all BALDUR models. SPICE was developed by NATIONAL – ELECTRONICS and has a database with a multitude of components and also tubes. SPICE is an expensive software tool for professionals and is used in development and research. Only those who can rely on such tools have the right to act as reputable developers. Everything else are hobbyists and amateurs, whom you can not trust – because you do not know what you are doing!
Such a simulation is always the basis of a design for the amplifier before we start designing a printed circuit board. Only when all the results have been determined and styled to the optimum values with the SPICE simulation, does the construction of the appropriate circuit board begin as a so-called masterpiece. This work can take many months. I am now chatting something from our “sewing box” using a few examples so that the customer understands why we are so successful with our products worldwide.
The following drawing shows the driver of our Balduren. The condition here is maximum signal amplification and stroke with the smallest distortion factor and low output impedance in order to overcome the input capacities of the end tubes. Some values are blacked out so as not to provide a template for the competition. And dear readers, forget the review in the STEREOFILE at BALDUR 70 workbench sample, that was before that time.