Und hier der Test aus der STEROPLAY 1984 …..der erste von zig Test`s die in den Folgejahren erschienen.
Eine kleine deutsche Firma möchte mit einem Röhrenverstärker Kopfhörer zu Höchstleistungen anspornen.
KIein, aber fein
Helmut Becker, 30, hatte eine großartige Idee. Er wollte etwas konstruieren, was nirgendwo zu kaufen war. Und dafür gab es einen guten Grund.
stereoplay untersuchte im Test, ob der Dynamp der kleinen Firma Audio Valve in Lemgo das vom Konstrukteur versprochene Ziel erreicht. Immer dann nämlich, wenn er Lust hatte, seine HiFi-Anlage aufzudrehen, vermiesten ihm lauthals protestierende Nachbarn sein Klangerlebnis. Wenn er sich aber verärgert den Kopfhörer überstülpte, konnte er ebensowenig frohen Herzens genießen. Denn die Wiedergabe mit seinem 800-Mark-Verstärker konnte ihn nicht zufriedenstellen. Was lag also für den gelernten Elektronik-Techniker, der in der Medizingeräte-Technik tätig war, näher, als einen Kopfhörer-Verstärker zu bauen, der höchsten Qualitätsansprüchen gewachsen war?
In der Tat ist die Idee nicht schlecht, denn mancher HiFi-Freund, der Aktivboxen besitzt, muß auf Kopfhörer-Wiedergabe verzichten, wenn sein Vorverstärker keinen entsprechenden Anschluß besitzt. Es gibt aber auch Musikliebhaber, die aus Platz- oder Kostengründen nur Mittel-Klasse-Lautsprecher besitzen und über Kopfhörer Musik hoher Güte hören wollen – die weitaus billigste Art, HiFi zu erleben. Becker ist Anhänger der guten alten Röhrentechnik. Er studierte sehr genau gewisse Vorteile dieses einstmals glorreichen Bauelements gegenüber den modernen Halbleitern, die heute in allen HiFi-Komponenten zu finden sind. Für sein spezielles Vorhaben boten sich zwei Eigenschaften besonders an: Elektronenröhren können an hochohmige Lasten vorteilhaft angepaßt werden, wie sie dynamische Kopfhörer mit ihren typischen 600 Ohm darstellen. Und für elektrostatische Hörer, die nach extrem hohen Spannungen von einigen tausend Volt verlangen, bieten die Röhren geradezu ideale Voraussetzungen für harmonsches Zusammenspiel.
So ganz wollte der Erfinder aber auch nicht auf die heutige Halbleitertechnologie verzichten. Dort nämlich, wo die Röhren eher Nachteile besitzen – etwa in der Eingangsstufe oder bei Kontrollaufgaben für die Endstufenröhren -, setzte er folgerichtig Transistoren und integrierte Schaltkreise ein. Der Dynamp besteht also aus einem sinnvollen Gemisch von Halbleitern und Röhren (Hybid-Verstärker), wodurch sich Becker ein gewisses Optimum verspricht.
Äußerlich demonstriert der Verstärker kaum sein komplexes Innenleben. Das simple, schwarze Lochbiech, das als Ab- deckung dient, erinnert eher an Billig-produkte als an ein Qualitätsgerät. Die goldeloxierte Frontplatte zeigt ebenfalls, daß Audio-Valve noch eine sehr junge Firma ist, die vom Marketing nicht allzuviel hält. Becker verzichtete bewußt auf teures Finish und steckte das Geld lieber in die Elektronik.
Zum Hörtest steckte der Dynamp am ,,Line”-Ausgang des Referenz-Vorverstärkers Onkyo P-3090. Als Kopfhörer diente der dynamische DT 880 Studio von Beyer (Test stereoplay 5/1982), den die Tester abwechselnd am Onkyo und am Dynamp betrieben. Es waren nur wenige Hördurchgänge mit unterschiedlichem Musikprogramm notwendig, um festzustellen, daß es gravierenden Unterschiede gab. Der Audio Valve reproduzierte über Kopfhörer alles, was in den Rillen steckte, sauber und natürlich. Untadelig und volle Kraft brachte er dynamische Passagen oder auch getragene Stellen. Solostimmen wie komplexe Orchester kamen über die Kopfhörer in brillanter Darbietung ohne jede Verfärbung.
Gerald 0. Dick, Stereoplay 9/1982
Best Sound TAIWAN – test review
AudioValve Taiwan – test review
Carlos – test review
Dan – test review
Jean Paul Hiraga test review
Haute de fidelite
RKV2 – review china
Here we have the very sort of thing that drives me crazy. Four tubed headphone amplifiers (Holmes-Powell, Moth Audio, AudioValve, EAR) and three solidstate (Grado, Headroom, and McCormack), and after a respectable amount of listening, few sound anything like the others. What originally started out as four became seven, should have been eight, went through delays because of problems with delivery, and some last-minute auditioners entered the chorus line. Headphones offer a distinct difference from conventional listening, with both advantages and disadvantages. The ability to enjoy music when one?s family requires quiet is balanced by the possibility of enjoying music when you can get the little bastards quiet enough to not be heard through the ?phones. A true High End headphone set-up can also offer a kind of intimacy to the source that speakers will never match, by removing the room from the listening equation. Even a mediocre set-up can offer that improvement, but it may not convey the nuances that your high-quality speakers might. The main disadvantage to headphone listening is displacement of the soundstage. Instead of a three-dimensional soundstage appearing in a window in front of you, the soundfield is reduced to a plane inside the head. This has one virtue, though – with many CDs, the sound can be quite reasonable but produces a flattened soundstage that is no fun. Headphones render most sources equal in this respect, and many otherwise unenjoyable CDs pleasant.Since I use headphones every day in my studio, the finger of fate pointed at me for this survey. I do recording in a variety of ways: sometimes as a session musician, which can involve using headphones as the only way of hearing yourself – and can lead to pretty serious skewing of your sound to tape, if you adjust your tone to what you?re hearing, which with the most common studio ?phones doesn?t resemble a bit what?s actually being recorded. Sometimes I am by default an engineer using my own multi-track portable recording set-up. Here I prefer to have the best headphones available when using an open microphone in the same room with the equipment, but over the years it has become a little less critical in that one gets familiar with one?s methods and gear and learns to trust one?s work and instincts. The choice of headphones is frequently limited by the necessity of using closed-ear types to prevent bleed from the ? phones into the mikes, but I find that the best-sounding so far are always open-eared.In the first round of the reviewing process (my first headphone amp review appeared in 1993), I settled on the Melos SHA-1 amp and the Grado HP-1 ?phones, with the Sennheiser 580 ?phones as an alternative. But time marches on–the Melos started developing problems I couldn?t get fixed, it was drilled wrong for proper rack-mounting, and was unwieldy. So I found the original Grado Labsbuilt Grado Signature HPA-1 headphone amp as a reasonably low-cost, ultra-portable alternative.This time out, Scot Markwell procured the new Sennheiser 600s ?phones for me, which I immediately purchased, and the first amp to arrive came along with a set of modified Grado RS-1 ? phones, which I found uncomfortable, and so wheedled a proper set out of John Grado (wheedling being the foremost of the reviewer?s necessary skills).And so here we have the review set-up – these two sets of phones along with the old HP-1s driven by the tapeouts of the EAR G-88 with the Immedia RPM-2/Immedia Arm/Lyra Clavis DC for analog and the Theta Data III/Genesis Digital Lens/Theta Gen Va/96k DAC/Illuminati cable set-up for CDs. For comparison?s sake, music was also heard through BEL 1001 Mk IV or EAR 509 Mk II amps and a custom set of d? Appolito-configured dynamic speakers built by Richard Marsh. (Though if you really want to irritate yourself, try referencing between speakers and headphones a lot. I saved it for the clinches). We spent months waiting for the arrival of the much-hyped Cary CAD-300SEI tubed integrated/headphone amp. After many zig-zags, it became clear that we were not going to get it. Life goes on. The first amp to arrive was the $4,500 Holmes-Powell DCT-1 single-ended model. I love this thing and picked it as my one Golden Ear award victim. Nothing has happened between then and now to shake out of its place as pick of the litter (although the appearance of a fourth tubed amp, though a prototype and unreviewable, lessened my regret at losing the Holmes). The DCT-1 puts out 500mW at 30 ohms using 6072A input and 6005 output tubes. Holmes-Powell estimates a typical tube life of 5 to 10 years (and half that for commercial use, whatever that means). The thing will handle a driver load of 25-600 ohms, which means that, unlike the other tube units, no special accommodation need be made for switching ?phones.At the time of the Golden Ear deadline, I wasn?t confident in my assessment of the HolmesPowell?s accuracy, only of its romantic beauty. I now am more confident that it?s not particularly accurate – I simply don?t buy that the 1987 off-the-shelf CD of Abbey Road, which sounds so mediocre compared to vinyl elsewhere, truly sounds as good as it does with this thing. If this is right, then everything else is not good enough. But I?m just as certain that the DCT-1 is the most pleasurable (and significantly most costly) of the amps I reviewed. With either set of ?phones, it?s capable of enhancing the details of a recording to a degree of apparent intimacy that is both an education and a sensual delight. In only one instance was this too much of a good thing: the new CD of a 1971 Graham Nash/David Crosby Los Angeles performance entitled ?Another Stony Evening? released by Grateful Dead Records. I don?t want to overstate the negative effects of headphone listening with this one, but it was recorded straight from the board, and live mikes are rarely very good. In this case, they were the industry-standard Shure SM-57s that I avoid using in recording. And none of the amps reviewed could make up for the fact that the intimacy of the ear-to-driver relationship was just too much on the cheap mikes, including the Holmes-Powell. Of course, it?s just that ear-to-driver relationship that makes headphone listening so pleasurable and problematic. With a good setup, nothing can match the degree of detail you hear. Likewise, nothing can overwhelm the ear as fast – the better the set-up, the longer you can listen, but fatigue can set in fast, especially if you succumb to the temptation to listen too loud to get more of that intimacy. One of the hallmarks of a better set-up is a lessening of that urge to turn it up. Around the same time the big macher of amps arrived, so did its reciprocal: the tiny, inexpensive, wood-enclosed, battery-only (2-x-9v) Grado Labs amp. Pocket-sized, you don?t expect big things out of it — and you don?t get them. But for $350, it will outperform your basic single-chip tape-deck headphone output driving lower-impedance phones like the 32-ohm RS-1s. Compared to the larger and more expensive units, the Grado seems slightly coarse sonically, but on its turf, it holds its ground respectably. Only the lack of AC-option really irritates me about it ? one would like to leave it on to be assured (at least for reviewing purposes) of having it perform at its best. I went through one pair of 9-volts just doing what I thought was a decent warm-up ? and stopped. The Grado seems like a steal compared to the $1,333 solid-state Headroom Max. I couldn?t find any justification for this thing. It?s ugly and sounds dark and closed-in. It has a couple of circuits that might justify it if you find they work for you – they did zip for me. One is a kind of cross-talkinducing circuit that is supposed to ameliorate the hard left-toright imaging of typical headphone performance, along with a filter designed to compensate for some losses induced by that circuit. I could hear them working away, but found nothing valuable in them, or indeed the entire device. I recall a Headroom amp I listened to in ?93 with a circuit that was described as similar in function that I found more effective than that in the Max. If you?re going to throw $1,333 at the problem, then save a few bucks and listen to the tubed $1,190 Audiovalve RKV. Now, this thing represents good value for money and would probably be the winner of this sweepstakes if dollars spent vs. performance gained were the prime criterion. A dualmono OTL design based on PCL 805 or PCL 85 tubes, it uses an IC-based auto-biasing circuit. In its stand-alone form, it?s meant to drive ? phones with a load of 100- 2k/ohm. The company sent it with a little optional transformer box called the Impedancer ($390), which plugs into the main unit via a quarter-inch plug and provides additional outputs switchable from 8 to 16 to 32 ohms, perfect for driving the Grados. It has a stated output of 3 watts, 400 ohms, and a damping factor of 3500. Visually, it?s a nice squarish black and gold box that looks like Audiovalve?s amplifiers, smoky see-through on the sides for that nice tubular glow. A visitor suggested that it looked like an old-fashioned box camera. Sonically it?s a bit more straightforward sounding than the DCT-1, not quite as lush and warm, not quite the same sense of ? enhancement.? But respectable in every sense — open and beautiful.Much the same can be said sonically of the Moth Audio s2A3, with one important exception. It took me a long time to understand the difference between these two amps. If the HolmesPowell is Hawaii, a sound off by itself, the Moth and the Audiovalve are the two American coasts – of a continental body, cohesively in the same family, but not identical. I spent days going back and forth between them, trying to qualify that difference and realizing gradually that I was coming to prefer one. (It took the appearance of a fourth tubed contender to clarify the difference – one that plunked itself sonically squarely in the center – say Lawrence, Kansas.) That sonic exception is the way in which the Moth characterizes noise. After a bit, I called the designers to suggest they come by to check into why it was so noisy. Like any designers, they were taken aback. And this time, they were right – unplugging the input silenced it. Absolutely. No noise whatsoever. So what was bugging me? It was the way in which the unit treated recording hiss, whether from LP or CD.Accuracy is hard to judge when, to use the Japanese phrase I love, you?re playing ball on running water. Three sets of headphones, all different. Seven amplifiers, all different. How do you judge accuracy? Objectively, you don?t. You need to be intimately familiar with all aspects of the recording and production chain and process to get even close. Recording starts with an imperfect transducer, ends with an imperfect transducer, and what happens between is audio, which is still somewhat mysterious. So you listen and listen and bring all your experience to making an informed opinion. And it?s my informed opinion that the Moth Audio s2A3 exaggerates hiss; and though that may be less easily discernible in musical information, this quality made me feel easily fatigued. The Crosby/Nash CD is a great example, and the one I used to finally chase this down. After a while, the recording hiss became distracting only with the Moth. Moth sent over a technician to check this out and he heard it, plain as day, and agreed. We tried some measurement equipment he had brought, with all four tubed amps, and though the frequency-sweep and squarewave response tests showed us some interesting things, we could find nothing pointing to this quality. This is not to say it can?t be found, just that we didn?t with that simple equipment. I also found myself, without fail, turning the Moth up when I plugged into it on A/B rounds of the various amps – something I did with none of the others. Something about it made me want more ? oomph.? But let?s talk for a moment about the Moth?s appearance. This thing is beautiful – a few thought it prettier than the DCT-1 ?in a mad-scientist sort of way,? as one fan put it. Inside, it?s functionally elegant, which I learned because it?s apparently persnickety about its output impedance – you have to undo 16 small Philips screws to get at the guts, though once you do, changing the impedance is ingenious and fun. But the designers must assume you have one set of ?phones and so don?t want to change loads very often, or they?d do something about Second, the unit is a prototype, which TAS does not review. But it taught me a lot. It?s the Kansas resident that helped me understand the differing ways in which the Moth and the Audiovalve treated noise and other signals in the same audio band. Most importantly, using recordings I?ve done, on which I am playing bass, and also knowing de Paravicini?s characteristic rendition of low frequencies (his hand-wound transformer design is extremely wide bandwidth), I was able to determine something all three of the other tubed amps had in I use EAR equipment in my home system and as the primary components of my recording chain, including the tape recorder, and I am leaning on de Paravacini to design interfaces for high-bit and sampling rate hard-disc recorders for me. I bring this up to explain the final comparison between the $350 Grado and the $750 McCormack Micro Integrated Drive. For many recordings, I find these two so near to identical sonically, I?m unsure I heard a difference. But the opening track on Martin I want to digress one final time on the subject of accuracy and musicality in recording, and I am going to borrow a phrase from elsewhere in the fine arts: “Magic Realism.” (Think of the books of Gabriel García Márquez or the paintings of Edward Hopper.) If one thinks about some of the great audiophile recordings, such as the Layton or Wilkinson albums, one realizes that what is being heard is not particularly close to the sound of a real orchestra in any literal sense – i.e., the string tone may be “simply gorgeous!” but is in those 16 screws. I listened to it mainly with the Sennheisers, since that?s what the designers themselves recommend. I had them install a dummy load on the speaker outputs1 so I could pop my ? phones in and out – another convenience limitation, but one that is addressable. The chassis has two little windows that show you the drive tubes and a mirrored black finish on top out of which protrude the pair of 2A3 tubes, which are finely bulbous. A true audiophile delight, in need of its own stand or your top shelf. At $1,800, the fit and finish are a bargain. Okay ? now for the mysterious fourth tubed amp. I can?t review it for a variety of reasons, yet I must discuss it because in the end it proved crucial to my determinations. It?s a prototype EAR amplifier. First, I do business professionally with EAR principal and designer, Tim de Paravacini, and the sudden arrival of this prototype may well have been the result of my telling him that I was in the midst of reviewing tubed headphone amplifiers. common. It sounded like an audible phase shift from the mid-bass on down, as if the bass were spread out around the center of the soundstage, rather than focused in it. My guitar sounded rounded and a little hollowed-out through the DCT-1, the s2A3, and the RKV – all pretty much alike, which I may well have not picked up on with no other basis for comparison. In my other reference – my speaker system – I had to listen through a room. But the moment I heard the bass in the EAR prototype, I knew I was hearing the closest to accuracy in that sonic region. I was even able to demonstrate this to Moth Audio?s tech.The EAR prototype gradually became my reference point. I don?t want to belabor the point of accuracy, because to determine what is accurate in headphone listening is beyond me – maybe beyond anyone. But the EAR ? signature,? if such a range of products can be said to have one, is one that fits well into my listening biases. Carthy?s brilliant ?Signs of Life,? a solo vocal with extremely close-miked steelstring-guitar version of the BeeGees ?New York Mining Disaster, 1941,? finally proved the break I needed. Trusting the EAR bass as I do, I found the Grado?s rendition of the bottom end of Carthy?s guitar the more convincing of the two, i.e., more in line with the EAR than the McCormack and giving a somewhat greater sense of solidity. For practicality and appearance, I give the edge to the McCormack. While it costs more, I prefer its slightly larger size (less likely to follow along when you move with the ? phones on) and you can plug it into the wall. And on Telarc?s Arvo Pårt CD and John Gardiner?s Beethoven Ninth on DG, I couldn?t hear a difference between the two with confidence. Indeed, especially for the money, both acquitted themselves quite well by comparison to the more expensive and exotic amps, proving the old adage about how much more you pay for that final few percent of refinement. every sense much too filled with detail and shimmer to resemble what one really hears in a hall. The Neumann microphone capsule is far too non-flat in its response, near- or farfield, to give you the real thing. That much is sure. But equally sure is that the results nonetheless contain pure musical magic. And that is the best of audio. One could create a scale of 0-100 and place recordings anywhere along it, ascribing a value from the 0 of reality to the 100 of magic. I would put my favorite recordings of the Beatles somewhere near 100, and the more literal recordings of Altarus’ Chris Rice or the new solo piano recording by Tim deParavacini with his new MS line microphone2 somewhere around 50. The RCAs? Well, they’re pretty high up and vary with pressing.
Drawing a conclusion from all of this is not particularly easy unless one places some restrictions on the choosing: If I could, I would choose the EAR protoype above all other comers for its sense of accuracy and the useful relative compactness of its package, bearing in mind my somewhat neurotic quest for accuracy where I believe none exists.But the EAR is out. So, for pure visual and musical aesthetics, I still stand by the beautiful to hear and see Holmes-Powell DCT-1. In the price vs. performance race, the AudioValve RKV, at nearly one-fourth the price of the Holmes is nearly all one might want. I am reluctant to dismiss the gorgeous Moth s2A3 out of hand – I want to suggest that should the reader find one available for the listening, do it, and simply bear in mind my experience. Among the solid-state contenders, I give the slight sonic edge to the Grado (over the more ergonomic McCormack), which somewhat compensates for the nuisance of its battery-only operation. It is clearly the place to begin if one is just getting into this kind of thing.
RKV Mark II headphone amplifier
as reviewed by Carlo Flores POSITIVE FEEDBACK ONLINE © 2004 – HOME
Let me tell you one of the reasons I like Dr. Jan Meier. After he read my review of his HA-2 headphone
amp, he told me that I favored tube sound (I do), and asked if I had heard the Audio Valve RKV Mark II. A
week or so later, PFO received one for review. I do not know of another instance in which one
manufacturer offered another’s product for review, although I should point out that Dr. Meier distributes
Audio Valve products in North America. Meier seems to care more about his customer’s needs than he
does about hyping his designs. I mention this because I consider the HA-2 the standard for
performance/price, against which I must measure the RKV.
Audio Valve’s RKV Mark II is an OTL tube amp that measures a little over 5 x 9 x 12 inches in size and
is priced at $1050 shipped. According to Audio Valve’s website (www.audiovalve), it was designed by
Helmut Becker to drive any load between 32 and 2000 ohms, but it could not quietly drive my 40-ohm
Grado HP-1 headphones without a transformer (an option packaged as the $180 Impedancer), so I
used my Sennheiser HD580s. Finding replacements for the RKV’s set of four Tungstram PCL805
tubes is said to be easy, although I believe that tube rollers will find limited options. The amp’s piano
black finish with gold trim is more garish than elegant—it would look sharp in Snoop’s crib, but a picky
girlfriend may give grief. Its paralleled pair of single-ended inputs means that it can act as a twosource
headphone amplifier or function between a source and preamp. An IEC receptacle and two
headphone jacks are included. The top lid is made of a transparent material and is secured with metal
thumbscrews, which allows easy access to tubes and fuses as well as amorous glances at its sexy red
There’s a lot I like about the amp. It was so good during the first month that I felt seduced. I think of
music reproduction as a three-part process—attack, body, and decay—and I give the RKV good
marks in each. It has an almost lush sound, full but not bloated. Even when paired with an averagesounding
digital source like my modified Sony CE-775, the amp contributed an analog-like reverb to
strings. It sounded noticeably fatter and sexier than the HA-2. For example, Pulp’s Intro—The Gift
Recordings has lots of crazy riffs that sound electric and awesome with most amps, the HA-2
included, but dominating with the RKV. For you audiophiles, Norah Jones sounded huge.
I can’t overstate that the RKV makes music sound damn good. It’s all about midrange, bass, and
decay, though I’m not saying that the high frequencies suffer, because they don’t. I am not talking
about impact or detail, but about finding the music. The word that comes quickest is “wet.” Notes
sound wet when played through the RKV. A groovy acoustic guitar, such as Jonathan Richman’s, has
adequate groove, which is an accomplishment for a system featuring the HD580s. I’m also talking
about the kind of soundstage that makes me forget I’m wearing headphones.
Magnifying this is bass performance that pushed the Sennheisers to their limit. I prefer a quick
midbass and a direct relationship between the lowering of frequency and a note’s thickness, and the
RKV gives me what I want. The Sonics’ foundation, Serge Gainsbourg’s pace, and Mos Def’s beats
just sounded right, and involved me as a listener. I’ve heard more expensive amps mess up the lower
notes. Unlike them, the RKV ‘s separation between bass notes is distinct, and while their impact is
somewhat weak, instruments have adequate weight. When the foundation of notes is this good, I find
myself turning into a bass head.
What did I lose to get that scale? A great amp gives up very little, if anything. HA-2 doesn’t even try to
sound big, preferring to achieve frequency balance, and it offers Dr. Meier’s cross-feed to recordings
that need consolation. The RKV ignores audiophile sensibilities, offering gray backgrounds and little
resolution at low levels. While the stage is very wide, placement within that stage is fuzzy at best. It’s
easy to focus on one instrument—to ride a stringed instrument or be caught in a piano—and get lost
when listening to the RKV. However, place that instrument in relation to the others, and things turn
messy. As with badly set up speakers, the image of each performer is soft and indistinct. People who
want scale in a small room with reflection problems know what I’m talking about—the nuance is gone.
Albums sound good, but hardly ever interesting. If you owned this amp, why would you invest in highquality
recordings when you cannot hear their full potential? This is a music lover’s amp, not an
I have not mentioned my reference headphone source, the Audio Note 2.1x CD player, because it
does not complement the RKV and the HD580. Instead, it yields an unbalanced but juicy sound,
appealing at times (Nick Cave’s piano in the song “Into My Arms”) and irritating at others (Nick Cave
and The Bad Seeds’ album Murder Ballads). Unlike the HA-2, which mates well with even the most
flavored sources, the RKV gets in the way. In the end, the RKV is a designer Band-Aid that will help a
system that needs to add flesh to notes. It probably would have been great with my old reference, an
Arcam Alpha 9, or other typically dry British sources. The RKV only disappears at moments,
depending upon song and instrument. As much as I like this amp, I believe it has too many flaws—its
inability to drive low-impedance headphones, its high noise floor, and its lack of balance—at $1195.
The HA-2 can be the foundation of a system. Find the headphone you want and it’ll drive it. Choose a
flavored or unflavored source and you’ll hear the characteristics the designer wants you to hear. It
costs almost half as much, and it comes with cross-feed. For me, this just isn’t a contest.
New fashion of headphones—new fascinating headphones of this month
Overall drive! Another classic of tube-transistor hybrid amplifier
By Lin Jialiang
In the global spectrum of acoustics, “Made in Germany” always symbolizes preciseness and extreme high standards while its sound aesthetics represents a style of order, balance, strength, powerful action, self-restraint expression, decisive attitude and heroic spirit. (To illustrate with a pianist, Wilhelm Backhaus will be the very representation.) Besides, there is a major feature shared by the traditional German acoustics due to the consonants in German, whether being voiced, voiceless or even double consonants, they will always be produced clearly with powerfully cadence, which has virtually shaped the majestic and powerful style of German acoustics as well as the detailed and clear end sounds.
All those features mentioned above can be found in the brass brands such as T+A and Burmester as well as small brands such as MBL and Audio Valve. Noticeably, the German Sound based on the nationality tends to be more evident at small German brands and this is because the brass brand acoustics will adjust to local tastes according to aesthetic standards of different areas during the process of globalization. While the small brands are free from such problems and can do better in upholding its own style, and therefore it is more common to hear sounds from ASR and Audio Valve with strong German flavor.
Acryl cover—good in promoting music performance
Audio Valve is owned by Helmut Becker, whom I neither know nor meet in person. And I even don’t know how he entered this industry of acoustics. However, based on limited information from the English world, with a particular and strict taste, he will do everything himself. He won’t stop midway unless he has developed the product to the best, or publish the key techniques unless he has obtained patent rights. You can search for Helmut Becker’s life story on the internet. Otherwise, you can catch a glimpse of his personal style from the Audio Valve products because “You are What You Create”.
With a distant view, people will tend to associate RKV MK2 with its sister product MBL due to the black framework and golden knobs, and also connect it with another small yet refined brand: ASR, because of its acryl cover, which is as thick as 1cm. As far as the overall view is concerned, RKV MK2 impresses people with its majestic and magnificent style peculiar to German.
However, why the acryl cover? According to the study of material and sound, the acryl plate is smooth, gentle, soft and flexible with good music performance. It can also filter tiny details and noise in acoustics. Metal materials, which increase details, linearity yet with a sharp and hard tone, and the acryl plate are mutually complementary. And the proportion of mixture will indicate the ability of sound tuning of each manufacturer. Since Helmut Becker, who is famous for his particular taste, applies the design of acryl cover, it will definitely show his tuning skills.
[Text to picture one:
It is easy to associate RKV MK2 with its MBL due to the black framework and golden knobs, and also connect it with another small yet refined brand: ASR, because of its acryl cover, which is as thick as 1cm. As far as the overall appearance is concerned, RKV MK2 impresses us with its majestic and magnificent style peculiar to German. ]
OTL double single-track vacuum-tube amplification and Automatic Bias Regulation (ABR)
As to the music performance, I will talk about it later as I share my personal view about RVK MK2. What we know for sure in the least is that, the manufacturer who applies the acryl cover must be very proud of its circuits subconsciously, and don’t worry about the plagiary problems (after all the product is protected by patent rights) and tests by experts. Therefore, what is special about the circuit design of RVK MK2? Its amplification circuit applies the structure of OTL zero-output transformer and double single-track vacuum-tube differential amplification. Designed in this way, basically, vacuum tubes take the full control of the output of amplifier. In other words, Helmut Becker is very confident of the performance of vacuum tubes. What kind of tubes does RKV MK2 apply? They are PCL 805 (18GV8) of Elektronska Industrija (EI), which used to be applied as the five-stage tube on TV set. Frankly speaking, except RKV MK2, I can’t remember of any amplifier manufacturer, which has ever applied this kind of tube for amplification. With these rare tubes, Helmut Becker shows qualities and specialities, which will be testified soon later.
I’d like to remind you of its signal amplification circuit, which connects the Operation amplifier as DC server with four Ei PCL 805 tubes, and many ICs and active/passive units placed nearby for the purpose of bias regulation, which comprises the special design of bias regulation for vacuum-tube amplifiers. And this famous patent of ABR (Automatic Bias Regulation) of Audio Valve will not only integrate qualities of transistors and tubes, supply a maximum output voltage of 80V, a high voltage output of 3 W (100-400?) for each track, and the standard impedance factor as high as 3600, which is enough to drive any kinds of headphones with various impedances and voltages (the manufacturer states that the headphones can range from 32 to 2000 on its website), but also automatically adjust the output power of each tube according to its working conditions so as to minimize their effects on the performance of RKV MK2. Then, even it becomes necessary to replace tubes, replacing one tube is enough for one time and the tube matching and complete replacements are not necessary. To sum up, ABR is definitely helpful with stabilizing the performance and extending the lifespan of tubes. By the way, the former version of RKV Mark II, the so-called second version, was designed in 1982 to celebrate the 25th anniversary of the brand.
Need warming up like good wine
In the formal test, I applied the USB DAC digital current Onix DAC25A as signal source, Furutech GT2 as leads, and windows 7 + Foobar2000 + WASAPI as playing software, and the control group consists of DA&T HA-1A and Kingrex HQ-1, and as to the headphones for reference, I have tried AKG K701, Sennheiser HD800, Grado RS-1 and Denon AH-D7000, with various test results, among which AKG K701 did the best on the whole because it didn’t change the original characteristics and brand features of headphone (I think this point is of special importance to the fundamentalists of headphones), and therefore, all the following opinion comes from the arrangement of RKV Mark II with K701.
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This equipment has two sets of RCA input jacks and no pre-amp switch, which make it convenient for the users to input two signal sources. ]
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The ABR (Automatic Bias Regulation) that makes the manufacturer feel proudest is also applied, which has made use of the tube-transistor hybrid circuit to the best. ]
Within half an hour after turning on, RKV Mark II played extremely comfortable music, soft and smooth in tone, with a strong flavor special to tube amplifiers; however, something was missing in its music quality, and that was like the wine, which had not been decanted and therefore tasted a little acerb, was short of sweet aftertaste. However, after half an hour of warming up, its performance was totally different. It activated its full potentials so that the weak point of being loose and short of power at bass frequencies was fully recovered, and the bass sound became more condensed, powerful, and flexible and clearer, which continued smoothly with clear arrangements, grain and rich scales. What’s more fascinating is that the musical cadence was taken fully under control when RKV Mark II was used to drive K701, which was quite difficult to see in tube-structured amplifiers.
Who can say no to such powerful and clear bass frequency quality? It was not only K701 that could make such fascinating chemical transformations; however, when RKV Mark II was connected with HD800, which performed unsatisfactorily at bass frequencies, or other headphones, the performances at bass frequencies were all improved. The differences just lied in how better for each headphone or, with the bass frequency being improved, whether it could harmoniously join in with tweeter frequencies. Obviously, with RKV Mark II as the drive, as far as musical qualities such as tone, density, speedy and resolution were concerned, the tweeter and bass frequencies of K701 joined in more closely and smoothly; while playing human voice, the midrange frequencies could improve the resonance within the singer’s chest and the eruption as well as the sturdy linearity (fleshliness), which made the music sound stronger, vivid and dynamic. In addition to the warm treble, it also could filter noise, embellish the music, and make necessary compression to avoid Peak break, and with all these together, human voice sounded more vivid, emotional and touching.
Both improvements of depth of bass frequencies and width of sound field
Warm, strong, clear, pure, soft, comfortable, pressureless, low base noise and high resolution were the key points I constantly wrote down when I listened to different headphones such as K701 that were driven by RKV Mark II, and only when K701 was connected with it, could I put down so many advantages (certainly with the most notes). Furthermore, as we known, K701, which lacks in base sound, is a kind of headphone with strong temperament, which will be lost as most amplifiers try to power it up; if the temperament of headphone is fully taken care of, it is usually unavoidable to limit the types of music that K701 can play. Back to RKV Mark II, it will not only bestow K701 with powerful momentum, but also reserve its original refined temperament. Sorry, I shall say it becomes better.
Finally, there were improved results as RKV Mark II was connected with various headphones, and it was because it extended the depth of the sound field and at the same time strengthened impression of being surrounded by sound. Take the arrangement with K701 as example, the open-designed K701 could not create such vast found field as that of HD800 and HD650, which could be described as open and natural (especially natural). Driven by RKV Mark II, the sound field, compared with the control group, became deeper and broader with clearer resolution as well as clearer arrangement and position. What’s more surprising was that the sound image was created right before one’s eyes instead of his head, and its sound field could cross over the upper limit of “180 Degree Line of Headphones”—Joan Baez’s Diamonds and Rust in the Bullring. Listening to this album, the cheer and applause of the audience on the back were also reproduced vividly making a live impression of “as one falls, another rises”. It could be found that this amplifier did quite well in reproducing details and vividness in open space.
Among the best
To sum up, although my personal idea is that the arrangement of RKV Mark II with K701 is the best, I believe that it is highly possible for fans of other headphones to love this vacuum-tube amplifier. After all, warm and mellow tone, strong linearity, rich flavor of analogy, touching impression, and excellent music quality are advantages many amplifiers can never have. As far as the acoustic quality is concerned, the vacuum-tube structure of RKV Mark II is almost immune to the influence of impedance of different headphones. With high voltage output, it can easily drive any headphones and reproduce the record’s dynamics. Furthermore, the performance of RKV Mark II in clarity, speed and resolution are among the top rank in the vacuum-tube amplifier spectrum. Its performances when arranged with various headphones are beyond the standard with the difference being: whether the headphone itself can withstand such powerful drive. Therefore, although I am not sure whether the fundamentalists of headphones will like the sound qualities of RKV Mark II, I am sure that RKV mark II is among the best amplifiers that I’ve listened to! (Dean Lin Audio Company Ltd.: 03-2127378)
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A patent right has been obtained for the special vacuum amplification circuit designed by Helmut Becker for RKV MK2. ]
Figure 1 is the FFT frequency spectrum graph of this equipment with 1 KHz sine wave signal, a load of 200? and an output of 10mW and it is clear that the second-harmonic generation is about 100pW, and the 60Hz harmonic is also 100pW with a THD+N reading as 0.015%; Figure 2 is the FFT frequency spectrum graph of this equipment with 1 KHz signal, a load of 200? and an output of 100mW and it is clear that the second-harmonic generation is about 100nW with a THD+N reading as 0.015%; Figure 3 is the frequency response of 1mW, 10mW, 100mW and 1W, and it’s clear that the high frequency can extend to 80 KHz (-3dB). Figure 4 is the coordinate graph of output to distortion, and it is clear that the signal harmonic begins to increase with an output above 50mW and the maximum power without cutting wave shape is 4.4W. (Guan Peiqing)