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:::   ultra high end dynamic headphone OTL tube amplifier   :::
 you'll have to look far before you find one better ....

  :: Audio Valve is celebrating the 26h anniversary of the RKV since 1984 ::

 

Eric - a member of HEAD-FI.COM

About AudioValve RKV mark2, what I can say is that it is a great amplifier that works very well with a very good synergy with electrodynamics Sennheiser HD -600 and HD -800.

It can also be used with Stax headphone (SR- 009) through a Wee box (WooAudio Wee energizer) and Jack Adapter --> Input the Wee HP with using multipliers transformers tension Wee (Ratio: 1:50): very good results, at least as good, see better (in a blind test) compared to the amplifier Stax SRM 727 (best amp Stax currently producing approximately 3 K Euros) and even that amplifier Eddie Current Electra (one 4K dollars amplifier).

You can get an even better sound by shunting the Wee transformers (which retained only for use for the bias voltage generator 580 Volt) for the fifth pin Stax headphone: advantage: its the best ever sound obtained with a Stax SR-009 (best that with the SRM 727 and Electra amp) (sound more transparent, natural and more presence); disadvantage: limited level of between 70 to100 dB (SPL) with listening with headphones Stax SR -009 with sensitivity at 101 dB / 100 Volts RMS, knowing that the mk2 RKV can get 80 volts RMS for an input of 2.8 volts RMS signal with a very high impedance headphones (145,000 Ohms for the Stax SR- 009).The amplifier will work mainly in voltage, where he excels.

My last posts :

http://www.head-fi.org/t/681814/amplifiers-shootout-for-stax-009-eddie-current-electra-audiovalve-rkv-wooaudio-wee-stax-srm727-srm007t2/30#post_9988050

http://www.head-fi.org/t/690015/new-audiovalve-rkv-mark-3#post_9988031

http://www.head-fi.org/t/569024/question-about-amps-for-the-stax-sr-009/525#post_9981082

 

 

 

Das bislang älteste Proukt aus dem Angebot von AudioValve ist der 1982 entwickelte RKV. Mit nur kleinen Änderungen versehen, wird dieser Verstärker inzwischen seit annähernd 30 Jahren kontinuierlich  verkauft und zählt mit zu den erfolgreichsten Produkten der AudioValve Verstärker - Reihen. Traditionelle Röhrentechnik wurde hier komplett über Bord geworfen und mit völlig unortodoxen Lösungswegen ein Konzept geschaffen, was bislang im Verstärkerbau einmalig geblieben ist.


Auch auf modernste Halbleitertechnik wurde nicht verzichtet und so entstand ein Produkt, in welchem sich zwei Generationen Elektronik in einer Symbiose vereint , widerspiegeln. Das dt. Patentamt hat diese Idee 1984 unter der Nummer DE 3200 51 geschützt.

Warum so könnte der Leser fragen - Kopfhörer verstärker ? Genügt da nicht mein Ausgang am Reseiver ? Die Antwort lautet ganz - Nein. Gute dyn. Hörer benötigen für hohe Dynamiksprünge - wie sie z.B. von CD Playern kommen - aufgrung ihrer hohen Impedanz Spannungspegel, die weitaus höher sind als die Versorgungsspannung vieler Transistorverstärkern. Dies gilt auch für HI-FI Anlagen. Hohe Pegel zu bringen war also eine Bedingung die der Verstärker erfüllen musste. Darüber hinaus galt es Kurzschlußfestigkeit, hohe
Dämpfung und ausgezeichnete techn. und musikalische Daten zu erzielen, unter Berücksichtigung Röhrenklanges. Alle diese Eigenschaften besitzt das vorliegende Konzept Im RKV von AudioValve. Wegen der Anpassung an hohe Abschlußimpedanzen bot sich das Konzept das OTL Prinzip`s als Basisknzept an. Mit Hilfe eines Op-Amp pro Kanal konnte ein Servokreis geschaffen werden, der
alle neg. Eigenschaften der Röhren ausregelt, wie da wären Fertigungstoleranzen, Alterung etc. Die im RKV befindliche Elektronik kann dies mit Bravour. Das geht sogar soweit, das der Arbeitspunkt unabhangig von Röhrenalterung autom. stabilisiert wird, sodas auch
alte Röhren gut den Dienst weiter versehen.

Zusammenfassend kann gesagt werden, daß durch diesen autom. Regelkreis selbst bei Verschleiß der Teile, keine Qualitatseinbuße in der Musikalität in Kauf genommen werden muß. In der Beurteilung des Klanges ist besonders die hohe Dynamik, verbunden mit einer sehr hoher
Dämpfung, des Verstärkers hervorzuheben und der für
Röhrenverstärker charakteristische Klang. Die Basse kommen straff und gewaltig, die Mitten sind luftig und von einer sehr seidigen lebendigen Durchsichtigkeit, und im Hochtonbereich zeichnet eine sehr gute Auflösung verbunden mit transparenter Räumlichkeit. Kostspielige Kopfhörer wie die z.B. von GRADO oder AKG verlangen
nach Leistung, und da ist der RKV nun mal bekannter Maßen die beste etablierte Wahl.

Diese Eigenschaften besitzt der Verstärker natürlich auch bei seiner Verwendung als Vorverstärker für Endstufen, sofern dies gewünscht wird. In diesem Fall wird dieAusgangsspannung des RKV reduziert und auf ein weiters Paar Cinchbuchsen der Geräterückseite gelegt. Das war nun schon der zweite Einsatzfall dieses Verstärkers. Aber damit nicht genug - es gibt noch einen dritten Fall. Die Leistung des Verstärkers von fast 2 * 3 Watt ist auch geeignet um Lautsprecher mit hohem Wirkungsgrad zu treiben. Dazu bedienen wir uns des sog. "IMPEDANCERS", der die Ausgangsipedanz des RKV auf die der Größe von Lautsprecher Impedanzen reduziert.

Im Grunde also hochwertige Übertrager, welche die Ausgangsspannung untersetzten. Mit Lautsprechern ab 93 dB ist damit richtig Musik zu machen. Der RKV als Universalgenie in diesen drei Bereichen der High End Wiedergabe findet kaum einen Konkurenten, der bei diesem Preis auch nur annähernd dem RKV das Wasser reichen könnte. Für all diejenigen, die auch nur zwei der genannten Möglichkeiten für sich in Betracht ziehen, ist der RKV die einzig richtige Entscheidung, dass können Sie auch überall im Internet nachlesen.

Tube amplifier for dynamic headphones – preamplifier and power amplifier at the same time

 Up to now the RKV (tube amplifier for dynamic headphones), developped and admitted to our distribution in 1982, is by far the most successful tube amplifier in our product range.

 Traditional Tube technology has been abandoned and replaced by completely unorthodox approaches to create a concept which is still unique in the amplifier fabrication. Also it has not been resigned latest semi-conductor technology and so a product occurred which reflects 40 years of electronics. The German patent office has secured this idea 1984 with the number DE 3200 51.

 “Why headphone amplifiers” – so the Reader might ask. “Doesn’t my output at the receiver suffice?” The answer is simply No. Good, dynamic headphones have a high impedance. For high dynamic jumps, e.g. from CD-Players, they require much higher voltage levels than the supply voltage of transistor amplifiers, which would otherwise be a possibility. The same applies to Hi-Fi systems. So it was one requirement for the amplifier to bring high levels. Moreover it was important to achieve short-circuit strenght and excellent technical data, under the special note of tube sound. The existing concept possesses all this qualities.

 By reason of the conformation to high terminating impedances the OTL principle has been appropriated. This concept is geared now to the classic example of the so-called transformerless power amplifier. With the help of semi-conductor technology it has proved to be a felicitous symbiosis of the last 40 years electro-physics.

 Also all negative existing aspects of the tubes, like weathering and tolerance hum, had to be eliminated. The RKV-electronic manages this problems effortless. An Op-Amp in the signal path creates a servo circle that compensates all above mentioned negative characteristics of the tubes.

It is even able to stabilize the operating point automatically, regardless the weathering of the tube, so that even older tubes continue working without problems. This automatic control circuit has no influence on the quality of the sound, even at the abrasion of the parts.

 When judging the sound especially the high dynamic of the amplifier and the typical tube sound are to mention.The bass is tight and enormous, the middles are aery and from a liveley transparency and the high range shows an excellent release combined with transparent space.

 Other products on the market, which want to force their headphones to diabolic peaks by the use of smaller battery voltages or 40mWatt output power, just fail here. Cost-intensive headphones, for example by GRADO or AKG, require effort and just there the RKV is the only reasonable driver source.

 Of course the amplifer comes with all this qualities as well in his function as a pre-amplifer for power amplifiers. In this case the output voltage of the RKV is decreased to his 15th part and laid on another pair of Cinch Sockets on the backside of the amplifier.

 But there is even a third way of using the RKV. The performance of nearly 2*3 Watt is also adequate for driving loudspeakers. Therefore we use the so-called “Impedancer”, that reduces the output impedance of the RKV to the size of the loudspeakers impdedance. Basically high-class transmitters which scale down the output voltage. With loudspeakers starting from 93 dB you can receive an excellent musical result.

 The RKV as an universal genius in this three category groups of Hi-Fi technology has no competitor that is nearly able to hold a candle to him in this prize class. For all the people who only consider two of this mentioned possibilities for their own use the RKV is already the only right decision.

 

 

Le RKV, développée à 1982, est notre produit aînée. Avec simplement petites changements ce amplificateur est vendé continue depuis 30 ans. Il est un de notre produits célèbres. On a pas utiliser la technique tube traditionnel mais créer un concept avec des solutions non orthodoxe qui est individuel dans le marché des amplificateurs.

 

On a aussi pas abandonné le technique semi-conducteur moderne et composé un produit, qui combine deux generations d` électronique. Le bureau des brevets a protéger cet idée à 1984 avec le numéro DE 3200 51.

 

Pourquoi un amplificateur pour des casques d`étoutes? Est-ce que mon sortie de receveur ne suffis pas? La réponse est simplement Non! Des casques d`é coute bons et dynamiques ont un impédance hautement. Pour des sauts dynamiques hautes (par exemple de platine lasers) ils ont besoin de niveaus audiofréquences qui sont largement plus haute que le voltage d`alimentation de beaucoup des amplificateurs à transistors. C`est vrai aussi pour des installations hi-fi. C`était un condition pour l`amplificateur de donner des niveaus haute. En plus c`était important de totaliser tenue aux courts-circuits, haute amortissement et des dates techniques et musicale excellentes considérant la technique tube. Le concept d` AudioValve RKV a tous ces propriétés. En vertu de l`ajustement à des impédances finales hautes le principe OTL était assorti comme concept base. Avec l`aide d`un OP-Amp pour tous canal on a crée un rond servo qui élimine tous aspects négative des tubes (comme le tolérance des fabrication et viellissement). L`électronique dans le RKV peux ca sans problèmes. Il peux même stabiliser le point de fonctionnement automatique, indépendant de viellissement des tubes. Comme ca, aussi des tubes âgés peux continuer faire leur service.

 

On peux dire, que cet système asservi automatique n`accède pas à une perte de qualité ou musicalité, même au abrasion des partie du corps. Quand juger le timbre on faut particulièrement accentuer le dynamique haute, le bien amortissement et le son caractéristique d`amplificateurs tubes. Les basses arrivent tirés et ènormes, les milieus sont aérés et avec une transparence soyeuse et vivante. Le fréquence des tons hautes caractérise une bien dissolution combiner à un spatialité transparente. Des casques d`ècoutes coûteux (comme cet de GRADO ou AKG) dèsir d`alimentation et pour ca le RKV est comme on sait le choix meilleur.

 

Cet propriétés l`amplificateur à bien sûr aussi quand on l`emploi comme préamplificateur pour des dernier étages quand on veux. Dans cet cas le tension de sortie deviens réduit et metter dans un autre couple de Cinch-douilles au dèrriere de l`amplilficateur. Ca c`était déjà le deuxième fonction du RKV. Mais il y a une ultérieure possibilité de l`employer. La performance de presque 2 * 3 Watt est aussi approprié pour soutenir des haut-parleurs avec une haute efficacité. Pour ca nous utilisons le soi-disant «Impedancer» qui reduit le tension de sortie dans des impedances du haut-parleurs.

 

En fait des translateurs de grande qualité, qui démultiplier le tension de sortie. Avec des haut-parleurs depuis 93dB on peux bien faire de la musique avec ca. Le RKV est un génie universel dans cet trois domaines du High End-rendu qui a peu de concurrents dans cet classe de prix et cette qualité. Pour toutes cet personnes qui peux seulement imaginer deux de cettes possibilités le RKV est seulement le bonne choix.

 

 

 

go to read new magazine test:

TAIWAN 2010-dec/1
TAIWAN
2010-dec/2
TAIWAN
2010-dec/3

 

tech. describtion:

  • OTL - transformer outless tube amplifier
  • double mono construction
  • Alps volume control
  • 1 pair 6,3 mm stereo jacket for headphones
  • tubes: 4 * PCL 805 (PCL 85 or 18 GV 8 - german old TV "vertikal" ampl. tube )
  • power output: each channel 3 watt SINUS,  ( between 100 to 400 ohm loads )  
  • bandwide: 15 - 100 000 hz
  • damping 3600 !
  • distortion 0,002 % at 1 Watt-200 Ohm load
  • max. output voltage 80V
  • sens. 0dBm
  • IC - full autom. - controlled bias
  • class - a
  • power consumption min. 60 watt
  • size 360*200*120 mm (d.w.h.)
  • weight 6kg
  • patent full automatic servo tube biasing

Impedancer unit

  • 4 different loads switchable
  • 1 pair speaker terminals
  • 1 pair 6,3 headphone jackets
  •  

 

 

actual international test reviews:

 

A ROYAL TREAT FOR YOUR EARS
AudioValve
RKV Mark II


1) Special patented circuitry, OTL amplifier, stable and long lifetime vacuum tube. 2) Opulent sound carrying the luster of nobility with broad sound field. 3) Base frequency with detailed characteristics and controllability, a demonstration of high performance. 4) Strong drive to present a realistic earphone power.

SUGGESTIONS


1) For earphones with impedance lower than 100 Ohms, use the matching impedance provided by the original manufacturer. 2) For best sound effects, use high quality earphones. 3) This earphone amplifier brings out the most beautiful and comfortable sound without distortion. So please properly adjust the volume control to avoid too loud a volume that may damage your listening pleasure.

On the RKV back panel, there are two sets of RCA terminals. Why two sets? This is because these two terminal sets are connected in parallel. When one terminal is used as the input, the other terminal can then be used for recording output or connected to the front amplifier. The panel has two earphone inlets. The manufacturer recommends that simultaneous use of two low impedance earphones is to be avoided.

I have always had some doubts about the earphone amplifier: 20 years ago, there was no such thing as an earphone amplifier. Nor in a recording room I saw the sound man use such a device. Is it really necessary to buy an earphone amplifier and discard the traditional earphone equipment? AudioValve does think the earphone amplifier necessary or it would never be put into production. The modern audio signal source such as CD has wide dynamic range which is in fact the voltage range that drives the earphone. Earphone output from an ordinary amplifier cannot handle the wide range of voltage variation and hence fail to respond or give good performance.

USE OF SPECIAL TUBES

Targeting at the earphone amplifier, the AudioValve originator Helmut Becker set out his research. What would be the optimum voltage amplifier element? It is without doubt that the vacuum tube is the ultimate candidate. What is the limitation of a vacuum tube? We need to output sufficient current for a low resistance earphone. The first generation RKV was born in 1984. Then, the special PCL 805 pentode for TV use was employed.
Next, the RKV Mark II adopted the OTL full vacuum tube differential amplifier circuit without output transformer. For this special purpose, AudioValve filed the patent rights of the circuitry (No. DE 3200 517). Helmut Becker considers this as a breakthrough of the 40 year progress in audio technology. Using the Op Amp for power supply coupled with complete vacuum tube amplifier for the signal path provides optimal combination of the vacuum tube and transistor technology. The circuitry uses the DC servo Op Amp network for power supply which automatically adapts to the routing conditions. The manufacturer claims that this circuitry will function normally throughout the lifetime of the vacuum tubes.

A BASE FREQUENCY WITH EVERY DETAIL AND CONTROLLABILITY

We used to give advices on the earphone. Nonetheless, an earphone can never produce a heart-rending base energy like a large speaker. Testing an RKV Mark II on Sennheiser HD-580 (300 Ohm resistance) which I have used for years, I can feel the base frequency copiously reborn with every characteristic detail and controllability. The feeling becomes very close to the effect of a large speaker. Comparing to my Graham Slee Voyager, a portable earphone amplifier, I can instantly discern the superiority of RKV Mark II as I can feel a better listening. Where does this better listening come from? More characteristic details? I quickly switch between the two earphone amplifiers. I find not much difference in the characteristic details. But after long listening, I start to pick up the merit of RKV Mark II as its sound is broader, fuller, and more stable. There is the characteristic of thickness and relaxation that makes you feel very comfortable without any pressure. Also, the sound from the RKV Mark II possesses some warmth and luster of gold, yet without any antique tube noise. It is the warmth as well as the luster that brings out the quality of the string instrument. It provides more elasticity to the guitar sound.

VERY STRONG DRIVE POWER

If using Beyerdynamic DT 990 Pro (250 Ohms), the difference becomes more pronounced. For Graham Slee Voyager, the volume must be turned to the 9 o’clock position to have more amplification gain and yet the sound drive is still not full enough. If changed to RKV Mark II, the sound becomes fully open and the dynamic state and stability are of first class. This brings out the real value of the flagship earphone device. As to the two low resistance earphones of AKG K240 Studio (55 Ohms) and Grado SR60 (32 Ohms), the performance can perfectly meet the standard requirement. But in reference to the earphone amplifier, the difference is not so obvious. To match the AudioValve with low resistance earphone (under 100 Ohms), we recommend the use of impedance matching device with a panel switchable between 8~64 Ohms in four divisions. The panel also should be provided with a speaker output terminal so that it can drive high sensitivity speakers.
  Indeed the RKV Mark II is quite expensive. However, according to my experience, a good earphone device can last for a long time and will never be outdated. Therefore, it is definitely a worthwhile and necessary investment. The RKV Mark II is absolutely the top choice of all the earphone devices. I believe that an audio fan should value their ear highly. Using the RKV Mark II is a royal class enjoyment.

 

Un plaisir royal pour vos oreilles

AudioValve

RKV Mark II

 

FOYER

1) Connexion breveté speciale, amplificateur OTL, le tube de vide stable et de longue vie. 2) Le son opulent portant le brio de noblesse avec un Sound field large. 3) La fréquence de base, des caractéristiques détaillées et la contrôlabilité, une démonstration de haute performance. 4) Une forte poussée pour présenter une performance d`écouteurs réaliste.

 

SUGGESTIONS

1) Pour écouteurs avec une impédance inférieure à 100 ohms, utilisez l'adaptation d'impédance fournie par le fabricant original. 2) Pour obtenir les meilleurs effets sonores, utiliser des écouteurs de haute qualité. 3) Cet amplificateur casque fait ressortir le son le plus beau et confortable, sans distorsion. Alors s'il vous plaît régler correctement la commande de volume pour éviter un volume trop fort qui peut endommager votre plaisir d'écoute.

 

Sur le panneau arrière du RKV, il ya deux couples de terminals RCA. Pour quoi deux couples? Parce que cet deux terminals sont connectés en parallèle. Quand un terminal est utilisé comme l'entrée, l'autre peut ensuite être utilisé pour l'enregistrement de sortie ou connecté à l'amplificateur avant. Le panneau a deux entrées écouteurs. The manufacturer recommends that simultaneous use of two low impedance earphones is to be avoided. Le fabricant recommande que l'utilisation simultanée de deux écouteurs à basse impédance doit être évitée.  

 

J'ai toujours eu des doutes sur l'amplificateur casque: Il ya 20 ans, il n'y avait pas une telle chose comme les écouteurs amplificateur. Ni dans une salle d'enregistrement, j'ai vu l`assistant de son que vous utiliser un tel dispositif. Est-il vraiment nécessaire d'acheter un ampli casque et jeter le matériel écouteurs traditionnels? AudioValve croire aux nécessaire d`amplificateur casque ou il ne lui serait jamais mise en production. La source de signal audio modernes comme le CD possède une large plage dynamique qui est en fait la gamme de tension qui anime l'écouteur. Sortie casque d'un amplificateur ordinaire ne peut pas traiter le large éventail de variation de tension et, partant, ne répondent pas ou donner de bonnes performances.

 
 

UTILISATION DES TUBES SPECIALE

L'amplificateur casque avoir pour but, l`origine d`AudioValve, Mr. Helmut Becker, a commencé sa recherche. Quel serait l'élément amplificateur de tension optimale? Il est sans doute que le tube à vide est le candidat final. Quelle est la limite d'un tube à vide? Nous avons besoin de courant de sortie suffisante pour un casque à faible résistance. La première génération RKV est né en 1984. Ensuite, la spéciale PCL 805 pentode pour utiliser la télévision a été employé.

Ensuite, le RKV Mark II a adopté l'ensemble du tube à vide OTL amplificateur différentiel circuit sans transformateur de sortie. Pour cette destination particulière, AudioValve à déposé les droits de brevet du circuit (n ° 3200 DE 517). Helmut Becker considérez cela comme une percée de l'état d'avancement 40 années dans la technologie audio. Utilisation de l`amplificateur OP pour l'alimentation couplé avec un amplificateur à tube à vide complet pour le trajet du signal offre une combinaison optimale du tube à vide et de la technologie des transistors. Le circuit utilise l`amp DC servo OP réseau pour l'alimentation s'adapte automatiquement aux conditions qui routage. Le fabricant affirme que ce circuit va fonctionner normalement pendant toute la durée des tubes à vide.

 

UNE FRÉQUENCE BASE DE TOUS DETAILS ET LA CONTRÔLABILITÉ   Nous avons utilisé pour donner des conseils sur l'écouteur. Néanmoins, un écouteur ne peut jamais produire une base de l'énergie déchirante comme un grand haut-parleur. Quand testé un RKV Mark II sur Sennheiser HD-580 (300 ohms de résistance) que j'ai utilisé pendant des années, je peux sentir la fréquence de base caractéristique copieusement renaît avec chaque détail et la contrôlabilité. Le sentiment devient très proche de l'effet d'un grand haut-parleur. En comparant à mon Graham Slee Voyager, un amplificateur de casque portable, je peux instantanément discerner la supériorité de RKV Mark II que je peux sentir une meilleure écoute. D'où cela vient d'une meilleure écoute? Plus de détails caractéristique? Je basculer rapidement entre les deux amplificateurs écouteurs. Je ne trouve pas beaucoup de différence dans les détails caractéristiques. Mais après longtemps d'écoute, je commence à chercher le mérite de RKV Mark II que le son est plus large, plus entière et plus stable. Il est la caractéristique de l'épaisseur et de détente qui vous fait vous sentir très à l'aise, sans aucune pression. Ainsi, le son du RKV Mark II possède un peu de chaleur et brio de l'or, mais sans aucun bruit tube antique. C'est la chaleur ainsi que le brio qui met en valeur la qualité de l'instrument à cordes. Il offre plus d'élasticité au son de guitare.

 

TRÈS FORTE PUISSANCE DE COMMANDE  
 

Si vous utilisez Beyerdynamic DT 990 Pro (250 Ohms), la différence devient plus prononcée. Pour Graham Slee Voyager, le volume doit être tourné sur la position 9 heures pour avoir  le plus augmentation d'amplification et pourtant le lecteur son n'est toujours pas assez pleine. En cas de modification de RKV Mark II, le son devient entièrement ouverte et l'état dynamique et la stabilité sont de première classe. Cela porte la valeur réelle de l'appareil phare de l'écouteur. Quant aux deux écouteurs à la résistance bas AKG K240 Studio (55 ohms) et Grado SR60 (32 Ohms), les performances peuvent parfaitement répondre à l'exigence standard. Mais en référence à l'amplificateur de casque, la différence n`est pas si évident. Pour faire correspondre l`AudioValve aux écouteurs avec une faible résistance (moins de 100 ohms), nous recommandons l'utilisation du dispositif d'adaptation d'impédance avec un panneau commutable entre 8 ~ 64 Ohms en quatre divisions. Le panneau devrait donc être muni d'une terminale de sortie haut-parleur afin qu'il puisse piloter les parleurs à haute sensibilité.

En effet, le RKV Mark II est assez cher. Cependant, d'après mon expérience, un dispositif écouteur bon peut durer longtemps et ne sera jamais dépassée. Par conséquent, il est un investissement utile et nécessaire. Le RKV Mark II est absolument le meilleur choix de tous les dispositifs écouteur. Je crois que d'un adhérent d`audio devrait valeur son oreille hautement. Utilisation de la RKV Mark II est un plaisir classe royale.

 

                                                VERSION - 2014


  new development in 2014  

As of spring 2014 AudioValve a Step up Transformer for Electrostatic headphones (Stax - etc.) include in the setlist. The name of this model is EST. It can be powered from 8 ohm amplifiers, but particularly also from the OTL output of the RKV 2 + 3 (100 VAC). The device provides both the required for the operation of the headphone-static voltage of 580 VDC, and up to 550 Vrms signal voltage. The bandwidth achieved while annähnerd 100 Khz. The following diagram is a triangle - and also rectangular voltage on the oscilloscope at 10 Khz shown with 470pF load. On the sides of the triangular voltage can be seen particularly well, which is the reproduction free of all non-linearities. The price for the EST is identical to that of the Impedancers. It has also the same dimensions.


 

A ROYAL TREAT FOR YOUR EARS

AudioValveRKV Mark II , The Earphone Amplifier

Patented circuitry, full vacuum tube OTL differential amplifier, 6.3mm stereo earphone inlet2, vacuum tube PCL8054, output power per channel 3W, bandwidth 15~100KHz, damping factor 3600, distortion 0.002%, maximum output voltage 80V, size 360200120mm, weight 10kg. Imported by Dean Lih Audio Company Ltd. (03-2127378).

FOCUS

1) Special patented circuitry, OTL amplifier, stable and long lifetime vacuum tube. 2) Opulent sound carrying the luster of nobility with broad sound field. 3) Base frequency with detailed characteristics and controllability, a demonstration of high performance. 4) Strong drive to present a realistic earphone power.

SUGGESTIONS

1) For earphones with impedance lower than 100 Ohms, use the matching impedance provided by the original manufacturer. 2) For best sound effects, use high quality earphones. 3) This earphone amplifier brings out the most beautiful and comfortable sound without distortion. So please properly adjust the volume control to avoid too loud a volume that may damage your listening pleasure.

 

On the RKV back panel, there are two sets of RCA terminals. Why two sets? This is because these two terminal sets are connected in parallel. When one terminal is used as the input, the other terminal can then be used for recording output or connected to the front amplifier. The panel has two earphone inlets. The manufacturer recommends that simultaneous use of two low impedance earphones is to be avoided.

I have always had some doubts about the earphone amplifier: 20 years ago, there was no such thing as an earphone amplifier. Nor in a recording room I saw the sound man use such a device. Is it really necessary to buy an earphone amplifier and discard the traditional earphone equipment? AudioValve does think the earphone amplifier necessary or it would never be put into production. The modern audio signal source such as CD has wide dynamic range which is in fact the voltage range that drives the earphone. Earphone output from an ordinary amplifier cannot handle the wide range of voltage variation and hence fail to respond or give good performance.

USE OF SPECIAL TUBES

  Targeting at the earphone amplifier, the AudioValve originator Helmut Becker set out his research. What would be the optimum voltage amplifier element? It is without doubt that the vacuum tube is the ultimate candidate. What is the limitation of a vacuum tube? We need to output sufficient current for a low resistance earphone. The first generation RKV was born in 1984. Then, the special PCL 805 pentode for TV use was employed.

  Next, the RKV Mark II adopted the OTL full vacuum tube differential amplifier circuit without output transformer. For this special purpose, AudioValve filed the patent rights of the circuitry (No. DE 3200 517). Helmut Becker considers this as a breakthrough of the 40 year progress in audio technology. Using the Op Amp for power supply coupled with complete vacuum tube amplifier for the signal path provides optimal combination of the vacuum tube and transistor technology. The circuitry uses the DC servo Op Amp network for power supply which automatically adapts to the routing conditions. The manufacturer claims that this circuitry will function normally throughout the lifetime of the vacuum tubes.

A BASE FREQUENCY WITH EVERY DETAIL AND CONTROLLABILITY

  We used to give advices on the earphone. Nonetheless, an earphone can never produce a heart-rending base energy like a large speaker. Testing an RKV Mark II on Sennheiser HD-580 (300 Ohm resistance) which I have used for years, I can feel the base frequency copiously reborn with every characteristic detail and controllability. The feeling becomes very close to the effect of a large speaker. Comparing to my Graham Slee Voyager, a portable earphone amplifier, I can instantly discern the superiority of RKV Mark II as I can feel a better listening. Where does this better listening come from? More characteristic details? I quickly switch between the two earphone amplifiers. I find not much difference in the characteristic details. But after long listening, I start to pick up the merit of RKV Mark II as its sound is broader, fuller, and more stable. There is the characteristic of thickness and relaxation that makes you feel very comfortable without any pressure. Also, the sound from the RKV Mark II possesses some warmth and luster of gold, yet without any antique tube noise. It is the warmth as well as the luster that brings out the quality of the string instrument. It provides more elasticity to the guitar sound.

VERY STRONG DRIVE POWER

  If using Beyerdynamic DT 990 Pro (250 Ohms), the difference becomes more pronounced. For Graham Slee Voyager, the volume must be turned to the 9 o’clock position to have more amplification gain and yet the sound drive is still not full enough. If changed to RKV Mark II, the sound becomes fully open and the dynamic state and stability are of first class. This brings out the real value of the flagship earphone device. As to the two low resistance earphones of AKG K240 Studio (55 Ohms) and Grado SR60 (32 Ohms), the performance can perfectly meet the standard requirement. But in reference to the earphone amplifier, the difference is not so obvious. To match the AudioValve with low resistance earphone (under 100 Ohms), we recommend the use of impedance matching device with a panel switchable between 8~64 Ohms in four divisions. The panel also should be provided with a speaker output terminal so that it can drive high sensitivity speakers.

  Indeed the RKV Mark II is quite expensive. However, according to my experience, a good earphone device can last for a long time and will never be outdated. Therefore, it is definitely a worthwhile and necessary investment. The RKV Mark II is absolutely the top choice of all the earphone devices. I believe that an audio fan should value their ear highly. Using the RKV Mark II is a royal class enjoyment.

 

 


 

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.

[Text to picture

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. ]

[Text to picture

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. ]

Test results

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)

 

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