a unique story that started here – at STEREOPLAY 1982:
For the hearing test, the Dynamp was plugged into the “Line” output of the Onkyo P-3090 reference preamplifier. Beyer’s dynamic DT 880 Studio (test stereoplay 5/1982), which the testers operated on the Onkyo and Dynamp, served as headphones. Only a few listening cycles with different music programs were necessary to determine that there were serious differences: the audio valve reproduced everything that was in the grooves through headphones, cleanly and naturally, and with impeccable and full power it brought dynamic passages or worn areas. Solo voices like complex orchestras came out brilliantly on the headphones without any discolouration Gerald 0. Dick, Stereoplay 9/1982
::: 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 1982 ::
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.
The following photo shows you a screenshot from the oscilloscope from a channel on RKV 2 – Model 2016 6F5P with attached Verto and 8 ohm load at the output. You see, this clearly represents the new model series more power at the output at your disposal, as the past has been the case. The re-sizing of some components and small circuit corrections deliver today on RKV 2 in OTL mode at the beginning of Soft Clipping per channel 8 watts.The following photo shows you a screenshot from the oscilloscope from a channel on RKV 2 – Model 2016 6F5P with attached Verto at the output of the STAX socket. Due to the increased power of the RKV 2 the yield of STAX signal now arises voltage is at Verto following measures.
A ROYAL TREAT FOR YOUR EARS
RKV Mark II1) 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.
The picture below shows you the max. Output voltage before start soft clipping in OTL mode at 220 Ohm load per channel – at 43 Vrms are on each channel 8,3 watts
The following photo shows you a screenshot from the oscilloscope from a channel on RKV 2 – Model 2016 6F5P with attached Verto and 8 ohm load at the output. You see, this clearly represents the new model series more power at the output at your disposal, as the past has been the case.
The following photo shows you a screenshot from the oscilloscope from a channel on RKV 2 – Model 2016 6F5P with attached Verto at the output of the STAX socket. Due to the increased power of the RKV 2 the yield of STAX signal now arises voltage is at Verto following measures. Its round about 1500 AVCpp
nearly 600 VAC for STAX headphones ( 1500 VAC pp ) – same what deliver LUMIARE or SOLARIS …