Download A ROYAL TREAT FOR YOUR EARS AudioValveRKV Mark II , The

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. (032127378).
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.
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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)
[Text to picture
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)