行云流水的顺畅感－Audio Valve Challenger 250后级扩大机
先前已经听过好几次Audio Valve扩大机，包括Assistent 30综合扩大机与Solaris耳机扩大机，这两台我都写了器材评论，另外还有一次是去婕韵音响试听Robert Koda K-10前级时，搭配了Audio Valve Baldur 300单声道后级，再加上这次写Challenger 250单声道后级评论，一共四次，每次听完都加深一次我对Audio Valve的好印象：这绝对是个值得关注的好品牌，虽然目前能见度相对来说还不高，但可别因此忽略它的好！
Audio Valve的Challenger系列有3种机型，却可提供5种甚至更多的功率选择，从145瓦、160瓦、180瓦、300瓦，到最高的450瓦都有。为什么？因为Challenger系列均使用Audio Valve自家的ABR（Automatic Bias Regulation）自动偏压调整电路，会自动侦测功率管的种类与工作状态，自动调整栅级偏压，因此可换用同系的不同束射5极管。例如Challenger 115、Challenger 150与Challenger 180的机型架构相同，用的功率管不同，分别是EL34、6550与KT120，输出功率就有145瓦、160瓦、180瓦三种。Challenger 250出厂时便搭载6支KT120，输出功率达300瓦。Challenger 400配备12支KT120，功率更达到450瓦，峰值输出650瓦，十分惊人。Challenger 250与Challenger 400也都可以直接换用诸如EL34、6550或KT90管，管子不同，功率便不同，音色也各异，对于爱玩管的发烧友而言是莫大的方便。
更方便的是，ABR会根据每支真空管的状况各自提供适合的偏压，因此新旧程度不同的管子一起插上去也没问题，只要管子是正常的，Challenger 250便可正常工作，而且还唱得很好。要是其中有某支真空管不能正常工作了，那支管子旁边的LED灯便会亮起，告诉你这支管子该换了，是不是很方便呢？我觉得ABR这功能最大的好处不只是方便，还有省钱。试想，6支1套配对好的KT120要多少钱，如果坏了一支就要整套一起换，岂不是很伤。但Audio Valve扩大机只要换一支管就好，其他的继续留下来工作，实在省很大！
Challenger 250和Audio Valve其他后级有一个很大的不同，其他后级都是塔型机体，也就是瘦高型身材，只有Challenger 250是宽矮身型的，为什么？据Audio Valve表示，这是因应消费者的需求而做出的设计。Challenger 250的机身比例和一般扩大机相同，因此能放入大多数的音响架，不用担心层架高度的问题。这时你心中可能就有一个问题了：管机的散热很重要，Challenger 250的高度仅20公分，虽然能放入音响架，但如果上层靠得很近，这样散热好吗？我觉得问题不大。Challenger 250左、右各有一具散热风扇，位置刚好就是信号管与功率管阵列的两侧，风扇运转时一进一出，让内部的热快速由侧面散逸，机身上方的热度就不会太高，因此摆放时只要上方留有适当空间即可。不用担心这二具风扇会对声音造成影响，试听过程中，除了眼睛看到在转，其他时候都不曾感觉到有风扇，安静的很！也不必过虑风扇震动是否会劣化声音，因为你的音响系统中该担忧、注意的环节多着，风扇在担忧列表上还排在很后面。
Challenger 250面板上有二个开关，右边是电源，左边是待机，Audio Valve有建议的开机顺序。在关机状态下，两个开关都应该是关闭的。开机时，先开右边的电源开关，此时灯丝与低压先送电，因此真空管会缓缓亮起，面板logo位置亮红灯。约莫一分钟后，再开左边的待机开关，此时高压才会送电，然后完成开机，logo位置则变成蓝灯。关机时顺序相反，先关左边，再关右边。
Challenger 250面板中央还设有一个小小的表头，可显示当下的输出状态。或许你会问，这么小的表头，指针那么小，从老远怎看得到指针在跳动，这设计是否太过理想化？没错，从远处的确不容易看到指针跳动，但这表头除了指针，其实还会发出温暖的黄光，而且亮度会随着输出不断变化，指示的效果绝不输给指针。低输出时，表头只亮着黯淡甚至快熄灭的微弱灯光；高输出时，灯光立即亮起，显示Challenger 250正凶猛地工作中。目光所及，左、右表头明暗步调的变化并不同步，这是因为左右声道的音乐讯号本就不同，可见表头亮度确能精准反应音乐强度，且随着音乐看着灯光明灭，在视觉上十分显眼。
Challenger 250背板提供RCA与XLR输入各一组，输出则有4欧姆、6欧姆与8欧姆三种，可迎合各种不同阻抗的喇叭。一开始我先用我们的两对参考喇叭分别试听：Capriccio Continuo的Admonitor Preference Plus书架喇叭加Submonitor MKIII低音柱，以及Dynaudio Contour 60。Challenger 250搭CC的声音比较讨喜，较有滋味，有种灵魂快要被勾去的感觉。相比之下，Challenger 250搭Contour 60就像是纯净的水，清澈干净，初饮似乎无味，细细品尝才会知道当中的甘甜。不过，体型较大的Contour 60更能凸显出Challenger 250的优势，像是开放、雄伟的规模感，平直的响应，清楚而严谨的音场结构，以及良好的音场层次，因此接下来的试听，我便决定以Contour 60做为搭配。
试听过程中，我发现Audio Valve的ABR功能似乎不断在调整Challenger 250的工作点。当音量由弱变强时，可以看到Challenger 250内部的红色LED灯亮起，同时伴有继电器切换的声音。当音量再由强转弱时，LED灯则会熄灭，继电器再度运作一次。由此可知，ABR功能时时刻刻都在运作中，持续感应音乐的变化，同步调整真空管的工作状态。我觉得，它的好处是不会让真空管一直处在高档状态，而是需要能量的时候才「加油点火」，也因此Challenger 250不像其他大型管机总是持续发出高热，到了炎夏只要冷气不够强变觉得热气逼人。Challenger 250即便连听几小时，也不过略为发烫而已，让人觉得真空管的寿命应该可以维持得更久，荷包更省了。
虽然不是随时採足了油门，Challenger 250的控制力依然优异。以Dire Straits同名专辑为例，当中鼓声的轮廓就像是画出来般清晰，一颗一颗的，形状、大小分明。大鼓踩踏饱满又短促，带有适当的尾巴，贝斯颗粒有很棒的Q劲，可见Challenger 250控制力不只是好，而且好的恰到好处，既精准又适宜。这张专辑中让我眼睛为之一亮的还有吉他Clean tone的音色，不仅有丰富的水分，又能保持澄澈透亮的干净，甜润感简直迷死人。第2轨《Water of love》中的slide吉他更是飘逸，高频有种往上自然晕开的轻松感，显示高频的延伸非常优异。又例如Dire Straits「On Every Street」专辑第6轨《You And Your Friend》一曲，这是一手很慢的歌曲，电贝斯一弹就是长音，而且低频的量录得蛮多，透过Challenger 250的播放，低频质量均优，线条清晰流畅，既饱足又不失应有的清爽感。这首歌开头的音量蛮弱，如果一开始开大声，到了结尾的音量便颇为巨大，但Challenger 250完全不当一回事，照样唱得气定神閒，依然维持着极佳的频段比例与清楚的音场结构。
Contour 60搭配Challenger 250充分展现了它们共同拥有的一项优点：音乐起伏时的流畅感与丰富阶调。音乐由弱至强是一个变化的过程，能表现出的动态越大，当中的阶调就越多，能量的输出越平顺，就越能听到自然顺畅的起伏，而不是压抑紧绷、使不上力的收敛。Contour 60与Challenger 250都是在这方面具有优异表现的器材，两者相配，那种起伏感更是畅快淋漓。例如「乐来乐爱你」电影原声带第9轨《Audition》，就是蜜亚在片中最后一次试镜时讲她姑姑故事的那段，她从口白开始讲，然后清唱，接着钢琴进来伴奏，然后弦乐，一层叠上一层，到了约2分20秒时定音鼓与弦群齐扬，带出一个庞大的起伏，扬到最高处又有些微摆荡。就是这个地方，音量与能量顺畅地拉起，气氛也为之昂扬，此刻若Challenger 250的输出稍有迟滞，听者情绪的起伏恐怕也要跟着打折扣了。
但说实在的，上述文字只是我刻意要把Challenger 250的声音表现描写出来而做的表述，其实Challenger 250的声音是如此的自然、流畅，它似乎未刻意要强调什么，却又什么都没遗漏，音乐与时间就在不知不觉中流过，留下的尽是舒畅与愉悦。
Audio Valve Challenger 250
输出功率：300瓦/4, 6, 8欧姆
频率响应：15Hz – 85KHz
Audio Valve Challenger 250,德国至尊250后级,Audio Valve Challenger 250后级扩大机
TAIWAN Music forum, Equipment Review, By Liu Hansheng
One of the best power amp I’ve ever listened to.
Power amplifier (high-end special version)
Vacuum-tube single-track power amp, launched in 2010; one 12A*7, two 12AU7, six KT120; bandwidth: 15Hz-85kHz; single-track output: 350W RMS; gain: 28dB; SNR: -69dBm; input impedance: 47k?; damping coefficient: 8; size: 420*400*200mm; weight: 30kg. TAIWAN eneral import agent:
Equipments for reference:
Signal source: Esoteric SA50+Weiss DAC 202 analog-to-digital converter
Pre amp: AudioValve Conductor
Speaker: ATC EL 150P
Vivid G2 Giya
The AudioValve, established in 1982, was owned by Helmut Becker, who has been interested in vacuum amplifier since he was 15 years old. He even assembled the equipment on his own for a few years before he quit his job at the medical equipment manufactory, and concentrated on his dreams. So far he has had more than 40 years of experience in this field. He is a guitar player and music amateur with a particular taste. Over the years he, together with his wife, establishes an enterprise, while he works at the circuit design and his wife the external shape. Their company is moderate in size; however, its products have won a wide range of favor. I have listened to their products for several times; however, I cannot remember I’ve ever listened to such a powerful single-track power amp as the Challenger 250.
Never be particular with the tubes
The Challenger series were launched as early as in 1987. With so many years of improvements from the 115, 150 to 180, now the 250 that I listened to was promoted in 2000. It’s special because it can use many power tubes such as KT88, 6550 or EL34. Just plug in the tube and then you can listen to the music, without anything else to worry about. Of course, different tubes will decide different output power. Furthermore, the Challenger series apply the Auto Bias Regulator, and therefore to it is unnecessary use matching tube. This company has repeatedly pointed out that it is unnecessary to buy expensive tubes to match its vacuum-tube amplifiers because ordinary tubes will also make beautiful sound. Besides, the Challenger series are built in completely balanced architecture from input stage all the way to output stage. Even transmitting through non-balance input terminal, the music signal will be split into two groups: positive and negative, which will then be conducted into the back-end balancing circuit. Because of the balanced architecture, the power amps of this company apply the PPP (Parallel Push Pull) drive, which is different from the common SRPP (Series Resistance Push Pull) drive. Finally, its power amps apply the Cathode Follower output architecture, which is quite uncommon, because the Cathode Follower is generally used to match the impedance or used in the pre – amp.
As we know, generally there are three ways of connecting vacuum tube, which are Common Cathode, Cathode Follower and Grounded Grid. To obtain high voltage gain, the best choice is the Common Cathode, which, however, will lead to high input and output impedance, opposition phase output and limited bandwidth. In order to obtain normal phase output, high output impedance, low input impedance, good performance in bandwidth and linearity, it is better to use the Cathode Follower, which, however, has no voltage gain (≤ 1), and can be used as a buffer stage, and therefore, the fore end has to have sufficient gain. The advantages of Grounded Grid are high gain, good performance of bandwidth and linearity; however, it also has weak points such as low input impedance and high output impedance. One consideration for applying the Cathode Follower at the output stage of AudioValve Power amp, I guess, is to avoid the influence of the peculiarity of power tube (never be particular with tubes), which enables the user to enjoy beautiful music without applying expensive power tubes. However, to apply the Cathode Follower at the output stage means that the voltage amplification of the fore end becomes more important, otherwise the whole equipment may fail.
Refined in external shape …
As a matter of fact, from the perspective of the price of the Challenger 250, its external shape is, although far from being noble and exquisite, quite unique. Its cover is built out of black metal plate carved with grid. The panel is also directly carved out and replaced with the acryl and at the center is placed an analogue VU meter, and it looks quite classic. On each side of the meter there is one button, with the right one being the power switch and the left one the Standby button (it will not shut the power of this whole equipment, but only the plate voltage of the vacuum tube, which will still keep the tube warm at any moment). The backboard is also quite simple, with both XLR and RCA input terminals, and two speaker terminals, one of which is 8 ? and the other 6 ?, and nothing else. If anything can be counted as noble, they are those four gild legs. The arrangement of black with gold is always the noblest, isn’t it?
It is quite easy to remove the cover of the Challenger 250, and without any screwdriver, anyone can remove the gild screws on four corners of the cover with bare hands. With the heavy cover being removed, it’s clear to see three small tubes (Russian Electro Harmonix tube), six KT120 power tubes (KT-90 is also usable and it can be replaced with any beam power tube.) and a circuit board with THT (Through Hole Technology) components without any surface mount component. On the back of the cabinet there are a round power transformer and an EI output transformer. Beside the power transformer there are eight Rifa filter capacitors, rectifier, relay and so on. There are quite a few internal wirings, all of which are of thick wires.
What’s special about the cabinet is that on its both side there are two radiator fans, which will start to rotate to remove the heat when the power is on. The radiator fans are usually placed on the bottom and extract the air from the below to cool the vacuum tubes, while those on the Challenger 250 extract the air from two sides. Put your hands over the cover of the cabinet while listening to the music, you will feel no hot air rising upward, which has been extracted sideward. On the user’s guide, the company specially points out that it’s better to plug normal speakers into the 8 ? terminal, and if the speaker is of 4 ? or 16 ?, please plug it into the 6 ? terminal.
The Challenger 250 is a single-track amplifier with quite a moderate size, although the output per track is up to 350W.
Effective Auto Bias Regulator
Each power tube of the Challenger 250 is controlled by the Auto Bias Regulator, and you don’t have to adjust the bias manually and can enjoy the music as you like. One LED is placed on the right side of each power tube, which will remain off while the tube is on normal operative mode. And if anything is wrong with the power tube, the nearby LED will be on, and then the defective power tube must be replaced. After the replacement, this LED indicator will be off. If the LED is still on, please check the fuse on the back of the power tube, below which there maybe a flickering LED. In that case, please replace the fuse, and mind that it has to be the 630mA time-delay fuse. If the LED is still on after all those procedures mentioned above, the equipment may need repairing. By the way, if the amplifier is on Standby mode, the LED beside the power tube will still be on, which is normal, please don’t worry. Besides, if the equipment is playing music at high volume, those two LEDs beside the power tube will flicker, which indicates that the Auto Bias Regulator is now controlling the bias, which is also normal, please don’t worry.
One of the high-end amplifiers
It has been a long time since I last time listened to the AudioValve equipment, and this time when I listened to the Challenger 250 power amp, it took me by surprise: how could it sound so beautiful? I beg your pardon, because I don’t mean that the previous AudioValve equipments sounded bad. They had already reached a considerably high level long before. However, this time I listened to the Challenger 250 power amp with the power-disconnected Conductor pre-amp of this company (the forum awards to it the Best Performance in 2010), and I think that the beauty of its sound and the 20 Factors of Music far exceed its previous impression in my mind. Is it because I misinterpreted the performance of the AudioValve before? Or is it because the AudioValve has made ground-breaking progress in recent years? No matter how, the Conductor pre-amp and the Challenger 250 power amp can definitely edge into the top rank of amplifier.
The matching digital signal source is Esoteric SA50, which is used as the turntable, and it is connected with the Weiss DAC 202 analog-to-digital converter and two pairs of speakers of ATC EL 150P and Vivid G2. The former is good at creating the feeling of massive scale and relax feelings at the middle and low frequency. While the advantages of the latter lie in precision, sweetness, lightness and static reaction. And the final version is about the joint performance of these two pairs of speakers.
Pure, clear and full tone
Since the AudioValve amplifier used to impress me with its beautiful tone, I listened to Tsai Chin’s Golden Concert Hall at first. Just as expected, the Challenger 250 didn’t let me down, and the tone of this whole CD was very beautiful and it sounded pure, mellow, soft, clear and full. Let me put it in another way, it is just like beef noodle soups made in two different ways: one is made instantly by mixing pure water, soy sauce and other sauces; the other is made by stewing bones slowly for the whole day. What are the differences between these two soups? The former tastes monotonous and lacks in flavors. While the latter tastes full and smooth. If these two kinds of beef soups are kept in cold storage for one day, it can be found that the former will still be water-like liquid while the latter will be like jelly. Why are there such differences? It is because that the beef soup that is made out of long-time stewed bones is full of colloid substance, which is released from the bones and condenses to jelly when it meets the cold. The instant beef soup that is made out of sauces will never taste fresh but mouthful of sauce flavor, far from being like the bone soup that is full of colloid substance. And the performance of the Challenger 250 is just like the bone soup, which is full and fresh with lingering aftertastes.
With the Golden Voice Concert Hall played, I took out the Outcasts. Similarly, the tone of this whole CD got improved greatly. The Challenger 250 made the tone of cello more beautiful, which used to sound coarse and hard. Well, to be honest, “more beautiful” as I said is faulty in wording because it would not make the cello sound more beautiful, and it just reproduced how it sounded originally. At first the Challenger 250 impressed me with the good tone. No! It should be the joint impression of the Conductor pre-amp and the Challenger 250.
Having listened to two test software, I laid the emphasis on the clearness and details, using Dim Sum of Ying Quartet of Telarc. After hearing the first two pieces, a sense of admiration for the Challenger 250 arose in my heart. Why? It was because the music that I heard was very clear, so clear that even the stringed instruments could be seen floating in the air without any sense of artificial recording, and it felt like a live performance before my eyes. Is there such clearness in the world? Yes! And ordinary amplifiers can never make such clearness, and only real good amplifiers can do. It has nothing impurity, but is full of brightness.
Besides, I also heard unspeakable details, which included the string strumming that had not been degraded through artificial recording, and even details much subtler were also represented vividly. To be honest, I was taken by surprise, because it was quite difficult to perform such clearness and details, even for quality transistor amplifier, and I think I only had such experiences with the top single-ended direct-heated triode amplifier. However, since the Challenger 250 was not transistor amplifier, its performance with such clearness and details was quite unbelievable. Additionally, since the Challenger 250 represents the original string music with good tone, it has all that we need.
Having listened to the Dim Sum, I was surprised by its high clearness and rich details on one hand; what I’d like to remind the reader on the other hand, is that the amplifier with such good performance must be matched with high-level signal source, or it will become “garbage in, garbage out”. You have to be very careful with the speaker, and the bright-style speakers are not appropriate because then the tone of the music may become monotonous, and the self-restraint style or neutral style will do. Furthermore, if you feel that the music from the Challenger 250 lacks in clearness, you can correct it by change the signal source cord or speaker cord, which may cause such problems due to its deterioration. If the music sounds too bright as to be uncomfortably dazzling, besides the cord materials, you still have to consider whether the environment belongs to hard style, and it is because this kind of space will extend the high-frequency reverberation so that the tone may not sound warm enough.
Sound comfortable with excellent low-frequency performance
Then I wanted to listen to some music that will make me feel relax and comfortable, and I selected Anne Bisson’s Blue Mind. I found that the singer’s voice and the accompaniment were both full and smooth, which was not simply soft but also with proper elasticity and resonance. What was more fascinating was that the brightness and sweetness of both the instruments and the voice were so good that it was just like that they were burnished by bee wax (please just imagine such scenes). Besides, with high clearness, the music was very bright with all the details emerging from the bottom. As to the proportion of the accompaniments with human voice, it was very healthy and decent without being too large or tiny.
With those CDs mentioned above, I should begin to test the greatest weak point common for vacuum tube amplifiers: the control over the low frequency and the elasticity. At first I listened to the Super Bass 2 of Telarc and first of all, I felt that the elasticity of Bass was surprisingly excellent and the Bass note concentrated in clear shape, which, however, was not massive at all. It was strange because its damping coefficient was only 8, how could it manifest such elasticity? This was quite unexpected. It was just because the Bass that was full of elasticity and not huge in size, it represented much vividness. To be honest, it is very rare to hear such elastic and clear Bass notes with vacuum tube amplifiers.
What was more fascinating was that the Bass that the Challenger 250 performed was good in tone, even with some sweetness. Wait, did this sweetness belong to the high frequency of violin? Did the chief editor know what he was talking about? No, this was real, and it was due to the excellent tone. Besides the excellent tone, the Challenger 250 was also among the best in representing the spaciousness and such details as the live audience’s position, applause, cheers while playing this live music, which I could only describe as the “vivid live-ness”.
After the Bass test, it was necessary to test its low frequency performance with popular music, and I selected Jiang Hui’s Red Line. First of all, what fascinated me was that the whole music was sweet and bright, as if being smeared with honey, and what followed next was the drumbeat, which was more clear than I had ever heard. Did the drumbeat also have resolution? Yes, it felt like viewing images through lens of high clearness. Besides, various accompaniments in the music were reproduced clearly with nothing lost. Finally, Jiang Hui had very sweet and pure voice.
Rich details, strong vividness
“View through lens of high clearness”? This may be difficult for some readers to understand, I will take another example to explain. Although many people have this CD named Belafonte Sings the Blues, they don’t understand why the Music Forum regards it as excellent music. Does it sound ordinary without any appeal? The problem lies in your acoustics, which lacks in good clearness and cannot reproduce enough details as well as strong vividness, and therefore this CD sounds unattractive. If the equipment lacks in clearness, this CD will sound “dull” without enough brightness. Without enough details, Belafonte’s voice and the accompaniments will not sound real. Without vividness, the slow blue music will sound sluggish and boring. However, the Challenger 250 can reproduce quite high clearness (nothing dazzling), many details and good vividness, and therefore, whenever this CD is played, even though the blue music is so low as to make one feel sleepy, it always sounds vivid.
One of the best power amp I’ve ever listened to
Speaking of listening to music, the most important is to be comfortable, and what comes next is the exciting sound effect. If there are only exciting sound effects, it will not be long before the ears get tired and the nerves become stressed. However, if the music can only make one feel comfortable with nothing exciting, it is just like listening to the background music on the bed, which is quite usual. The AudioValve Challenger 250 is a power amp that is good at these two aspects. When you use it to listen to music, you will feel comfortable from inside but never tiresome even after a long time. Furthermore, due to the catalysis effects of its details, clearness, vividness and elasticity, your blood will be accelerated all the way to your head and feel excited. With this quality plus the fact that it is never particular with the tube, I hereby enter the Challenger 250 on the list of the best power amp that I’ve ever listened to.
It is clear to view the interior of the Challenger 250. Each track applies six KT-120 power tubes, and many LEDs on the circuit board indicate different modes. The radiator fans of the Challenger 250 are placed on its two sides, without applying the common up-down ventilation.
Figure of 20 Factors
1 tone 2 timbre 3 high-frequency sweetness 4 middle-frequency fullness 5 low-frequency truth 6 size of music field 7 density and weight of sound 8 clearness 9 layer 10 position 11 vividness 12 simulation and substantiality 13 resolution 14 speed and static reaction 15 strength contrast and dynamic contrast 16 proportion of accompaniment with human voice 17 accompaniment, voice quality and spaciousness 18 detail reproduction 19 spaciousness 20 total balance
The Figure of 20 Factors is an index of the reviewer’s subjective impression for single equipment, and its result will vary with different equipments, environment and mind and body conditions. Its results, if taken as reference the comparison of two equipments, will be biased.
Five Elements of Music
Metal: open, live and bright
Wood: warm, self-restraint and intimate
Water: gentle, neutral and smooth
Fire: quick, enthusiastic and impulsive
Earth: heavy, full and stately
1 the tone is gentle, pure, clear and mellow without any coarseness; 2 excellent clearness and rich details; 3 better control over the low frequency, resolution and elasticity than ordinary vacuum-tube amplifiers.
1 the priority is to use the pre-amp of the original company in order to match the external shape and sound quality; 2 if the pre-amp is of other brand, the light and sweet-style ones are better than those stately-style.
There are one RCA and one XLR terminal on the backboard of the Challenger 250, and it is suggested to use the balance terminal prior to the RCA terminal, and it is because the RCA input terminal will require one extra procedure of phrase splitting of music signal.
Software for reference
Belafonte Sings the Blues was recorded in 1958, and it was not as good and popular as the version of Carnegie Music Hall because on one hand it was Blues, and on the other hand, it was not a live recording in the music hall. However, it was still a good record, and people may have different opinions about its contents. Just as I said, it can be used as a touchstone for the acoustics, which will be all right if it sounds good. If not, it is because that the acoustics lack in clearness, details and vividness.