This article is reprinted from Puluo Audio-Visual Network
Over the years, although ARC's pre-amp lines have continued to evolve, the resolution has improved, and the sound quality has become more and more delicate and pure, but the sound I heard has the unique natural and warm sound base of the vacuum tube, the abundant and full sense of energy, the 3D stereoscopic audio and sound field, and the open and loose replay momentum. It shows that ARC has found a good sound equation for the vacuum line, so that it can control ARC's unique replay style so accurately and stably.
Every time I write about Audio Research's preamps, I can't help but feel nostalgic for the LS2 MKII preamps I had twenty years ago. I still vividly remember that evening when I brought the LS2 MKII home from the second-hand store, couldn't wait to connect the cables, and then turned on the power. I don't think I'll ever forget the emotion of this preamplifier in my life. It was a sound full of "water", which instantly filled my listening space, the shape and sound quality of the instrument is so full, the sound stage is so open, and the transience and rhythm of the music are so vivid, whether it is a vocal, a piano or a violin, the LS2 MKII can show a very natural and moist texture. Since then, Audio Research has always been the first brand that comes to my mind whenever someone asks me to recommend a pre-amp.
At the time, the LS2 MKII was only a mid-range model from Audio Research (ARC), and at that time it had another backplate with a Reference 2 preamplifier with balanced input and output terminals. Who could have imagined that 20 years later, the latest generation of the Reference 6SE preamp in the Reference series is right here in front of me, waiting for me to audition. Is this a dream? You can't imagine how happy I am to be with Reference 6SE this month!
▲The SP3 preamp, launched in 1972, is ARC's best-selling product in history, and perhaps the best-selling preamplifier in the history of Hi End audio.
ARC has launched a number of preamplifiers over the years, but the most talked about by audio fans is probably the SP3 preamplifier launched in 1972, which sold thousands of units in the five years that it was discontinued in 1977, making it the best-selling product of ARC's history. I checked the review of Stereophile magazine at the time, which wrote that the distortion of the SP3 was lower than the minimum standard that their instrument could measure at that time, and it was very close to the ideal state of the pre-amp design of "signal line with gain", which shows that ARC has already broken the myth that the distortion of vacuum tubes is higher than that of crystals.
▲All products under development and each product sold by ARC must be fully matured and auditioned by Warren Gehl, the master of the "Golden Ear", to confirm that the sound performance meets the standards before it can be officially shipped.
不过，别忘了ARC创始人William Johnson的名言：「优异的测试数据并不代表器材可以发出好声（It measures well doesn't assure that it will sound good.）。 」ARC之所以名满天下，关键就在于他们能在理性的测试数据与感性的听感上掌握绝佳均衡点。 如今William Johnson虽然已经仙逝（1926-2011），但是Audio Research的经典之声，依然由阵中老将「金耳朵」Warren Gehl严格把关。
Warren is said to have an amazing memory for sound, and can clearly distinguish the difference in sound from each of his devices. Before each ARC piece of equipment comes out, it must be fully matured, and Warren will listen to it to confirm that the sound performance meets the standards before it can be officially shipped. Over the years, although ARC's pre-amp lines have continued to evolve, the resolution has improved, and the sound quality has become more and more delicate and pure, but the sound I heard has the unique natural and warm sound base of the vacuum tube, the abundant and full sense of energy, the 3D stereoscopic audio and sound field, and the open and loose replay momentum. It shows that ARC has found a good sound equation for the vacuum line, so that it can control ARC's unique replay style so accurately and stably.
To put it simply, if you want to embrace the natural and warm taste of the tube, but don't want excessive sound coloration and noise from the pipe, then adding an ARC preamp to the sound system is undoubtedly the best solution. Don't assume that any vacuum tube preamplifier will meet the above requirements. Many modern vacuum tube preamplifiers are committed to the pursuit of transparent sound quality and a bright sense of speed, eager to get rid of the stereotype of the tube machine is dizzy and warm, but it also makes the charming tube taste become weak. It is really rare to find a vacuum tube preamp that retains a strong "tube flavor" like the ARC preamp, and at the same time combines pure sound quality and low distortion.
▲The line of the Reference 6SE has evolved from the original Reference preamplifier in 1995, which can be regarded as an integrated version of the power separation preamplifier Reference 10.
On ARC's official website, there are currently three preamplifiers listed, from high to low, they are Reference 10, Reference 6SE and LS28SE, the latter two are evolved from Reference 6 and LS28 respectively, and ARC celebrates its 50th anniversary with a special Edition. What is the difference between these three preamps?Reference 10 was launched in 2013, the line is transplanted from the 40th anniversary limited preamp launched in 2010, the power supply separation two-box design, the preamp amplification line uses 4 6H30 double transistors per channel, and the power supply line adopts vacuum tube voltage stabilization.
The Reference 6SE's line has evolved from the original Reference preamp in 1995, using three 6H30s per channel. The power supply line is also regulated by a vacuum tube, which can be seen as an all-in-one version of the Reference 10. Warren Gehl "Golden Ear" also said that the sound performance of the Reference 6SE is very close to the level of the Reference 10.
LS28SE is developed from the LS25 launched in 1998, and the input stage is amplified by JFET and the 6H30 is used as the amplification stage to form a tube-crystal hybrid line. Obviously, if you're looking for a pure vacuum tube amplified all-in-one ARC preamp, the Reference 6SE is the only option in service.
From the differences of the previous Reference series, we can see the evolution direction of the ARC pre-line. The first generation of the Reference 1 was introduced in 1995 and used a total of eight 6922/E88CC vacuum tubes for the amplification line. The second generation of the Reference 2 was introduced in 1998 and was also equipped with eight 6922/E88CC vacuum tubes, but the power supply line began to be regulated by vacuum tubes. Two years later, it evolved into the Reference 2 MKII, which looked like a facelift, but in fact the lines were very different, with JFET amplification in the input stage, and two 6H30 lines per channel in the amplification line. The use of 6H30 vacuum tubes is the most important feature of ARC's tube machines in the past 20 years, but the Reference 2 MKII is not the first time ARC has used 6H30 tube preamplifiers, the LS25 MKII was the first ARC to use 6H30 preamplifiers, which was launched half a year earlier.
In 2004, the Reference 3 preamplifier was introduced, and although the amplification stage also used four 6H30s, the JFET input stage was canceled and the amplification was changed back to pure vacuum tube. The power supply energy is greatly increased by 50%, and the voltage is also regulated by vacuum tubes. It is worth noting that the 6L6GC, which is used as one of the vacuum tubes, was replaced with the 6550 during mass production, but the Reference 3 model was not changed.
In 2009, the successor model was launched, but it skipped the taboo 4 of the Chinese and directly launched the Reference 5, and the amplification line also used 4 6H30, but the line planning was greatly changed, and the power supply regulation line used 6550 and 6H30 vacuum tubes each.
In 2010, ARC celebrated its 40th anniversary with the launch of the Anniversary Edition, which was sold for one year only. It adopts a two-piece architecture with power separation, and each channel is equipped with 4 6H30 vacuum tubes. The power supply line uses 6550 and 6H30 for each channel for voltage regulation. Two years later, the Reference 5SE was launched, with the same vacuum tube configuration, but with the introduction of key elements of the 40th anniversary preamp, and the sound performance was significantly improved.
In 2015, the Reference 6 was launched, with a major overhaul of the exterior and a new generation of styling laid by ARC in 2014 with the launch of the G series, as well as significant changes to the wiring design. The total number of 6H30s in the amplification line increased to 6. Power transformers have more capacity and lower noise. The filter capacitor is changed to special components, and the pins are made of PCOCC single crystal oxygen-free copper, which can be seen with care, and the volume control circuit has also been improved. The addition of two 6H30s to the amplification line is undoubtedly the biggest change in the Reference 6, but there is no difference in the specs, and both the gain and the output level are the same as the previous generation of the Reference 5SE. The real difference is reflected in the sound performance, the original factory claims to add 2 6H30, the dynamic range is wider, the micro-dynamic performance is more delicate, the distortion is lower, and the music background is quieter.
Four years later, as Audio Research celebrates its 50th anniversary, they unveil the latest version of the Reference 6SE. The original manufacturer said that the motivation for this upgrade came from the results they obtained during the development of the Reference 160 post-amp and the Reference 750SEL mono flagship post-amp, replacing the capacitors in the Reference 6 power supply line, and replacing all the in-machine wiring with specially developed custom products, totaling Reference A total of 28 components have been updated in the 6SE, which may not seem like a large improvement, but in fact, each replaced component is tailored to the circuit characteristics of the Reference 6SE, and after a long audition, it is confirmed that each updated component can be harmoniously matched with the overall circuit before the final decision is finalized, and it is by no means a direct application of the capacitors and wiring of the Reference 160 and Reference 750SEL amplifiers.
▲The preamplifier of the Reference series has always been a fully balanced design, and in the past, the signal output and input were all only available with XLR balanced terminals, and it was not until the Reference 6SE that the RCA terminal was provided for the first time.
It is worth mentioning that for this upgrade, Warren wrote a special article on the official website of ARC, saying that the Reference 6SE is the most improved upgrade in the 25 years since the launch of the Reference series, further unleashing the potential of the vacuum tube amplification circuit. The main purpose of the update is to fine-tune the performance of the Reference 6SE in terms of time phase, so that the subtle signals in the recording can be completely released, the sound quality is clearer and more transparent, and any ambiguity is completely eliminated, and the music replay is more realistic. The sense of spatial sound, the sense of positioning and the ability to focus on the shape of the audio and video have reached the ultimate expressiveness of the integrated preamp he has heard, which can make any speaker easily invisible in the soundfield stage. The capacitor replacement allows the Reference 6SE to have an extremely abundant power supply, which can more quickly and quickly display any changes in the strength and weakness of the full frequency band, and more easily and directly display the density, tension and energy of the music. Regardless of transient reaction or dynamic behavior, it can easily surpass any crystal preamp. In particular, this article is signed by Warren Gehl at the end of the article, and is not an official promotional text. Warren Gehl, who has always been low-key and stealthy behind the scenes, made a rare statement with such a firm and confident tone, which shows that the improvement of Reference 6SE is definitely not small.
▲The focus of the upgrade of the Reference 6SE is that the capacitors in the power supply line of the Reference 6 have been replaced, and all the wiring in the machine has been replaced with a specially made product developed in-house, and a total of 28 components have been updated.
This magazine once commented on the Reference 6 pre-amp in issue 331, which was written by Editor-in-Chief Liu at that time. The route architecture of the Reference 6SE is basically the same as that of its predecessor, and it will be introduced again in this article. The Reference 6SE is equipped with a toroidal transformer and an R Core transformer, the former supplying power to digital logic-related lines such as display windows and relays, and the R Core transformer for analogue amplification lines. Don't underestimate this design, the digital high-frequency noise of the logic circuit will be connected into the analog line to pollute the music signal, and the use of independent transformer power supply is the most elaborate way to solve the problem.
The array of filter capacitors is huge, and it is more than enough to make an amplifier. The four conspicuous golden capacitors are used at the output end. The power supply uses solid-state bridge rectification, equipped with nine sets of independent voltage regulator lines, in addition to FET voltage regulation, it also uses 6550WE and 6H30 vacuum tubes for voltage regulation.
It is worth noting that the 6550WE used in power regulation is a special selection tested by ARC, if you replace it with KT88, the replay performance will deteriorate, if you need to replace it, it is recommended to purchase the dedicated 6550WE directly from ARC. ARC is very particular about the testing and pairing of vacuum tubes, although it is not a rare old NOS tube, but the sound performance level is extremely high, and the quality and durability are trustworthy.
For the amplification circuit, the Reference 6SE is a fully balanced, pure Class A, non-negative feedback design. Although 6 6H30 dual triodes are used, it is the simplest DC direct cross-connection and first-stage gain amplification architecture. The vacuum tube regulator mainly supplies the preamplification circuit, which can eliminate the higher harmonic distortion and show a more open replay character. In the volume control section, a volume control chip with a miniature R2R resistor array is used, and 103 steps of fine adjustment can be performed.
ARC is very particular about the selection of components, and even the circuit board material used in the Reference 6SE is exclusively patented. Over the years, I've interviewed Audio Research brand ambassador Dave Gordon and several other OEM representatives, all of whom have all emphasized to me that the material of the circuit board has a great impact on the sound performance, which shows the depth of ARC's research into the details of the components.
▲The two sides of the chassis of the Reference 6SE are composed of thick aluminum plates, and the solidity of the chassis structure is greatly improved. Both the top cover and the bottom panel are transparent acrylic, and ARC compared it and found that the sound was better than that of the metal cover.
The new styling of the Reference 6SE is definitely worth mentioning, designed by Livio Cucuzza, Industrial Design Director at ARC's McIntosh Group. Don't worry, Livio Cucuzza is definitely the best choice, because his father was a distributor of Audio Research, and Livio grew up surrounded by ARC equipment, and there is probably no one in the world who is more familiar with ARC's classic styling elements than him. The new ARC shape designed by him does not deviate too much from the original appearance, but cleverly modifies the details to be more refined, more classical, and more high-quality temperament.
In terms of chassis construction, ARC's chassis has not been called a heavy armor level in the past. The new shape of the Reference 6SE has finally been reborn, and the two sides of the Reference 6SE chassis are made of thick aluminum plates, and the structural solidity of the chassis has been greatly improved. In particular, the top cover and bottom panel of the Reference 6SE are made of transparent acrylic material, which is not designed for aesthetics, but after ARC actual test and comparison, the sound performance is better than that of the metal cover.
Going into the actual audition, I can't wait to relive the impression that the LS2 MKII brought to me back then. Titfu specially sent ARC GS150 post-amp for me to match, this post-amp uses 4 KT150 power tubes per channel, with an output power of 155 watts, I didn't expect to drive the Triangle Genese Quartet speaker with high sensitivity (95dB), the sound quality is not rough at all, showing the replay characteristics of natural roundness and fullness, and the full frequency band is very balanced and loose. The source is equipped with an Italian Norma Audio Revo DS-1 CD disc and a Mytek Brooklyn Bridge streaming DAC. The Norma Audio Revo DS-1 has a delicate and soft sound, which is even more prominent when paired with the Reference 6SE, and the natural softness and warmth of female voices and strings may not be surpassed by other combinations in my listening experience. Replaced with the Brooklyn Bridge, which has the characteristics of studio listening, the sweet sound quality has become lighter, but the natural and smooth quality is still there. In terms of equipment reviews, the latter combination may be more appropriate, but please forgive me for loving the bel canto charm of Norma and Reference 6SE so much that I can't bear to listen to this combination in the rest of the audition.
I started with three piano recordings in shifts. Listen to RR's "Dick Hyman Plays Fats Waller" first, when the piano leaks for the first time, the feeling of being "electrified" by the LS2 MKII is immediately recovered, the piano tone is not only transparent, but also sweet and moist, the overtones are not deliberately easy to extend, the fast scale is played as smoothly as flowing water, and the piano sounds are scattered like mellow pearls. Who says that the sound of the ARC is heroic and the sound quality is not delicate enough? Please be sure to listen to this recording of the interpretation of the Reference 6SE and GS150 amplifier, and you will find that the original ARC sound can also be so smart and pure.
Listening to Ciro Longobardi's "Nuit" album, the piano touch energy of this recording is particularly direct and powerful, the sound quality is particularly transparent and pure, and the retraction speed is also very bright and neat. The Reference 6SE does all three of these things, with direct and powerful treble touches, but no gruff. The sound of the piano is not only transparent, but also sweet and watery. The speed at which the piano is retracted and played is also not in any sign of mud and water. What impressed me was still the overtones that seemed to be constantly swirling and extending in space, I really had never heard such long and rich overtones in this album before! The point is that although the overtones of the Reference 6SE are rich, they are definitely not achieved by emphasizing the volume of the high frequencies, and the high frequencies I heard do not have any deliberate protrusions, and the sense of balance in the mid and high frequencies and even the whole frequency band is very good. Even at loud volumes, the high frequencies are not irritating and tight, and are even warmer and more natural than most devices. What kind of magic did ARC put into the line to extract such a sweet and watery treble? I really can't find the answer. In short, it's very charming and good-sounding.
The third piano recording, for something special, I listened to Jean Rondeau's harpsichord album "Vertigo". In the past, my impression of the harpsichord has always been clear and gorgeous, and I focused more on the performance of the mid and high frequencies. But the Reference 6SE and GS150 made me hear very different things. First, I heard the harpsichord's plucked strings with a strong bouncy that I hadn't noticed before. Secondly, the continuous flow of piano sounds is like gentle ocean waves rushing towards me, and the layers of piano sounds show a very rich sense of layering. It's something I've never experienced on a harpsichord recording. Finally, when the piece is played to the top of the pitch, the openness is very different from what I have heard of on the harpsichord before. To be honest, I've never heard a harpsichord play with such undulating tension. This kind of performance can't help but make me wonder if it will be paired with the GS150 post-level, and the sound quality will become particularly full.
I tried swapping the amp for a Lindemann Power 1000 and wondered what would happen to the Reference 6SE with a neutral amp. As a result, the fullness has indeed decreased a little, but the direction of mellow sound quality and energy has not changed. Generally speaking, the preamp is not responsible for driving the horn, so it should not cause much change in the sense of energy, but the Reference 6SE can make the whole system feel full and energetic. This is another special feature of the Reference 6SE that is difficult to explain.
Then I tested the strings and listened to the familiar Zeng Yuqian "Reverie" album, I have heard two replay interpretations in the past, one of which is very direct, although it is in line with the recording situation, but it is inevitably a little unpleasant. The other is particularly soft, although pleasing to the ear, but it is difficult to show the explosive power of Zeng Yuqian's 1722 Strativari famous piano. The performance of the Reference 6SE and GS150 belongs to the third type, on the one hand, the sound is direct and powerful, and on the other hand, the sound quality is particularly dense, and the sound fluctuations are delicate and rich. This combination of straightforwardness and mellow is undoubtedly the interpretation that fascinates me the most.
I also listened to Sibelius's "Violin Concerto" performed by Hei Feiz, who was sharp and precise, but not stiff, showing a magnificent momentum, and the strings played in unison without looseness, and the overall performance was majestic. Listening to large-scale music on ARC's enlarged machine is really enjoyable and satisfying.
When the album was released in Denmark in 1965, the album was originally called "Ghosts", but when it was re-released in 1973, it was renamed "Vibrations", and the collaborators included bassist Gary Peacock, cornet Don Cherry, and drummer Sunny Murray. Albert Ayler had already begun to break away from the traditional key and present a free-jazz style, with brass recordings that were particularly wild and direct, and it was easy to feel too dry when listened to in a normal system. The rich and moist sound of the Reference 6SE can awaken the vitality of this performance.
After a month with Reference 6SE, I can't get enough of it. I've been trying to find the flaws between the Reference 6SE and the GS150, but in the end, it turned out to be even more powerful, delicate, analytical, and smooth. The warm, plump, watery smell of the tube is a charming trait that most modern tube machines have long forgotten. But the Reference 6SE is more than just a tube, it has a transparent sound, a crisp speed, and excellent balance across the entire band. The Reference 6SE is indeed one of the best preamps I've ever heard, and I really recommend it.
Specification:
Type: Vacuum tube pre-amp enlargement machine
频宽：0.4Hz-200kHz（+0/-3dB）
Vacuum tube: 6 x 6H30 signal amplification, 1 x 6550 and 1 x 6H30 are responsible for power regulation
Gain: 12dB (balanced), 6dB (unbalanced)
Input impedance: 120k ohms (balanced), 60k (unbalanced)
Maximum Output: 18V rms (balanced), 9V (unbalanced)
Distortion: Less than 0.01% (2V rms balanced output)
体积：480x198x410mm
Net weight: 17 kg
Audio Research - ARC
Agent in Beijing, China - Hongxin Audio
Company address: 135, District 1, Artist Workshop, Intermediate Art District, No. 50 Xingshi Road, Haidian District, Beijing
Business hours:10:30 a.m.-6:30 p.m. (no time limit for telephone appointments in the morning and evening)
Contact: Chen Yun
Phone: 13691398688/13699187626/010-62673769