A Scholar-entrepreneur in Music Space & Time

I have little knowledge about amplifiers of Music Space Time before I knew Mr. Li Kejian. A Taiwan friend of mine established a factory in Zhangjiagang, Jiangsu Province to produce power amplifiers. The products are only exported to overseas countries, so few people know the factory. The friend surnamed Wu manufactures power transformers and output transformers with toroidal transformers. He has made some breakthrough and accumulated much experience in the past few years, but there are still limitations in some bottleneck. His products sound soft and slow, but there is always weakness in high frequency extension. There are many choices such as EI, EE, C-CORE and R-CORE from the shape of transformers. The latter two types are characterized by high efficiency, low magnetic dispersion and iron loss. But the cost of materials is high since very thin iron core is needed in reeling, shaping, incising and grinding. In addition, the higher magnetic induction will easily cause distortion, so few people adopt them. At the first sight of Music-300B WE integrated power amplifier of Music Space Time, I was impressed by the four big metal shield cylinders. Since a small factory in Wenzhou, Zhejiang Province has launched their amplifier products at an unreasonable low price in the past two years due to application of out-of-date parts, I got a false impression that the products of Music Space Time, which also apply toroidal transformer and are made in Zhejiang, will not be superior.

I have been to Jiaxing for several times and am impressed by some famous traveling spots, such as Xitang town, Wuzhen town, Haining tide, Building of Misty Rain in South Lake and Nine-dragon Mountain. In Jiaxing, you can visit former residential places of several cultural celebrities such as Maodun, Xu Zhimo and Wang Guowei. I also love chrysanthemum of Tongxiang, Fenhu wine of Jiashan and cookies of Wu town. Mr. Li Kejian was just born in Jiaxing and grown in such an environment with deep cultural foundation. His soft and melodious words are comfortable and genial indeed.

Mr. Li used to work as a civil servant for many years and also live in Shanghai for long. After he left the financial industry, he returned to his hometown and began his second career, starting from his favorite, audio. When he was a student, he was interested in electronic technology. He used to purchase the kinescope, shell and all kinds of parts of television and re-assembled them at home. The best record of assembly at one night is 18 TVs. In the course of DIY, he accumulated rich experience and skills and was good at solving problems people thought impossible. At first, Mr. Li opened an audio store and was engaged in the sale of Elan speakers from Germany and Castle speakers from U.K as well as domestic and foreign power amplifiers such as Cary and Unison. He communicated with fans in Jiangsu and Zhejiang closely at that time and decided to produce amplifiers under encouragement.

He named his own brand Music Space Time, which means eternal music and boundless space and time. He spent many years in preparing since 1999 to officially launching the products, time for researching and developing output transformer alone exceeding one year. Although he had rich experience in electronic industry, he was modest and consulted with other fans for each newly designed type. Only if all the fans thought highly of the product, he would put into production. His sincerity even moved the predecessor Mr. Tang Daoji from Wuxi deeply. Mr. Tang is almost 70 years old and is a member of China Institute of Electronics, Acoustical Society of China and China Science Writers Association. He used to be Director of Wuxi Electronic Institute Audio Technology Professional Committee. He has written several books on power amplifiers, one of which sells 400,000 volumes, so he has profound theory basis.

Let’s first look at the specifications indicated on power amplifiers of Music Space Time instead of sound performance. On advanced Music-34WE and Music-88WE integrated amplifiers, frequency width is indicated as 20Hz-100kHz-1dB and 18Hz-100kHz-1dB respectively and the signal to clutter ratio exceeds 90dB. The frequency width, in particular, may break new record of domestic amplifiers. As far as I know, several large-scale domestic amplifier manufacturers, such as Spark, Melody, Meixing, Opera and Kebao, have their own speciality in different field, but none of them can reach the surprising l00kHz-ldB frequency width for electronic tube power amplifier. Mr. Li did not allow me to visit the reeling of transformers due to commercial confidentiality. He only disclosed that they adopt Z10 audio specialized silicon steel sheet imported from Japan (generally Z11 silicon steel sheet is adopted, Mr. Tang thinks it had better not apply silicon steel sheet with super-high permeability and grain to EI iron core), non-oxygen copper insulated wire produced by a Suzhou factory under the investment of Taiwan and special reeling for output transformer, namely in way of layer by layer and segment by segment, so as to reach the result of 100KHz±1dB (connected with audio lines for test).

Mr. Li said the inspiration of their transformer craft originated from American Mclntosh. They spent more than one year on the experiment of all kinds of silicon steel sheet and insulated wire and finally made decision. What is hidden inside the round metal shell is EI transformer of more than 300 watts instead of toroidal transformer. As we know, the output transformer decides over 50% effect performance of power amplifiers. As long as the output transformer is well done, the power amplifier succeeds half. Ideal output transformer should be no loss and weakening of full frequency, infinite preliminary inductance (may have good bass), no magnetic dispersion, no iron loss, no distributed inductance between stages (super-high frequency signal can go through), no direct current resistance (transience, analytic ability and dynamic range can maintain the best status), but such output transformer will never turn up. The designer has to approach such an aim as closely as possible. But there are many contradictions, such as phase reversal caused by excessive amplification of preliminary inductance in order to pursue ideal bass and distortion caused by large signal intensity. Therefore, each domestic amplifier manufacturer has its own theory and practice and no other manufacturer can compete with Music Space Time in specifications.

In a word, transformer leakage shall be reduced and turn number of preliminary coils shall be increased in order to reel a transformer with ideal capability and excellent low frequency. At the same time, distributed capacitors between stages shall be reduced so as to improve high frequency. As what is said above, there are contradiction between reeling coils, leakage and stage capacitor. More coils will cause larger leakage and distributed capacitor. So choice of materials is quite important, iron core in particular. A shell structure is adopted with an aim to increasing inductance and reducing leakage as much as possible under limited number of turns (conducive to lessen distributed capacitor). At the low frequency end, low frequency characteristic is easily caused by magnetic saturation due to less resistance and big current through coil. In order to avoid magnetic saturation of iron core, air spacer should also be put between the upper and lower iron cores, which however will result in leakage increasing. According to my knowledge, materials of transformer are important for hysteresis curve, preliminary permeability and maximum permeability. Usage, current flow and magnetization extent should be taken into consideration in selecting proper materials, for example, nickel steel sheet is not absolutely better than silicon steel sheet. A Japanese magazine named KJ Radio published an article about how the design department of TAMULA chose iron core material of F7000 Collection and discussed the usage and timbre of different kinds of alloys as well as finally clarified the importance of heat treatment to material capability. These are secrets of each manufacturer and also key to timbre performance.

Mr. Li repeatedly emphasized their efforts on the output transformer but declined to disclose. I guess multi-layer coil reeling he mentioned should be arranging preliminary and secondary stage at intervals and adopting efficient high-permeability iron core so as to achieve decrease of loops and reduction of magnetic leakage under the principle of no reduction of inductance. In addition, the way of reeling layer by layer and segment by segment can maintain consistency of total reactance between the upper and lower output tubes. More layers are conducive to reducing capacitor between stages and improving frequency response. Mr. Li said they used to help a power amplifier manufacturer in Shanghai to produce a batch of products exported to Germany by way of OEM. The manufacturer is famous for its output transformer, but the foreigners were greatly surprised at the products manufactured by Music Space Time after test since they were beyond their expectation and imagination. In fact, same technology of transformer is also applied to Music-34MK, Music-300BMK and Music-88K, which are at relatively low prices in Music Space Time (frequency width of 300B only reaches 38kHz±1dB due to limitation of single-ended output transformer). So I think the excellent transformer technology alone can enable Mr. Li Kejie to succeed.

Besides the excellence of transformer, all the amplifier products of Music Space Time use imported parts with high quality as many as possible: including WIMA, RIFA, MCap and Kimber audio capacitor; Black Metal, Phillips, Siemens and ELNA high-speed electrolytic capacitor; metal-film resistance from Japan, America and Taiwan; and power switch as well as Alps potentiometer made in Japan and U.K. The cases are made of imported 15mm high-quality boards and WE advanced adopts 12mm thick aluminum-magnesium alloy boards, which are processed by Italian Euromac digital equipment. The circuit plate uses ordered products with double thickness. American Teflon silver-plating lines are adopted as internal wires and the socket and loudspeaker socket are products from CMC. Due to his interest, Mr. Le has collected a large number of antique rare electronic tubes and he took out one antique Telefunken tube for audition, whose performance was really fantastic. Electronic tubes adopted in formal products are mainly from America, Czech and Russia and are through 24 hrs dynamic aging before going out of the factory. Music Collection products also provide free-charged repairing services within one year and lifelong maintenance (half year for electronic tube).
Mr. Li was proud of their products since no malfunction had occurred during normal application, excluding problems occurred in earlier products without rated pressure lines. All current products have the design of rated pressure, which leads to better stability. In the audio room, we listened to several amplifiers of Music Space Time successively, from the advanced version to ordinary version, and exchanged comments. We got a comprehensive impression that these amplifiers were especially excellent in mid and low frequency. Even if the output power is less than 10 watt, single-ended 300B can produce persuasive bass strength and energy with good control ability. Besides that the timbre of 300B inclines to warm, super-high frequency extension and transparency of EL34 and KT88 are outstanding due to the clear and energetic sound base. Mr. Li disclosed that his aim of rectifying sound is Mclntosh but with more modern sense, higher analytic ability and clearer segment. He also thought that products should first have accurate electronic standard and then timbre. Qualified basic parameters play an important role in product performance. On a test document of Hangzhou Quality Supervision Bureau, product parameters of Music Space Time are excellent. So a same machine can create various performance styles by way of changing electronic tube.

In addition, we noticed that there is real difference in product performance between the ordinary version and advanced version, but the price of the ordinary version is more suitable for most consumers. Mr. Li said frankly that enabling everyone to enjoy music pleasantly is his biggest wish. He does not plan to become the largest manufacturer, but he hopes to provide maximum satisfaction of music for all the people. I recalled that there is a definition for modern scholar-entrepreneur: 1. adopting morality as principle; 2. persistent in integration of benefit and loyalty; 3. good at competition; 4. management based on people; 5. innovative awareness and ability. So Mr. Li Kejian is a scholar-entrepreneur in music space.

Main Product—Music Space Time Music-88WE
Many people think the timbre of KT88 is far from delicacy. Music Space Time has broken the myth and its push-pull output reaches 70 watts. Pentode EF80 is adopted as the front stage. Double triode with medium amplification coefficient 12AU7 acts as phase reversal and transformed long-tail pair circuit is coupled with front stage directly, resulting in simplification of circuit structure, enhancement of transient characteristics, relatively large plate current and high power supply voltage, as well as sufficient excitation voltage provided for output stage. The output stage applies low distortion and high efficiency power beam tube KT88, which is with standard push-pull and fixed bias voltage. The machine applies large loop voltage negative feedback inclusive of output transformer, which can improve the capability and damping parameter of the machine as well as ensure stable operation. High-quality output transformer is the basis of this machine and ensures little phase distortion and wide frequency response. This machine can replace KT88 power tube with 6550 and only the bias voltage is needed adjusting. 6550 has soft timbre while KT88 has powerful timbre. MK ordinary version changes to use two 12AT7 and 12AU7 double triodes respectively.

Main Product—Music Space Time Music-300BWE
The price of this machine is two times of MK ordinary. 9-watt output power is not changed but the vacuum tube and structure have small changes. The powerful output strength and strong mid and low frequency performance is obviously different from ordinary single-ended 300B. Pentode 6AC7 works as the first stage and can obtain enough excitation voltage, which is typical resistance coupling amplification. Anode output of triode 6H6 acts as push and has little non-linear distortion and sufficient driving force. The two triodes are not in parallel connection but in direct coupling with the front stage. Directly heated power triode 300B-98 works as power output and rated bias voltage as well as little loop negative feedback are imposed. Two 5U3 current rectifying tubes are also added in addition to large-scale choke in power part. MK ordinary version changes to use 6J4P pentode, 6N6 triode and 5Z3P current rectifying tube.

Main Product—Music Space Time Music-34WE
This machine also has MK ordinary version but with different lines and vacuum tube. The front stage of WE consists of FP80 pentode. The second stage is long-tail phase reversal circuit consisting of double triodes 12AU7 and is in direct coupling with the front stage without coupling capacitor. The basic structure is similar to Music-34WE. The output stage adopts standard push-pull of pentode EL34. Rated bias voltage is applied in order to achieve maximum power output. Bias voltage value of each tube is adjustable, so it is easy to achieve balance. Negative feedback of loop voltage from the secondary stage of output transformer to the cathode of first stage, including the output transformer, can reduce distortion caused by the output transformer and further improve the capability of machine. The output transformer of special design can ensure the capability of the machine. MK ordinary changes to use four 6N1 double triodes with same output power of 45 watts. But the weight is reduced by 7 kg.

Extracted from《New Audiophile》 2005-51 Author：Lai Yingzhi