A Scholar-entrepreneur in Music
Space & Time
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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years due to application of out-of-date parts, I got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¡À1dB (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¡À1dB 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¡ªMusic 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¡ªMusic 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¡ªMusic 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£ºLai Yingzhi |