User tweak the sound
the XLR version, user can connect the output either real XLR output
and SE output to get the total different sound flavor and sense.
For both XLR and SE version,
user can swap the tube A and B to get the different sound flavor,
before swap, must mark the sign on the tube .
Please note before place the order¡G
Because the vacuum valve life only several thousand hours, the
vacuum valves warranty 3 month, other parts warranty 10 years
follow our warranty policy .
avoid the sound quality degrade, we are recommend replace the new
vacuum valves after 5000 hours, (Every day 3 hours, it is around 5
years) . After replace the new vacuum valves, it need around 150
hours burn in.
Vacuum 1 design and building may different to others.
It is the most pure
vacuum valve unit, in the power supply and signal channel, only
built with resistors, caps and vacuum valves.
It had not built in power
regulators for vacuum valve's filament and signal channel.
It had not built in
choking coil and electrolytic caps in power supply, only with the
small capacity film caps and vacuum rectifiers for rectification and
It through the especial
design boost the SN over 98DB on the normal listen volume .
So its sound may has some different than some vacuum
units you have ever listened with .
With Vacuum 1, you
can not hear the vocal sound like thick but that like the singer
stuff something in the mouth. You also can not hear the much warm and
slow sound .
With Vacuum 1, you
can hear the transparency , detail and dynamic sound but with the tubelike and musical sound ,and a little warm.
The different between Single Ended and
The single ended version
mean the product has built in two channel amps for Left and Right
The balanced version mean
the product has built in four channel amps for Left and Right
balanced signal process.
While I design and
adjust, the balanced version in the full balanced system, can
improve the transparency and sound stage on sound quality, so for
kept the best musical, the four channel amps had separate total.
Based on this design,
while the balanced version connect the balanced sources, it can
output full balanced signal and single ended signal, while it
connect the single ended source, the power amp can connect XLR
output socket but the hot output is without signal.
For more fun to the user
of full balanced system, face to the front plate, the Left side XLR
output sockets have the full balanced output , the right side XLR
output sockets only have the hot signal output (mean single ended),
user can through the XLR cable to experience the different sound
flavor between full balanced and single ended.
Below describe is base on the
Vacuum 1 SE
Design concept ¡G
All active components
have the nonlinear character , it can not has the perfect on every
side . While we designed the unit, we had to choice the perfect area
of the components .
We had consider the most power amp that had around 1V input sensitivity,
while the preamp output 1V level, the power amp got the full power
output, so we decided make the perfect area on the 2V and below
output level , though its max output over 15V .
About the frequency band,
we have not looking for the best specs on paper, but we have through
the long term listen and adjust to confirm the final parameter .
Vacuum 1 had built in two pc same board for L and R
channels, we have not design the mirror board, because the vacuum
valve can not as the transistor that can assemble in the mirror
design board with invert the part's forward, the vacuum valve can
not assemble with invert forward, if apply the mirror design,
must make the different layout cause the different performance between L and R channels, and
effect the sound quality.
The power filtering caps and
signal couple caps all applied the SOLEN film caps , and the built in vacuum valves
which is we had test some lot different models and this is finally
choice , they is the best combo based on my over 15
years building experience .
We are advice the users
even have the DIY skill and tons money, but don't change any built
in parts for keep the unit has perfect match on musical and precision .
Most vacuum preamps have around 20DB gain, nowdays most sources have
over 2V output level, that make the volume control become difficult
Vacuum 1 had 11DB
gain, it allow control the volume quite smooth .
Vacuum valve course of mine :
In early of 1990'S, the local business men bought some warships and
took off the parts for
sale , but no one bought the vacuum valves, so I can got
several hundreds KG vacuum valves and start the vacuum valve course
After 15 years built and studied (I was stop build vacuum valve
units in 2007) , I picked up some experience .
1¡AFilament must power supply by AC for got the pure tubelike sound.
2¡ANever apply electrolytic caps , must apply film caps and can not
apply large capacity caps.
3¡ANever apply power
4¡ANever apply choking coil, it offer the choking coil sound but not
5¡AMust apply the
vacuum valve rectifier .
6¡AFull wave rectification is necessary but if you looking on our
design diagram, the full wave rectification is different to most of
7¡ANowdays the sources have high output level, the preamp only need
low gain design.
8¡AThe most pure
vacuum valve design has the most pure tubelike sound.
Especial design of the
Some vacuum valve units have applied the DC power regulator for the
filament, high voltage or big caps or choking coil for improved the SN
went with other way , it had applied the especial design to improved
the SN .
not only improved the SN but improved the transparency, detail and
distortion on sound .It is the key of the unit .
Current mode volume control system :
The normal volume control had applied the potentiometer ,the signal must
through the potentiometer then feed to next stage , the
potentiometer must effect the sound quality a lot .
had applied the current mode volume control, the signal only through
a resistor then feed to the next stage, without through the volume
control port . I publicised the design on <Radio & TV> in
Improve on distortion :
Vacuum valve is nonlinear components , its character is input signal
level higher cause distortion increase , and the low and high output signal
level cause the distortion increase .
We have design the dual volume control ports for improve the
The first port places at
the preamp input, for limit the input level avoid the high signal
level cause the
distortion increase .
The second port places on the gain vacuum valve
output, to select and apply the perfect area of the vacuum valve.
For the stronger
output ability, there are two vacuum
valves parallel connect as the buffers after the second volume control port.
Through the especial design, the THD+ noise under 0.05% , and you
can see the level is flat between 20Hz -10KHz, and roll off over 10KHz .
The well know character of the vacuum valve is sound musical , but
another is the bad discreteness .
We had test the same batch vacuum valves, the best
and the worst cases which had around 100X times different on
the THD level .
For promise on the sound quality and
performance, we have spent a lot time to check every vacuum valve in
the heat state by the Audio Precision equipment, then choose the
matched vacuum valves assemble in the units , return the un-fit vacuum
valves to the distributor .
Improved on the transparency and detail :
This theory may difficult to understand if you don't know the electric
The vacuum unit has high noise output level , if the
detail music signal has low level which is similar to the noise
level, it will be kill by the noise and lose , you can not hear this detail
music signal .
Allow me to try to
explain by my poor English .
For example, the preamp output noise level is 0.5MV, which is a good
preamp level .
While the output
music detail signal less than 0.5MV, it will
kill by the noise . Even the music detail signal level over
than 0.5MV, like 1MV, because the noise kill half of it, it become
the larger distortion signal but not the original signal anymore.
image, with the normal vacuum preamp , most time listen the music
signal up to 300MV or 500MV in home, but lost all signal less than 0.5MV, how
bad of the dynamic and how large signal had lost .
With Vacuum 1 design, the 1MV output detail music signal, the unit
will gain it up to tens times, then through the second volume port
attenuation back to 1MV .
This operate has some advantages
1, gain the weak
signal up to tens times , far away the noise level for avoid effect by the noise level .
2, The vacuum amp
has increase the distortion while the output is weak, gain to tens
MV can reduce the distortion .
3, Attenuation the music signal
from tens MV back
to 1MV but in same time the noise also had attenuation . For example
if attenuation 20MV music signal back to 1MV, the 0.5MV noise has reduce to 0.025MV , so the SN
has a larger improve.
SN had been improved :
quality good or bad is depend on the personal sense , but the SN good
or bad , customer can feel it easy . Some vacuum valve preamp , on
the normal listen volume, pause the music , may can hear the hum at
1 or few meter from the speakers .
I have checked an USA made preamps over USD8000 in Chinese market,
it had 84DB at 2V RMS unweighted .
Vacuum 1 SN
Because the especial design, put 2V RMS as standard, the unweighted SN
level while the volume on 10 steps, SN is 109DB, and volume on 30
steps, SN is 104DB, and volume on 50 steps, SN is 98DB , and volume
on 70 steps , SN is 91DB, volume on 90 steps has over 2V output, SN
is 84DB if still count 2V standard but in fact it should has higher
The SN is supper excellent on the low volume can promise the low
volume has more detail reproduce without lose . On the other hand, some
vacuum preamp, in low volume, the detail lose more than high volume
Usually I listen the music with volume 30-50 steps, it mean the
Vacuum 1 can promise the SN over 98DB in normal listen.
Volume control character :
Vacuum 1 has 95DB volume control range , under 15 steps, the
volume increase few DB on every step, over 15 steps, it has 0.75DB
increase on every step, allow smooth and precision to adjust the
For avoid the noise pick up, the volume control board had shield by
a copper box .