Audio-gd products had
design and test based on the AP SYS-2722 (The top-drawer
professional equipment in world)
The unit applied input short design :
Nowdays a lot high and middle range preamps, headphone amps and
integrated amps had applied the input short design .
Without the input short design , if the amp connect to multi-ply
sources and all source had playing , different sources will had
the signal crossing cause the sound quality degrade .
For example, the input 1 connect to a DAC and the input 2
connect to a CDP, while both had playing, the CDP signal will
crossing to the input 1 , mix with the DAC signal cause the
In world there are more than 99% DACs and the sources had allow
the outputs short , if your DAC decalre can't short the output ,
please custom order the amp without input short , but in the
case , while you connect multi-ply sources, you are better only
let one power on and others power off for avoid the signal
Fully balanced pure class A design built by discrete analog stages without any OPA or coupling caps in the signal channels.
Non- feedback ACSS analog output stage.
Total applied 12 pcs exact matching 150W transistors ( In total
1800W ) as the
output stages and PSU stages for implement large class A output
Uses three R-core transformers (In total 135W ) separate power supplies
for the digital control components, right and left channels.
More than 55,000uf audio grade NOVER capacitors are used to ensure
ample and smooth power delivery.
A total of 9 groups of PSU's for dedicated DC supply.
Uses most Hi-end grade parts and exactly matched transistors, OCC
Four-channel 100 steps digitally controlled relay-based volume
control avoids channel imbalance and improves sound quality .
Supper Exponential Volume Characteristic, easy match the
volume with very high headphone / speaker without change the
20DB gain can drive the low sensitivity headphone very well.
5 groups input:
RCA X2, XLR X2, ACSS X1
Preamp output :
XLR / RCA / ACSS
Headphone amp output: 4pins XLR X1 / 3pins XLR X2 /
Static storage mode control software for avoid disturb sound
quality , the MCU output once control data and save in the
perform parts ,then stop output data until users next operation.
Modification guide on
headphone jack for 4-pin balanced headphone output.
Click here to read:
Parts for the modification is USD30. (Includes one female 4-pin plug
and one male 4-pin plug, some tapes and some tin solder.)
Detail of the Current Conveyor Technology
There are a lot different DACs in worth, they had different design
and output impedance . For avoid the sound quality effect by
different DAC's output impedance, in the Master 9, it had design 4
groups expensive class A FET cascode buffers in the input . All the input
signals through these FET buffers, the output impedance had become
very low, even the source had high or low output impedance.
buffers working on pure class A state, and it is so short signal
journey , it can keep the sound quality without coloration ,dry and
Master 9 is a true balanced design applying the newest ACSS
design which can improve the XLR connection to sound as good as the
ACSS connection. They seem complex , but in fact they are the most simple design
the world has ever had , their a lot components to process the power
supply. The simplest and shortest signal journey brings out the
most neutral and least colored sound.
Master 9 applies ultra-low distortion
single stage ACSS amplifier and soldered directly on the motherboard.
It is a fully class A preamp / headphone amp and applies class A power supplies.
The ACSS is a non-feedback
technology made with discrete amplifiers. Most people know the global
feedback design can offer better specs in test measurements, and
non-feedback can't do well in test measurements but can offer better
sound for the human's ears. Here is a conflict of the classic circuits.
But the ACSS opens a new field, it can offer a least coloration sound
which is more neutral with very low distortion and high linearity. So
it can retain the dynamics, detail and neutral sound but not sound
bright or harsh.
All signal gain is in current, all transistors
work in pure class A mode.
The Master 9 output buffers
had applied 4 pair power transistors ( 150W / 15A ) working on pure class A
state, the output
impedance is only 1 ohms , it can drive most headphones and amps
as well .
Master 9 has all components of four channels
exactly matched before installation.
Strong class A output stages:
The Master 9 had design 4 groups diamond difference output stages as
the balance drive stage, every
parts had exact matching before assemble so don't need any human
The output stages had four pair 150W transistors ,they also working
under pure class A state , the
balance output mode had 4X times power than the same state
single-ended mode .The pure class A design had larger
drive ability than the specs, it drive the headphone not worst than
a double power class AB design , not to refer, the pure class A is
the best sound design in worth.
The balance drive mode can kill the
noise and distortion in the end of the headphone, much improve the
sound stage, background and the transparency ,ect.
Three special transformer are used to supply power
separately for the audio and control circuit.
Master 9 uses 8 groups of
high-quality PSU .
class A parallel connection PSU has very high input impedance to avoid
pulse through the PSU from affecting the preamp and low
output impedance with very fast speed and high linear, so it is a very
Master 9 applies seperate linear PSUs for the
display and control parts, avoid the disturbances through power line
from affecting the amplifier.
Master 9 can input
not only XLR balanced signal or RCA unbalanced signal, but also the
top-grade ACSS current signal. It can also output RCA signal, balanced
signal, ACSS current signal to the power amplifier. Using RCA input, Master 9 can convert to balanced ACSS signal and output real balance
signal from XLR and ACSS.
The ACSS input /
output can compatible with KRELL CAST products and SATRI technology
gears . The XLR / RCA can compatible with any audio devices in
Master 9 can output RCA, XLR and ACSS at the same time
in preamp output model , in headphone amp model, Master 9 can output XLR
,single end for headphone.
The input channels of
Master 9 adopt separated
shielding method. When switching, the idle signal lines linked to the
equipment and the ground wire are completely disconnected. The idle
input ports of the equipment are shielded. In that case, the sound
quality won't be affected even with more connected equipment.
The volume control is also different from conventional
technology. Conventional volume control technology is
the volume control implement in the analog amp
input stage through a volume pot to reduce the signal . The
volume pots quality effect the sound quality direct , the low
quality volume pot cause lost the detail and channels imbalance
cause the soundstage distortion . Even the high
performance volume pot still cause the detail lose. Whatever
quality volume pots, must cause the S/N worst .
the Master 9 , we applied the I/V conversion volume control ,
the volume control just a
variable passive I/V conversion place at the ACSS amp output ,
where the output is the current signal, not the voltage signal. The
volume control is I/V conversion, and the volume depends on the
current (I) conversion to the voltage (V). (Like R-2R D/A chips
output passive I/V conversion)
It can keep the signal frequency band flat and
not lost any detail.
It can't degrade on sound
quality in every volume level . After the volume , there are four
diamond non-feedback buffer output stages offer the
very low output impedance .
Mark Levinson also knows that current volume control has great
benefits, so in their Top End preamp NO.32 volume control, they use
many components to change the signal to current signal (I), then
implement the volume control
, and then change back
to voltage signal (V) again. But Master 9 is simply a more complete
work in terms of the current signal, and technically, it is superior
to conventional technology.
The less conversion bring much neutral sound .
control quality is much important in the real balance gear . It must guarantee the
four channels signal control exact to achieve the performance of the
real balance gear . If the cool and hot of the balance signal
can't guarantee exact, the balance output will has large distortion
cause the sound quality and performance even much worst than a
single end gear waste the balance gear design and the cost.
In Master 9
is applied a four channels digital control relays based volume
control. .Master 9 has total four channels through changing the
DALE resistors to control the volume for avoid channels
imbalanced ,achieve the best performance and sound quality of
Master 9 have 100
steps volume control, control range achieve 90DB (usually the
steps volume ports, potentiometer volume port, relays base
volume control all have around 70DB range ), very smooth
control range on first 50 steps , cooperate with 20DB high gain,
so can very
easy adjust the volume for both high / low sensitivity
headphone and speakers.
While change the volume, the different relays break or
close, it may had slightly switch sound on output and disappear
while stop change the volume.
Supper Exponential volume characteristic
The Volume steps comparison to normal volume knob
Master 9 has complete separation of left, right
amplifier channels, power supply, and transformer.
Master 9 uses heavyweight all-aluminum alloy chassis to prevent the
eddy current of transformers from interfering on circuit board.
Uses all audiophile grade
components, including DALE resistors, WIMA caps, custom
order NOVER (UK brand) caps, all audiophile grade input & output
sockets (Neutrik ) and gold IEC socket. Master 9 all parts of four channels had exact match before install.
Static storage mode control software:
control softwares design, the MCU will continuously output data to
the perform parts , the MCU had the very high speed, so the output
data become high frequency impulses disturb the audio signal
circuits make the sound worst .
This product had applied static
storage mode control software , the MCU output once control data and
save in the perform parts while just power on and users operate
,then stop output data until users next operation. This design make
the sound quality improve on the clear and transparency .