Custom order High Gain model
for the HE6 and low sensitivity headphones:
The product default had 16DB gain, customers can
custom order extra +6 DB to +12DB gain, in total 22DB gain, had better
match with the headphone which is
sensitivity low than 95DB.
Price is USD45.
If the headphone sensitivity lower than
100DB, choice extra +6DB.
If the headphone sensitivity lower than
90DB, choice extra +12DB.
Audio-gd products had
design and test based on the AP SYS-2722 (The top-drawer
professional equipment in world)
Connect with KRELL amplifiers:
Master 9 is compatible with KRELL amplifiers CAST inputs.
A cable can be made
with one side connecting to Master 1 ACSS outputs, other side to
a KRELL amplifier CAST inputs.
The ACSS output
Pin 1, GND
Pin 2, Hot
Pin 3, Cold
Pin 4, GND
have lower gain versus audio-gd Master series amplifiers when
using the CAST connection, so customers can custom order the
Master 9 to have higher ACSS output gain if expecting to connect
to KRELL amplifiers.
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 power .
Uses three R-core transformers (In total 135W ) separate power
supplies for the digital control components, right and left
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,
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 gain mode.
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 / 6.3MM X1
Modification guide on
headphone jack for 4-pin balanced headphone output.
Click here to read:
Detail of the Current Conveyor Technology
There are a lot different DACs in world, 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 Single
polarity 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.
The FET buffers working on pure class A state, and it is so short
signal journey , it can keep the sound quality without coloration
,dry and harsh .
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
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
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 adjustment .
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
Three special transformer are used to supply power separately for
the audio and control circuit.
Master 9 uses
8 groups of high-quality PSU .
The 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 clean power
applies seperate linear PSUs for the display and control parts,
avoid the disturbances through power line from affecting the
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 XRL 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 world.
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 groups diamond non-feedback
buffer output stages offer the very low output impedance .
volume 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.
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 the gear.
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
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.