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 1 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 pins:
Pin 1, GND
Pin 2, Hot
Pin 3, Cold
Pin 4, GND
KRELL amplifiers have lower gain versus audio-gd Master
series amplifiers when using the CAST connection, so customers can custom
order the Master 1 to have higher ACSS output gain if expecting to
connect to KRELL amplifiers.
What's new in the Master 1 2017
The analog circuits design is
slower develop compare to the digital design. Especial the
Master 1 released since 2012,
we have not change its design , we always like to upgrade the
design but we can't .
Now we are release the new version,
the most improve is applied the single polarity FET buffer
stages in input and output, which is had a bit lower distortion
and improve on the sound quality.
The Single polarity FET stages are
the non feedback design and applied the Toshiba K170 , which is
even had money but can not buy from market nowdays.
The others improve on power supplies
for less noise and darker black back stage.
parts let users can disable the input short by themselves
without soldering work.
Master 1 summarize :
Fully balanced class A design built by discrete analog stages without any OPA or coupling caps in the signal channels.
Non- feedback ACSS analog output stage.
Uses three R-core transformers (135W total) with separate power supplies
for the digital components and right and left channels.
More than 45,000uf audio grade NOVER capacitors are used to ensure
ample and smooth power delivery.
A total of 8 groups of high-quality class A parallel PSU's,
four double-stages for dedicated DC supply.
To achieve a high S/N, the control circuit is powered with
Uses high grade parts and exactly matched transistors.
Four-channel 99 steps digitally controlled relay-based volume
control avoids channel imbalance and improves sound quality.
5 analog inputs:
RCA X2, XLR X2, ACSS X1
XLR / RCA / ACSS
Memorizes all settings and resumes the last settings when
Master-1 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-1 applies ultra-low distortion
single stage ACSS amplifier and soldered directly on the motherboard.
It is a fully class A preamp 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 class A mode.
The XLR /RCA output buffers are
Non-feedback, for low impedance, we applied a two-stage parallel
connection, the output impedance is only 10 ohms.
Master-1 has all components of four channels
exactly matched before installation.
Three special transformer are used to supply power
separately for the audio and control circuit.
Master-1 uses 8 groups of
high-quality class A parallel connection PSU, four double-stages for
dedicated DC supply.
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-1 applies two linear PSUs for the
display and control parts, avoid the disturbances through power line
from affecting the amplifier.
Master-1 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-1 can convert to balanced ACSS signal and output real balance
signal from XLR and ACSS.
Master-1 can output RCA, XLR and ACSS at the
The input channels of Master-1 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 .
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-1 , 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
dual FET non-feedback buffer output stages offer the
very low output impedance .
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-1 is
applied a four channels digital control relays based volume control.
.Master-1 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.
Master-1 allow users
select between 99 steps exponential characteristic volume
control and 70 steps linear characteristic volume control,
whatever volume control allow users smooth to control the volume
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.
Master-1 has complete separation of left, right
amplifier channels, power supply, and transformer.
Master-1 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 & SOLEN caps, custom
order NOVER (UK brand) caps, all audiophile grade input & output
sockets (Neutrik ) and gold IEC socket.Master-1 all parts of four channels had exact match before install.