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USB isolator upgrade for Amanero combo 384 as default configure.
USB isolator can avoid the computer electric interrupt feed in the
DAC cause the sound quality worse . In AB compare , it can
improve on sound transparency slightly .
24th. Feb. 2018 : Separate pure class A PSU
power supply for Amanero upgraded.
Since the USB isolator
upgraded, the Amanero had to power supplied with USB power , it make
the sound improved ,less digital but some customers have concerned
the unclean USB power may degrade on sound quality.
Now the product had include the
separate pure class A PSU power supply for the Amanero to boost the
USB connect sound quality better . After the upgraded, the USB
connect don't spend any USB power, and can working with not only
computers but Iphone and Ipad.
Audio-gd products had
design and test based on the AP SYS-2722 (The top-drawer
professional equipment in world)
The different between
dual ES9038 Pro and single ES9038 Pro is large:
The different not only the DNR, but the
dual ES9038 Pro working under mono mode, the channel crossing is
improve and offer a larger and exact sound stage.
of dual ES9038 Pro:
In 2014 we began to design
the Dual ES9018, but we had failed even though we have tried try a
lot of methods . The dual ES9018 can sometimes work fine but
some times had delay on one channel, even though the human ears
may not hear the delay but it is easy to show on the oscilloscope
We could not sale this product.
The problem has been
The ES9038 pro had been released
more than 9 months ago. Since its release, we developed single
ES9038 but I still I was missing the dual ES9038 Pro design just
like miss an old friend.
I solder the dual ES9038 Pro in the old development
boards, I failed again.
I have given up the old development boards but I had
not given up the project.
I start design a new board with the FPGA to
separate the channel data and control the ES9038 Pro timing .
Then, the problem has been fixed.
The FPGA is
important in the NFB 7.77:
The FPGA is
Programmable Array Logic.
Nowadays the FPGA had
applied in a lot high end grade DACs,
like the popular ROCKNA WAVEDREAM DAC.
Its internal hardware construction can through the
complex software design and arrangement , be upgraded through the
Upgrade to the firmware is the same as same as upgrade
to the hardware. That design is much more flexible . It can
improve on sound quality and add the newest functions , it can
never become out of date.
What the FPGA duty
in the NFB 7.77:
1, Separate the data feed to
dual ES9038 Pro for working in mono mode.
2, Clock re-clock process and FIFO design for all inputs
, the output data can be exactly synchronised with clock signal,
to reject jitter.
3, Built in high performance SPDIF interface
, bypassing low performance SPDIF interface
of the ES9038 Pro .
discrete output stages:
The signal last stage is the
analog output stags , they greatly effect the whole DAC sound
The output stages working after ES9038 pro, they are full
discrete transistor built with hole parts but not SMD parts
The high speed ACSS amps
work as the signal gain and processing , they are of non feedback
design and working in current signal mode . the dual ES9038 pro
output [current signal] goes through the ACSS amp
.I don't like other design with multiple conversion to the signal
between current and voltage.
The output buffers are the pure class A design , built
with 4 pcs 150W
(in total 600W ) on every channels, to drive the most headphones
without difficulty .
In our design output stages working in pure class A ,
and without any negative feedback for the most pure and life like
sound reproduction .
There are 4 pcs OPA built
in as DC servo , so the DAC can
work well without coupling caps and output the most neutral sound.
Heavy power supplies design:
The DAC had
built in 3 R-core transformers, in totol of
150W of power to supply digital sections also Left analog and
Right analog section .
There are in total of 14 groups of pure class A PSUs and
3 groups linear PSUs
to provide power to different parts . All the PSUsprovide ultra
high speed and ultra low noise performance.
The DAC has
separated the digital, Left analog, Right analog and power
transformer parts, every part has been separated by 5MM thick
aluminium boards avoid the interference between each others.
The Left and Right analog parts are symmetrically placed
beside the digital parts , keep the wires and distance of the same
length. That helps to create more exact sound stage.
quality adjustment :
Some people may don't like the
sound of ESS chips.
They are consider to sound artificial . We want to change this
At first we want to let the unit fully burn in, then
adjust the parameters layout and design to lower the distortion
to absolute minimum . This is easy part..
Then we have to spend a long time on listening tests
and constantly comparing sound quality . Than we adjust the
parameters to change the Odd and even harmonics to let the sound be
life like and palpable.
At the end the DAC may
not have least amount of distortion but has the most neutral sound
with life and realism.