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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.
problem of dual ES9038 Pro:
Since 2014 year, we had start to design
the Dual ES9018, we had fail even though try a lot methods . The
dual ES9018 some time can working fine but some time had the delay
on one channel, even the human ears may can not hear the delay but
it is easy can show on the oscilloscope .
We can't sale this
The problem had fixed:
The ES9038 pro had release more than 9
months, since it release, we are not only develop the single ES9038,
I still miss the dual ES9038 Pro design just like miss a old friend.
But solder the dual
ES9038 Pro in the old develop boards, I am fail again.
I give up the old
develop boards but I had not give up the project.
I start design a
new board with the FPGA to separate the channel data and control the
ES9038 Pro working timing .
Then, the problem
The FPGA is important in the NFB 27.77:
The FPGA is Programmable Array Logic.
Nowdays the FPGA
had applied in a lot high end grade DACs, like the popular ROCKNA
Its inside hardware
construction can through the complex software to design and arrange,
and it can upgrade through the software upgrade.
While upgrade the
firmware, just same as upgrade the hardware. The design is much
flexibility , can improve on sound quality , addition the newest
functions , and it can never become out of date.
What the FPGA duty in the NFB 27.77:
1, Separate the data feed to dual ES9038
Pro, let them working in mono mode.
2, Clock re-clock
process and FIFO design for
all inputs , the output data can exact synchronization with clock
signal, reject jitter.
3, Built in high
performance SPDIF interface , give up the built in low performance
SPDIF interface of the ES9038 Pro .
Full discrete output stages:
The signal last stage is the analog output
stages, they can much effect the whole DAC sound quality.
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 as the signal gain and process, they are non feedback design
and working with current signal , so the dual ES9038 pro output
current signal can through the ACSS amp , don't like others design
want to multiple conversion 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 with difficult .
In total the output
stages are working in pure class A state, and without any negative
feedback for the most pure and real like sound reproduce.
There are 4 pcs OPA
built in as DC serve , so the DAC can working well without couple
caps and output the most neutral sound.
Heavy power supplies design:
The DAC had built in 3 units R-cores
transformer, in totol 150W power for supply digital part, Left
analog part and Right analog part .
There are in total
10 groups pure class A PSUs and 3 groups linear PSUs for power
supply to different parts . All the PSUs had ultra high speed and
ultra low noise performance.
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 NFB-27 , 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 .
The 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.
is applied a four channels digital control relays based volume
control. .NFB-27 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
NFB-27 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 13DB high gain,
so can very
easy adjust the volume for both high / low sensitivity
headphone and speakers.
change the volume, the different relays break or close, it may had
slightly switch sound on output and disappear while stop change the
Exponential volume characteristic
Volume steps comparison to normal volume knob
The DAC had separate the digital, Left
analog, Right analog and power transformers parts, every parts had
separate by 5MM thick aluminum boards for avoid the interrupt of
The Left and Right
analog parts had symmetric place beside the digital parts , keep the
wires and distance in same , made the sound stage is better exact .
The sound quality
Some people may don't like the sound of
ESS chips. They are consider the sound is like fake . We want to
change this concept .
At first we want to
let the unit had full burn in, then adjust the parameter , layout
and design to boost the distortion in minimum . This is easy
Then we had to spend a long
term to listen and compare the sound , adjust the parameters to
change the Odd and even numbers distortion to let the sound life and
Finally the DAC may had not the
minimum distortion but had the most neutral sound with life and