The different between dual ES9038 Pro and single ES9038 Pro is large:
The difference is not only the DNR, but the dual ES9038 Pro is working in mono mode, the channel crossing is improved and offer a larger and more precise sound stage.
The difficulties of dual ES9038 Pro:
In 2014 we have began design of 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 fixed:
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 i 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 software upgrade.
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 It can improve on sound quality and add the newest functions , it can never become out of date.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 .
Full discrete output stages:
The signal last stage is the analog output stags , they greatly 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 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 .
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 PSUs provide ultra high speed and ultra low noise performance.
The overall arrangement :
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.
The sound quality adjustment :
Some people may not like the sound of ESS chips. They are consider to sound artificial . We want to change this perception .
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.