YULONG DA-ART Aquila II, an Affordable 768kHz 4Watt All-in-One Performer
Apr 10, 2020 at 11:52 AM Thread Starter Post #1 of 67

YULONG Audio

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Aquila II setup 012.jpg


DA-ART Aquila II is our latest premium All-in-One DAC/Amp/Pre for Personal Audio application. It incurred numerous technologies from our Reference product DA10 including the high precision low noise JIC (Jitter and Interface Control) System, our proprietary FPGA solution to enhance audio performance by optimized data integrity, de-jitter and minimized digital artifact before the digital audio signal transmits to the DAC chip.

The Aquila II measures exceptional well, and it also sounds incredibly resolving and realistic. It is designed around the ESS flagship ES9038Pro 32-bit DAC chipset offering768kHz and DSD512 decoding capability. It takes advantage of the new ESS design and facilitates a dual digital processing circuit offering two distinctive synchronous modes. The analog audio circuit has incorporated a high precision analogue volume control to make sure the pre-amp and headphone amp output preserve every bit of resolution and dynamic even at low volume level.

Aquila II Color.jpg


Key Features
  • Proprietary high precision low tolerance YULONG JIC (Jitter and Interface Control) System:
    • Optimize data integrity and enhance digital signal quality.
    • De-jitter and minimize digital artifact.
  • Outstanding digital audio capability:
    • Design around ES9038Pro DAC chipset with industry-leading 32Bit/768kHz and DSD512.
    • Widely recognized XMOS XU208 solution with customized (with license) Thesycon driver to enhance sound quality and stability.
    • All inputs interfaces support DoP64 and DoP128, USB input interface supports Native DSD64/128/256/512additionally.
    • Choices of 3 digital filters to fine tune your system for different music genres and personal preference.
  • Custom developed dual digital processing circuit offers unique digital audio options:
    • Synchronous mode: sounds more engaging and musical with an analogue presentation.
    • Asynchronous mode: excels on clarity and ow-level detail.
  • State-of-the-art analogue implementation:
    • 99 steps digitally controlled analogue volume for Preamp and headphone output.
    • DC coupled Class AB amplification, delivers upto 4000mW per channel at 32Ω.
    • Outstanding headphone performance specially optimized for low impedance headphones, ensure low distortion and outstanding handling capability even at 16Ω loading.
  • All-in-one design with comprehensive connectivity:
    • Fully balanced design, low impedance DAC line output, high current preamp and headphone amplification.
    • USB Audio supports MS Windows, macOS,Linux.
    • Special attention to enhance support to Android and iOS mobile and tablet devices.
  • Multi-stage independently regulated power supply from two toroidal transformers with low noise regulators.
  • Intuitive control through single high precision probably-damped volume knob.
  • Seamless, compact and sleek aluminum chassis with large IPS wide angle display, supported by unique claw-style suspension feet.
Aquila II Functional Diagram.jpg


Technologies

From technologies point of view, Aquila II is a significant advancement from the original Aquila, we have revamped the complete digitalaudio design and enhanced performance on both DDC and DAC.

JIC (Jitter and Interface Control) System

This is a digital audio technology that will convert the input audio signals into low-jitter I2S bit-stream, apply FIFO input buffering while synchronize with the built-in Femtosecond Oscilators. The system will then pulled in and locked the signal by a dual PLL. Our FPGA will distribute and synchronize the signal and then output high quality low-jitter I2S bit-stream through FIFO.

Dual ESS Digital Processing Circuit

This will allow user to switch between two different synchronous modes through on-screen menu:

Synchronous mode:this is a fully FPGA based digital processing. We have bypassed the ASRC circuit within the ES9038Pro DAC and execute dynamic frequency distribution in different sampling frequency range. All processing are conducted at original sampling frequency and will enhance musicality with excellent analogue presentation.

Asynchronous SRC mode: input signal will be optimized by FPGA and then process by the ESS internal digital processing circuit. The built-in ASRC function will up-sample the signal to a higher sampling frequency and will enhance clarity with refined details.

Optimized for MAS (Mobile Audio Source)

Aquila II incorporates XMOS XU208 in its USB Audio design and takes advantage of our FPGA based JIC technologies. In this implementation, we have paid special attention to optimize the compatibility and stability with iOS devices such as iPad Pro and iPhone, we see MAS (Mobile Audio Source) as inevitable norm and shall continue to develop necessary support for Android and iOS device as audio source of our DAC/Amp.

Aquila II Black and white.jpg


Technical Specification

Yulong Aquila II Specification.jpg


The Suggested Retail Price of DA-ART Aquila II is US$700. It is available immediately at Shenzhen Audio.
 

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Apr 10, 2020 at 12:12 PM Post #2 of 67

YULONG Audio

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Jul 18, 2020 at 8:30 AM Post #5 of 67

marcusd

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Jul 18, 2020 at 8:49 AM Post #6 of 67

YULONG Audio

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Thank you marcusd, this is a very detail "first contact", We were on the assumption that this will be a brief introduction, we didn't expect a comprehensive explanation to this level..

We are very interested in the paring with HEDDphone, we read a lot of good reviews about this headphone, but we can't find a demo pair to try out with Aquila II so far, we are looking forward to your detail impression. :beerchug:
 
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Jul 18, 2020 at 5:43 PM Post #7 of 67

YULONG Audio

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The Aquila II has incorporated THREE important digital audio technologies, namely JIC (Jitter Interface control), Dual ESS digital Processing, and MAS (Mobile Audio Source). JIC is our proprietary technologies and we'll explain that in more detail later. The MAS is an emerging application, there is no industrial or de facto standard and the landscape is still evolving, we might not be able to get it right in our first attempt, but we gathered sooner is always better, so we didn't wait and try our best to optimized our Aquila II to cope with MAS (Mobile Audio Sources)

So what exactly is Dual ESS Digital Processing, the name is very generic, it can be anything, or it can be nothing but a fancy name? :

In simplified term, this is about manipulating the ASRC (Asynchronous Sample Rate conversion) function of ESS DAC chipset. ESS described their ASRC as “Various embodiments perform sample rate conversion of a sample series at an input rate to an output rate. A version of the sample series is corrected with timing error information generated by a digital loop. The digital loop is locked to a first rate and clocked at a second rate." (US Patent US7436333B2). ASRC is not a unique concept of ESS, but the industry generally agreed that ESS has implemented this concept sophisticatedly, it is one of the core technologies of ESS DAC chipset, providing a high resolution edge over its competitors.

On the other hand, some audiophiles consider ASRC as the root of the ESS “digital” sound signature. Others have experimented with DACs that have defeatable ASRC and noticed that while mediocre source with high jitter will be benefited by the ASRC, the DAC, when feed by a high quality source with low jitter, can sound better when ASRC is disabled.

The problem is we don’t have the choice with ESS in the past. The ASRC of ES9018 and ES9028Pro is non-defeatable, but now we have this option in the latest ES9038Pro, it’s complicated to implement, will increase jitter and downgrade audio specification if not handle correctly. Given YULONG’s long track record with ESS DAC chipset since 2011, we decided to become one of the very few manufacturers to implement “synchronous” mode ES9038Pro DAC, especially at below $1K budget.

To bypass the ASRC feature of ES9038PRO, the operation of the DAC must remain in Synchronous mode and that will require the FPGA us to alter the Master Clock frequency according to the sampling frequency simultaneously. Dynamic clock divider itself is not complicated, it can be straight forward if we ignore the jitter and phase noise introduced by software synthesized clock. The high fidelity approach will involve high quality femtosecond oscillators with phase locked loop keeping everything in sycn.

So finally, we have created the Dual ESS Digital Processing that allow user to switch between two different synchronous modes through on-screen menu:

Synchronous mode: this is a fully FPGA based digital processing. We have bypassed the ASRC circuit within the ES9038Pro DAC and execute dynamic clock divider in different sampling frequency range. All processing are conducted at original sampling frequency and will enhance musicality with excellent analogue presentation.

Dual ESS Digital Processing (Sync).jpg



Asynchronous SRC mode: input signal will be optimized by FPGA and then process by the ESS internal digital processing circuit. The built-in ASRC function will up-sample the signal to a higher sampling frequency and will enhance clarity with refined details.

Dual ESS Digital Processing (ASync).jpg



While the technical content is related to synchronous vs asynchronous, we want to avoid confusion with Asynchronous transmission in USB Audio, so our marketing team decided to skip the key words in the feature name and called this Dual ESS Digital Processing
 
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Aug 3, 2020 at 5:16 AM Post #8 of 67

YULONG Audio

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Aquila II Sales Guide 02.jpg


JIC (Jitter and Interface Control) in Aquila II

This is our proprietary FPGA solution to enhance audio performance by optimized data integrity, de-jitter and minimized digital artifact before the digital audio signal transmits to the DAC chip. YULONG started off with off-the-shelf solution in our earliest products, but when we improve our DAC handling and audio design in subsequent products, we feel the need to improve the Digital Audio processing BEFORE we feed the signal into DAC, especially when users are using sources that tablet or computer as their music source. We have noticed these high jitter music sources reduced the musicality of our DAC performance. Every so often when customers complaints the DAC sounds very “digital”, the quality of music source is frequent the focus of attention.

We started to work out FPGA applications on pre-DAC processing since 2017 and by 2019, we have developed our complete JIC (Jitter and Interface Control) FPGA solution. This is an accumulation our 15 years of digital audio experience and was first implemented in our reference DA10 All-in-One DAC headphone amplifier. We were amazed by the improvement over previous non-FPGA model and we didn't hesitate to pass down the technology to our mid-tier products when we redevelop the second generation Aquila.

To go into detail, our JIC FPGA module will convert S/PDIF bitstream and USB Audio data into low-jitter I²S data stream, we then apply FIFO input buffering in order to synchronize with the femtosecond oscillators in Aquila II. The system will then distribute the signal to various clock functions and perform synchronization before pulled in and locked the signal by a dual PLL. The final high precision, low noise, low-jitter I²S data stream will then output through FIFO to ES9038Pro for actual digital analogue conversion.

Aquila II Sales Guide JIC04.jpg
 
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Aug 4, 2020 at 7:44 PM Post #9 of 67

Cat Music

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Aquila II Sales Guide 02.jpg

JIC (Jitter and Interface Control) in Aquila II

This is our proprietary FPGA solution to enhance audio performance by optimized data integrity, de-jitter and minimized digital artifact before the digital audio signal transmits to the DAC chip. YULONG started off with off-the-shelf solution in our earliest products, but when we improve our DAC handling and audio design in subsequent products, we feel the need to improve the Digital Audio processing BEFORE we feed the signal into DAC, especially when users are using sources that tablet or computer as their music source. We have noticed these high jitter music sources reduced the musicality of our DAC performance. Every so often when customers complaints the DAC sounds very “digital”, the quality of music source is frequent the focus of attention.

We started to work out FPGA applications on pre-DAC processing since 2017 and by 2019, we have developed our complete JIC (Jitter and Interface Control) FPGA solution. This is an accumulation our 15 years of digital audio experience and was first implemented in our reference DA10 All-in-One DAC headphone amplifier. We were amazed by the improvement over previous non-FPGA model and we didn't hesitate to pass down the technology to our mid-tier products when we redevelop the second generation Aquila.

To go into detail, our JIC FPGA module will convert S/PDIF bitstream and USB Audio data into low-jitter I²S data stream, we then apply FIFO input buffering in order to synchronize with the femtosecond oscillators in Aquila II. The system will then distribute the signal to various clock functions and perform synchronization before pulled in and locked the signal by a dual PLL. The final high precision, low noise, low-jitter I²S data stream will then output through FIFO to ES9038Pro for actual digital analogue conversion.

Aquila II Sales Guide JIC04.jpg
The JIC implementation seems to me an innovation in search of perfection. My question is related in the sense that, what would happen if I pair Aquila II with a separate amplifier, would this JIC implementation stop working? Or does it just work regardless of which amp is paired?
 
Aug 5, 2020 at 6:44 AM Post #10 of 67

YULONG Audio

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The JIC implementation seems to me an innovation in search of perfection. My question is related in the sense that, what would happen if I pair Aquila II with a separate amplifier, would this JIC implementation stop working? Or does it just work regardless of which amp is paired?

You can perceive JIC as DDC before DAC, so whatever you used AFTER the DAC chain has nothing to do with JIC. The only thing that affect JIC is the mode of operation in DAC. In the case of Aquila II, we have implemented Dual ESS digital Processing which offers synchronous mode and asynchronous mode of ES9038Pro. The synchronous mode involve full JIC implementation, but when you switch to asynchronous mode, the ESS features ASRC will cover part of the pre-DAC processing, so only partial JIC is used. We have provided a detail explanation of Dual ESS digital Processing in post #7.
 
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Aug 12, 2020 at 3:27 PM Post #11 of 67

YULONG Audio

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Aquila II Sales Guide 05.jpg


Digital Audio Architecture

Yulong, founder of YULONG Audio, believe each high quality DAC chipset has its merits and inadequacies, there is no such thing as best DAC chipset, it’s all about proper implementation to maximize its strength and compensate its shortcomings. Back in 2013, Yulong has spent years to master ESS DAC chipsets ES9018 and ES9016, and delivered well-received products such as DA8. When DA9 superseded DA8 and DA8MKII, Yulong changed to AKM AK4497 chipset and stay with that when upgraded to DA10. However, Yulong didn’t forge the ESS chipsets. When he redesigned the Aquila, he decided to revisit ESS flagship chipset again and developed a new high performance and yet affordable All-in-one with ES9038Pro.

The Aquila II takes full advantages of the outstanding digital audio capability of ES9038Pro and decodes up to 32Bit/768kHz in PCM and Octuple-rate DSD (DSD512). We have fine-tuned our JIC to work with the ESS chipset and incorporates the dual ESS digital processing circuit to deliver full potential of the DAC chipset.

1597260230578.png


As you can see from the table, all digital inputs support DoP64 and DoP128. Since only partial JIS is used in the Asynchronous mode with the rest of processing relied on the built-in ASRC function, only DoP64 is supported and PCM is limited to 24Bit/192kHz which is closer to the original S/PDIF specification.

Being the newest digital audio interface, USB Audio offers more bandwidth, hence can handle higher resolution. We have adopted the widely recognized XMOS XU208 solution that can handle up to PCM 32Bit/768kHz and DSD512 native. To enhance the audio quality of USB solution and remain stable operation, we work with Thesycon and developed a custom driver for Aquila II. We have acquired the necessary licenses so that our users can use the Thesycon driver legitimately.

ES9038Pro offers eight preset FIR filters, but in our experience, if we offer all eight filters to our users, they’ll spending a lot of time to “select the right filer” when some of them only offer very subtle difference. We have gone through the filters after we finalized our design and selected three filters that offer more noticeable different:
  • PHASE: minimize pre-ringing effect and is the default filter setting, this is equivalent to minimum phase fast-roll off filter in ESS description.
  • SHARP: represents flat response, recommend for general purpose, suitable for most music, this is equivalent to fast roll-off, linear phase filter in ESS description.
  • SLOW: roll-off at high frequency gently, recommend for music that benefit from a smooth presentation, this is equivalent to slow roll-off, linear phase filter in ESS description.
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Sep 6, 2020 at 8:34 AM Post #12 of 67

Muataz

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what is the output impedance or the RCA/XLR ?
 
Sep 7, 2020 at 12:11 AM Post #15 of 67
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can this be used as a pure amp?

tried the DA10 and liked it alot except for the 4497 sound which i felt was too smooth for my preferences, otherwise great product

Not sure if I understand your meaning correctly. Do you mean can Aquila II be used as a pure headphone amplifier or pre-amp without the DAC? I don't think this is possible because you need to have an analogue input in order to bypass the DAC section.
 
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