HIFIDIY Prometheus ES9018 DIY DAC

HifidiY.net has released a new diy DAC board designed in collaboration with the China arm of ESS Technologies. Code name for this project is “Prometheus”, part of the “Titans” series from Hifidiy.

This is the first product out of the collaboration which aims at “HI END”. And to start this series of products, a 50% off group buy has been put together (and available until 7/6/13). I’ve summarized here some of the details shared in the discussion boards and product announcements.

(Photos and most words taken from TaoBao and Hifidiy website/forums…)

DESIGN OBJECTIVES

In order to address users concerns regarding design choices, Hifidiy recently published these words (translated from the original (in Chinese), so might not be 100% accurate) [link]

1 Regarding routing (and decoupling) of the power lines
Even though the designed has been criticized as lacking, several key test results have shown that this is not the case.

One data point of interest is that the -118dB THD performance number from the ESS official evaluation board is achieved without any close-by decoupling capacitor!

ES9018 is an an integrated DAC-DSP, therefore one cannot ignore its digital processing part and rely entirely on optimal routing/decoupling for its performance.

Suggest that you first try it yourself, and then you can question the design.

(???)

2 Regarding (people’s comments about) sub-par THD performance
First, this is a diy product for people to experiment; it is not a commercial finished product. Common sense says that there is a balance between performance and cost.

Prometheus frequency distortion (THD) is slightly higher, because we decided to design a diy mod-friendly design and also cared about esthetics. Extensive use of large-size parts, prevented us to squeeze the size of the PCB, resulting in the generation of spurious noise affecting THD measurements, but the performance is still better than most similar products on the market.

3 Regarding the J-TEST jitter and crosstalk results

Prometheus design highlights these two parameters and can be said that it has achieved the highest performance. In particular the jitter performance, almost reaches the limit (measurement limit?)!

J-TEST shows almost no spurious sidebands, we tested a lot of expensive products; only Prism Sound products were able to achieve this level of performance and in some areas Prometheus tested better (eg J-TEST background noise tests).

4- Why not pursue the best performance measurements possible?

When we started the project, we did consider this approach, but we did not want to lead the market in creating all ES9018-based DACs to look all exactly the same (we already have a tradition of copying; you know what I mean).

What we want is diversity of designs (百家争鸣), not “you see one, you them all” (千篇一律) designs.

So eventually we gave up that initial design goal of going after the best theoretical limits of the device. The ESS original evaluation board also did not reach the best possible measurements in all the key parameters.

However, our design was still  able to achieve very high performance.  Noise performance, crosstalk performance, jitter performance, intermodulation distortion performance (Prometheus’s CCIF IMD tests lower than -119dB) are all excellent!

More from here [link]

4- About the design

Prometheus is a milestone level design, completely different from HIFIDIY conventional designs. Prometheus is guided by uncompromising HI-END product concept.

Many members do not understand design which is normal, otherwise  the world would be full of hi-end products. There are also members with a “wait and see” attitude (on how good this board/design really is), we also understand this.

We are very grateful to the strong technical support from ESS and their financial sponsorship in order to lower than the price of the group purchase. At the end of the group purchase period, the price will revert to the normal price of 1980 yuan.

BOARD DETAILS

The DAC Kit. (All the parts shown will be reflow soldered. The user supplies the remainder parts: Output stage opamps, caps, resistors and AVCC opamp)

Prometheus is aimed at upping China’s diy audio products to a new level in quality and capability. Prometheus is so far the world’s only third party product officially authorized to use the “ESS” and “SABRE 32 Reference DAC” trademarks.

Hifidiy is an official partner of ESS Tech [link]

The board is “top industry military grade, 4-layer PCB with 2 oz copper thickness and 4 um Immersion Gold plating; each board is fully tested”.

Labels for layers 3 and 4 can be better seen on the other side of the board.

Size is 240 mm by 150 mm

This is a hand-soldered board with all the components from the group buy kit (the final kit will be reflow soldered). The decoupling capacitors are C0G dielectric.

Here is the board with the (user provided) film capacitors.

Other users would select different capacitors. This first group buy is also a “competition” for the “best implementation” of DAC with selection of the user supplied components (capacitors, resistors and opamps).

Both single-ended and balanced stereo outputs are available.

Only two SPDIF inputs (no I2S/DSD inputs): one isolated and the other non-isolated (they are situated in the upper right corner of the board above. A detailed photo of the inputs is shown below with the Crystek clock.

The board has been designed to be mounted in a chassis: both inputs and outputs are all on the same side.

Prometheus did not include DSD inputs because  “ES9018 is not a native DSD decoder”.

SPDIF isolation transformer

Apparently, there is some  flexibility with the regards to changing inputs, outputs and clocks. According to Hifdiy, there will be a series of “modules” available soon.

Prometheus open design for mods

In the red box on the right, a digital input modules have been designed to use add-on module. You can add modules for AES, BNC, IIS.

In the pink box on the left, one analog output modules have also been designed to use add-on modules. The DIYer is free to create modules for different output stages.

Clock in the center white square, it could be replaced with an SMA adapter plate, and different clocks can be installed.

The board is designed to be operated in hardware mode, but the I2C inputs are exposed for s/w control.

LEDs are used to inform the status of the board.

A fresh batch of ES9018 chips (Week 46, 2012 -the newest I’ve seen so far) and the (made famous by TwistedPear Audio) Crystek CCHD-950

The clock is designed to be powered by what appear to be an ADP-150 regulator (yes it is)

On-board low-noise LDOs (2xLT1963, 1xLT3015)

Prometheus +/-15V and 5V external power supply requirements for external power requirements are very low, just simple LM317/337 are needed, as Prometheus has strong built-in power management!.

EXTERNAL POWER

There is a companion power board to provide the external DC voltages. Built to the same specifications as the ES9018 DAC board, except it is 2-layer.

If you have the money, you can try a new 1,500 RMB “o”-core low noise transformer. Hand-wound with single crystal silver-plated Ohno Continuous Casting (OCC) copper.

There are plans for releasing “matching Prometheus transformers”. Optimized for analog and digital applications.

USB-SPDIF Interface

Since the ES9018 DAC board only has SPDIF inputs, there is a companion USB-SPDIF interface, the second of the “Titans” series of high-performance products. Code name is “Athena”

Ebony feet to mitigate vibrations (bad for the clocks)

It is based on the CM6631A chip with custom firmware and yes, just USB to SPDIF. As can be seen in the photos, it can be powered with either AC or an external DC supply.

PARTS

Selected photos from a DIYer in China [link] (Apparently the kit can be purchased fully populated or with all the parts without soldering)

Highest quality packaging following industry standards. Looks like the packaging I get when buying parts from Mouser and Digikey.

Moisture-sensitive packaging.

I like the container carrier for the ESS DAC…

Everything nicely labeled…

FIRST USER BOARDS

MEASUREMENTS

THD+N (Athena Interface)

Jitter Spectra (Athena Interface)

24Bit/192kHz test signal. Testing spectrum bandwidth 10Hz to 24kHz. Red trace is the DS3 signal source  inside the instrument (loopback test?) with a jitter value of 0.2 nsec (10-24KHz): silver trace is Athena output. Jitter is 0.3nsec (10Hz to 24kHz bandwidth)

Inter modulation Distortion (IMD) multi-tone test (Prometheus)

Noise (Balanced output, 6.67 VRMS)

<2.1uV RMS (22Hz to 22KHz A-weighted)
<2.9uV RMS (22Hz to 22KHz Unweighted)
<12.5uV RMS (10Hz to 500KHz Unweighted)

If we calculate the signal to noise ratio we get: 20xlog(6.67V/2.1uV)=130 dB

THD+N 1KHz (the customary measurement)

COMMENTARY

This is a good development for audio diy. It is good to see ESS Tech support diy. China diy must be large enough for the company to invest in this joint development. For a chip to be successful, large volumes are important. Let’s hope this will give incentive to ESS to work on a next generation DAC chip. If we take a look at what has been happening to the high-end DAC market, we realize that TI and Wolfson have stopped their investment in high-end DACs in favor of lower cost/higher volume products many years ago. Even the ESS chip is many years old.

Commendations are in order to Hifidiy and ESS for advancing and promoting the diy market. This first product is a solid product, but basic in features. It “lacks” many the features that diyers like to tinker with such as having all the input and output signals available (I2S), ways to mod the power supplies, clock options, etc. However, there are plans to build small modules for different inputs (including I2S), different output stages and a connector to use different clocks.

Perhaps both ESS and Diyhifi decided to limit modification on the digital portions and allow the user community to focus on modding the analog sections (output opmaps, resistor and capacitors). This way, the basic level of performance is set and mods will be focused in the “flavor” of the output sound. I believe this is a good approach since it will limit the number of modifications and the effects of the output stage will be better characterized.

Furthermore, building a product with basic functionality may also be a wise move. If you read this blog, you will realize that it took a lot of effort to understand the behavior of the I2S interface, especially the unlock problem associated with lower DPLL settings.

The fact that this product only has spdif inputs seems to also suggest that the spdif implementation by ESS is better than what is typically given credit for. ESS certainly pride themselves in inventing an implementation of spdif that has the highest resistance to jitter in the industry. Perhaps it is undeserving that the SPDIF inputs of the chip have been overshadowed by the I2S input.

It is also possible that ESS wants to release this product to a wider audience without introducing the complexity (and related “issues” such as signal unlocks due to low DPLL settings) of the I2S interface. The SPDIF interface of the ESS Sabre DAC is rock solid in comparison with the I2S interface. It is wise to avoid any kind of negative publicity first and then introduce the I2S interface after a solid reputation is obtained.

It is a milestone nevertheless, for a major manufacturer has decided that it is good business to work with the diy community in an official manner.

(update on I2S)

A beta tester published a photo of part of the schematic. The I2S pins seems to be totally disconnected and only DATA1 (h/w mode SPDIF input) is connected [link] as you can see. Thus, this board will not support I2S input, just a single SPDIF input.

Why would ESS Tech/Hifidiy only support a single SPDIF input on this board? could it be to promote their (highly innovative) SPDIF interface that most DIYers ignore in favor of I2S? If you look at the ESS white paper,

The SPDI F interface is more complex than the DSD and I 2 S since it must first derive the embedded clock in the bi-phase encoded data. In fact, experience with many forms of SPDIF decoder suggest that most fail in the presence of high jitter due to the lack of robustness in the clock recovery process. To avoid this potential problem the Sabre SPDIF interface avoids having to extract the clock at all: decoding is done using a method that does not require an explicit measure of the clock frequency. Specifically, the digital input is first corrected for 50% duty cycle by means of a discrete digital delay line that is able to delay either the positive edge or the negative edge of the signal such that after this delay line the signal is at 50% duty cycle. Thereafter an assessment is made of the width of each pulse based on its relation to recently seen pulse widths and a decision circuit assigns each a width of 1, 2, or 3 units. A state machine then operates on the assigned widths in succession; this state machine is searching for the block boundaries and the bit states. The state machine makes no attempt to re-time or otherwise decode the clock – it simply “time stamps” the event and passes it to the downstream processor. Using this method the SPDIF interface is able to accommodate 50nS of random jitter and 200nS of sinusoidal jitter in the incoming data.

(Update on ESS Tech promoting diy)

ESS and Hifidiy are having a diy competition.  There will be 3 grand prizes plus 10 additional “excellence” awards. The top 3 prizes will be 1- Best “open design” -any design based on the ES9018 chip, 2- Best sounding based on the “official Hifidiy board” (the mods are mainly around the output stage, wiring, connectors…) and 3- Most popular, again based on the “official Hifidy board”. In addition, five entries will be sent to ESS for audio measurements an evaluations.

Here are the trophies for the grand prizes

It is encouraging to learn the details of how ESS Tech is promoting the diy market in China. It is an indication of a vibrant diy community (of course many potential sales for ESS Tech would result from this activity). Not only has ESS Tech provided financial support for the group buy (which is ending 7/6/13 – if you wish to take advantage of the 50% off), but they are also promoting a contest with prizes. Plus the fact that 5 entries will be selected for actual measurements by ESS Tech. All the winners, details and measurements will be published.

It will be definitely be educational following the different contest entries, the selection of the winners and especially the measurement of the winning designs. There will be correlations between mods, sound and measurements.

MORE INFO

• Additional info: [link]
• Forums discussions [link]
• Build thread [link]
• Taobao group buy: [link]
• Outside China group buy: [link]