The HifiDIY ES9018 DAC
Update: Schematic diagram [Prometheus MB SCHE]
Just received the Hifidiy ES9018 DAC.
HifiDIY has become the China distributor of ESS DAC products and has embarked in producing, in collaboration with ESS Technologies, a DIY-friendly version of the ES9018 DAC.
I was able to obtain a version of the board delivered with the optional components installed by the people of HifiDIY. The standard offering of the DAC board only includes the surface mount components as shown in the second photo below:
A DIYer is expected to select and install the remaining components (the output stage components, including the op-amps, the AVCC op-amp based supply and the decoupling capacitors of the on-board regulators). As can be seen, the designers opted to use through-hole components for wider diy appeal.
This is a “basic” implementation following the guidelines of the ESS datasheet but at the same time a vast improvement over the ESS evaluation board with respect to PCB material and choice of components.
Here is the DAC chip and the power lines decoupled with C0G ceramic capacitors. The chip has a date code of 033 (likely week 03 of 2013). Pretty new batch.
Some have negatively commented over the large distance of the decoupling capacitors from the pins. But as can be seen the photos the distance is not really “so large”. I believe a “diy-friendly” approach was more important to HIFIdiy than the potential “ultimate performance/measurement”. As can also be seen, there is sufficient clearance between the components for a diyer to solder or rework the DAC chip even with the decoupling capacitors in place.
The straight board trace from the bottom left is the spdif input line to the DAC chip
This is a very high quality 4-layer PCB with superb finish. Just for show, the 4-layers can be seen in this “window”. Front side of the board:
Back side of the board:
The 3.3v AVCC supply which is the most important supply for the DAC, uses a AD797 opamp (0.9 nV/√Hz noise) [datasheet:link]. It is implemented as a voltage follower per datasheet. The 3.3V reference signal is provided by the local 3.3V regulator.
- AD797: [Digikey: link]
- Electrolytic caps: 10uF, 50V. These are bipolar “TOWA” brand which are not available in the US market. Can substitute with any “good” electrolytic cap such as Panasonic FM or FR or ELNA SILMIC [Mouser: link]
- The decoupling capacitors are Vishay ERO MKP 1837 [link] 0.1uF, 160V. These ERO brand are not available in the US market. Vishay-branded MKP 1837 are available [Mouser: link]. These are pricey caps at $1.32 each. Can substitute with WIMA MKP2/4 for lower price.
The 3.3V reference voltage is further filtered with a CRC filter. Note also the compensation resistor for the opamp to prevent oscillation. This is indicated in the datasheet: “With the AD797, additional input series damping is required for stability with direct output to input feedback. A 100 Ω resistor (R1) in the inverting input (Figure 37) is sufficient; the 100 Ω balancing resistor (R2) is recommended but is not required for stability.”
Clock and clock supply is implemented with an ADP150 regulator [link] (Ultra low noise: 9 μV rms, independent of VOUT). The “LEJ” marking signifies a 3.3 Vout part. These parts are already installed in the basic configuration.
The input to the regulator is taken from the 5V external supply that also feeds the on-board 3.3V and 1.2V regulator. C5 and C5A are output capacitors for the regulator. Notice that there is no input capacitor except for the output capacitor of the 5V supply. Some improvement could be had by locating an input capacitor near the regulator and by ensuring the 5V external supply is well implemented.
The resistor (R5A) is to pull-up the enable line of the clock.
The Crystek CCHD-100 MHz oscillator [link] has become the standard for ES9018-based DAC implementations. This part is a “-50” part meaning 50 ppm frequency stability. Other implementations have used a “-25” as in 25 ppm frequency stability. Whether 25 ppm or 50 ppm, they all have the same jitter specification. Whether you can purchase a “-25” or “-50” parts likely depends on availability. A quick check on Digikey, shows that the “-25” part is out of stock…
This board only supports a single input (and because it only uses DATA 1 (a single data line), it only supports spdif input).
One can select between the transformer-isolated (+/FG) or the non-isolated input (+/G), but can only use one input. The SPDIF input level is boosted by a TI LMV7219 comparator [link] to the 3.3V required by the DAC.
It is possible to support I2S inputs if one is capable of tapping to the chip pins. According to these photos, the remaining input pins are not connected to anything.
with steady hands and a proper soldering tip, it is quite possible to connect the I2S/DSD inputs to external wiring. (For now I think I would just leave it as is since i have other ES9018 DACs with proper output connections)
Shown below is a 30 gauge wire in comparison with the pins of the ES9018 chip
The board is designed to work without a microprocessor. In “hardware mode”, upon power-in, the chip defaults to stereo and “auto input” with SPDif input assigned to DATA1. Even though in this mode one can also use I2S input, I think ease of use/configuration was a desired design criteria for this board and therefore the other inputs were not been enabled. (Switching between SPDiF and I2S would require mechanical switching as DATA1 is shared between SPDIF and I2S).
However, the I2C inputs are available for software control such as for using the digital volume control and the selection of the built in filters.
ON BOARD POWER SECTION
In addition to AVCC and the clock supply, there are 4 additional on board supplies. From left to right:
Digital 3.3V for powering the DAC’s 3.3V supply, the spdif comparator and also as a reference to 3.3V AVCC; digital 1.2V for powering the DAC’s 1.2V supply; +12V and -12V for powering the output stage opamps, and the AVCC opamp. So in total, there are 6 local regulators.
Apparently it uses Panasonic FC capacitors (the gray ones). These are not available in the US. Apparently the supply of parts is much greater in that part of the world (where a lot of stuff is manufactured) -whether new or old stock or even special runs that the factories made. HIFIdiy made great efforts to obtain authentic parts, so I am confident that there are no questionable parts.
The aluminum electrolytic decoupling caps can be replaced with newer Panasonic FM or FR with the same or greater values. For example: Panasonic FR 220uV, 50v [Mouser: link]
With regard to the WIMA film decoupling caps, here is a link explaining the different series: [diyaudio: link]
The green ones appear to be WIMA FKP2 (Film and Foil caps) [link].
The input capacitor decoupling is the same for each regulator: an aluminum high value electrolytic capacitor with a low value film capacitor in parallel. The output capacitor decoupling varies, but they are equally effective. The two output film capacitors (red WIMAs) may not be required as each opamp already has local decoupling.
The 1.2 supply is a “lowly” LD1117 fixed 1.2V regulator [link]. It is implemented a per datasheet. The resistor (a 120 ohm shunt at the output) is a requirement for the 1.2V fixed regulator. I would have liked to see a lower noise regulator such as the LT1963.
It would be beneficial to increase the value of the output capacitor for this 1.2v regulator.
There are 8 LEDs indicating power supply operation and signal lock status.
The output stage is implemented as per the ES9018 datasheet. The only difference is that for the balanced output, it is buffered.
Use of top-notch components.
The opamps are the AD797 “B” grade (which is the higher grade of the AD797 opamp) and only available in SOIC packages. Thus the use of chip carriers.
HIFIdiy developed teflon PCB adapters for the SOIC opamps. According to them, this preserves the performance of the opamps.
Vishay 102K Foil resistors [link]. The decoupling capacitors are Vishay ERO MKP 1837 [link]. (ERO was an original ROEDERSTEIN brand). This brand of capacitors is not widely available anymore. Either these are old stock or only available in the Asia market.
The balanced output is buffered with a AD826 opamp [link]. “The AD826 is a dual, high speed voltage feedback op amp. It is ideal for use in applications which require unity gain stability and high output drive capability, such as buffering and cable driving. The AD826 features high output current drive capability of 50 mA min per amp, and is able to drive unlimited capacitive loads.”