$99 ES9018 DIY DAC BOARD
Just received the board. Very good quality, some photos below… This is the V2 version of the board. This version came quickly after V1 and (to my surprise and delight) implemented many of the things I suggested in the diyaudio thread. That is pretty good response from the creator of this board. In this eBay website, he mentions that this design will keep on evolving, thus I would encourage anyone interested in this board or future iterations to provide feedback and suggestions at his diyaudio thread.
It is good to see another DIY version of this DAC especially at this low price. But this requires the most work. Keeping in mind that the chip alone would cost $60, the price of this DAC board is near cost. So if you are handy with soldering small components, this board should provide plenty of fun and audio satisfaction.
All the input lines are available (e.g.: not grounded) -this is an improvement from V1. The output is stereo, so it can be used as stereo or mono but not 8-channle. However, having all the inputs available, we can leverage the internal mux and auto-detection to switch between different inputs.
There are pads for U.FL connector for clock input on the other side of the board. This is also an improvement from V1
Pads seems fairly easy to solder. I believe it can accommodate a 1206 SMD capacitor or a 5 mm-leads radial capacitor. Footprint for any size oscillator including the Crystek CCHD-950/957
This gives you an idea on the dimensions of the solder pads:
The first thing to figure out are the power bypass capacitors. The board has space for both SMD capacitors and through hole capacitors. One idea is to mount both of them (of different values) in order to improve filtering:
According to this application note from TI [link]
The most common values bypass capacitors are: 47 µF, 22 µF, 4.7 µF, 0.1 µF, and 0.001 µF. The higher value capacitors (47 µF and 4.7 µF) work well at relatively low frequency (low-frequency bypass). The 0.1 µF targets the middle frequency range, while the 0.001 µF or smaller capacitors handle higher frequencies (high frequency bypass). Choosing two or three capacitors with different capacitance ranges will effectively filter a wider noise bandwidth.
Seems using a 0.1 uF SMD capacitor with a radial 0.001 capacitor is an excellent idea…
(Update 1/4/13: more photos)
Front side of entire board. Since I probably got the first V2 board, the ADP 1.2 regulator was not soldered… The solder pads are all silver in color. The coloring is reflection of the surrounding, including the sky…
Back side of board
Input connections details (front and back)
Notice that D5, D4, D3 and D2 are tied together for default stereo I2S operation and connected to the front “data” pad. In order to use the inputs separately, one needs to cut them.
(Update 1/4/13: Chip bypass)
I’ve traced the power supply bypass positions and labeled them. There are 8 bypass locations for the most important supply the 3.3V analog (AVCC), 3 bypass locations for the 1.2V and 2 bypass locations for the 3.3V digital supply. I am not sure if the 1.2V locations would just require a 10 uF bypass (which are indicated in the ESS available documents) I think having a 0.1 uF SMD together with a 10 uF electrolytic on the other side is a better bypass.
Every AVCC pin has its bypass capacitor, but not every 3.3V Digital and 1.2V has its own bypass capacitor. Doesn’t seem to be enough space (or required?), but the seller did put the bypass where it most counts, the analog AVCC
(Update 1/5/13: Reset, power supplies)
Two external supplies are to be provided: a supply for the analog section and a supply for the digital section. The 3rd power supply is the 1.2V and it is provided by a local regulator that must be installed (I believe the current boards already come with this regulator installed).
The 3.3V analog or AVCC supply is the most critical. Preferably, choose a low noise shunt-type. I have yet to decide what to use. I may built up some of the Placid V1 boards I have.
For the 3.3V digital, I plan to use the TPS7A47 Eval Board.
(Update II 1/5/13: Differential Vout, chip address, AVCC/2 offset, I/V)
I am a fan of using the Sabre32 DAC in differential voltage out mode. I have been using the Buffalo II DAC this way since day one and still do not have the motivation to add an I/V stage :-). There has been comparison of this DAC in voltage mode against other DACs and I’ve documented some here: [link].
BTW, if you are concerned that only an optimally routed fabricated and designed board can produce good sound, you should take a look at what Mr Abraxalito is up to: [link] :-)
I plan on using this DAC in voltage mode also, at least from the beginning. You can take the raw differential outputs as shown below and take the GND from any nearby GND pads
The chip address is already set at “o” -connected to GND. If you are using the board in stereo mode, there is no need to do anything here. For mono operation you would have to cut the trace for one of the boards and connect the address pin to VDD (set to “1″)
The 2 10K resistors establish the AVCC/2 offset voltage that is used by the I/V stage
The I/V output stage is an implementation of the circuit in the 2-channel eval board [link]
The schematic calls for 1 uF bypass for the power supply lines and voltage offset lines. Probably a good idea to use a 0.1 uF SMD bypass together with a 10 uF electrolytic bypass.
(Update 01/6/13: Correction on reset circuitry)
Seller sent me a message indicating that the reset circuit must be populated or else the DAC will be unstable. This makes sense as the pin is floating if none of the components are installed. I’ve corrected the instructions above.
(Update II 01/06/13: Buffered differential output)
The board only implements output pads only for single ended output, but since this is diy, you can take the output basically anywhere you wish.
The buffered differential outputs can be taken off the outputs of the opamps. By implementing the opamp I/V converter, you “force” the DAC into current mode allowing for better THD.
And then add the low pass filter specified in the ESS documentation
(Update 01/08/13: More on using the DAC in voltage mode)
Using the DAC in voltage mode means not needing to populate the opamps. According to the designer of the DAC:
… The current mode is simply when the current going in and out the pin of the chip is being sensed. This mode has the benefit of cancelling 2nd and 3rd harmonics of some of the internal analog circuitry.
The “voltage mode” is when the pin of the chip has a voltage that is being sensed. While this has the 2nd and 3rd harmonics (at the -100dB level or so), some people have even claimed this mode is more “tube-like”. It is all personal preference. [link]
(Update II 01/08/12: Using Hifiduino s/w and Arduino controller)
The current version of the Hifiduino s/w [link] supports the following configurations for the board:
1- The board in its default configuration which is I2S and SPDIF in Data 7 and Data 8 simultaneously
2- Inputs modified to match the input wiring for Buffalo II: will support both I2S and DSD with an input board such as Amanero and also SDPIF on Data 1 if not using I2S
3- Inputs modified to support “smart” wiring: will support both I2S and DSD with an input board such as Amanero and also SDPIF on Data 1, Data 7 and Data 8 (SPDIF in TTL levels – 3.3v)
- SPDIF inputs are TTL level. You cannot just take the spdif output from a consumer device such as a DVD player.
- Unused inputs should be grounded
- All inputs should have a termination resistor
Continue reading here: Part I: [link]