This is a custom PCB that add a four channels DAC to the EuroPi.
The DAC is a MCP4728 :
- 12-Bit Resolution
- 4 Buffered Voltage Outputs
- Single-Supply Operation: 2.7V to 5.5V
- On-Board Non-Volatile Memory (EEPROM)
- Normal or Power-Down Mode
- Internal or External Voltage Reference Selection
- Rail-to-Rail Output
- Low Power Consumption
- ±0.2 LSB DNL (typical)
- Address bits: User Programmable toEEPROM
- Standard (100 kbps), Fast (400 kbps) and High Speed (3.4 Mbps) Modes
The voltage reference is a LM4040, 3.0V.
The DAC outputs are connected to the EuroPi 3, 4, 5 and 6 outputs as follows :
EuroPi output | DAC channel |
---|---|
1 | |
2 | |
3 | D |
4 | B |
5 | C |
6 | A |
This specific order of the channels was chosen to facilitate the PCB routing.
The EuroPi outputs 1 and 2 do not change and are still driven with a PWM output from the Pico.
Power supply :
This custom PCB swaps the 10-pin Eurorack power connector for a 16-pin one and removes the onboard power regulator, opting to use the 5V directly from the Eurorack power supply instead.
Schematic :
Here is the schematic of this PCB : dac-board-v2.1.pdf
Project files :
github.com/francoisgeorgy/europi-dac
Why build this custom PCB?
This PCB project was mainly a fun excuse to experiment and learn:
- KiCad practice: a good opportunity to get better at PCB design.
- SMD assembly with JLCPCB: tried out having the board made and assembled by an external provider.
- Eurorack power filtering: played around with filtering power right on the PCB.
- DAC vs PWM outputs: wanted to see if DAC outputs really outperform PWM for basic CV voltages.
- Just for fun: because DIY projects are always more fun!