- DAC: ES9038Q2M is selected for the highest possible performance
- I/V stage/balanced output: 2 OPA1622 opamps are used as the I/V stage, creating a fully balanced output that can deliver 100mW into 32 ohms load. The opamps' output is biased by 15mA JFETs so that for a reasonably sensitive headphone with reasonably volume, the opamps are always in class A condition.
- Single ended output: 1 TPA6133A2 headphone amp is used to create single-ended, ground referenced output through a gold plated 3.5mm jack.
- Clock: Low phase noise audio grade 49.152MHz XO is used to generate MCK for the DAC.
- LM27762 is used as the first stage LDO to generate +4.3V and -4.3V rails from the USB +5V supply.
- 4 ultra low noise LDOs (LT3042) for DAC's DVCC/AVCC/VCCL/VCCR supplies, as the part of the second stage LDOs.
- 2 dedicated TPS7A39 dual LDOs for each channel, generating the +3.3V and -2.4V for the left and right channel I/V opamps.
- Dedicated digital power and ground for the RPi
- Dedicated analog power and ground generated by a isolated DC-DC converter for DAC and amps.
- Digital isolators are used for I2C and I2S signals.
- Custom driver is needed to use the DAC, please see https://github.com/VinnyLorrin/ES9038Q2M-Linux_Driver for the code and installation procedures.
- The DAC is operated in master mode and the internal NCO is used to generate precise data clocks for all supported sampling rate by using a single XO. The jittery RPi clock is avoided for the highest possible sound quality.
- DoP is functional with the custom driver
- The DAC datasheet can be found at http://file2.dzsc.com/product/18/05/25/829029_170233543.pdf
- The balanced output is NOT ground referenced. The common mode voltage is 1.65V, Do NOT short the balanced output to ground. Do NOT connect single-ended headphone into the balanced port.