An I2S stereo audio DAC with an internal master clock PLL and a charge pump for direct-coupled ground-centered audio output.
The MAX98357A 3-watt I2S amplifier is wonderful way to output tunes from CircuitPython synthio, but because it produces a balanced Class-D output that only works with speakers, it doesn't interface well with standard unbalanced audio inputs on guitar amplifiers or a workstation's DAW (Digital Audio Workstation). After a couple of somewhat successful attempts to reintegrate the digital speaker signal with special analog amplifiers, it became obvious that what was really needed was an I2S stereo DAC like the discontinued Adafruit UDA1334A DAC (PID#3678).
A search of in-stock and active I2S DAC chips yielded the Texas Instruments PDM510xA family of I2S audio DACs that could meet the overarching project requirements of:
- Provide an unbalanced ground-centered stereo line-level audio output using a single power supply.
- A direct pin-for-pin compatible breakout stackable/replacement for the MAX98357A amplifier including shutdown capability (
SD). - Approximately the same size as the UDA1334A breakout.
The PDM510xA family does not require a master sample clock as the internal phase-locked-loop (PLL) extracts the master clock from the bit clock (BCLK) input. Also, the ground-centered audio output is achieved with an on-chip negative voltage charge pump, eliminating the need for bandwidth-limiting DC blocking capacitors on the DAC output pins.
A printed circuit board (PCB) for any member of the chip family was designed in KiCAD and set to OSH Park for fabrication. After assembly and testing with the PCM5101A chip, the board worked as designed. A second version is currently in the works. The new version adds ferrite beads to the audio output signals, removes the LDOO test point, and eliminates the SCK jumper.
PCB design repo: https://github.com/CedarGroveStudios/PCB_PCM510xA_I2S_DAC
The PCM510xA Stereo DAC PCB design via OSH Park: https://oshpark.com/shared_projects/WVrOgntC
PCB Bill of Materials: https://github.com/CedarGroveStudios/PCB_PCM510xA_I2S_DAC/blob/main/media/PCM510xA_I2S_DAC_bom.pdf
The Texas Instruments PCM510xA data sheet: https://www.ti.com/lit/ds/symlink/pcm5101a.pdf?ts=1697537958587
Assembly of the PCB (YouTube):
Eurorack Control Voltage (CV) Signals from synthio and I2S DAC
see https://adafruit-playground.com/u/CGrover/pages/eurorack-control-voltage-cv-signals-from-synthio
