TLDR; If you want your SD card to work, hook up the ground next to the 3.3v pin, but ALSO hook up the other ground pin labeled "G" on the board. If you don't do both, it will not recognize the SD card.
Details: I wired together a Teensy 4 and Rev D Audio board wired on a perf board with short wires between pins. I tested output with both a simple set of headphones, and also a small portable speaker.
The Guitar demo worked fine, but was oddly noisy with the speaker, but OK with the headphones. Which was odd.
Then I tried running the WavFilePlayer script, and found that it would NOT find the SD card if I used the headphones, but it would find it if I plugged into my speakers. However there was no sound, just odd static.
Guessing it might be a ground issue, I discovered this: I had only hooked up GND that is next to 3.3V, and NOT the GND labeled "G" next to pin 0. I just figured ground is ground, and redundancy wasn't needed. But when I wired up GND G to GND, instant success. It found my SD card, and it played my WAV files fine.
So - at least with Teensy 4 and Rev D board, hook up BOTH grounds, not just one.
Details: I wired together a Teensy 4 and Rev D Audio board wired on a perf board with short wires between pins. I tested output with both a simple set of headphones, and also a small portable speaker.
The Guitar demo worked fine, but was oddly noisy with the speaker, but OK with the headphones. Which was odd.
Then I tried running the WavFilePlayer script, and found that it would NOT find the SD card if I used the headphones, but it would find it if I plugged into my speakers. However there was no sound, just odd static.
Guessing it might be a ground issue, I discovered this: I had only hooked up GND that is next to 3.3V, and NOT the GND labeled "G" next to pin 0. I just figured ground is ground, and redundancy wasn't needed. But when I wired up GND G to GND, instant success. It found my SD card, and it played my WAV files fine.
So - at least with Teensy 4 and Rev D board, hook up BOTH grounds, not just one.