Audio board : Build12 Aug 2019
I haven’t been very good at gettings posts done in the last month, and most of the projects I’ve been working on haven’t been very interesting to anyone else so I haven’t had much to post.
The PCBs for the audio board turned up, but when I went to do the order, one of the components was out of stock until the end of July, so I had to wait.
I got the parts two weeks ago, and spent some time each morning before work this week getting everything soldered together.
I have found a few little mistakes on the board:
- The virtual ground for the op-amp in the headphone amplifier uses +3.3V instead of the +5V it should have (fixed with a mod wire).
- The output from the DAC is much higher than I expected, and guessed from the datasheet. It claims to have a 2.1V output, and going by the other datasheets I found I assumed this was Peak to peak RMS, but it’s really just one side, so I’m amplifying the output far too much in the heaphone output.
Now I’ve got to look at all the other bits of the board and check they work as expected, then I’ll have some time to get it doing interesting things.