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by hoc 469 days ago
Due to the missing DAC on the Pico this always runs into that fully discrete vs. resistor ladder/network vs. external dac (i2s or other) decision.

Great that the author chose one and finished (and published) the project instead of stopping at that annoying junction :)
1 comments
mordae 469 days ago
For headphone audio it's plenty to just PWM, inductance of the headphones and mechanical low pass characteristic of the speaker itself will mostly do the rest.

If you want to smooth the things out because you target a line input, simple LC filter will work just fine here.

Like this: https://shorturl.at/z3eYG (link to Falstad's Analog Filter Tool)

If you want to get better bit depth, you should use PDM instead of PWM.

link
hoc 469 days ago
Indeed. fast PWM is a great approach and fits in well with the analog conversion side effects.

I still find the principal question of "if I need additional components anyway, should I just get the more complex ones" interesting. It's located somewhere between quality, price, the definition of simple and optimal, as well as one of ones personal (or this week's) perspective on the art of the craft.

The projects is not a discrete player that basically pushes SD card data via a few digital standard ICs out as PWM, it uses a pretty sophisticated MCU after all. So, is a I2S DAC the logical solution or the fast PWM, I still find it hard to decide, especially when i have to order (even the simple or mechanical) parts anyway, or should I have a few I2S DACs in the drawer with the Pico these days.

Not sure if I can bring that point across. It's more about what are your default parts these days. I always have a few i2c OLED displays in that drawer, and the project uses one, too, thirty years ago it might have been resistors, LEDs and a few logic ICs instead. So I wonder, would I go discrete (or "simple") for that particular part of the solution for a particular reason or not. And also, why do I still have no I2S DACs stocked in that drawer, while I have display, sensors etc.

So maybe it's just about audio being a somehow ignored interface in (my) embedded tinkering. Or it's more general and about a modernized selection of stocked parts and using those more naturally while still being aware of the simpler solutions. I use pretty complex (but inexpensive) I2C sensors these days, after all.

Ok, many words on that small part of the overall decision making...

link