Dear all,
I'd like to get some advice on the best way to connect the DAC of a micropython pyboard [1] to a THD0188N breakout [2] based on the PAM8304 class-D amp [3], connected to a single 8 ohm, 1.5 W speaker. Attached is a schematic of my current circuit. I tested it with an 8-bit, 16 kHz wav file of "Lilac Wine", by Nina Simone [4], which provides many samples of voice, piano and silence. My results so far are:
- Sound quality is acceptable for my purposes but far from hi-fi.
- There is a low level of white(ish) noise in the background. Right now that's my #1 complaint.
- The white noise disappears when I deactivate the DAC pin of my pyboard, and reappears as soon as I start using the DAC pin (e.g., when repeatedly outputting 3.3 V at 16 kHz).
- Connecting the GND and A- pins of the amp has no audible effect. I suspect these pins are connected internally.
- Removing the 10 nF capacitor increases both the white noise and the music itself.
- The noise is not affected by adding capacitors from 1 nF to 10 uF between the battery pins, or between the VIN and GND pins of the pyboard or the amp.
- My earlier circuit had a 1K resistor on the A+ branch, between the 10 nF cap and the 5K resistor, with the intent of creating a low-pass filter, but I found that removing it has no audible effect, which I did not expect.
As you can probably tell, I'm no expert. Any explanation/advice/suggestions regarding how my current design could be improved would be very welcome.
Thanks!
- Mathieu
[1] https://store.micropython.org/product/PYBv1.1
[2] https://www.petervis.com/Electronics_Kits/pam8403-audio-amplifier/pam8403-audio-amplifier.html
[3] https://www.diodes.com/assets/Datasheets/PAM8304.pdf
[4]
I'd like to get some advice on the best way to connect the DAC of a micropython pyboard [1] to a THD0188N breakout [2] based on the PAM8304 class-D amp [3], connected to a single 8 ohm, 1.5 W speaker. Attached is a schematic of my current circuit. I tested it with an 8-bit, 16 kHz wav file of "Lilac Wine", by Nina Simone [4], which provides many samples of voice, piano and silence. My results so far are:
- Sound quality is acceptable for my purposes but far from hi-fi.
- There is a low level of white(ish) noise in the background. Right now that's my #1 complaint.
- The white noise disappears when I deactivate the DAC pin of my pyboard, and reappears as soon as I start using the DAC pin (e.g., when repeatedly outputting 3.3 V at 16 kHz).
- Connecting the GND and A- pins of the amp has no audible effect. I suspect these pins are connected internally.
- Removing the 10 nF capacitor increases both the white noise and the music itself.
- The noise is not affected by adding capacitors from 1 nF to 10 uF between the battery pins, or between the VIN and GND pins of the pyboard or the amp.
- My earlier circuit had a 1K resistor on the A+ branch, between the 10 nF cap and the 5K resistor, with the intent of creating a low-pass filter, but I found that removing it has no audible effect, which I did not expect.
As you can probably tell, I'm no expert. Any explanation/advice/suggestions regarding how my current design could be improved would be very welcome.
Thanks!
- Mathieu
[1] https://store.micropython.org/product/PYBv1.1
[2] https://www.petervis.com/Electronics_Kits/pam8403-audio-amplifier/pam8403-audio-amplifier.html
[3] https://www.diodes.com/assets/Datasheets/PAM8304.pdf
[4]
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