I use a PAM8403 class-D amplifier module (~ 2$ on ebay), which is very good, and stereo.
The output volume is too loud. If I lower the amp's input volume (via software), then obvisouly the output volume is lowered, but there's a noise buzz. That's why I would like to lower the output volume rather than the input volume.
I noticed randomly that putting a 10k resistor in series between OUT+ and loudspeaker's input makes the volume lower.
It works, I am quite happy with that. But:
1) Is it a good practice? Why does it work?
2) This 10k resistor seems (by ear) to make something like -20dB volume reduction.
Is there a formula to find R for -10dB reduction?
Here is how it looks like:
PS: I don't know my earphones's impedance but I can say it's standard earphones shipped with my Samsung phone.