P = I X E
Power = current times voltage.
So 18v @ 500 ma = 9 watts.
so 9 = 2 times ? drum roll please 4.5 V Close to USB spec.
Buck converters are ~ 85% efficient so use 9 X.85 for watts out. 7.7 watts.
A class D audio amp is 80-90% efficient so you can get 5 watts of audio out which should be enough.
Power = current times voltage.
So 18v @ 500 ma = 9 watts.
so 9 = 2 times ? drum roll please 4.5 V Close to USB spec.
Buck converters are ~ 85% efficient so use 9 X.85 for watts out. 7.7 watts.
A class D audio amp is 80-90% efficient so you can get 5 watts of audio out which should be enough.
Just get any board that can take 18V like TPA3116/8 and limit the gain. You should be able to get around 2W (1W per channel) with 8ohm speakers. That's enough for casual listening if the speakers have decent efficiency.
EDIT: It might be difficult to fit one of those boards in a pedal. Maybe this combo instead...
https://www.aliexpress.com/item/HT6...-Audio-Power-Amplifier-Board/32572143474.html
https://www.aliexpress.com/item/DC-...7V-28V-to-5V-3A-Fixed-Output/32636482278.html
EDIT: It might be difficult to fit one of those boards in a pedal. Maybe this combo instead...
https://www.aliexpress.com/item/HT6...-Audio-Power-Amplifier-Board/32572143474.html
https://www.aliexpress.com/item/DC-...7V-28V-to-5V-3A-Fixed-Output/32636482278.html
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Just get any board that can take 18V like TPA3116/8 and limit the gain
Or just use the Plimit function
500 mA of average current is enough for a very high volume with audio signal and a real speaker, if you somehow provide also the high peak currents. How? With a big capacitor, and maybe with a current limiter between PSU and cap if the PSU cannot handle overload properly. No need to limit voltage this way.
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