I use arduino uno, sparkfun mp3 shield and mono amp breakout with push buttons, when the button is pressed the mp3 will play the assigned track. everything work fine when is use power source from usb plug in. however when i use a 9V battery, only sssssss sound can be hear from the speaker. please help! i have no idea why that is happening.
what i had done to try fixing:
try using different uno….. not working
add external voltage regulator (5V output)….not working
please help me.