I'm using the mp3 player shield from sparkfun and an Arduino UNO. Everything is OK, I formatted my Samsung micro SD cards with FAT, I converted mp3 files with ffmpeg, I load the examples file and modified them a bit, I can play mp3! Great. This is with an earphone.
But.. if I try to connect some 20 euros speakers I hear a strange low-frequences buzz/white noise. Even if the shield is not playing anything.
I'm aware on this pdf on connecting analog output and I've tried to read it but I didn't understand anything.. It explains how to avoid interference caused by long cables but my is not a long cable.. Can it be useful? What can I do?