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?
Best Answer
You likely have a ground loop, between the chips GBUF and the speakers GND, caused by the speakers power supply. Note the SFE MP3 player is like your referenced vs10XXan_output.pdf Section 2.1 Figure 4 or 5 (minus the ESD).
Note the GBUF (the return of the headset) is not GND. The VS1053's output is likely a Class D amplifier. Hence it's switching at high frequency, in reference to the return (or GBUF). Section 3.2 recommends that when the VS1053 is driving a amplifier, it requires the addition of C1,R1,C2,R2 as shown in figure 8.. The SFE MP3's schematic does not have these. leading to some complaints, such as your.
The SFE MP3 and UNO with a no-name amplified speaker set works for me. But I believe my speakers have AC isolation within, as it only has hot and neutrual and no ground, yours likely has some connection to ground. Hence you are hearing the switching across GBUF. Additionally there are warnings stating this can be harmful to the amplifier.
Until SFE changes their design, the only solution is either a isolated amplifier or hack a cable to include the addition AC coupling (aka R's and C's).
Regardless the VS1053 and its open source Library are a great companion for the Arduino. I have seen many successful projects using it.