SparkFun Forums 

Where electronics enthusiasts find answers.

Have questions about a SparkFun product or board? This is the place to be.
By desmith
#188529
I'm using the Arduino MP3 shield (DEV-12660) with the audio amplifier (STA540, KIT-09612). I'm having trouble with loud background noise from the amp output while the MP3 shield is decoding. The noise is present when an MP3 is being decoded, but goes away when the MP3 file ends. The noise is present when using either a battery or an ATX power supply to supply power to the devices. The noise goes away when I use separate power supplies for the Arduino and for the amp, but unfortunately the application I need this for requires a shared power source. The noise is present if the amp and MP3 shield are sharing a power source and the MP3 shield is decoding, even if the MP3 shield's audio out is not connected to anything, and stops when the MP3 ends. There is no noise if I connect an iPod to the amp, unless the Arduino is plugged in and powered up and the MP3 shield is decoding something. There is no noise when I connect headphones to the MP3 shield. Any ideas?

I've tried a capacitor from power to ground as a noise shunt on the power source, but it did not noticeably change the behavior. I've also tried the "line out" decoupling jumpers on the MP3 shield in both positions. The noise is better in the "line out" position, but still not usable.

Anyone else tried this configuration? The products are advertised together. :-) Any ideas how I could isolate the amp on the power source to remove the noise?