If you're getting no voltage on mp3 shield right output then I think it's safe to say it's either solder/wiring issues on the Arduino/shield end of things, or possibly something with the audio file or software/firmware settings. Hooking a separate mp3 player up to the amp would confirm that the amp works, but it seems almost certain to me that the problem is before that, so I'd skip that step if I were you and go straight to diagnosing the mp3 shield and Arduino.

 

Hi Allen,

Your amplifier works (or it wouldn't hum)
For a quick test, swap left and right from the MP3 module - if the problem stays at the right side, the problem is between the MP3 module and the amplifier input. If the problem moves to the left channel, it must be in the MP3 module itself (or the wiring up to the amp).

If you have a crystal earpiece (probably near impossible to come by these days), they have a terrible sound quality, but are rather high impedance, so can be used to listen for an audio signal along the signal path. A crystal mike can be used as well, but is just as rare (and low quality) and finally, a piezo disc in a holder (but only the disc, no driver circuitry) might do in a pinch.

A sound card oscilloscope would be even better (just make sure to make a probe with over voltage protection) and several free programs exists, where you just send the signal into mic-in on your PC.

Play eg. a 1kHz sine from the MP3 and then look/listen for the signal in the middle of the troubled part. if there's a signal, you go forward and halve the remaining part etc. and if there's no signal, you've passed the error. Always go in the middle of a troublesome part, it's the fastest way to find an error

 

Hello Soren, ebeowlf17 and the AAC forum,

Realized that I promised to post when this project was complete and
forgot to keep the promise. The biggest change I made was chunking
the Velleman amplifier and substituting a SparkFun ST540 which is
a 38 watt stereo amp. The completed project is posted at
http://www.instructables.com/id/Auto-MP3-Player/

Thanks for your input.

Allen Pitts, Dallas Texas