Hey everyone, new user here and to sparkfun in general. I’ve been building a star wars droid over the last year and just got to putting the audio system together.
Im using the MP3 Trigger (WIG-13720) and it seems to work, but I’m having a hard time solving two issues…
1 - audio quality - regardless of the bitrate, size or whether the mp3 is stereo or mono, I’m getting a warbling or distortion in all audio files regardless of volume. The same files played via the same amp with a different device (with the same 3.5mm) play normally, so I THINK its the Trigger. I’m using a 32gb Class 10 Lexar Micro SD card (the only non-64gb card i have). The card is FAT32 with 32kb allocation size. I have also tried 16kb on the advice of one of the droid builders but to no avail.
I’ve tried a second identical card and it does the same thing. I’ve read through the SD card documentation but not being the same board, I’m not sure investing in yet another card is worth it, unless the team or folks here believe its a good starting point. The sound is NOT static which would be common in a ground loop issue and is NOT present when no audio is being played.
2 - track play delay - i have an arduino nano connected via UART playing random tracks within 3 different file name ranges. this is meant to simulate different moods for the droid and is controlled by a toggle on my flysky radio. However, in two of the file name ranges, tracks can be switched through as fast as I am able to press the trigger… whilst the third bank seems to choke and require multiple attempts to play a track. When this “choke” occurs, i get no green led on the trigger showing that it is not seeing the serial command but the nano IS outputting (as verified by serial monitor and an LED test).
I’m not sure if this is an overflow on the trigger where it cant keep up or if there is an issue with file size or encoding or bitrate (all files are encoded the same) but it sure is frustrating.
I can share my code if needed, but I’ve done all I (and ChatGPT) know how to do in order to take care of this (i’m a mechanic, not a coder 
).
THanks everyone, appreciate your help!
-Aaron
Try dropping the volume on the MP3 trigger itself and see if that improves your overall audio.
Hi, how does one do that? I didn’t see any reference to a volume command to put in the .ini file…
Hookup guide has what you’re looking for.
Thanks, I feel like a doofus for overlooking that hehe. I’ll play with it and see if it changes anything
HI YellowDog,
I tried a few things… dropping the volume level did nothing, the warbling and clicking is still present.
A bit of background - I have my amp, the Arduino and the mp3 trigger sharing 12v and ground from a fuse box. All grounds are good and were tested between each other and the main fuse panel (0.1ohms at all connections) and the nano controls the trigger as expected. At idle, there is an ever so slight “hiss” from the amp that I am not concerned about, but details, yes? 
I bought a second Class 10 SD Card of a different brand, but the warbling/clicking distortion noise was still present.
The odd noise is present wether or not the Arduino is being used (it is present just using the jog wheel).
I gave each the trigger and the amp its own 12v power supply and tied the grounds together for a ground reference between the two (the trigger would not boot otherwise) and I still get the noise. This was done completely independent of the Droid being powered up.
I tried a ground loop isolator but that simply causes the trigger to not boot.
It’s worth noting, the trigger will NOT boot without having the 3.5mm from the amp plugged into to its 3.5mm jack. The red LED will flash once and then I get no further action from the trigger. As SOON as the 3.5mm jack is plugged in while the amp is powered, the board boots… red led solid, triple flash from the green led. It’s like the board is missing a ground reference and has to see it from the 3.5mm jack. That can’t be normal…..?
At this point Im not sure what else I can do to test easily… it really seems like a bad unit. 
Thanks,
-Aaron
Something is off.
If you remove the mp3 trigger from your system and use just a power supply and headphones, does it work correctly?
No, I tried that before i went to bed. there is no output and the board does not boot (only a single flash of the red LED, no green LED).
Can you share a photo or diagram of the wiring scheme? I’m thinking there’s a bad ground or a line is tied to ground when it shouldn’t be
Is the 12v power supply a decent/mean-well unit? Do you have a 12v battery you can test with instead?
hi Russell, the powersupply i was using is a 12v wall adaptor style rated for 12v at 5amps. The batteries I am using are 3S Lipo’s in parallel. Without the 3.5mm from the amp plugged in, it will not power on. The Arduino Nano sends serial directly to Rx on the trigger via a digital pin. however, even with the serial disconnected at the trigger, it fails to work properly.
I will upload a drawing of the power supply when I have some time this evening so that you know. Thank you!
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Russell, Yellowdog…
Figured it out. SIlly old me forgot there were 12v pins on the back of the board, so I connected it there and low and behold, the board works! Checked continuity from those pins to the barrel and turns out the ground on the barrel jack is broken somewhere. I tried to reflow the surface portion, but no luck.
At least it works for now, thanks for your insights!
-Aaron
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