Arduino continually resets when connected to external power supply, but not USB I'm working on a seemingly simple Arduino project which plays a sound and flashes an LED when provoked by some trigger.

The problem:

When powered by an external power supply, the Arduino continually resets after playing ~1/4 seconds of audio. When powered from USB, it works fine (however the LED, being powered from the external power supply, of course does not work here).

Wiring diagram:



Parts list:


Arduino Pro Mini 5V
Adafruit MAX98306 3.7W amplifier
Sparkfun FemtoBuck LED Driver
4 Ohm 3W speakers
3W LED


I am using a 9V 1A power supply. Again, when no speakers are connected, the Arduino and LED work as intended. It's only when a speaker is connected that the board resets over and over again. Playing roughly 1/4 of a second of audio and then resetting implies to me that there's insufficient current, however, the problem persists even after using a 2.5A power supply.

Things I have tried:


Increasing the power supply to 12V 2.5A
Desoldering the LED driver (even with the LED driver removed, the board still resets)
Checking continuity and staring at the wiring for long periods of time while scratching my head


Overall, I'm at a loss as to why it would work when powered via USB instead of through my external power supply.

What am I doing wrong? Any insights are greatly appreciated!
Most likely lack of current - lack of current able to be provided by the Mini. The audio is powered from the onboard regulator on the Mini, which has limited current capacity. 

If too much current is drawn it will either get too hot and go into thermal shutdown until it cools down enough, or it will drop the output voltage, making things reset and crash.

Power the audio system from an external 5V regulator.