Powering your device - BleepLabs/Arduino-Light-And-Sound GitHub Wiki

Power

USB power is the default option for the Teensy and is the safest method but it’s not to hard to use other batteries. A simple USB wall charger works but it might introduce noise into your audio output.
A portable USB power source works well but they have a tendency to turn off if the device being “charged” is not using enough current.

The Teeny has a “Vin” voltage input pin in the top left corner. If USB power is being used 5V is seen here as that’s what’s supplied over USB. This is then regulated down to 3.3V for the Teensy.
USB and external power can be connected at the same time but it is not recommended.
The best option is to use 4xAA batteries and a holder like this.
Non rechargeable AA output 1.5 V so you’re right at the 6V input limit which is fine.
Rechargeable AAs are 1.25 V and work just fine.
The Teensy might use 25-100mA so with a 2200mA hour AA you’d get a full day or two's worth of juice

To use a 9V or higher supply you’ll need a voltage regulator.
The 7805 is a classic and just needs a couple caps to work but can get very hot if you use anything higher than 9Vs for the input. A multimeter is recommended at you can test the polarity of the input and the output voltage from the right pin of the 7805 before attaching it to Vin.

Parts:
LM7805 or similar 5V output regulator. 78l05, LM1117-5, LM1117T-5.0, MCP1700-5 all work.
.47uF capacitors. Really anything from .22u to 1u will work on the input side and .22 to anything on the output.
Other large capacitors for attaching between 0 and 3.3V. 10uF on up is fine. Here's a 220uf
DC barrel connector if using a guitar pedal type supply. 1n4001 diode or similar. Not necessary but if you have the input polarity of a power supply backwards you’ll blow everything.

There are lots of other options and you can directly make 3.3V and connect that to the 3.3V pin of the Teensy but this method is generally more reliable.