You can perform a couple tests on the amplifier without hooking up the i2c pins - it'll be fixed at 6dB and the default AGC is on but you should be able to hear audio through speakers

Power

You can power the amplifier from 3-5V DC. If you want to use a wall adapter, a 2.1mm terminal block is handy

or you can use a 3xAA battery holder as we do in the photos below

Connecting Audio

Testing the amplifier is really easy - no firmware or special configuration required to get a little audio out. In these images we'll assume you're using a breadboard but the wiring is the same if you soldered connections directly.

The easiest way to test your amplifier is to connect a 3.5mm audio pigtail cable to the audio inputs. Connect Right to R+ and Left to L+ then since a 3.5mm audio cable is single-ended, connect the ground wire to both R- and L-

You can connect the power to the board via either a breadboard rail with 3-5VDC on it (say from an Arduino power supply or battery pack)

If you want to plug in a 3.5mm jack into the breadboard instead of having the cable pigtail, you can wire up a stereo jack as shown below. Tie ground to R- and L- and left and right to L+ and R+

With just an audio source you can sort of see how the AGC system works - the amp will try to 'normalize' the volume to be constant