Below is a means to provide an outside signal to your PinWoofer Amplifier for test.
This is an example, other music players, a computer or laptop, or a mobile phone headphone jack might also work.
It is critical that your amplifier is fully connected in the machine, and the LED on both the power board and the amplifier are glowing blue to indicate power is applied.
The speakers must also be connected.
Note the rectangular black box in series with the audio cable; this is a ground loop isolator. A ground loop isolator may not be required, but it may make the difference between a low quality sound without, compared to a higher quality sound with.