No sound output

Hi all,


Currently I am making a bluetooth speaker out of a 70's speaker to get a bit of a retro look.



I connected a 12V battery to a step down converter parallel to an amplifier board. The step down converter is to power a bluetooth audio receiver.



When I checked yesterday, I powered the bluetooth audio receiver to a different power supply for testing if the Amp worked and I got nice sound out of it. However, today I connected the bluetooth receiver to the step down converter and turned it on and didn't work. The bluetooth gets power and I can connect to it with my phone and play music, however no sound comes out.



I unplugged the bluetooth and got it on the independent power supply again, to see if something happens there, but also again, no sound comming out.
I did some tests and if I turn on the amplifier, I get a sound for about 1 second before it turns off again, this is with just the 12V battery powering the amplifier and nothing else.



Does anybody know what can be the cause of this? I tried checking the signal with a multimeter on AC onto the speakers directly and I do get around 3mA of signal, but nothing happens. Can this be a broken amplifier board or broken speakers?



Things I checked.
I have 12V on the amplifier board.

There is a direct connection from the sound input (at jack level) to the sound output (at the speaker)

There is a connection between the ground of the speaker and the ground at the amplifier board.



Any help would be appreciated