Raspberry Pi Audio Circuit very low volume

Hi,

First of all thanks for your tutorial "Raspberry Pi Zero Audio Circuit".
I tried it out but the volume is very very low (as if it's produced by headphones).  Here's my build:

I used a Raspberry Pi 2 B to test, but I will swap it later with a Zero.

Amixer and alsamixer are both on 100%. When I connect the input straight to the amplifier (without the filter), it's a bit louder and ofcourse a lot of noise but still not very loud. It's as if the amplifier is not amplifying the sound, but it's still processing the input...

Am I missing something? The speaker is 3W btw.

Thanks!