I have Amp+ and I am using the test image from hifiberry, which has the autodetection.
Well it has detected the soundcard correctly and all the setting are exactly as mentioned in
The output of
**** List of PLAYBACK Hardware Devices ****
card 0: sndrpihifiberry [snd_rpi_hifiberry_amp], device 0: HifiBerry AMP HiFi tas5713-hifi-0 
Subdevice #0: subdevice #0
I suppose it is correct.
I have connected the speaker wire to the screw terminal.
But still when I use
aplay test.wav, I get following output, but no music
Playing WAVE 'test.wav' : Signed 16 bit Little Endian, Rate 8000 Hz, Stereo
Any ideas what i am doing wrong?