Auto amplifier diagnostics, output very low

[Guest]

Hi,
I'm testing an amplifier by connecting it to an ATX power supply. My audio source is an iPhone and the load is a 50W car speaker (small, usually mounted in door). The problem is, that the output volume is very low (unconnected iPhone plays louder). Besides that the sound is distorted, especially low frequencies. I tried changing source to laptop, but the result is the same. I would appreciate any thoughts on troubleshooting this device. I may also add more info if needed.

[peikis]

Forgot to log in

[elec_sham]

Dear

Audio source is an iPhone and the load is a 50W car speaker is not clear. Because to drive a 50W may be 4 ohms load speaker a power amplifier is essential. To raise the volume to the desired level, after iphone headphone socket a Buffer amplifier is required. From the buffer amplifier output the signal is then fed to main Car amplifier. Hope you understand this and follow accordingly.

Regards,
elec_sham