Pi 3B+ audio issue in bartop

[chubsta]

I am getting towards the end of my bartop project and have run into an issue with getting sound out of the Pi. The HDMI is connected to a 7inch screen but the screen has no audio capabilities or audio out on its boards.
I have utilised an old pair of headphones and by cutting the cable I have connected the Pi to the mini amp.
The amp is one of these - https://www.ebay.co.uk/p/Pam8403-Gf1002-Digital-Amplifier-Board-2-3w-Stereo-Module-USB-Power-470uf/848723847#ProductDetails

I have tested the amp and speakers by connecting them to my phone using the jack cable and it works fine, the sound is good and it goes up and down when I turn the knob.

However, when I plug the jack into my Pis jack socket all I get is a crackling noise.

Is there a better way of getting sound from the Pi, such as through the GPIO pins to the amp - I have read about this being done with the zero w but couldn't find anything about the 3B+.

Any help would be much appreciated as I am starting to bang my head against the wall with this!

[mitu]

Try adding the following parameters in the /boot/config.txt file

disable_audio_dither=1
audio_pwm_mode=2

then reboot and see if it makes a difference.