The Arduino forum shows a volume control, not a filter. Your amplifier already has a volume control.
Instead you need a lowpass filter. Use a series 4.7k resistor from the WT588D PWM output feeding the input to the amplifier's volume control AND feeding a 22nF filtering capacitor to ground. Turn down the volume control and slowly turn it up then tell us how it sounds. It will probably sound without distortion but very muffled then try smaller capacitor values.

Audioguru Again and dendad:

Thanks so much for the clarification and drawing. Visuals are something I can understand, so that drawing is great!

Just a few questions:

1. Does the pot indicated here correlate to the one on my amp package?



2. For this to work do I have to tie together the grounds of the WTD588 sound board and the TDA 7297 amp? Or does the .022µF capacitor go to just one of the grounds (and which would that be)?

As I wrote above the sound board is powered by 3V, the amp by 12V.

Apologies if these are stupid questions.

Best.

Shawn

 

Yes, the pot in post #21 is one of the two volume controls on your amplifier. For Mono in both channels, connect the amplifier volume control inputs together and to the filter capacitor an resistor that feeds the filter capacitor.
Yes, connect together all the ground of the WTD588D, the amplifier and the filter capacitor.

 

Yes, the pot can be to one on the amp board, as long as the map does not have a preamp before the pot.

Yes, tie the 3V and 12V 0V (ground) pins together. They both need to share a common reference, unless you incorporate some sort of isolation, like an audio transformer.
The 3V can be generated from the 12V with a 3V regulator.