I`ve read through all of the thread this time. 
Another version of the amplifer
http://www.ebay.co.uk/itm/2-2W-4O-PAM8803-Class-D-Audio-Amplifier-Board-Simple-/350604041652?pt=US_Home_Audio_Amplifiers_Preamps&hash=item51a1a11db4
I wonder if 64 steps volume control is fast enough to do some basic envelope shaping?