Alain about your suggestions:
1> I think you are right I have not implement an rc filter. AN note is VERY usefull here I think. (although I have read it before I did not use rc filter just decoupling caps). I have some 750ohm and 330nf around here so I can give it a try.
2> for the moment no ground plane just a proto-raster board (this of course causes problem by itself)
3>samples is already there but I get only 4samples maybe get 8 or 16 and see what happens.

ALL the suggestions you make is not difficult to imlemented so I will give them all a try and let you know

(...and shhhhht ,yah waiting for your enhancements!!)