o.k.first of all,the schematic isn't mine,it's Chelsea's.it is his project,I know that certain resistor values are not available,but these are on the diagram.Bearing in mind the tollerances of resistors,there is scope for substituting the nearest value.I've tested hundreds of resistors,and there can be a lot variation either way.Personally I don't know what he is trying to achieve,I asumed it was just something to post to ISIS ect.,I don't think anyone would waste their time building this circuit.I've not had any response from him,so I don't think I will bother untill he does.Your comments on the project are correct,and I fully agree with them.Anyway I'm still waiting for replies to my own threads.