Adding voltage to a circuit

[Tobias]

Here is what I have. It seems to work good except that the digital pot does effect the value from the turn pot. Is there a diode arrangement I can use so the two turnpots don't work against each other. For example with the turnpot at 100% it reads 4.41v when connected to the entire circuit. When standing alone it reads 4.47v at 100%

Thanks for your input