I may be the only one who has used the virtual balanced input as a means to improve measured noise and distortion in an audio interface or amp, but it worked when using the Delta 1010LT, even with the balanced inputs. I suspect that is due to the card having both balanced and unbalanced inputs. REW may be sensing that the 2i2 has no unbalanced inputs, therefore the virtual balanced input option is disabled. What I want to do is use that option in sum mode to combine the two inputs with a splitter sending the same signal to both channels. The sum mode sums the two, then divides by 0.5, exactly what makes it work for the distortion calculations.