When you plug into IN#2, IN#1 shorts the 1Meg resistor, thus the input impedance looking into IN#2 is 136K, Looking into IN#1 it's ~1Meg (I'm ignoring grid impedance).
P.S. IN#1's input impedance is, more exactly, (34K+Gz)||1Meg, where Gz is the, mostly capacitive, grid impedance (|| means in parallel with).
P.S. IN#1's input impedance is, more exactly, (34K+Gz)||1Meg, where Gz is the, mostly capacitive, grid impedance (|| means in parallel with).
