I have not heard this, and I have no idea what Pete might have done, but the specs on those NuTubes are not promising. The good is that they run at low voltages and have a mu of 12 which is probably nice for a traditional tube to buffer hybrid amp without too much gain. The bad is that they have a plate impedance of 300K (higher than most pentodes), don't draw enough current to even really push a buffer, and draw nearly as much grid current as they do plate current. Gm is 40uS (0.00004S - compar