There is also the factor that the cathode voltage of the 6080 is 0 at startup, then slowly climbs as the tube warms up. With headphones plugged in (even 600 ohm ones), the parallel resistance of the 2.49K resistor and the headphone voice coil become very low, singificantly reducing the presence of this startup voltage. FWIW, Doc and I have both left our HD-800's plugged into stock and Speedballed Cracks during startup plenty of times without giving it a second thought.
