Originally Posted by edisonwu
How much approximate percentage of the headamp circuit is sharing the preamp's?
When switching between Headphones & pre-amp only input/gain tubes, #1 and 2, back left corner, are being used all the time, for example, in pre-amp mode, #1, 2, 3 and 4 tubes are used as fully balanced dual mono pre-amp, no signal is passed to the four "5687" ,headphone drivers, as their inputs is shorted to the ground. When B-52 is switched to the balanced headphone amp, the inputs of tubes #3 and 4, which are the pre-amp drivers, are shorted to the ground & the signal is passed from tubes 1 and 2 to the four front tubes, # 5, 6, 7 and 8, these drivers are the buffers that power the headphones in a fully balanced mode. No signal is shared at all, as it is either a fully dedicated balanced pre-amp or fully dedicated balanced headphone amp all in one very well put together package.