listen and listen closely..
first off do not plg the b52 in any power conditioners of any kind, plug it strait into the wall. sonics will be destroyed. get used of it without power crap then try it if you so feel after weeks on end of strait to the wall.
every power cable i tried also hurt the sonics, a nice thick stock wire will do.
do not double load her, either balanced headphone or unbalanced at one time, it can drive both but again sonics go down.
since your only using the headphone out and not the pre out then forget to play with the back right two tubes..those are pre outs only.
12ax7 on the inputs are two high of gain, dont waste your time and money.
12au7 telefunken and 5687 tungsols are a dream match for headphones..best match i found for the gs1000 and 600's. the 650s may have a bit to much bass with this combo, for them i would try different 12au7's with the tung's. another headphone that sparkles is the 701 with this match on the b52..omg!
try out enigma onemal ic's also, i found them better then my Cardas Neutral that i had before. plus if you sold the cardas that could be more money for tubes.
the power supply has no heat but considering you have 8 tubes on top i would give the head section good clearance. with my setup the top of the unit barely gets warm.
if your going to stack the two units with the stock spikes watch it! one wrong move and you'll have a cute scratch on top of the power supply like i do on mine.
keep the phono input at one end and the cd input on the opposite end of the selector.
keep your xr-2 away from the power supply, not much will happen but youll notice if you move them close while listening to a silent section of the vinyl..
and one more thing..
What are you only using her for headphones? get into speakers somewhat and enjoy her REAL beauty. try 600's with cardas balanced if you get bored and have money..its soooooo ****ing nice!
i have pics up here all over the place if you search...maybe we should start a tube rolling b52 thread huh? congrats on the best pre amp i ever heard..preamp..hehe