since the amp is new let the stock tubes stay in awhile to get used to the sound. my 502b came with stock eh 6550 and i later bought eh kt88. for the driver tubes i am using ge 6201 or mullard cv4024 in the 12at7 slots.
tungsol ecc803s in the 12ax7 slots. you can also sub 12au7 for 12ax7.
tungsol ecc803s in the 12ax7 slots. you can also sub 12au7 for 12ax7.