Report The Headcase Stax thread in Headphones Posted August 3, 2013 Doesn't mean anything past the usual upgrades Stax made to their long running designs. The SRA-10/12S went through at least 4 different power supply layouts though they are all pretty much the same. Two preamp revisions too but it was mostly change of parts. Which brings me to your issue, just sub that part with some modern Jfet. Stax moved to the 2SK30A in the SRA-12S so that might work (too lazy to compare the data sheets), K117, K170 and all the Fairchild Jfets. Just find one that's close and the right Idss and try it. Just watch out for the pinout. Thanks for that, I was looking at the 2Sk117 (BL version) which has a max idss at 14mA. Just checked the 2SK170 (BL version as well) and it's rated at max 20mA. Guess it works, I'll order some of each kind. From here onwards it's pretty much shotgun troubleshooting.