I had a thread here asking about alternative rectifiers for the st-70 and never got any conclusive answers on the gz37. Anyway I researched it some online and decided to go for it. I got a nos mullard gz37 for about 2/3 the cost of a 5ar4. I put in in the amp and I can honestly say it's working great. Everything biased normally and the power transformer doesn't seem to get noticeably hotter than before. I've had it on for about 10 hours now without a problem.
Basically it's cheaper than a mullard 5ar4 and it has a higher current rating/should have a longer life. Also it looks sick compared to the bland 5ar4's
Basically it's cheaper than a mullard 5ar4 and it has a higher current rating/should have a longer life. Also it looks sick compared to the bland 5ar4's