My humble arrangement. The top pix was off a web page...must be an erlier 4Bst going by the caps' color.
That's the question, because my first 3BST from 99 had the newer caps I just assumed they were in all the units from 1999 on, now I know it's not the case.
But then there are also black ones.
, anyway not a big deal as we're comparing amps from over 10 years ago so it's all water under the bridge (must be age getting me to repeat clichés) but the purple ones do have an increase in capacity, 10,000 to 12,000, at least on my first 3BST so there may be a slight increase in dynamic headroom.
Here are some shots of a pro version from 2001 with the black ones.
http://www.gzhifi.com/xinyi/goods.php?id=189Now to find out more about those ATC-Frost transformers!
Robert