https://bottlehead.com/product/iron-upgrade-kit-for-s-e-x-kit-2-0/These are a 40H plate choke (close to the BCP-15), and a 4K output transformer that can be configured for a variety of different secondary impedances.
The EXO-45 is quite difficult to find. BCP-15 chokes are not as hard to find, but the lower current configuration with the smaller air gap and extra inductance is not so easy to find.
Sowter does have a 5K parallel feed output transformer with some nickel in the lam stack, and they could make you a 100H/40mA choke to go with it that would be lovely.
I believe Monolith Magnetics and Intact Audio could also make you appropriate iron sets.
Definitely avoid the old Sony/Akai 5K tape recorder transformers, as they will be a tremendous bottleneck in this application.
« Last Edit: January 11, 2022, 12:45:14 PM by Paul Birkeland »
Paul "PB" Birkeland
Bottlehead Grunt & The Repro Man