I too am shocked at the differences between rectifiers, including differences between direct-heated and indirect heated rectifiers. Fun to roll in my Woo headphone amplifier.
BTW, this is the first I am hearing of Bill Thalmann’s death. I met him in 1974 when he sold me my second pair of Advents while he was a salesman at the old Atlantis Sound in Falls Church, VA. The next year he very kindly helped me build an Ampzilla amplifier kit. I last spoke with him last fall as he was closing his shop. What a wonderful guy…it’s very sad news.