rodabod said:Oliver Archut's 47-inspired mod:
http://recforums.prosoundweb.com/index.php/m/0/26173/96/13216/#msg_num_14
Oliver is now selling these transformers: http://www.compasspointstudios.com/bulldog/bulldog-tnc_upgrades.html
The circuit designs all look fairly standard, and seem to be typically cathode-biased. The transformers could be good on a budget though. From what I understand, the BV8-inspired model is made from off-the-shelf lams and is built to be machine-made to save cost.