That's what i get for posting when I should have been sleeping. Indeed, the maximum I could squeeze out of this transformer would be a 2.5k primary impedance for an 8 ohm load - too bad, as it looks to be an authoritative chunk of iron for the money, with an impressive bias current rating. On the other hand, this high current rating may mean it's deficient in the inductance department. Back to the drawing board - I'll probably call Edcor and ask what kind of designs they have in their vaults. I'm looking for a transformer with 5k impedance that will stand up to the voltage swing associated with 700V B+,with at least 120 mA bias current capability. I'm in no big hurry, as I have many projects in line ahead of this one (an 813 pentode-mode "Super Schade"), but it would be nice to have the means at hand when I finally get that uncontrollable urge.