Edited by GermanGuy - 6/8/13 at 1:55pm
just got the message that my decoding of the tube codes is correct.
As assembling the valve components was predominantly done by hand - women were preferred for their manual dexterity and nimble fingers - the sonic differences might be attributed to individual worker skill. Another factor could be raw material sourcing, as obtaining the `ingredients' required to make valve parts was far more localized back then, so it's possible that the Blacburn and Mitcham factories used entirely different suppliers.
Though the above is pure speculation on my part! Why not e-mail Steve at Mullard Magic and ask his opinion, as he is Mr. Thermionic!
Just heard from Mr. Kunzig and regrettably he doesn't have any LORENZ DF91/DF92 nor PHILIPS MINIWATT DL92 in stock.
He does have Telefunken and Siemens valves, plus a few Valvo and Ultron. Does anyone know if the latter two makes are any good?
P.S. I'm inclined to believe that ianmedium has bought the entire world supply of LORENZ DF91/DF92 and sits at home polishing the valve pins at night!
It is a bit of a blow, as if a German tube dealer can't source any LORENZ what chance do us amateurs face acquiring them?!?