They make some interesting claims regarding AC701 made after 1965, foremost that there is no difference between AC701 and AC701k if made after 1965. Curious what you lads have to say about that?
Tube Depot is correct: the AC701's quality improvements lead to the omission of the now redundant "k" (low microphonics).
What that leaves out is that far too many of these, "k" or post- "k" tubes were not automatically suitable for microphone use- further, long-term, selection in situ is necessary:
http://repforums.prosoundweb.com/index.php/topic,1150.0.htmlWhat's not correct on Tube Depot's AC701 web page: Telefunken did not issue the fake East German copies with the white lacquer dot (indicating the anode lead). Neumann never equipped any of its mics with these RFT-made tubes, nor were they offered as spare parts.