To the OP: don't lose sleep over this: even though the EL34 are rated to 800V for Va & Vg2 max, nobody in his right mind runs them that hard. Most if not all commercial gears run them wisely at 400-500V for about 40-50W output per pair. Even the factory plate curves stop at 450V. Under these conditions, they're no worse nor better than the 6L6GC.
This is as surprising as the 2 kV plate voltage rating in the 1st line. But note the (b) remark for both that the Mullard datasheet unfortunately doesn't explain. There are two different voltage ratings in any datasheet that we find at the WWW nowadays. I guess these have been taken from comprehensive tube data books in which we'd find general explanations.
Out of experience and from Valvo and Telefunken databooks that I own I know that the higher values refer to the cold electrodes, i. e. immediately after powering on.
Best regards!
Out of experience and from Valvo and Telefunken databooks that I own I know that the higher values refer to the cold electrodes, i. e. immediately after powering on.
Best regards!
Philips and Telefunken give pentode curves that go up to 750V.
Svetlana up to 600V.
Others (incl Mullard) don't go beyond 500V.
For new builds I wouldn't go beyond 500V.
However, one of my many pending projects is restoring two Dynacord Eminent 2 amps. They run at ca 750V.
Dyncord Eminent II and similar amps, also the Gigant and similars with two pairs, should be equipped with NOS EL34's, if possible.
Best regards!
Best regards!