Umn:
There are many different versions of the Mullard el34/6ca7. I still own the xf1/double getter & the xf2/single getter versions. I recently (last 4 years) listened to/compared later XF3 & XF4 versions (can't remember the getter details on them, but the plates were of a different construction type and they did not sound the same to me as the earlier versions).
To make this even more complex (or maybe not) I have also owned/used XF1/single getter and XF2/double getter versions, these having different getter construction than those noted above that I have kept.
The "maybe not" part is that I considered the XF1 single and double getter versions interchangeable in push/pull amps as they both had the same sound. The same is/was true of the single/double getter XF2's. However, there was a difference in sound (to me) between the XF1 and XF2 tubes (same goes for the XF3 and XF4 types). Other's may even hear a difference between single/double getter versions within the same type/code. Just because I did not hear a difference does not mean that others cannot.
This makes your question a tad more complicated than it seems.
I'll suggest that you research the various Mullard types as well as the "various" Svetlana types @ Audio Asylum in their tube forum (audioasylum,com).
Yes, there are now various Svetlana el34's as well. Svetlana USA (think that's the name) can now label any tube with the Svetlana brand and they have been doing just this from what I have seen/read. I believe that the original Svetlana el34's were produced in the St. Petersburg plant (sp) and this is no longer necessarily the case.
I have no idea as to what/which tubes the above posts are referring to (and neither do you). A bit of work, but again try searching @ Audio Asylum (lots written on this).
There are many different versions of the Mullard el34/6ca7. I still own the xf1/double getter & the xf2/single getter versions. I recently (last 4 years) listened to/compared later XF3 & XF4 versions (can't remember the getter details on them, but the plates were of a different construction type and they did not sound the same to me as the earlier versions).
To make this even more complex (or maybe not) I have also owned/used XF1/single getter and XF2/double getter versions, these having different getter construction than those noted above that I have kept.
The "maybe not" part is that I considered the XF1 single and double getter versions interchangeable in push/pull amps as they both had the same sound. The same is/was true of the single/double getter XF2's. However, there was a difference in sound (to me) between the XF1 and XF2 tubes (same goes for the XF3 and XF4 types). Other's may even hear a difference between single/double getter versions within the same type/code. Just because I did not hear a difference does not mean that others cannot.
This makes your question a tad more complicated than it seems.
I'll suggest that you research the various Mullard types as well as the "various" Svetlana types @ Audio Asylum in their tube forum (audioasylum,com).
Yes, there are now various Svetlana el34's as well. Svetlana USA (think that's the name) can now label any tube with the Svetlana brand and they have been doing just this from what I have seen/read. I believe that the original Svetlana el34's were produced in the St. Petersburg plant (sp) and this is no longer necessarily the case.
I have no idea as to what/which tubes the above posts are referring to (and neither do you). A bit of work, but again try searching @ Audio Asylum (lots written on this).