The E34L is more like a KT77 than a traditional EL34. It usually requires a different bias setting and the plate dissapation is greater than a standard EL34. KT stands for kinkless tetrode and was a specialty of MO valve company in Britian. Kinkless meant that it didn't have a kink in the waveform at the bias point when viewed on a scope. MO stood for Mullard Osram. A beam tetrode is a design that has a beam (the beam of electrons flowing through the tube) forming plate, in addition to the suppressor grid. The standard EL34 is not a beam tetrode but a pentode. A pentode has an additional grid to adjust the internal capcitance of the tube. (triode = cathode, anode, control grid, Tetrode= cathode, anode, control grid, suppressor grid, pentode= cathode, anode, control grid, S grid , additional grid)
I really like the American version of the EL34; the 6CA7 in the bigger bottle. It also has stronger, tighter bass than a traditional EL34 but still sounds and responds mostly like an EL34. Their were two brands; Sylvania and GE.
The EL34 was invented in the early 1950s by Phillips in Holland. Phillips and Mullard were different divisions of the same parent company. Mullard was based in Britian, and Phillips in Holland. Amperex was also a division of Phillips. All the tube companys developed their own EL34s for sale. I also like the German EL34s for traditional EL34 tone. The Siemens EL34 was identical to Mullard's. The Telefunken was in a slightly smaller bottle. The Siemens was also built by the RFT company and sometimes by Mullard and sometimes by Phillips. Actually RFT and Siemens were close to the same company. After WWII the German radar company GEMA was absorbed by Siemens in the west, and became RFT in the east.
In Cechzslovakia the standard tube company was Tesla. When Tesla went under in the early 90s it was taken over by JJ.
