EL 34

RAM tubes :-) Roger Modjeski but still going strong w super matching and testing, $45 gets you a killer valve

in my experience

ranked by overall sq (including midrange beauty) - we are talking old stock tubes here, not the new/modern day russian/czech/chinese tubes

best
gold lion gec genalex kt77 (uk made)

close/next best
mullard/amperex el34 (uk or dutch made)
matsushita el34 (seam top) - (japan made using mullard tooling)

close/next best
svetlana sed winged c - russian old stock st petersburg plant
tesla yugo el34 brown base yellow print

not as close, next best
philips/national east german thin bottle dimple top el34
yugo ei fat bottle 6ca7

amps i have/have had in which i developed this ranking - vac pa90c, air tight atm-3, primaluna hp prem dialogue, linear tube audio zotl40 reference, marantz 8b, cj prem 11a xs

When anyone tells me the TOP is a little harsh, I always ask if they can BIAS a little lower. The valve is breaking up to soon.. 50% of the time it increases the mids and highs and usually increases the  peak to peak by a bit. What I do notice is low volume playing (VERY low) is not near a clear or pleasant.

Swapping a signal valve or two always smooths out the rest. Telefunken or Mullard Blackburns will do it..

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 Electric EL34 and KT88s, on the Leben 600X. Gives an idea of what room for improvement might exist over the stock EH for your type amp.

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I'm just assuming you can use a 6550 too. There are GREAT 6550 (W) Russian surplus and new that are wonderful valves.. That W means they are MiG tough.. That's pretty tough.. They are a thick black plated valve.
Super stout banded/base.. Just make sure YOUR vendor checks the factory match.. Their QC for boxing valves sucked.. CHECK for matching.. Mids and highs.. 6550s..:-)

Regards

Has anyone used the Siemens EL34 from RAM tubes?