So it has been a while since I read a recent update on your personel experience with modern made EL34 tubes for the older (original) Dyanco ST70 amps. My amp has been restored (removed selenium rectifier, new caps, etc.), and has the original transformers and uses a 5AR4 rectifier. The driver board is original with RCA 7199 tubes.
I did a search on this topic but most of the recommendations are for the new VTA model ST70 that has a higher rated PT so I see the typical KT88s, etc; or if relevant to the older ST70s the recommendations are dated back to 2010 and 2011.
I saw older postings of using the Russian made 6P3S-E and other variants of 6L6s. My prefernce is to stick to either a EL34 or KT77 tubes.
The present tubes are SED Winged =C= which are no longer in production so prices are higher. My experience has not been all that great. Two tubes went bad after only 300 to 400 hours of use. In one tube the getter was white as snow and the other tube the getter was flaking off the tube. But my experenice with this tube is only once, and I have read numerous examples of positive results using this tube.
Any inputs....good or bad?
BTW, I know nothing can beat the older British and American made tubes but present budgets do not permit spending $300 to $400 for a quad. At this price point Psvane tubes are also out.