I have a vietnam V30 and am looking for my next set of power tubes. I'm being extra proactive because these amps are known for running hot and having some voltages past spec in the power section. Mine came with sovteks with the cool blue light in them. As far a replacements I could stick with OEM but wheres the fun in that. Sovteks are generally considered a tough tube I believe. People tend to like JJs but there seems to be mixed reviews on if they stand up well to these amps abuse. I remember someone mentioning they liked Mullard RI. I have a set I may try but they are a bit expensive specially if they burn out after a month so I was hoping to hear more first. I also have a set of NOS rca or ge. One the one hand the old designs may be most robust but they may be getting delicate in their old age and are even more expensive. Aiken amps seems to think the EH may have the edge over the JJ in robustness but the JJ has a slight edge in tone by his ear. http://www.aikenamps.com/ Here is his conclusion: Conclusions Both the listening tests and the measured data indicate the two tubes are remarkably similar in performance and tone, given the differences in construction and appearance. The JJ/Tesla tubes put out a bit more power into the same load impedance, and in my opinion, have a slightly better tone. However, the increase in screen dissipation of the EH tubes makes them a nice choice for amplifiers that tend to go through tubes more often. The EH would be highly recommended for amplifiers that run the tubes (especially the screens) at high voltages. How about the sov el84M? Is that the same tube as the current 7189 available. How about the russian 6p14p? What other tubes may be a good bet for the right combination of tone and reliability, specially in these punishing amps.