Check out the many threads here on this subject. 6H30-DR tubes are considered the best.
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I support the opinion of Rgurney. I started a similar thread a couple weeks ago in this section simply titled "6H30" if you want to refer to that. I am going to be picking up 2 pairs of the 6H30-DR tube for my VK-31SE from Conus Audio (highly recommended). It is to my understanding that BAT no longer uses the NOS 6H30 in any of their pre-amps with the exception of the $18K Rex. You can purchase the NOS tube (considered to be the nes plus ulta of the 6H30) from BAT for approx $300/each!. Since your pre requires 6 tubes, that would be quite a financial committment.
Yes, Victor has a special stash, which alledgedly are the best of the best, but will set you back $300/tube, if you act quickly. That price has gone up three fold in the last 5 years, so they won't be getting any cheaper as the supply dwindles.
Also, Adam, the VK-52SE uses (8) 6H30 tubes, not (6), so it would cost $2400 to re-tube the VK-52SE with Victor's special stash.
Hi Canadiandog - I would assume that BAT would use the best tubes for the 52SE but I'm just re-iterating what I read in a post from my "6H30" thread. See below:
Victor is currently using the NOS tubes only in the REX, all other preamps are using the new production tubes.
Keep in mind though, that Dgarretson did that comparison on an amplifier, not in a preamp. Others have had different opinions about the 6H30Pi vs. DR in preamplifiers. Some, such as Guidocorona suggest in his "ARC Ref 3: Tung-Sol 6550 in power supply?" thread that the 6H30 tubes start degrading sonically around 2000 hours too. So it's also possible that tubes with "only 2500 hours" may have left their optimum performance in the past. Remember, that the 10,000 hour projection is for 6H30 tube life, that's when one would expect it to die. One would expect the tubes sonics to be on a long, gradual decline until death, though I do find 2000 hour mark to sound a bit short. I only have about 500 hours on my 6H30's, so I cannot confirm this number.
There are many threads out there regarding the 6H30 tube, probably the best thing for Frontier1 to do would be to search the archives.
My thought is that the amount of time that a tube performs "optimally" before audibly degrading is the practical measure of its lifespan & should be considered when judging its value. In the VK75SE at least, a fresh 6H30pi(EB) sounds better than a DR aged 2500 hours. Someone with the bling for new DRs who actually listens to lots of music might be interested in knowing that at 2500 hours he would be better off with a fresh set of Pi(EB).
I forgot to add that I've been using Pearl Tube Coolers on those DRs. The Coolers purportedly extend useful tube life 2x or more. My own experience with Coolers and output tubes suggests that 2x is a bit optimistic, but one might suppose that a tube that runs hot like the 6H30 should benefit to some degree.
Another possibility is that Russian factories are getting better at manufacturing new Pi(EB) tubes. Someone who knows about these things told me recently that in particular, EH-manufactured tubes are improving. I'm hoping that someone who purchases new DRs at $200-$600/pair will have at least $50 remaining to try a pair of Pi(EB) for comparison and report to this forum.