My McChanson marzE SET amplifier uses EC86s at its driver stage. Recently, thanks to Eric Chan, the maker of the amp, I was able to audition a range of EC86 and Russian equivalents.
The EC86s inluded a number of well-known brands: Lorenz, Valvo, Telefunken, Siemens-Rohre; and a couple of lesser ones: Hoges and Magnadyne.
The Russian valves were ex-military and designated as 6S3P-EV and 6S3P-DR. The DR has some special features compared to the EV (notably the presence of a gold grid) and is reputed to last up to 10,000 hours.
The parameters I used in the listening tests I did were very subjective but pretty straightforward. The subjectivity comes in because I only used my own ears to listen to the performance of each pair, so really it's just my opinion based on how good or bad my ears might be. In terms of sound reproduction I was looking for how well each of the different drivers handle bass and high end, clarity across the mid-range and the extent to which they added any colour to the sound.
In my current configuration of the marzE, I use EC86s to drive Winged C SED 6L6GCs. The amp allows for pentode or triode mode and I kept it in triode mode for the auditioning. The amp also uses a 5AR4 / GZ34 rectifier and I have a NOS Mullard loaded at that stage.
I was already very familiar with 6S3P-EV as my version of the marzE shipped with these. They are very good valves that excel at delivering clarity on recordings that are centred around the human voice. The high end is good and the bass end is fine. They did not add any colouration or warmth to the sound as far as I could tell.
The other valve I was already familiar with was the Telefunken EC86. Sadly these valves have never performed well. They add huge amounts of colour to the sound and while it is pleasant, warm and cosy even, it really was not a sound that I liked. Overall I thought their whole dynamic was rather limp compared to the others and if it had been a race, the Telefunkens well and truly ran last.
Valvos I had playing in the system before Eric threw some extra EC86s into the mix. The Valvos are bold. They are gutsy, clear and have a great bass end. Upper range is decent. At this stage they were the preferred EC86s.
Okay onto Eric's valves now:
The Hoges -- I loved these on first hearing and over several more hours of play. Great clarity and such a sweet upper range (possibly the best so far). At first I thought the bass was okay, but on switching back to the Valvos and 6S3P-EVs, I realised that the bass was actually quite lacking with these guys. But nice valves if you don't need much bass. I do, so the Valvos were still the preferred one.
Next came the Lorenz. Big name and big reputation. But they just struck me as lack lustre. They didn't do anything wrong, but there was simply nothing about their sound that impressed me at all. Bass, clarity and high end could all be beaten by others. Just a good average all rounder in my opinion.
Russian 6S3P-DR (the guy with the gold grid). This was the first one that I listened to that gave me goose bumps. What a brilliant driver valve for the 6L6GC Winged Cs. The clarity it produces is exceptional, especially on the human voice, and bass and high end just blend perfectly with the mid-range. A big improvement on their little brother, the 6S3P-EV.
After the 6S3P-DR, the Siemens-Rohre EC86s had a hard task. On the first listen I thought they were very good, ahead of most of the others I had heard, but lacked what the 6S3P-DR had to offer; the clarity, the wonderful wonderful clarity. A few days later, I moved on to the last one, thinking that the 6S3P-DR, with that magic gold grid (which you cannot see BTW) was the clear winner.
The Magnadynes were the last I put in, and as soon as they fired up and the music played I knew we were in goosebump territory again. I had another clear winner.
In the end three valves went into the final shoot-out. The Magnadynes, the Russian 6S3P-DR, and the Siemens-Rohre. The latter was placed back into the mix because it was clearly ahead of the rest of the field, and I did feel I hadn't given it much of a chance by playing it directly after the 6S3P-DR. For a week or so I listened to these valves against each other and came to the conclusion that all three were exceptional performers. And I did occasionally put the end of the field contenders in just to make sure that I wasn't making it all up, but every time the Lorenz went back in, and the others, it was the same result. Magnadyne, 6S3P-DR, and Siemens-Rohre were clearly way ahead.
If I was asked to give a clear winner then that would go to the 6S3P-DR, based on two things: amazing clarity and when it's available its very cheap. This is not to say that Magnadyne or Siemens-Rohre are not exceptional. They have a certain element of magic that the 6S3P-DR may not have. Perhaps the 6S3P-DR, at times, is just a little too focused on clarity and occasionally the other two top contenders get the music better.
Some caveats: I have already stated that this was a very subjective review of the range of EC86s that are around. That is, my ears only. But there are other issues as well. All valves are new old stock (NOS as it is known) but I had no way of knowing whether any of the valves had been too long on the shelf and whether any deterioration had occurred. A physical examination suggested not, but that's not a great way of determining any changes in the metal components over the years. Also there is the question of burn in period. Would some of the valves I sent to the end of field have performed better than my best three if they had burned in longer? I suspect not, but it might be possible.
A final factor that worries me is that of valve matching. Since I did the EC86 tests, my more recent experience has shown that some drivers work better with certain power tubes, and others don't.
So at the end of all this I can only happily conclude that EC86 6S3P-DRs, Magnadynes, and Siemens-Rohre are exceptional driver valves for SED 6L6GC Winged Cs (the lovely ones made in St Petersburg).