I had a pair of EH EH-34s that never got rid of their glare, and from what I've read, that's not uncommon. My advice is to get the Svetlanas -- I did, and the problem was solved immediately w/no "break-in."
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You must differentiate between SED's and Svetlana's.
Present day Svetlana's are nothing more than Sovteks in disguise. The really good Svetlana tubes are now called SED and they are made in St Petersburg. The logo on the tube is a 'flying C'. The change over took place several years ago so before buying "Svetlana" tubes investigate.
I use, on different amps, SED KT88's, 6550's, and EL34's and highly recommend them for their tone and ruggedness (I've never had one fail, yet).
I give any power tube 48 hours or so of break in before making a final judgment.
Ditto positive comments on the SEDs, especially the EL34s. Running a new quartet of these in a CJ CAV50 and they have all the extension and soundstaging I could ask for. Inner details and quiet backgrounds they do in spades, exactly what I was looking for. Likely one of the best brands of current issue EL34s for audio.
Don't know about a Cayin - probably depends on the sound you are after. You will likely hear a fuller and warmer sound with the KT88's and a more linear sound with the 6550's. I'm running KT88's with EH drivers in one amp and 6550's and EI drivers in another. Both sound great in that combination. So, once you pick your power tube consider how it will sound with the driver tube - makes a considerable difference.
Well, after much experimentation and help from all you guys I believe I have whipped the Cayin into line. Damn it's sounding good now!
My take on the amp:
The stock tubes are marginal at best- which is surprising considering the glowing reviews the amp has received.
The EH KT-88's I bought to try are too "edgy" in that amp- detail is good but everything has a noticeable level of attack.
I now have a quad of Svetlana "Winged C" KT-88's from Upscale Audio that were thoroughy tested and matched. I also replaced the Chinese 6SN7's with 2 NOS Sylvania 6SN7W's.
Man- it's like night and day- an altogether different amp. Great transparency, liquid vocals, in the room realism with good material, and better bass than I had with either the Cary SLI-80 Signature or the Manley Shrimp/Conrad Johnson MV-60 combo.
My final touch comes next week when I receive my NOS RCA Red Base 6SL7's to replace the 2 remaining Chinese driver tubes.
I'll report back after that move!
I paid $170.00 for the Quad of Svetlana Winged C KT-88's from Kevin Deal at Upscale Audio. Yeah, I could have bought them cheaper, but I wanted a thouroughly tested and matched Quad.
The Sylvania 6SN7W's replaced the two Chinese 6SN7's that came in the Cayin. The Cayin also employs 2 6SL7's, which is where I'll stick the RCA Red-Base when they arrive next week.
The Sylvania's were about $110.00 for the pair. The RCA's were $150.00 for the pair. Expensive, yes, but with a 10,000 hour lifespan they're worth it in my opinion.
The Cayin A-88T is WAY sensitive to power cords...if you buy one experiment and find what works best in your rig.
Also remember this amp is NOT self-biasing, regardless of the false info in some publications. Biasing it is easy, but you must remove the bottom cover and stand the amp on it's side to do so. Pain in the ass? Yep, but the amp is worth the trouble.
I have a similar take to yours on the EH vs. SED versions of the KT88 as for how they sound, but a diametrically opposed opinion on which I prefer. I enjoy the clarity and speed of the EH, and didn't really care for the warmer SED (I prefer their 6550C more in my VTLs as a viable compromise, and admire their EL34 too).
I'd also found the Chinese 'Ruby' 6SN7 to be a very competent driver in a CJ amp, close to the same ballpark as some NOS American versions (something I couldn't say about the Sovtek). But of course we all have different systems and tastes, glad you've identified something for yours.
I've generally found that power tubes take a couple days' worth of *playing time* to open up and flow, which for most people means a week or two. And whenever I've had incipient problems with glare, it's always turned out to be traceable to microphony of the input tubes; other than trying to get the best-sounding and least-microphonic NOS examples you can, I would also recommend trying some type of tube dampers here to help tame glare.
Once you get all that squared away and if you still have them hanging around, you may want to revisit the KT88EH's after a while, let them finish burning-in and see what you think again. They will always sound leaner and less 'tubey' in comparison with the SEDs (to me they're more neutral), but I feel they hold a few other advantages in fidelity, provided the tonal balance can work with the rest of your system. (BTW, if you -- or anybody -- is in the market for a spare matched-pair of little-used SED KT88's, email me.)
Rumor has it that those GEC clone flat plate KT-88s from Shuguang are incredible. Is that really misguided??
BTW I am late to this thread, the answer is absolutely, you must burn in a new tube to get the best sound it has to offer. They burn in but do not take as much time as many as people say, for an input tube, in particular. They (inputs) will IMHO retain their sonic signature after at most 40hrs. I think people who say 200 hrs are just hearing things.
Output tubes are a different animal altogether they may need 100 hrs or more to settle into their final state they have been quiky in my amps, but they just seem to bounce around. They always seem to start thin and flesh out but even a matched quad will have a tube or two that takes more time and they can go through a really flat sounding period on the way, others flesh out right away.
Can't comment on the 6SN7s burn in every pair I own (may 10 pairs or more- I love tube rolling) is NOS and well burned in.
Bartokfan...KT-88's and KT-90's are two very different tubes. Compare the KT-88 with the winged C 6550 insted. KT-90's to my ear are much more punchy and a bit more agressive then the winged C 6550. Usually KT-90's have a bit more output as well. What was the tube your Jadis amps were 'voiced' with? BTW as far as I know Jadis does not make their own tubes and buys them from China, Russia, Yugo. etc. G.Garfield
The real term is aging, yes then the cathode emission becomes stable and the tube does not drift. The recommended time is circa 36 hours.Me, vacuum tube gear, late 1950's, Stategic Air Command. Delt with tubes. i'm thinking of doing a online consulting service, does this sound like a good idea, to all? won't be free, but i'll teach audio also to component level including transformers.
I am considering tube swapping on my Cayin as a necessity. For the last couple of days I have been hearing some loud pops in the right channel during the first ten minutes of warmup. After that the unit appears to be fine. I have never attempted biasing and tube swapping before but I am eager to learn. Dan thanks for e-mailing me the biasing info.
Change the small tubes from the right channel to the left channel and vis a versa. If the popping changes channels you've sourced your problem and potential solution. IME your complaint is typical of small tube deterioration. If that doesn't work change the power tubes in the same manner - if they were matched, biasing for this simple change may not be necessary. If you have to replace one or a pair you will then need to re-bias the new tube(s).
Merchans, I am using the Shuguang KT88's in my Cary SLI80 and they are as good as rumored. I got them from Penta Labs, which offers the "GEC clone" version of this tube. In my system this tube was better than either the EH or SED's. I didn't like the EH's at all, but thought the SED's were a good tube. There's a bunch of discussion about the Shuguang tube over at Audio Asylum.