New Tubes- Need Burn-In?

Bartokfan-

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.)

Zaikesman- All good points. I noticed that the EH KT-88's had improved significantly as I used them. I am hanging onto them for precisely the reasons you mentioned.

Thanks for making me think!

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.

I've been very happy with the SED flying "C" EL34's in my Dynaco MkIV amps. I also loned a spare quad to a friend with Antique Sound Labs amps which he will be keeping.