New Tubes- Need Burn-In?


Hey guys- a question.

I just put a new matched quad of Electro Harmonix KT-88EH in my Cayin A-88T Integrated. I properly biased the amp, and after a couple of hours of warm up there is still a touch of "glare" or hardness evident.

I know these brand new tubes need time to burn in...how long a wait is reasonable before I decide whether the EH tubes are the ticket or not? Any tips on what to expect?

Thanks!
danlib1

Showing 5 responses by danlib1

Well guys, based on the feedback thus far I believe I'll buy a quad of SED "Winged C" Svetlana. Question is- should I try 6550 or KT-88 in the Cayin A-88T.

Opinions welcome!
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!
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.
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!