KT-88 in Conrad Johnson Premier 11a

I read some discussion about replacing 6550 in Conrad Johnson Premier 11a by KT88 may/will tighten bass and improve overall midrange and treble performance.

I talked with CJ and they said they never tried KT-88 in 11a (well I really doubt it) and it may not be able to bias KT-88 in it at all.

I really would love to try KT-88 in my 11a but I need to make sure I can bias it correctly... Any one got experience in it?

I've used Chinese KT88s and Ei KT90s in a couple Eleven-As and they bias just finely. Never heard of an amp designed for 6550s that wouldn't bias KT88s...but what do I know? :-)
I use the svelenta KT88s in my preimier 12s bias adjustment is pretty close to the 6550s,you can use them no problem.
I used a variety of KT-88 and KT-90 in my Premier 11a and Premier 12's. They were all wonderful, so it is very much a matter of taste.

This is the only line of amps in my experience where I ended up preferring 6550 to KT88 or KT90. Usually I prefer the slight touch of ripeness added by these latter tubes. But CJ gear already sounds sweet with 6550's and the KT88 and KT90 were a little over the top for me by comparison.

But I don't think you can go wrong try ing it out, its a huge part of the fun of the hobby.

Thanks everyone! I read some discussion saying KT88 needs to be biased differently on some amps as it works best in a slightly different current flow.

Anyway I am really tempted to try KT88... Artmaltman, which brands of KT88 did you try on your 11a and how would you compare them?

I wish I can try GEC if I had the money. =p I am choosing from Svetlana, Electro-Harmonic, or SED. I found on some tubes store websites that SED is re-branded Svetlana... but SED costs more. Anyone knows the story behind this?

Hi, Hklai:

Svetlana was a venerable tube manufacturer with a plant in St. Petersburg, Russia. Several years ago, a company in the USA named Sovtek purchased sole rights to the brand name
"Svetlana," as well as other famous brand names, such as Tung-Sol and Mullard. So now Sovtek makes and markets tubes labeled Svetlana which are considered my some to be inferior. Meanwhile, the original (real) Svetlana makes tubes labeled SED-C with a winged 'C' logo, and some older production SED-C tubes carry the name Svetlana on the boxes. Sovtek markets some tubes that are said to be musical, including the Electro-Harmonix KT-88. Go to the above link to see a photo of a real Svetlana SED-C KT-88.
Best wishes,
Correction: New Sensor markets Sovtek, Electro Harmonix, Tung-Sol, Mullard etc. Apologies for the error...
Thanks Jburidan. Yes I used the older Svetlana KT-88, which would now be SED brand. The KT-90's were EI from Yugoslavia. I bought these all from Kevin Deal of Upscale Audio, if I recall correctly.
Thanks Jay and Art!!

I'm really curious to know how the NOS Genalex KT88 sounds... and wonder if they can really live up to their price.


Art, did you happen to try Electro-Harmonix as well? I wonder how it compares to the SED... I will pick either one of them...

The EH KT88 will sound more dynamic, tighter more powerful bass, a bit brighter top & extension.

The Svetlana KT88 will have a slightly romanticized midrange, with a burnished sound, more tubeish sounding, the EH sounding less tubeish. The highs have a bit of cloudy coloration.

It amounts to a matter of taste and the gear it is in. If the Premier 11a sounds lush with the stock Svetlana 6550 (which are leaner & more analytical than the Svet KT88), you might prefer the EH KT88.

By the way, I had both old winged C Svets, and didn't hear a difference between the New Sensor Svetlana and the winged C, and they looked identical in construction.
Hi, Hklai:

I believe the NOS Genalex KT88 is the best ever, but almost impossible to find. Beware of fakes on e-bay.
Best wishes,