Tubes for Conrad Johnson Premier 11a ????

I tried KT88's in my CJ 12's. This is the first time I've seen a situation where I did not flat out prefer KT88 over 6550. The KT88 had a bit more power and more full sounding, but the CJ is already by nature full and sweet sounding. I think the 6550 had a bit more detail and nuance at least in my setup. It boils down to what are your other components and your personal taste. If I had very neutral speakers (e.g. Thiel) the KT88 would probably have been a revelation but my Spendors are already warm sounding, and so the 6550 proved to be a better match IMO.

Trying KT88 in the CJ is fun and whether or not you end up keeping them I don't think you'll regret trying it out.

Art

ps: CJ does not suggest using KT88 in the amp. I've spoken with them about it and they just seem to prefer the sound of 6550's with their gear. They don't indicate that KT88 would damage the amp, just that they have not optimized the amp for it.

I have been using Sed KT88's in my 12's.and i prefer the the better bass,and warmer sound.I just purchased some Golden Lion KT88s so far they seem to sound a bit more vibrant.Need more time to listen.

I know this isn't to point but I thought I'd offer this experience: I changed the small tubes to NOS RCA's with what I considered to be quite dramatic effect. I won't try to detail the change but there was significant across the board improvement.

My experience in speaking with CJ about using KT88's instead of 6550's was similar to Art's. I never tried the KT88's because CJ said that I would not be able to bias them in my amp.

The Premier 11s and 12s are wonderful CJ classics - both were designed and originally voiced for the GE6550A. Those have become a bit scarce lately, but if you run across a quad, they're well worth paying a bit more. The SED (nee Svetlana) 6550C is an Ok replacement. The original Tung-Sol 6550 is a bit of a wholly grail tube difficult to locate and v. expensive.

Rolling the small driver tubes can change the sound of the amp more so than the power tubes. The RCA clear-top 6FQ7/6CG7 is very nice and the ~1958 Sylvania 6FQ7 is even better. The RCA black plate 5751 2 mica makes the stock CJ National seem rather lifeless.

Check with Andy at Vintage Tube Services.
 
Tim