time to discuss kt-88's

I recently traded my JJ KT 88s from my Audio Aero Capitole amp into my McIntosh 2102 amp just to see what would happen. the Svetlana Kt 88s made an amazing improvement to the Audio Aero. so much so that only now do I realize just how wonderful this amp sounds. I got on line and bought another set of Svetlana KT 88s to put back into my McIntosh. While I was at it I changed out most of the rest of the tubes in my system.

Anyway, you will find lots of support for the Svetlana KT 88 tube and perhaps even more support for electro harmonix which I have not yet tried.

I really like my Electro Harmonix KT-88EH in my ARC VT-50. The bloom I enjoy without the slight dryness of 6550. Just my 2 cents.

I'm also running EH KT88s, 16 of them, on my ASL Hurricane monoblocks. A worthy upgrade to the stock tubes!

I have a suggestion of another avenue. I have tried Sovtek, Svetlana, JJ, and other KT-88's in the past in my Sonic Frontiers SFS-80. I mention this due to it using a pair of output tubes per channel as well. I was constantly tube rolling and was talking with Kevin @ Upscale Audio and he suggested I try Ei KT-90 type III tubes. He also warned the drawback of taking 400 hours to burn in and fully open up. Well, after tracking hours and about 385 hours into play time on the new tubes I was ready to give up. The mids were a bit analytical and not as open, the bass prowess was much better than any KT-88 I had tried, and the top end was clean and extended. Yet without the mids being open and relaxed, why have a tube amp? Uncannily a few days later while in the office, I got off the phone and noticed the piano (George Winston) sounded THERE... and I was down the hall a few rooms. I kid you not - 412 hours logged and there was a transformation! The sound was what I was searching for over many, many tubes. Overall, the bass was the most controlled and defined, the mids were open, airy, hamonically correct, with clean & extended highs. They were the most neutral of the lot and the least colored. The Ei KT-90 type III's also produced the best macro and micro dynamics.

I will mention the midrange was best with NOS GEC (Genalex) KT-88's from 1966... however quite expensive and a bit colored, with sloppier bass and highs a bit rolled off.

Currently I ordered my Quicksilver V4's with the Ei KT-90's from my experiences in the past. I haven't questioned my power tube choice once.

Some find the KT-90 to be more "analytical" sounding (and THEY ARE for the first 400 hours or so) but after that it seems to be extremely neutral. I tend to prefer to use NOS Mullards in the preamp, or a tube that is slightly warmer to "tune" the overall sound to your preference. That way you get the best control of bass, dynamics and a neutral power tube, and can tube roll relatively inexpensive on the preamp tubes.

You may want to make a call to Upscale Audio and get their advice on KT-88 / KT-90 comparison.

Good luck on your search!

Thanks, guys. I'm still surprised there isn't more folks here who want to discuss kt-88's.
The first time I tried the silver 90's was a short trial, and they had svetlanas. I remember the sound as being REALLY clear and smooth in the midrange, but soft in the bass and lacking the deepest bass completely, and vary soft on top. While I was really unsatisfied with these shortcomings, the mid was so beautiful that I proclaimed "these amps could actually get a guy laid".
The silver 90's I have now came with kt-90's, and I did not like them at all. They also came with cv378 rectifiers. I soon replaced them with chinese kt-88's and then was pleased, as the highs came back I was lacking with the kt90's, and the sound opened up the way I knew it should. I then replaced the rectifiers to the 5ar4's it called for and the sound became tighter and punchier. Did not seem to have the mid range clarity I remembered with the first pair though.
I got on the web with upscale audio, (that is where the tubes were sourced), and to my surprise they had this 'cv378' rectifier where it explaines you may "lose highs and lows", along with some plate voltage warnings. I put the kt90's back in (with the 5ar4's) and no longer do they have the severe lack of highs and definition they had before. In fact, they seem to have very good definition. They are very detailed, have good presence and 'punch', and great bass. they are, however, real flat in dimension and not very open sounding.
I thought that perhaps they were starting to burn in some when I read audiofankj's post. They are starting to sound a lot better, some 30 hrs later. I think I maybe played them for 150 to 300 hours when I got the amps, and I don't know how long before I got them, so I will continue to let them cook. I might be living on the edge, though, as it seems the reason for the cv378 rectifiers was to lower the plate voltages so the amps could handle them. The amps call for 100ma with kt-88, but with kt-90's, the plates on one of the tubes in each pair glow just a LITTLE in the crease, so I have them at 90ma to minimize this.