KT-88 KT-90 KT-100 6550 which has the best bass?

I'm with Bigkidz. It depends on how you define "better bass".

I have KT88 and KT90 tubes, and consider the bass of both to be excellent, though quite different. The KT88 is punchier, warmer, and bloomier in the midbass by a significant amount, and not as extend. It is more classically tube. The KT90 is more evenhanded, leaner, taut, and extended. It's kind of like comparing the tube and solid state sounds. KT88 tube, KT90, more like solid state.

Again, depends in part on the electronics, though Joe and I both have used Jadis as a reference. In my JA80s, Joe's (Trelja's) and Peter's (Bigkidz) descriptions of KT88 vs. KT90 are accurate; I found 6550s (Svetlanas and Philips) to be a little fuller and warmer than the KT90s (EI Type 3), but nowhere near as rich and full as the KT88s (Gold Lions) and lacking the finesse of the other types in the midrange and highs (more of a brute force-type tube, may have a little more power). For rock at loud volumes, I'd go with either the 6550s or KT90s, depending on how lean or rich you like your sound.

Oh, David(by the way, how have you been?), I forgot to talk about the tube companies, since you mentioned EH and Svetlana.

In my experience, I have only tried the Ei KT90. They are no longer produced, thanks to the NATO bombing in the former Yugoslavia, but still available. It looks like EH is beginning to make them. It only makes sense, whenever you see a group of people fret over something no longer being available, it's wise to bring that product to market.

As far as KT88 goes, I prefer the JJ, which seem to have that punchy bass and beautiful tone. Svetlanas sound more neutral and 6550/KT90ish to me, though still a recommended tube.

Joe-Thanks for your input, as well as everyone else.You ask how I've been? I was in a car wreck the 20th of July.Out of work for another 3 weeks.Other than that,alls well.No one has mentioned the KT-100.The amp I 'may' get is supplied with KT-100'sI'll take a guess.Its similar to the KT-90??Joe,I recently bought a Threshold S/300 stasis.This amp gets HOT when pushed.Im keeping my bare foot off this amp! :~)

Whoa, that is horrible news, David! I am so sorry to hear it. Is there anything we can do? Honest. I do hear a ray in your words that suggests you are improving, and I hope that is true.

Russ was also down for a while, but is now back, looking great. Hopefully, he will make this a trend, and you will follow.

Yes, keep the feet away from Threshold amps. No bare feet, and no kicking them, as they hurt either way.

I don't know much about this KT100, but think I saw a Houston amp using it. Is this possibly the amp you are considering? They made an 845 based SET that I always lusted after, but can never find on the used market. It's a Chinese company, but they seem to be OK. I know that recent ASL efforts, such as the 1009, are better than most anyone would expect.

Given you listening preferences, you may want to look into a pair of Granite monoblocks. I have a pair, and they can run just about any tube, those you listed, plus EL34 and 6L6, you can find a very wide range of sounds with it, and maybe whatever you are looking for. If you are set on a stereoblock, if the Rogue 150 sound trickles down to one of those, it may be one to think about also. I could be wrong, but it may already exist in the Model 90 - apologies for not keeping way up on these things.