What is your favorite tube type?

I'm on my second set of Gold Lion KT88's - running in my PrimaLuna Integrated. I've tried the EL34's, KT120's and 6550's. But the 88's are my fav.

I agree implementation matters.  However, a well designed 300B should sound different than a well designed KT88.  

The origin of this questions stems from a brief discussion in terms of the sound profile of 845s vs 300Bs in two well designed SETs and they do sound quite different.  

It got me wondering how many people are loyal to a brand of amp and explore within the brand vs to a tube type and explore cross brands vs. a pure explorer who wants to hear the best and seek the brand that delivers the best implementation for the tube they are listening too that day.  

I thought i would start off inquiring about tube prefernece and see what people’s thoughts are.  

Personally I can't afford to buy a bunch of different amplifiers. Having said that, my amp uses EL34 output tubes and 12AX7 / AT7 small signal tubes. I've used the original Chinese EL34's that came in the amp, the re issue Gold Lion KT77's, 1980's era Tesla, and Holland made EL34's. I take the Holland made over all the others. For the small tubes, it's been the original Chinese tubes, the new Gold Lions, standard Telefunken smooth plate, Telefunken ECC801S and vintage Tesla ECC803S, the latter two being my preference.

This is a hard question, because tubes standing alone don't make any sound unless you drop them on the floor and the glass breaks.  Even if you limit the discussion to optimally implemented power tubes and limit the discussion to only top tier tubes, e.g. Elrog 300Bs vs. NOS Mullard EL-34s,  it is a tough question, because you have to deal with system synergy etc.   But I see you didn't ask what tube was the best, but rather what is my favorite.   So I am going to answer.  6AS7.  It has taken 3 years and a good bit of system and room optimization work to get there, but I will take my OTL 6AS7 amps to my grave.