
stephen sawall
Well-known member

I have seen Bob set up and re-tube several amps .... He tends to set the Bias very hot with all amps I noticed. This is the way he likes it and it does have certain advantages and sounds, feel, etc....
What Bob does is he finds KT88's that are so far down on the scale that they are in the range of your amp. These tubes because they are far at one end of the range do not behave or act like KT88's in the normal range. But they can be used in many amps designed for 6l6 and El34 amps. This is also a way for tube sellers to sell KT88's that are not in the normal range... because most KT88 users would never want KT88's this cold in a amp designed for normal KT88's.
This same kind of thing can also allow you to put 6V6's in your amp. But the 6V6's would be at the other end of their range than KT88's in your amp.
I have tried them all a long time ago .... this is what I remember.
EL34 .... great crunch, less low end that makes it less loose in the bottom. Do not sound very good clean when compared with 6L6.
KT77 .... a lot of the same character of a EL34 but with a fuller bass more like a 6L6. The high end is also a little more aggressive.
6CA7 (old).... Great crunch with a focused full bass .... best over all for me and feel they blow away everything else. I was recommended these by Mesa a very long time ago and they also feel this is the best tube in the amp. (warning vintage 6CA7 are not cheap at all.)
6L6.... good cleans and a very full big sounding bottom with distorted sounds.
5881 ..... not as warm as 6L6 and a different midrange. Great sound especially for blues and point of break-up sounds.
KT66.... best clean sound and a huge bass end. Sounds great for leads but tends to be loose for crunch playing.
6V6.... much like a 6L6 but breaks up faster and more bass in it's tonal balance.
EL84 (Yellowjackets). Best harmonics and almost magical high end. Lacks bass and is loose on the bottom.
KT88 .... also a very big sound like the KT66 with a tighter bass and not near as warm. Kind of cold sounding (not in a bad way).
6550 .... big clean sound, does not break up much at all till it is really pushed and then gets pretty nasty (also not in a bad way).
Every individual tube is like a snowflake.... it has it's own voice, tonal balance and point of breakup. So all the things said above are greatly effected by the rating of the individual tubes and what kinds of sounds you are trying to achieve.
So in the end what tubes I put in my amps depends a lot on what my goal is at the time....Myself I trust Mesa when it comes to their amps a lot more than Bob...
If there is something I missed or whatever ... do not be afraid to ask. I went kind of crazy with all this stuff about ten years ago, still recovering ....
