After about 1 year of playing with KT88s , I have arrived at the
opinion that it is, at least for me, the best tube. I also arrived at the
6SL7/6SN7 being the best tubes to pair with the KT88. 
 
I claim no rights to anything , as this has all been done before by
people who dedicate their lives to glass, cathodes and anodes. 
 
I ABīd my circuits with KT88 versus E34Līs, KT66, 6l6.
 
The KT88 just has more BODY and girth and , geewhiz, just
sounds fing great. I donīt like the fixed bias route. For me it
removes the mojo, but many it may well be great. One can also get
more power with fixed bias. but cathode bias, with a 22uf bypasss
and 42watts plate dissipation is the shit. 100uf bypass cap and you
start kickin the shit out many marshalls. 470ohm grid 2 resistor for
me is MAX. higher values and the circuit craps out, my circuits that
is. 
SE as well as push pull. 
 
I will update my site next week as many people have emailed
wanting schems and answers. Plus the amps have all been rebuilt so
may odf the pictures are of amps which no longer exist in those
formats. 
 
OTīs
125ESE can handle the 42 watts plate dissipation at 100mA no
problem . Sounds about as good as the 1627SE and weights
1/10th. The 1627SE is for Hifi and for awhile I really liked it for
guitar, but it makes no sense to use a 11lbs OT for 20 watts and
portability. at guitar frequencies, the 125ESE is just fine. 
 
 
The 6sl7, actually the 5691īs and especially teh red base, are for
me the ultimate in warm wood cream tone. I got myself a life time
supply of the red bases, I sold a lot of blood for those. But they are
worth it. 6sn7 also my favorite. 
 
8 tele 12ax7 flat plates with nothing to do. (hint: I need a EV12l) 
 
again check my website next week, I remind everyone. 
 
Dr.dr. KT88-6sl7