Tube Characteristics

My fav is EL-34 and E34L tubes. KT90, KT60 are much harder sounding tubes, IMO.

90s sound more like heavy duty EL34s than KT88s, even though kt90s are a drop in replacement for KT88s. The kt90 is also going to output more power in most cases than a kt88 at the same bias. I think the bass on the kt90 is much better, but that is subjective. It is definitely a leaner and more SS sounding tube than a kt88. but to me the kt88 sounds tubby. take that how you will.

KT-90 great dynamic range, good low end, take a while to break in and bloom. Mids not as good as KT 88 but better top to bottom. I favor Electro-harmonix KT 90 over the EI KT 90.

Svetlana (original) are excellent kt88's. EH KT88 are very good .

to my taste top is great on el34...