Conducted an output tube "shoot out" today. In my high output Inspire SE amp which runs tubes hard and in single-ended pentode, producing 17 wpc with KT88 and GZ34.
Used my old trusty Conrad-Johnson PV10A preamp, a high gain preamp. Genalex GZ34 rectifier and Westinghouse 6SN7gtb used with each tube set.
Tubes compared were vintage GE 6CA7 vs new Russian Genalex KT88, Tung sol KT120, Tung sol KT150.
6CA7 sound had less deep bass definition and mildly rolled off highs. A fuzzier, smoother overall presentation.
KT120 had good definition and strong bass. Highs just a bit less prominent. Background percussives weren't quite as distinct. Midrange and vocals were smooth. A bit of that classic tube sound with more power and deep bass.
KT88 and KT150 were very similar. I'd say the KT150 had a touch more deep bass power and maybe a tiny bit more high frequency air. While the KT88's midrange was a smidgen silkier. Close enough that I think I'd have a hard time telling the difference in a double blind comparison. Bass definition on acoustic bass guitar was very good though both, I could hear the strings vibrating on low notes. Piano was excellent on both, where the KT120 had a tiny bit less bite on high notes.
Have no idea how these would compare running in triode mode.
My amp looks so much better with KT88 or KT120 than with those strange KT150 tubes.
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