by Thermion » Thu Feb 27, 2020 6:44 am
I have used KT120s as a direct replacement for KT88s in my Eiclones. The KT120 tubes will drop into any KT88 circuit with no problems. The opposite is not true. If an amp is designed for KT120 tubes you will probably have problems and short lives from any KT88. The KT 120 tubes have higher dissipation and max voltages. A KT120 in a KT88 amp will last a lot longer.
Honestly neither tube is really pushed in the Clementine. I have three Clementine amps, one using 1625 tubes, one using KT88s, and one configured as a headphone amp using 1626. Since the Chubby Clementine amps are a modification of the Darling 1626 amp, the limitation is the 6SL7 voltage swing. If you really want to take advantage of their power, the amp would need to be redesigned with higher voltages and a better driver.