It's pretty simple this one. The Leben CS1000 was designed around the KT120. Yet many find the KT150 sounds superior. After checking heater ratings etc the KT150 can be substituted directly. I'm running at the same bias and therefore HT current /output level so no greater stress on the HT.

And boy! Does it sound good! Greater solidity, detail and dynamics. The KT120 sounds quite wooden by comparison

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