What heater voltage is the 101D?Two days of listening and I’m going to propose WE 101d’s as the king of DHT’s for compatible non-pentode Lampi DACs. It’s hugely better than the KR 242’s, although it’s lower gain. That’s probably a good thing for most folks whose preamps were overloaded by KR 242’s. Sadly, they’re rarer than hen’s teeth. But you just have to find a quartet. They’ll outlive you. But they’re very hard to find NOS. They cost me less than my 242’s. I won’t sell them at 10x the price I paid for them. Mine came from Italy. Here’s the guy I bought from. You can ping him directly if he has or can find more. He doesn’t list any more.
I read your findings with interest, as I've never thought to try a 101D. My favourite is the 46 or PX4. They look tiny too!