Loewe AD1 really is nice if you can manage to get a pair that works. I had to buy another one, as no matter what I did one kept making gargling noises.
The filament voltage is odd on this one in the sense it takes a long time for it to stabilise. Like no other I have come across so far. Literally 30 + minutes. Crazy, but true.
But it is gorgeously spacey and enticing. Don't pair it with an etchy, precise, high resolution rectifier. It risks sibilance at incorrect levels.
A smooth, warm, Westinghouse VU71 and it's just lovely.
There's a smooth, slippery quality to it that's so easy to like. It's less than accurate but in a really nice way with a lot of material.
BTW we were talking about Tesla AD1n voltages a while back, and maybe a need for over voltage. I still think a Lampi DAC should use the 300B setting. But note it does run fine at exactly 4V in this unlampified affair.
Loewe AD1 is definitely ranking and skankin' with the best/upper echelon if you can find a pair and a nice recti match. It just has slightly higher microphony than I would like.
If I am honest about it it does things Tesla AD1n can only dream of, but fails in other areas. The only relevant one is microphony. It's a big valve so it's not surprising, and like most highish power output triodes, never designed for small signal output.
With the current material I am listening to it is just glorious.
It is definitely worth exploring if you care enough to try and get a working pair. Not easy and pricey unless you get lucky.
