ASL HB-1 hybrid headphone buffer - best tubes?

jpelg -- if you mean tube 'rush', the answer is no. In fact my friend's 32ohm Grados sound really terrific. Many folks don't realize that this unit isn't strictly an amplifier. So, some worry that high impedance cans might not be loud enough, but no one seems to have had that problem.

I'll look into the Amperexes. Thanks!

How is the S/N ratio on the HB-1 using sensitive cans like the Sony's? Are you experiencing any tube thrush?

Wrt you query, I've read the Amperex 7189's are a good choice.