Tubes Asylum: RE: 12BH7A impressions by Len

All 12BH7 productions are actually respectable, IMO, but they do sound very different from one another. You'll just need to find one that best suits your system and preference.

RCA's black plate is generally regarded as the most desirable 12BH7/12BH7A, and this is the tube I use. It's a big-tone 12BH7 with a touch of warm (what RCA doesn't :P) and good dynamics. The earliest version come with D getters, followed by halo getters. RCA's later gray plate production is also quite nice, albeit with a little less focus/snap compared to the black plates.

If you want the opposite type of sound, Tung Sol 12BH7 is worth investigating. This is a detailed, tight, open sounding tube that favors treble over bass/midbass. GE is similar to Tung Sols; I prefer the Tung Sols because it sounds more refined.

Sylvania and Raytheon 12BH7s are somewhere in between, being solid performers but having no especially defining attributes to make them stand out. There's a few more productions, but these are the ones you'll likely encounter.