(http://www.balanced.com/) Click on, "The 6H30 Tube - One Designer's Perspective" for some info. That was dated before the tube was readily available in the market. I still personally prefer the upper crust of the NOS 6922 family(ie: Siemens CCa or E188CC). They just sound more natural to me.
Why 6H30 Tubes?
Curious why so many manufacturers have gone with the Russian 6H30 tubes in their designs?