I'll add this - Mullard is the original designer of this tube and set the standard as well. It started with xf1 series, and the xf2's are very close in quality, but hereafter the decline begins.
I have yet to hear a tube surpass them, although some come very close - The earlier, original Czechoslovakian Tesla's, and the older, original 1990's Svetlana's are 2 that come to mind. These stand out not only because of sound, but quality of manufacture and longevity.
I have yet to hear a tube surpass them, although some come very close - The earlier, original Czechoslovakian Tesla's, and the older, original 1990's Svetlana's are 2 that come to mind. These stand out not only because of sound, but quality of manufacture and longevity.