The Blackburn Mullard is fully burned in. The weakness of the tube is the anemic bass and midbass, producing an unbalanced sound spectrum. The upper mids and highs are glorious, however, detailed, harmonically layered, 3-dimensional and natural sounding -- among the best I have heard. This tube is great for a narrow range of music (in my system), but not for general use. For instance, a soundtrack of nature sounds from the forests and savannas of Africa is the most layered and natural sounding that have heard thus far. I use this recording as a test for soundstage and imaging. Another downside of the Mullard is a more restricted dynamic range compared to a Siemens 6922. I wonder if the Mitcham production fills in the bottom frequency range, offering as detailed but more balanced sound.
