I've not tried the Brimar's but immediately chose the Siemens E82cc/12au7 over two different Mullard's, including the CV4003. I also preferred the Siemens over the Radiotechnique 12au7.
Brimar vs Mullard cv4003/12AU7
Has anyone heard these two NOS tubes pitted directly against each other. The virtues of the Mullard are well documented; certain sellers (cough, Upscale) praise the merits of the Brimar to the heavens, and they *are* considerably less expensive. Thoughts?