Contrary to some views, the CV4003 from the 80's is NOT a bad tube. However, it is system dependent, it will sound hard in many. They should also be low-noise, low microphonic tubes too, like from Upscale Audio (no affiliation). Older Mullards, whether CV4003, M8136, ECC82, etc. are sweeter, with a warmer midrange.
From the 12au7's I have heard, late 50's, early 60's Tungsol 12au7 and a little known Brimar 13D5 are very good value tubes. I also like new issue JJ 12au7's, I think it is a nice tube.
Good luck,
From the 12au7's I have heard, late 50's, early 60's Tungsol 12au7 and a little known Brimar 13D5 are very good value tubes. I also like new issue JJ 12au7's, I think it is a nice tube.
Good luck,