But I don't know how easily you will find either of those two tubes, S23chang! If you do, you will pay dearly for them...seriously big money! The Amperex 12AU7's [Bugle Boy] or the Telefunken 12AU7's [ECC 82's...European designation] might be suitable for your rig, Mechans. You might also try RCA's premium 12AU7, the 6189. DO NOT LET ANYONE SELL YOU A "MULLARD" CV4003 FROM THE MID-1980's...these are not NOS tubes, and sound nothing like old Mullards! FYI, the Mullard brand name isn't even printed on the CV4003.
I would suggest that you contact Andy at Vintage Tube Services...he the "go to guy" for all your tube needs, especially expert information.
I would suggest that you contact Andy at Vintage Tube Services...he the "go to guy" for all your tube needs, especially expert information.