Vintage RCA (Black & Gray plates) do have extended HF's for a 12ax7, IMO (more than the Telefunken and Mullard's I've used).
Old production Holland 12ax7's do also, but they are really expensive now.
Old production Sylvania 12ax7's have gobs of HF, but they are lacking the mid's and LF's that you like.
You might try a new tested pair of the Russian EF86's (old production winged C/SED are still available for $40/pr) in the event that yours have lost some HF extension.
Old production EF86's are also currently super expensive.
Remembered I used the EF86's in a couple of guitar amps that I was retubing for a neighbor for which I pulled a Telefunken EF86 from an old Pilot pre/tuner (don't really know how they sound in HiFi gear).
You might check prices on RCA 12ax7's (I'd look for new testing old organ stock to save money as the Baldwin (Conn?) labeled tubes were supposedly thoroughly screened for their intended purpose).
Not familiar with new production 12ax7's.
Oh, and here is a blurb I placed on favorites and forgot to include in my previous post.
https://www.audioshark.org//pre-amps-9/wolze-triode-line-level-preamp-4421.html
DeKay
Old production Holland 12ax7's do also, but they are really expensive now.
Old production Sylvania 12ax7's have gobs of HF, but they are lacking the mid's and LF's that you like.
You might try a new tested pair of the Russian EF86's (old production winged C/SED are still available for $40/pr) in the event that yours have lost some HF extension.
Old production EF86's are also currently super expensive.
Remembered I used the EF86's in a couple of guitar amps that I was retubing for a neighbor for which I pulled a Telefunken EF86 from an old Pilot pre/tuner (don't really know how they sound in HiFi gear).
You might check prices on RCA 12ax7's (I'd look for new testing old organ stock to save money as the Baldwin (Conn?) labeled tubes were supposedly thoroughly screened for their intended purpose).
Not familiar with new production 12ax7's.
Oh, and here is a blurb I placed on favorites and forgot to include in my previous post.
https://www.audioshark.org//pre-amps-9/wolze-triode-line-level-preamp-4421.html
DeKay