The 5814 and 7730 CBS Hytron are excellent examples of premium 12AU7.
Telefunken has long been an audiophile favorite for the 12AX7. Tele 12AX7 was my all time highest performer for both Aesthetix line and phono stages.
The 5814 is a military version and more rigid than standard 12AU7, typically improving signal to noise and reduction of microphonics.
Regardless of what you choose, low noise, low microphonics and good matching are important for any preamp.
Other popular choices are Amperex Bugle Boy from late 1950s and Siemens. The difficult part is knowing what each of these sound like in the circuit and then choosing which best suits your need.
Unfortunately the only way to find that out is buy and try. The good news, these tubes continue to go up in value, so if it's not perfect for this application you have a solid investment.
I have hundreds on hand in my collection.
Telefunken has long been an audiophile favorite for the 12AX7. Tele 12AX7 was my all time highest performer for both Aesthetix line and phono stages.
The 5814 is a military version and more rigid than standard 12AU7, typically improving signal to noise and reduction of microphonics.
Regardless of what you choose, low noise, low microphonics and good matching are important for any preamp.
Other popular choices are Amperex Bugle Boy from late 1950s and Siemens. The difficult part is knowing what each of these sound like in the circuit and then choosing which best suits your need.
Unfortunately the only way to find that out is buy and try. The good news, these tubes continue to go up in value, so if it's not perfect for this application you have a solid investment.
I have hundreds on hand in my collection.