Tube concept equivalent for 12AU7 vs 12U7

[daschnoz]

We all know about the 12AU7 and 12AX7. There is a 12U7, which is basically a 12AU7 that was redesigned to run on a car battery. Simulated, it works perfectly fine at 48V.

So the question... is there a 12AX7 equivalent of this concept? Using the same naming convention, I would think it's called a 12X7, but the google isn't finding anything (unless it's dimensions for something, 12x7 ).

 

[gyraf]

..the letters in american tube namings are not systematic like the european, and rarely if ever thought out for ease of ident..

The 12u7 dosen't look that much like a 12AU7 to me - so I don't quite follow what "similarty" parameter you're after..

Can you specify?

/Jakob E.

 

[daschnoz]

From the Sylvania datasheet:
" ...It is designed for operation where heater and plate voltages are supplied directly from a 12 volt automotive storage battery."

Looking at the curves, with a B+ of 12V, the cathode voltage and plate current are actually usable. You can bias up 0.3mA at -0.5V using "normal" cathode resistor value.