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.

 

[gyraf]

Over here we had e.g. ECC86 and EF98 that were car radio tubes..

 

[rock soderstrom]

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.

Years ago it was once a forums topic to build guitar (pre)amps with such low-voltage tubes. Allegedly a starving 12AU7 works just as well or better with low voltages as the 12U7.

So the question... is there a 12AX7 equivalent of this concept?

I have not seen a high gain tube suitable for audio that can work with really low B+ so far.

Over here we had e.g. ECC86 and EF98 that were car radio tubes..

I've already played around with both. They sound good but have little gain and anode current, which limits the possible applications somewhat.