6BZ8 Valve

Noval socket, 9 pin miniature (USA pico-9) B9A Filament Vf 6.3 Volt / If 0.4 Ampere / Indirect / Specified voltage AC/DC Quotations 2 Quotations Bibliography Essential Characteristics, GE 1973

The "Doppio Triodo" you mentioned appears to be Italian and translates to "Double Triode" in English. As for the 6BZ8, it is an electronic vacuum tube that is a type of double triode. The 6BZ8 tube is commonly used in audio amplification circuits. If you are referring to a specific "Doppio Triodo" that is identical to the 6BZ8, it may be a particular brand or model of the double triode tube that shares similar specifications and characteristics with the 6BZ8. It's not uncommon for different manufacturers to produce tubes with equivalent specifications but under different designations. If you have more specific information or context about the "Doppio Triodo" you're asking about, please provide additional details so I can offer more accurate assistance.