AZ12 Telefunken tube NOS/NIB equivalent to RGN 2004 / RGN 2504 / AZ4, and via GZ34, 5U4, 5V4 adapter. Fast duo-diode 2.3A.

The Telefunken AZ12 NOS/NIB equivalent of the RGN 2004 / RGN 2504 / AZ4, and via a GZ34, 5U4, 5V4 adapter. A fast 2.3A duo-diode.

The Telefunken AZ12 in the "German Steel Y8A" base has been avoided until now due to its rare European socket. Yet, it is the electrical equivalent of the famous, sought-after, and exorbitantly priced RGN 2004 (2 amps) and RGN 2504 (2.5 amps). Telefunken produced them in the 1950s and 1960s, during its heyday.

Now, thanks to our "friends" from China, we can use relatively inexpensive adapters not only as a direct replacement for RGNs (4V filament), but also, thanks to special AZ12 to GZ34/5U4 adapters (5V filament), use them in modern audio and guitar amplifiers, enjoying their incredibly detailed, open signature influence on the sound.

A very solid, durable tube. And a "solid plate" tube is superior to the famous mesh anode RGNs in many applications. Because mesh tubes are very bright and have a thinning effect (of course, female vocal enthusiasts overlook this). However, for more "universal" applications where dynamics and body are needed, solid plate tubes are better. The AZ12 isn't as bright, but rather more balanced.

Note - the tube for sale does not include the sample adapter shown in the photo. You can buy it on Western and Eastern marketplaces.

I have a few of these NOS (a whole box of them) in mint condition, as if they had just left production yesterday.

Measurements on a calibrated Elpo P-508 (using a 220V variac):

Perfectly even and powerful halves:

Ia1 = 80mA

Ia2 = 80mA

Ia NEW = 50mA

measured at Ua = 20V