7 pin X

[Salas]

Does anybody know the type of the 7 pin mini tube in the attached picture? I found 4. Maybe they are useful for audio. There is a screen with a stamped X rib between the 2 constructions in the tube.

 

[JohnAtwood]

7-pin tube

This looks almost for sure a 6AL5 dual diode (or possibly a 12AL5, the 12V version). This is sometimes used as a bias supply rectifier, but is more often used as a detector in FM tubers and TVs. Many classic tube tuners from the 1950s and 60s used these.

- John Atwood

 

[kevinkr]

Looks like a 6AL5 dual diode to me as well. Sometimes used in FM ratio detectors or discriminators. Some people have also used them as bias and very low voltage/current full wave rectifiers.

 

[Colt45]

I'm thirding 6AL5

 

[gianis]

6al5

may be 6al5 dedector

 

[Salas]

Thanks guys. Bias rectifier...hmmm, I got some 2A3 RCA by Volterex, and I think of making a PP 2A3 in the future. Should not be bad to use fix bias 2A3s driving a 6K6 PP OP, and use the mini rectifiers for a regulated bias circuit with a 12B4 pass and a 12AX7 controller. Maybe LTP input EF86 to 2A3 I am thinking. On the other hand...maybe too low 2nd harmonic vs 3rd, 5th etc. Have you listened to an excellent 2A3 PP circuit that you can recommend?