Back to roots...

[Eli Duttman]

That MOV/GEC KT66 data sheet is dated 1963, which is fairly recent.

This 7581A data sheet states that the type is a unilateral replacement for the 7581 and 6L6GC. I read the remark as stating it's OK to use the more capable type in locations calling for other variants. With the exception of the KT66, the 6L6 variants all draw 900 mA. of heater current. At 1.3 A. of heater current, the KT66 is "the odd man out".

 

[anatech]

Hi Eli,
That might be it, heater current. I have seen 7581A also labeled with KT66, which would be okay since the heater current would be lower. I wonder why they are running the KT66 cathode hotter?

-Chris

 

[TheGimp]

I found a datasheet showing 30W dissipation for the 7581, it showed identical specs to the 6L6GC. It states it has different zero bias characteristics.

http://www.tungsol.com/specs/7581-tung-sol.pdf

The "A" version has the 35W plate and came later.

 

[Turbon]

Hi Gimpy, long time no read 😀.

I have stepped down in my desire for power - at least until I have made my first build.
With the help of a Swedish friend I am probably building something with 6L6GC.
Let's keep in touch in this endeavour 🙂.

Regards

 

[anatech]

Hi TheGimp,
Thanks very much for posting that. Of course this makes perfect sense, being the non "A" model prototype for the current tube.

Best, Chris

 

[Turbon]

TheGimp. Do you have a special design in mind with your 6L6GC's?

Regards