[Ian Bell[_2_]]

John Byrns wrote:
In article ,
Ian Bell wrote:

The 6SN7 is said to be a good tube for audio and the 6CG7 is apparently
its B9A direct equivalent. Looking for sources of the 6CG7 on the
internet I found more examples of its supposed equivalent the 6FQ7 than
of the 6CG7 itself. Looking at the data sheets the two seem extremely
similar and the 6FQ7 even has slightly less plate to grid capacitance.

So, is the 6FQ7 a worthy alternative to the 6CG7? Are there any real
differences between the two? Presumably there must be some difference
else why have a different number.

The main difference that I am aware of between the 6CG7 and the 6FQ7 is that the
6CG7 includes a shield between the two sections. Presumably this added shield
is helpful in some types of applications, such as RF and others.


I had not noticed that but now that you mention it the data sheets I
have show a shield on pin 9 for the 6CG7 but NC for the 6FQ7. I agree
with your supposition that this may have been for rf work. The
ECC88/6dJ8 for example also has this shield and they were typically used
in cascode for VHF front ends. Makes sense to me.

Cheers

Ian