[Ian Bell[_2_]]

Patrick Turner wrote:

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.

Cheers

Ian

The 3 tubes have virtually the same gm, µ, and Ra wherever you find
them.

Many varieties exist, with Siemans NOS probably the best. The CG7/FQ7
have slightly lower Pda ratings than the 6SN7.

I found the Siemans 6CG7 to have a slightly higher µ.

Anode and grid size varies with varieties, but as long as you keep the
relative distances inside the tube about the same the
gm, Ra and µ stay about constant.

Patrick Turner.


I simulated a 6sn7 in mu follower circuit and it gave very good
distortion figures - best I've seen yet - this was at 8mA Ia. So I
ordered some from Colomor valves in the UK so I can try them out. They
are the 6FQ7 version made by Matsu****a - didn't know they made tubes.
Does Matsu****a have a good or bad reputation for its tubes??

Cheers

Ian