I updated this to add the link to the RCA version as a second data sheet set.
This will be a continuing series on vacuum tubes and amplifiers.
Some folks do not realize that the 5751 vacuum tube produced today is little more than a 12AX7 that did not make the grade as a 12AX7. .....
Not a lot of physical microphonic issues with NOS versions of these tubes to say the least. This cannot be said of new production versions.