[timmy]

Originally Posted by Yamamaya42

12AX7 – High-Mu Twin Triode - generally used as audio pre-amp, very versatile.
12AT7 – Also a Mu Twin Triode, but intended for radio frequency amps, mixers & oscillators.
5847 – Pentode used mostly in IF amps

https://frank.pocnet.net/sheets/077/5/5847.pdf
https://frank.pocnet.net/sheets/049/1/12AX7A.pdf
https://frank.pocnet.net/sheets/093/1/12AT7.pdf

So are you saying this tube is a 12at7 because I don’t have the book that shows the 4 digit tube numbers camparing to an actual tube number that I can relate to.