The ECC83 / 12AX7 tubes are some of the most common tubes found in a range of guitar and musical equipment. It's a dual triode vacuum tube and has been in production for 60 years+. Most of the tube manufacturers have their own brand of this tube as well as variations.
All tubes on this page should be able to be used as a replacement for the ECC83 / 12AX7. However please consult manufacturer documentation.