I would strongly suggest not subbing those tubes .... if the circuit calls for a 12ax7 use one, or an accepted equivalent. Ecc83, ecc803, cv4004... a 5751 or 7025 are both lower gain ax7 subs.
I have a pair of early 60's RCA 12ax7 in the input stage of my amps and they are one of the most well rounded , balanced sounding tubes I've ever owned.
I bought the amps with those tubes and they probably have some serious hours on them. That said , I think I am going to try the Gold Lion 12ax7 as I have heard they are the best current production 12ax7.
I have a pair of early 60's RCA 12ax7 in the input stage of my amps and they are one of the most well rounded , balanced sounding tubes I've ever owned.
I bought the amps with those tubes and they probably have some serious hours on them. That said , I think I am going to try the Gold Lion 12ax7 as I have heard they are the best current production 12ax7.