12ax7 tubes can be enterchanged with xxx tubes?

Hi, Mechans:
The 12ax7 Sylvania USAF tubes I bought locally, friend-of-a-friend type deal. Almost all of my other tube purchases were made by going to vintage radio shows and an event called a "Hamfest" which is a swap meet for ham radio collectors. These are where I have found my best deals, when some elderly gentleman has a box of unsorted tubes he is selling for $20. I buy the box, plus any others I can find, and go home and sort the tubes and test the ones I decide to keep (I have a tube tester also). The majirity are tubes I cant use or have no need for, but I always end up with some I am looking for.
Just check your local paper, or go to a local electronic shop and ask around.
Good luck!
PS:
If you are interested in contacting me regarding tubes, my email is
Twinbugles52@comcast.net

Thank you Twinbugles-
I have heard of Hamfests but I am afraid they will peg me as an audio guy not a radio guy and jack up the prices. What do you do with all the odd tubes. I have bought lots like that in the past and don't have the heart or mindset to throw them out. I am in southwest Ct. near Danbury and the NY border for the time being. You can use the email feature they have to look me up . If you know a hamfest is happening in my area or a couple of hours by car please let me know Thanks again.

I know this is stating the obvious - but any ECC-83 is a direct sub for a 12AX7.

The most thorough discussion of tube equivalents can be found at Joe's Tube Lore on audio asylum.

I have not done substitutions in a Jolida, so my comments are just a general impression of various 12AX7 variants. For a warmer sound and big soundstage the Mullards and the Amperex are certainly good candidates. I have found that in a some applications, the Mullards sounded a bit phasey and the center image was not as well defined. In almost all applications, Amperex Bugle Boys sound great to me, though they can be somewhat pricey.

The blackplate 5751s are also a nice, reasonably smooth, yet dynamic sounding tube. They deliver considerably less gain than a 121AX7, so you need to experiment to see if they will work (in most applications that would not be an issue, it may be more of an issue in a phonostage).

I like the Telefunken ECC83, but, that tube is more on the lean, clear and dynamic side than on the warmer side. I run ECC803S in my phonostage, but, these days, they probably cost more than the Jolida (and they are VERY lean sounding).

The 1960's RCA 12AX7 that came with my phonostage sound quite dynamic and punchy, but, they are leaner sounding than the Mullards or Amperex tubes.

If one of the above posters is correct about the Jolida not pushing the small signal tubes very hard, then a purchase of new or relatively new premium tubes would be a decent investment because these older tube have PLENTY of built in life.

Good luck on your search.