how to choose tube???

[thehellz]

i'm new here and i bought a few module here and on ebay and near to change the tube but what the difference between 12ax7-el34-6l6 do they all fit in my module what the main difference between them
help me

 

[joey_truelove]

If you're planning on changing valves on the module, you will be looking into twin triode pre-amp valves called ECC8? in Europe and 12A?7 in the US. Usually that would be the ECC83 and the 12AX7 for which the module is originally designed, even though the pin-out is the same.

Then you'll have to choose brand and other flavouring features. Maybe you want a 7025 in a Fenderesque module. I'd go with the brand and type of valve that came in the original amp from which the module is designed or what your sources of inspiration use.