How to read tubes?

The different names, numbers only have to do with the country of origin, or whether they are military or consumer tubes. For example: 6SN7, VT231, and 5692 tubes can all be used for the same applications. Some of the lettering on some tubes has to do with maximum voltage and wattage. Again for example the 6SN7:

5692 - 275 Volts maximum & maximum 1.75 Watts per section
6SN7GT/WGT -- 300 Volts maximum & maximum 3.5 Watts per section
6SN7GTA/GTB - 450 Volts maximum & maximum 5.0 Watts per section
If you used a 5692 tube where you really needed a GTA, it would run hotter and not last nearly as long. (Assuming it does not blow out quickly). A GTB used in a lower voltage situation would work perfectly fine and would last a long long time since it would run cooler. The GTA/B I think were designed for the higher voltage needs of televsions, etc.

There is some information on tube basics, matching, biasing, etc, and what types are similar, etc (like above) at www.thetubestore.com

http://www.thetubestore.com/tubereviews.html

Viridian gives good advice. You cannot recognize tube parameters just by reading names because the info is not in the names. Here are a few online links that explain what the “operating parameters”, as Viridian calls them, are.

An online copy of an RCA tube manual (as mentioned by Viridian) that talks about the general measurements that determine how a tube performs. RCA Manual

The discussion about tube characteristics starts at page 10. Tube curves and load lines are about the most useful general info you can get about tubes and tube circuits.

There is also a discussion of how to use plate curves and tube load lines here. This is a classic article by Norman Crowhurst.

A short description of what a tube tester does is below. It gives you specific info about the tubes in hand that cannot be obtained from general info above. Rozenblit's site

If you want to buy a book Bruce Rozenblit’s book “Beginner’s Guide to Tube Circuit Design” describes all of this very well and is only about $25.

Cheers,