I bought an Orange Amp VT-1000. It's a valve tester. You chose a valve to test, insert it into the correct socket, press the center OK button, scroll right or left with the outside buttons, press OK again and wait. After about two minutes or so, you will get a Green Good light or a Yellow Worn light or a Red Fail light next to the corresponding word. If you get a Green light for your power valve, another light will light up next to the valve choices that indicates the valves matching number 1-15. So you can test multiple valves and match them using that number. When you test a 12AX7, it testes the double triode for that valve and you'll get two matching numbers or maybe even a single matching number. The closer those two lights in numerical sequence, the better. The only thing that I don't like is that it doesn't check EF-86 valves or rectifier valves. It can test EL34/6CA7; EL34L; 6L6; 6V6/6V6GTA; KT66; KT77; KT88; 6550; 5881 plus EL84/6BQ5 as well as ECC81/12AT7; ECC82/12AU7; ECC83/12AX7; ECC99; 12BH7 valves. The center socket is for EL-84 valves.