Smart way to check Preamp tubes?

Wanting to see if any of my new jj's are better than others for certain slots... ie high gain, any way to test them with a multimeter? Hows about putting stickers on them to know whats what?

Put them in, listen, compare, that's the easiest way to check which tube fits which slot in which amp :wink:

The only part of a tube that you can test with a multimeter is the heater for continuity. If you want to keep track of a tubes position before removing, mark it with a sharpie. Otherwise, as Jackie posted, and keep notes to remind yourself of the sound of each tube when tried in each slot. For the money, I like an Eico 667 tube tester. If you can afford it, an Amplitrex would be very cool.

The easy way requires no additional equipment that you already have. Use the first preamp tube position for testing various preamp tubes. It is the tone characteristic that determines if you will keep it or shelve it. Testers will provide the gain for each triode, but how does that relate to the bandwidth of the guitar. Where did it peak at, was there a hidden oscillation frequency, etc... The end result is how it performs in the amp. One tube may sound great in a specific Mark series, but just does not sound so good in a different series such as DR, TR, Caliber, etc... or a different MFG such as Fender, Vox, Marshall, etc....

If you decide to venture down the NOS path, and are willing to experiment with other tubes that may be compatible with the 12ax7, a tube tester would be a safe bet to ensure that what you thought you had was a dual triode preamp tube turns out to be a dual or multiple diode rectifier tube. There are some diode tubes that will fit a 12ax7 socket, they look similar, but will cause damage if you install it and power up the amp. I was looking for other tubes, and found may of the diode variety.