How to match tubes?

[pftrvlr]

Hi,

I want to find a matched pair of 6c19 from a bunch of 20. But I don't have a tube tester. All I have are DMM and o'scope. What is the best way of mathing them?

 

[ak_47_boy]

You can make a temporary tube tester out of the parts you would use for an amp and your dmm.

 

[Dave Cigna]

If you have a working circuit in which you intend to use them, then plug in each tube and measure the cathode, plate, and grid voltages with no signal. (The grid voltage can give an indication of grid current.)

If you have a signal generator (could use a test CD or even the sound card in your computer) then you can further rank the tubes by mu. Apply a signal to the grid and use your oscilloscope to measure the signal level at the plate.