Tube Specifications

[rlyach]

I recently purchased a matched pair of JJ 2A3s. In the tube box there is a test certificate with all the results of the various tests. I understand all the numbers except one. There is a Usat number indicating 30V a.c. and Isat at 80mA a.c. What are the saturation a.c. numbers and how do they effect tube performance?

Randy

[Paul Joppa]

You'll have to ask JJ for that.

[rlyach]

I sent the question to JJ and the rep told me that they put an ac voltage across the grid and anode and measure the current. I guess this is a measurement of the space between the grid and anode. I am wondering if a larger or smaller current is desired, since I have noticed that this number varies a lot (80mA to 100mA). What do you think?

[Paul Joppa]

That sounds like a tube-tester standard emission test. More current is better, but largely irrelevant - tubes are never operated in saturation. As long as it passed the test, the tube is OK. If you study up on tube testers, you will acquire an great amount of confusion but are not likely to find much consensus. The wikipedia article seems to be a good place to start...