Is this describing a blown tube, or two blow tubes?

I installed a new set of JJ e34’s a few days ago. Last night there was a very loud POP and one of the tube went bright so I moved quickly and turned of the midmonos.


After they cooled I inspected the tubes and they seemed fine so I reinstalled them thinking maybe it was some kind of impurity within the tube. I’ve never experienced a blown tube before.


The amps ran great this evening until just now, and another POP and bright tube, but it seemed like it was the other tube, but I can’t be sure. This was followed by a low whistle or hum and I turned the amps off again.


Is this simply a run of the mill faulty tube? Could two blow in one day, or could the first one POP like that and then continue to work for another day?


Since Ive never experienced a tube fail before, could this have anything to do with the Amp, or is it just a bad tube or tubes?


Should I worry about putting my old tube back in?


Thank you,





Tube testers are not very good for matching tubes, you may be able to weed out a shorted tube though.

I’m not sure vintage tube testers were meant to match tubes. I doubt TV repair techs needed to match tubes as a rule.

I have a Hickok 6000A Mutual Conductance tube tester that I use to test tubes.

User Manual

It doesn’t match tubes per say, example plate current, but it is useful in others ways.


Shorts. (A must) See page 6, manual.

(Quality). Good, marginal, bad, test. (Very useful.)

Gas (Grid Current) Test.

Mutual Conductance Test. (A must for me matching Mutual Conductance of the dual triode sections of a 6922/7308 signal tube.)

Life Test. When a tube tests low good on the meter, or marginal, the life test tells the user how much life is left in the tube or if it should be replaced.


Tube testers don't use real world plate current under load, so the life test doesn't mean much.


Yeah.. I checked with Mike Sanders when retubing although now you're making me wonder if it was kt150. The tubes I was using went with a pair of prima Luna prologue 6 monos that I sold a few months back. Had them biased at 42 and they were glorious sounding with a fuller lower end but at the cost of some of that mid-range sweetness. I decided I could do with a little less bass for that wonderful liquid mid-range sound. I have used the genelex 12au7 and 12ax7 and found them to be very detailed. I am running a CJ premier 11a now (winged c 6550 and nos Raytheon 6fq7 and 5751s) but work the quicksilvers into the rotation occasionally. Now that I think of it the exception of Kenrad preamp tube the only time I've ever had a tube blow it was a JJ. Have a great night