matched 6L6GCs
this source matches these tubes very well…..I use a 1 ohm resistor on each cathode so you can read the voltage out put on them as milliamps directly…they were all within about 2 ma. of each other ! GREAT JOB ! …and no high frequency oscillations like some others I have in stock for my quad 100W… one more great item on my bucket list after about 50 years in the field in hobby fashion.