Re: When to fit valve screening cans?
>What did 12AU7 do wrong to get left out?
The 12AT7 and its swanky cousin the E88CC has the high slope needed for an oscillator used with modern sissy crystals and ceramic resonators. The 12AX7 claims an especially low heater/grid capacitance which reduces its susceptibility to hum with an AC heater supply. So the 12AU7 falls between the two stools.
But really it's because there isn't a 12AU7 in my junk box.
Alan
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