When I was a kid, my dad bought an AC/DC stereo amp with a 35W4, two 50C5s and a 12AX7. When you first turned it on, the 12AX7 heater filaments would light up like a light bulb and then calm down as the other tubes heaters came up. It never failed to amuse me - and also never failed operationally.
In my Jolida LM1875 based JD 1301, I'm running a pair of RCA smooth plate 12AX7s that I've owned for 30 years. Upon power on, their heaters do something similar. While I can understand the "mechanics" of the series connected filaments in that old AC/DC amp, I fail to grasp why this is happening in the Jolida. A quick measurement of the steady state filament voltage shows nothing amiss; 12 point something... Should I be concerned? Or will these tubes also never fail despite my observation? Thanks!
In my Jolida LM1875 based JD 1301, I'm running a pair of RCA smooth plate 12AX7s that I've owned for 30 years. Upon power on, their heaters do something similar. While I can understand the "mechanics" of the series connected filaments in that old AC/DC amp, I fail to grasp why this is happening in the Jolida. A quick measurement of the steady state filament voltage shows nothing amiss; 12 point something... Should I be concerned? Or will these tubes also never fail despite my observation? Thanks!