Are you talking about the return of the heater current profile from an initial peak turn-on level to the steady-state level after a few seconds (for typical heater AC powering), or the time it takes for the initial start of cathode conduction from zero, or the rise time constant of cathode current, or the circa 90-99% rise-time of cathode current (ie. when nominal idle operating conditions start), or ?
I'm asking, as your comment doesn't quite seem right to me.
It's been a few years since I went through this so I'll try to recall. I used a twin bobbin choke with reactance slightly greater than the hot resistance to do two things. To filter noise, and to slow warmup time (to cathode emission). This ballast reduced the heater Voltage. Warmup was very slow and so I reverted to one half of the coil and found another way to balance the heater circuit. I then added a small amount of resistance to compensate the transformer Voltage.
It's just that kind of intermittent noise that's hard to tune out!
I find it much worse when I cough at a classical concert.
In my area is one of the finest acoustic rooms, a college hall, in the world according to one well travelled classical percussionist. Only- the seats squeak very aggressively at the least provocation!
I'd like to understand when the slower heater warmup time is an advantage and how. Wouldn't you end up with HT applied to cold(er) heaters for longer?
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