Paul wrote:
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But audio turn-on "thumps" do not last a full
second! I stand by my theory that the initial in-rush
of current is the charging up of the electrolytic
filtering caps, on the outputs of the rectifiers.
** PSU electros normally charge fully in two cycles of AC power.
The presence of a 75 or 100W lamp in series makes that take longer.
With a tube radio, it is the heater current surge that takes a few seconds.
With large iron core transformers, they are the main culprit with single cycle surges up to 150amps.
But apparently, you are correct that light bulbs
are sometimes used in series with speakers, to protect
them:
https://trueaudio.com/st_prot1.htm
** LOL - it is never a supply voltage lamp that is used.
12 and 24V halogen bulbs *are* used but only rarely to protect a woofer or whole speaker .
...... Phil