Hi friends,
Please look at the initial couple of seconds of this video clip.
When the owner turns on the power switch of JBL SG520 preamp driven by JBL SE408S power amp,
you see the woofers moving out with rather a big audible thump:
https://www.youtube.com/watch?v=StnL...ature=youtu.be
Okay, I heard the same audible thump from JBL SE400S, basically the same model as SE408S, all produced in late 1960s.
Some say this particular model has that thump due to its T-circuit electrical board, which I'm not sure of.
Do you think this is the normal thump? Does it cause any damage to the woofers over the long run?
On googling, I see something like this:
"Pre-amps can pass DC and some amps do not have a built in protection circuit which can be damaged by DC
and which can be passed on to the speakers which can also be damaged."
Is this the case with this vintage SE408S or SE400S? I heard the same thump from JBL SA640 power amp.
Thanks for your feedback and advice, as always.
PS: I don't hear any such thump when I use SG520 with a Crown amp.