Speaker "pops" when power amp shut off

Hi,

Anybody knows why my speaker "pops" when I shut-off my power amp. the problem just happen lately. will it damage my speaker if the problem left unsolve?
the "pops" shows even my preamp is in "mute" mode.
when I removed my pre to power interconnect to test. it doesn't "pop" at all.

I do not use any powerconditioner except a Oyaide power distributor.

my gears are:
ayre cx7e cdp
ayre k5xe pre
ayre v5xe power
von schweikert vr4jr speaker

cable used:
jorma 2 xlr ics.
jorma superpowercords.
jorma 3 speaker cable.

I wrote to ayre but there is no response.

please advise. thank you.

BB