Speaker noise after tube amp shut down

I doubt a tube sounds more like a capacitor discharging. Does this happen every time or only the one time. How old is the amp?

Last night it hapend same, agan noise from speaker after I powered down amp. Maybe litle louder, I'm not shure.
Amp is 5 years old, heavly moded Jolida 502.
Thank you

Exactly what kind of noise? Pop cracking fading ocean wave? Usually tubes make their aches and pains in the rear known when full power to the grid is present not de-energized.
Im gonna say for an experiment switch the speaker leads to the opposite channels and see if the noise follows to the the corresponding speaker. Lto R R to L This will eliminate the speaker for starters.

Ed