Help with Loud Pop in Denon AVR

Good People:
My older Denon AVR 4803 makes a very loud pop when turned on and off. It's connected to a cable receiver (via optical) and CDP (via digital coax). The AVR otherwise sounds and functions OK. Since the kids use it constantly, it's really annoying--any easy fix?
Fixing is not going to be easy or cheap. i would leave it on.
I leave my stereo stuff on 24/7 for years..
If my Denon 4806 started doing that, i would just leave it on 24/7
I only do not because i do not use it much.
If I did, then 24/7 on it would be.
You issue is some startup mute or relay not working
But to FIND it, and replace least a few hundred..
If there is a headphone jack that turns the speakers off when a plug is inserted you can buy a 1/4 inch phone plug and insert it when powering on or off. A 1/4" to 1/8" headphone adapter would also work and be less bulky.