If the Harvester stops blinking when you turn something off. Clearly that particular something is spewing HF junk into the line. I am going on the possible unmentioned ?fact? that the amps are plugged into the Furman? IF the amps are plugged into the wall.. Then yeah it is a mystery.
If the amps are plugged into the wall, and not the Furman. Try unplugging everything else going into the Furman .. except the amps left on. Does the (still also plugged in and turned on) Furman Harvester still blink?
Another crazy wild guess is the amps are sucking up whatever is on the line?? and when turned off that HF junk is free to wander.
(if the amps use a digital switching power supply those do make HF noise)
If the amps are plugged into the wall, and not the Furman. Try unplugging everything else going into the Furman .. except the amps left on. Does the (still also plugged in and turned on) Furman Harvester still blink?
Another crazy wild guess is the amps are sucking up whatever is on the line?? and when turned off that HF junk is free to wander.
(if the amps use a digital switching power supply those do make HF noise)

