Quoted from PinJim:I have an odd problem, hoping someone has seen it.
When I power off a few of my WPC machines, my subs often begin humming. A low volume, low bass growl.
I did some experimenting tonight to see if I could figure it out. When I turned off TZ, the humming began. So, I disconnected one of the input wires at the sub and the humming stopped, as expected. I reconnected it and it resumed. So, I unplugged TZ thinking that the removal of power to the machine would stop whatever feedback it was getting. Even with TZ unplugged, it continued. Odd. That makes me think it’s some sort of radio interference.
I tried to see if I could find external interferences like LED lights or my phone. No dice.
To be fair, the wire from the game to the sub is unshielded wire. Maybe that’s my problem.
My setup is 10” Polk subs, one per machine.
I have his issue with Gottlieb games mostly. The speaker in the lower cabinet acts like microphone and the gain on your sub must be high as its amplifying the sound to create a feedback loop. Doesn't matter if the game is on or off. On some of my games you can slap the cabinet and it will start humming. I solved it my plugging the subs into the service plugs inside the game if it goes on/off with the game, or wiring in a 110 plug on the switch side of the pinball machine. So when you flip the pinball machine off, the sub is off.
