yes, u can disconnect the coil for the popper if u want.

Stern's have a 'simulated' knock, which is a loud, distorted 'POP' through the speakers. There is no knocker assembly or coil to disconnect.

Pinball life at one stage did a run of knocker kits to suit machines from Striker Xtreme through to The Soprano's. Monopoly sits somewhere in between.

There is a kit on ebay US at the moment; http://www.ebay.com/itm/Stern-Pinball-Knocker-Adapter-Kit-/360370278520#vi-desc

From RGP:
There is an adaptor box in the kit that connects to where your coin
meter would connect in the games body. There are settings in the
software of the game so you can let it know a real knocker is
installed. You also disable the fake knocker (and give your speakers a
break!) in the software.

It also connects to the knocker mechanism and to a power source in the
game.

The coin meter output is too low and not powerful enough to effectively
drive a solenoid, or to drive it in a way that does not risk damaging
your machine WITHOUT some sort of adaptor.

The adaptor box eliminates this problem by taking the load of the coil
off the driver board's "low level" output.