Hello everyone.  I have a question about what I assume to be an extremely simple modification.

I'm looking to convert a headphone jack into an external speaker output on a small practice amp.  I would like for the amp's internal speaker to be disconnected when a connector is inserted in the jack.

The patient is an Orange Crush 10, which is a tiny little 10 watt solid-state practice amp with a 6.5" speaker.  I can't quite explain why, but I love the damn thing.  The word on the street is that it they actually sound quite good through a better speaker, so I'm ordering a 1x12 cab from Avatar with a Celestion G12H30.

The Crush has a 1/4" headphone output which I never use, and I'd like to turn that into my external speaker jack. Though I'm not a master-solderer by any stretch, I can handle swapping pickups in my guits, so I'm assuming I have the necessary skills. 

It's not clear to me how I should configure the jack to allow for the internal speaker to work when no cabinet is connected.  Any thoughts?

Also, I'm aware of the inherent dangers involved with capacitors retaining deadly voltages. Would this simple mod put me in any danger? 

I appreciate any insight you can provide.

Best,

samuelzero