Ir repeater to plug into the "remote in jack"

I am confused. It seems everything out there is an emitter based system. Is there not an option where  you have an "eye" and then it plugs into the "remote in" jacks on the back of your components? I am trying to control a Oppo 105d and a Parasound p7. The Oppo can be controlled via app and wifi but, the P7 must have a ir control. I see lots of emitter options and wonder if it is as simple as running a two ended mini jack off of it rather than the emitter? No one wants to help as they all want to sell some automated home dohicky. I'm really just short a volume control so reluctant to jump on that train. Thanks for any advice.