iPad 2 & Yamaha RX-V 1900

Not aware of any compatible iPad docks that work with the Yamaha, but you could use a 3.5mm-to-RCA phono lead to connect the headphone socket of the iPad to phono inputs on the Yamaha. Clickety

Or if you have a wireless network, you could buy an Apple AirPort Express, connect it to your Yamaha, and use the AirPlay functionality on the iPad to stream music wirelessly.