i have a denon av receiver x2300. I am planning to buy oppo udp 203 for both movie and music. for movies i obviously need to connect through hdmi as tv is 4k. question is what cable connection i need for best cd audio?
As has been stated, the real question is which DAC and associated circuitry is going to give you the best sound for your CD playback. It doesn't matter which digital output from the Oppo you use for CD, the receiver will be doing the DAC conversion and digital is digital (for audio there is no difference between using HDMI, optical, or RCA digital out). If the DAC and circuitry is better in the Oppo than in the receiver, you will want to connect analog RCA from the Oppo to the receiver. Why not hook it up both ways (HDMI as well as 2 RCA cables), set up the RCA as another device input, and switch back and forth to see which you like the most.
