RCA connectors are used with line-level unbalanced audio signals. These are used to connect the output of source components to a preamplifier or a preamplifier to an amplifier. The inputs on your television are connected to the line-level audio outputs from devices such as an external tuner (e.g., digital cable tuner, satellite tuner, VCR, or DVD). The output connectors on the AV receiver are binding posts or similar connectors that are used to connect the receiver's power amplification stage to speakers. These signals are incompatible with line-level signals, unless a matching circuit is used. These are not terribly common outside of recording studios. If the AV receiver has a line-level centre-channel output (preamp out), you should use this to connect to the television's line-level audio input. Check the manual if you are unsure. If the AV receiver does not provide line-level outputs for connecting to external power amplifiers, you should purchase a centre-channel speaker to use with the receiver. Don't try to match the receiver's amplifier output to a line-level input, because the quality of the audio can suffer. A reasonably inexpensive centre-channel speaker (e.g., US$250 and up) will outperform the speakers in the television, which are fairly modest. You also want to match the timbre of the centre-channel speaker to the left-right front speakers. It is unlikely the television's speakers would provide such a match.