Pioneer VSX-C300 Service Manual - Page 54

VSX-C300 7.1.4 Specifications of Speaker Detection 1. Purposes Whether the speakers are connected or not is automatically detected, and settings appropriate for the detected speakers are made to allow you to easily play surround-sound without making cumbersome speaker settings. 2. Method of detecting speakers Whether a center speaker and/or subwoofer is connected or not is detected 600 ms after the power is turned on. < Detection of the center speaker > The microcomputer sends a detection signal and after 10 ms will read the logic of the responding signal to judge whether the speaker is connected or not. The response signal will be read at A/D. A voltage of 3.5 V or more is judged as no speaker connected. The response signals at A/D are read every 2 ms, and if the same results (less or more than 3.5 V) are obtained, the detection result is considered correct. If a different result is obtained for the second detection, a third detection is carried out, and the two results that agree will outvote the other. If detection fails three times, then it is judged that no center speaker is connected. < Detection of the subwoofer > The logic of the signal from the phono jack with a switch is read by the microcomputer to judge whether the speaker is connected or not. The signals are read every 1 ms, and if the same results are obtained, the detection result is considered correct. If a different result is obtained for the second detection, a third detection is carried out, and the two results that agree will outvote the other. If detection fails three times, then it is judged that no subwoofer is connected. 3. Speaker settings According to the results of the detection, speaker settings are made as follows: Results of the Detections Speaker Settings Center SP Connected Connected Not connected Not connected Sub-woofer Connected Not connected Connected Not connected Front SP low high low high Center SP Surround SP low low low low Not connected low Not connected low Subwoofer ON OFF ON OFF 4. User's settings In Setup mode, more detailed speaker settings are available. Once the user's settings are made, those settings have priority. However, if the configuration of connected speakers has changed, then the detection results become valid and have priority over the user's settings until new user's settings are made. 5. Detection circuit for the center speaker Center Detection mute More than 100 kΩ POWER AMP Check signal from U-COM Detection signal to U-COM Mute About 8Ω 54