Hi Has I understand things the prologic signal is encoded in the stereo signal. If this is the case and I use a prologic/Dolby surround source such as a video, should my amp be able to detect the prologic signal? I have a Marantz SR4200 and have just always had in set in prologic II mode for TV/video. Today I had changed the amp setting to auto (can't remember why) and noticed that it said stereo and set itself into stereo mode. This got me thinking so I kept changing digital TV channels looking for something transmitted in surround but on all channels the amp just reported that it had detected a stereo source. I then decided to try it with my nicam video selecting a film that said Dolby surround but the amp still reported a stereo signal, now I'm confused Should the amp auto detect a prologic signal or is it up to me to manually change the setting to prologic etc. Please note when playing the video film the sound signal was outputting from the analogue stereo connections on my TV to the amp e.g. video connected by scart to TV, TV connected to amp with stereo phono's and auto selected on the amp.