1.  Volkswagen's problem with being caught cheating on emission tests reminded me of some audio history with Carver tuners (based on my memory). FM stereo is 23 dB noisier than FM mono so there is a great benefit in blending the channels (reducing separation) at low signal levels. I believe Carver had circuit that did that and added some artificial ambiance to retain the illusion of full stereo. Nothing wrong with that. However, to give better performance on the test bench, when sine waves were applied, the blend circuit was switched out so it retained good channel separation at low levels.

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