Quote:
Originally Posted by Ian - G4JQT
Audio compression - which when done properly - is quite complex - and if not done properly can make matters worse! (I'm sure software can do most of the work these days.)
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No that is not correct. The software I find is problematic and useless. All it requires is the NE571 compander IC.
One IC is "just" enough. After years of experiments with this issue for AM transmitters, I found that if you cascade two NE571's basic system in series you effectively create a constant volume effect that is equally is good as any radio station transmission (it ends up taking the fourth root of the average level). Since the NE571 was designed for two channel use, you only need the one actual IC to do it for mono. I could attach the schematic if you are interested, including the circuitry for the soft peak limiting and LED display of peak limiting, last time I attached it few were remotely interested.
It works exactly as though you had a human being adjusting the amplitude of the audio signal for the same listening (modulation) level for all music recordings regardless of their original level. There is a huge difference in the levels from various mp3 recordings as one example.