Hi Andy, > In broadcast audio processing group delay is deliberately changed - the > audiio is run through allpass filters that are typically third order. The > reason for this is that it tends to make an assymetrical audio signal more > symmetrical. (male voice is often very assymetrical).
If it works for AM I think it could be useful for speech processing in an SSB transmitter as well. If some harmonics could be phase shifted with respect to the fundamental, maybe tallest narrow peaks in the time domain (typical for some male voices) could be smoothed out thus allowing increased "talk power" for a given maximum PEP without introducing non-linear distortion (like clippers)? Hmmm.. Interesting. If some delay can be tolerated, some clever DSP algorithm could "look ahead" in the audio stream and tweak a number of allpass filters on-the-fly? Just a wild idea... 73 Johan, SM6LKM
