Quote:
Originally Posted by Yamamaya42
It's a bit confusing to me what is and what is not! 
Cause i see early BW sets with it pulled off after the video detector, and also color sets 45.75mh/41.25mh with it tapped from the 3rd IF before the video detector.
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Colour sets pull the sound off before the video detector to minimize the 4.5MHz beat. You will also notice colour sets have another detector after the 3rd IF which is in effect an intercarrier mixer to extract the intercarrier sound.
The intercarrier sound process was desirable because the audio is available over a wide range of the fine tuning control. In otherwords with intercarrier sets you can fine tune for best picture and not worry about the sound. Split sound sets the tuning is for best sound. Which means the Video IF alignment for split sound sets is more critical because if the video carrier is not EXACTLY at 45% on the nyquist slope on the IF resesponse when the sound is 21.25MHz for the spit sound IF channel, the picture will either be soft or excessively noisy.