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Never tuned a prewar with AM sound, but do remember tuning postwar TV with split-sound audio. As I recall, the basic definition of split-sound is the use of a separate detector for the sound signal. Some used a take off near the tuner to feed the audio IF; others connect it to a video IF. As I further recall, the much narrower bandwidth of the audio IF compared to the video IF would make it much touchier than an intercarrier set, all other parameters being equal. Am scratching my head, but I think I remember confirming the effect many years ago with a 630 clone. I just cheated and looked up the problem in a vintage Fink book. Local oscillator drift, especially on VHF-hi channels, caused the undetected sound carrier to slide out of the sound IF stage bandpass, which results in distorted audio, so it is/was much more touchy to keep in tune – at least until the LO settled down and stabilized.
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