TheCorfiot said:
HiFi Stereo was actually a frequency modulated subcarrier that was interleaved within the helical layered video signal on the tape, The extra heads required to read & decode the HiFi Stereo signal were also mounted on the helical rotating drum phase shifted from the video signal heads by 'x degrees.
This could be proved as adjusting the tracking control to extremes ( helical drum fine speed adjust ) would also cause the HiFi tracks to dropout as well as cause video interference.
That is true for later VHS, however most of the first hifi VHS recorders split the mono track into two smaller tracks for the stereo. It caused background hiss and wasn't great quality, so was scrapped when depth multiplexing was invented. This method was developed because there was no room left on the tape width to fit the stereo tracks separately to the video track. The audio head laid down the audio stereo tracks a fraction of a second before the video, which was then laid over the top of the hifi audio track. And on playback the video and audio heads ignore each other's signals, giving true hi-fi stereo on VHS.
And interestingly JVC stole the idea of depth multiplexing from Sony, who developed it a year earlier for the PAL version of Betamax. US Betamax didn't use this method. The NTSC Hi-Fi Betamax recorders used frequency multiplexing, placing a pair of FM carriers between the chroma and luminance carriers, with each head having a pair of carriers, so the tape held 4 FM carries and therefore 4 channels for audio. However PAL required more bandwidth than NTSC and there wasn't room to use this method so Sony developed depth multiplexing to embed the audio beneath the video.
However this causes a problem when editing and dubbing a tape for both VHS and Betamax. Because the hifi track is under the video track, you cannot dub over the video without replacing the hi-fi track. And you cannot dub to the hi-fi track without destroying the video. So to fix this problem the original mono track remained on most hi-fi recorders for dubbing in other audio onto existing recordings. Not the best solution, but it was was still useful for a soundtrack or commentary.
Not sure how interested anyone really is, but with SVHS pro editing decks actually recorded two linear audio tracks above the video track that were separate and could be dubbed or changed without effecting the hifi audio and video. Normally one of these tracks remained the mono audio track for dubbing, and the second was used to record LTC time code. However my Panasonic SVHS pro edit decks record VITC timecode which leaves the audio tracks alone and records the time code in the vertical interval of the video between each frame. Quite a cool timecode system and more accurate than LTC. However my Panasonic decks could also still access and control LTC/RCTC based players as well as VITC ones. Quite a unique and useful feature at the time as my Sony Hi8 camcorder used RCTC.
I preferred the use of a High Quality HiFi Stereo VHS machine for Audio recordings instead of compact cassettes.
Me too. And later I preferred to make audio recordings via hi8 camcorder, and then mini dv, which I often still use.
int:
fftopic: and then deleted my post! only to see you here off topicing with the others, i mean where's the justice?
PMSL I was reading through thinking exactly the same 
Either that or get a part in the next run of Jesus Christ Superstar!
