Norm to Hi-Fi

[colt4523]

Is it possible to convert "norm" audio to Hi-Fi? I have a JVC S9911U Vcr and some of the tapes I transfer have a noticeable crackling or hiss when I set the audio to Hi-Fi. If I set the audio to "norm" the crackling goes away but the overall sound quality suffers, not Hi-Fi. So can I convert the "norm" audio to Hi-Fi?

[JohnnyMalaria]

No...they are recorded on the tape in a completely different way.

Hiss is inevitable and, perversely, a good sign that the high frequencies are there. The linear "norm" audio sounds dull because it just can't record the high frequencies.

The crackling would be best dealt with by software designed to clean up vinyl recordings etc.

[Video Head]

When VHS first appeared it had just a single audio track, the "linear" track, because it runs in a line along the edge of the tape. Its fidelity is relatively poor, and the linear track does not support stereo recordings. Later, the linear track was split in two to record stereo. This made the linear track's noise performance even worse, so engineers added noise reduction to keep tape hiss at a bearable level. There was no room on the tape to add more audio tracks so VHS audio quality had maxed out.

Then, manufacturers figured out how to record two different signals onto the same section of tape. This process is depth multiplexing. In it, one signal penetrates deeper into the tape's magnetic layer than the other. With VHS hi-fi, the audio signal lies beneath the video signal. Because the audio heads sit on the spinning head drum, the effective tape speed is very high--this explains VHS hi-fi's CD-like audio quality.

Mostly plagerized, some made-up, but it tells the tale...

[orsetto]

The "crackling" noise you hear is caused by tape mistracking issues. Back in the days when we were all tape users, one of the biggest problems with VHS HiFi was the slight offset many tapes had between the video tracking and the hifi audio tracking, because VHS uses separate spinning audio and video heads to lay down the different tracks. A surprisingly large percentage of home recorded tapes are very difficult to get a good compromise tracking lock on: if you clear the audio you pick up some picture distortion, if you adjust for the clearest picture the audio starts drifting and "crackling". The worst offenders are tapes recorded on the first wave of VHS HiFi decks of the mid-1980s: when they mistrack the audio distortion sounds like an outboard boat engine- yeesh.

It got better later on, but tape interchange between home decks has always been dicey, especially the HiFi audio. Certain brands of VCR were less flexible in their tracking: Hitachi, RCA by Hitachi, JVC, and JVC's various OEM brands were often a giant pain with tapes they didn't record themselves and the vaunted 9911 is no different: mine is twitchy as hell. You can sometimes get better results if you switch off the automatic tracking and manually adjust it yourself: the machine rarely picks the best compromise on autotrack, it almost always skews the tracking towards better video than audio. Or if the audio on a tricky tape is really important to you, try playing it on recent (1997 or later) Panasonic, Quasar, Sharp or Sony VHS HiFi machine. These had somewhat wider range in their auto and manual tracking and are easier to dial a compromise into. Of course if the video requires the TBC and filters on the JVC 9911 you could be stuck and simply have to tolerate using the lower-quality linear audio track to get rid of the crackling sounds. Like Gilda Radner used to say on SNL, "Its always something".

Interestingly this is pretty much never a problem on Beta tapes, Beta HiFi came first and was one of the rare Beta tricks Sony got right the first time. Beta always had a slight edge in tape headroom over VHS because of its larger head drum and a few other factors, so in the Beta HiFi system the audio is actually blended into the video track using the same pair of heads for video and audio. There is no potential tracking conflict since there are no separate audio/video head passes like VHS was forced to use. On the very first Beta HiFi decks you would sometimes see an increase in video noise onscreen if the tracking was off a little, but this was easy enough to dial out. Beta had some definite issues (Sony's un-reliability and repair costs topping the list thru the 1980s), but the system had some nice technical advantages if you were lucky and got a machine that worked. For awhile NEC made some nice ones.