VHS mono audio track with "auto-filtering"

[tugatomsk]

I've learned that some VCRs have this annoying feature that I'd call "auto mono audio bandwith filter", in which they decide which frequencies are to be mitigated (based on tape quality, I guess), resulting in a rather lackluster mono audio quality. Furthermore, that filtering is kinda random, switching on and off on the same recording from the same VCR.

Do S-VHS VCRs have this annoying audio feature as well or can it be switched off like "edit mode off" for video? If so, does a S-VHS unit like the JVC HR-S7611 enable playing mono audio "as is"? The VCRshop has that model for sale.

What I mean is the MONO track audio behaviour as shown in this spectral view image:


[Attachment 70008 - Click to enlarge]

Notice how the audio suddenly loses amplification and the 5kHz band surroundings are almost cut. This dramatically changes the audio. The VCR does this on its own. What's more, if I go to that bad part of the tape, the video may or may not provide a good audio response. It's almost random. I was wondering if there are any VCRs that can disable this automatic audio filtering.

EDIT: The audio response shown in the spectral view image is from the same mono track. There is no HIFI track whatsoever. The VCR itself cannot playback HIFI as well.

[dellsam34]

Maybe you have a bad tape or bad VCR electronics, I'm not aware of such feature, I've been around VCR's since the 90's and never heard of "auto mono audio bandwith filter", Do another test with a commercial tape and report back, you can't judge a VCR from a single tape.

[pandy]

This is common for DNR systems, lower level of signal -> narrower signal bandwidth - try to disable DNR in your VCR

[tugatomsk]

This is common for DNR systems, lower level of signal -> narrower signal bandwidth - try to disable DNR in your VCR

There are no menu functions or specific function buttons (apart from the basic tape commands).

[themaster1]

I've learned that some VCRs have this annoying feature that I'd call "auto mono audio bandwith filter", in which they decide which frequencies are to be mitigated (based on tape quality, I guess), resulting in a rather lackluster mono audio quality. Furthermore, that filtering is kinda random, switching on and off on the same recording from the same VCR.

Do S-VHS VCRs have this annoying audio feature as well or can it be switched off like "edit mode off" for video? If so, does a S-VHS unit like the JVC HR-S7611 enable playing mono audio "as is"? The VCRshop has that model for sale.

What I mean is the MONO track audio behaviour as shown in this spectral view image:


[Attachment 70008 - Click to enlarge]

Notice how the audio suddenly loses amplification and the 5kHz band surroundings are almost cut. This dramatically changes the audio. The VCR does this on its own. What's more, if I go to that bad part of the tape, the video may or may not provide a good audio response. It's almost random. I was wondering if there are any VCRs that can disable this automatic audio filtering.

EDIT: The audio response shown in the spectral view image is from the same mono track. There is no HIFI track whatsoever. The VCR itself cannot playback HIFI as well.

The mono track is not read by the audio heads on the drum, these are for hi-fi (someone correct me if i'm wrong) so it's all about the AC head (audiomono a.k.a "linear") and control (speed of tape: sp,lp ep) as far as i know

Perhaps your Ac head is dirty or the part on the reel where this dropdown happen is damaged or dirty (oxyde). My best guess

S-vhs vcr (JVC's) have a feature called "b.e.s.t" (it can be disabled but not advised) which essentially check the tension of the tape and adjust accordingly, this happen when you insert the tape or before a recording i believe (not sure if it also happen during playback ?).

Then they have features like auto, edit, norm, sharp +/- (edit is the "raw" mode to simplify (very grainy, lots of details), then norm filter the video a little and then sharp modes sharpen more or less (not advised). The auto mode can be very blurry i noticed (edit or norm are the 2 best modes imo) only the high end JVC's hr-S8000 to 9000 have these 5, i know my S7700 lack the "norm" mode...anyway.

One video for you: https://www.youtube.com/watch?v=lRNv4uM6auI

[johnmeyer]

1. Linear audio is recorded on the edge of the tape in the exact same manner as audio tape (e.g., reel-to-reel, cassettes, etc.)

2. The audio bandwidth of linear audio is quite limited. Also, it varies depending on the recording speed. Supposedly, the SP (2-hour mode) linear audio bandwidth was 10 kHz. I think it was less than that. At the other end, the EP (6-hour mode) only has a 4 kHz bandwidth, about the same as AM radio.

3. The audio quality of that linear track can vary significantly depending on tape alignment, and with an old tape, this alignment can drift in and out, resulting in something similar to what you describe, where the audio is "OK" on one section, but then pretty muffled on another section.

Early VHS tapes were all recorded using the linear track. Hi-Fi audio, where the audio was multiplexed into the video signal, wasn't introduced until the mid-1980s and I don't think was widespread until the end of the decade.

You should always force your deck to play back only the Hi-Fi track, just to make sure there isn't any audio recorded there. Most Hi-Fi decks and camcorders defaulted to record both the linear and the Hi-Fi track, something which is often useful when digitizing tapes, because if one source of audio has problems, you can switch over to the other track.

[johnmeyer]

P.S. Like others have already mentioned, I am not aware of any decks which offered "single-ended noise reduction" (as opposed to double-ended noise reduction, like the various forms of Dolby, where premphasis is added to the high frequencies during recording, and then subtracted back out during playback). Single-ended noise reduction in the analog era, which was available on some audio tape decks, never worked very well. By contrast, you can sometimes get pretty good results with some current-day digital restoration audio programs. I use the professional version of iZotope RX and it has several audio noise reduction tools which can do a good job on noise.

I haven't updated for a long time so I don't know if they ever added band extrapolation, something which might be able to give a little more "life" to audio that is bandwidth limited, like what you're dealing with.