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:
SLV-135 audio auto-filter mono spectral view.jpg
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.