Hi!
I´ve bought a JVC HR-S7900U VCR + ATI 600 USB and started to convert my tapes. However, I've noticed that there is always a noise, centered around 58.7 Hz, with harmonics every 19,5 Hz that is interfering with the audio.
I´ve already changed cables and bypassed the ATI converter/computer, connecting the VCR directly to the TV, but the noise remained. I´ve also tried with different tapes.
I´ve also noticed that there is an audible sound coming from the VCR itself everytime I play a tape and when I recorded it and checked the spectrum, the 58.7 hertz noise was there.
Any idea about what is causing this problem? How can I fix it?
Attached is the spectrum from a converted tape and also a sample of the noise I recorded from the VCR with my phone.
Programatically it could be removed, but that's in regions where you don't want to be hacking out portions of audio without some serious mathematics involved.
Are you in a 50 or 60 Hz market?
Very basic troubleshooting to start with, although I'm sure you've considered there:
- Unplug any UPS in series and retest;
- Unplug anything else nearby which may be generating noise, especially anything with a motor.
58.7Hz is a weird place to end up though, it could be mains referred to 60Hz but at the moment that's just a finger in the air diagnosis.
Thanks for posting a frequency plot by the way, that's handy.
-Edit the plots look like characteristic reflected-power, (note the regular flat potion as each peak rises) which would point toward something being mismatched.
-- merged --
The more I look at that, given that it's enharmonic (it's a 1/3 interval, by definition strictly not harmonic) and with that waveform characteristic that looks like a big reflection or something has gone resonant.
This isn't an area I'm remotely expert in, I'd wait for a somebody more skilled but that's an interesting waveform nevertheless. It's quite musical I wager.
Decoupling would be my shoulder-shrug answer, but that's not especially helpful.
What recording device did you use? It's not impossible this is a capture issue? Does the machine have a headphone socket to take a sample from if that's not where this came from.
Edit - Read first post.
Is this on the linear (normal) audio or the HiFi track?
Noise is only an issue relative to the level of the wanted audio. Since we have no reference here it's hard to judge if the noise is excessive. Ideally, play something which contains loudest wanted audio followed by a passage of no signal, just the VCR's background noise.
Programatically it could be removed, but that's in regions where you don't want to be hacking out portions of audio without some serious mathematics involved.
Are you in a 50 or 60 Hz market?
Very basic troubleshooting to start with, although I'm sure you've considered there:
- Unplug any UPS in series and retest;
- Unplug anything else nearby which may be generating noise, especially anything with a motor.
58.7Hz is a weird place to end up though, it could be mains referred to 60Hz but at the moment that's just a finger in the air diagnosis.
Thanks for posting a frequency plot by the way, that's handy.
-Edit the plots look like characteristic reflected-power, (note the regular flat potion as each peak rises) which would point toward something being mismatched.
Thanks for the answer. I´m in 220V/60Hz, so I´m considering if the problems is the UPS as you mentioned, since the VCR is 120 V/60Hz. I´ve ordered an autotransformer to check it, let´s see what happens.
Quote:
Originally Posted by timtape
Is this on the linear (normal) audio or the HiFi track?
Noise is only an issue relative to the level of the wanted audio. Since we have no reference here it's hard to judge if the noise is excessive. Ideally, play something which contains loudest wanted audio followed by a passage of no signal, just the VCR's background noise.
The spectrum is from the linear (normal) audio after the capture, the mp3 I recorded from my phone near the video head. I agree with you that noise is relative and in this case it is quite noticeable when I play the entire captured video. Besides that, it goes up to the same frequency of the song, so it is difficult to clean. Any idea about a way to get rid of it is welcome
The spectrum is from the linear (normal) audio after the capture, the mp3 I recorded from my phone near the video head. I agree with you that noise is relative and in this case it is quite noticeable when I play the entire captured video. Besides that, it goes up to the same frequency of the song, so it is difficult to clean. Any idea about a way to get rid of it is welcome
This can be a difficult one if for you extracting the best audio quality from the tape is as important as the picture quality, as it is to some of us at least. But this is what can happen when in advice, VCR models are recommended solely or mostly on their high picture fidelity.
An alternative is capturing the tape again in another VCR with excellent audio playback, even if the picture quality is not great. I maintain a couple of older VCR's primarily for their excellent audio playback of the linear track. In fact only the audio needs to be captured, imported into the video editor and manually time aligned. It should remain in sync with the picture for the entire program.
Software like RX can often do a creditable job of filtering out steady, predictable tones like a hum and its related harmonic series but it's not ideal and can sometimes be very difficult to tune the filtering optimally.
If you would like to upload a section of just the audio of the song (render and export the section as just a wav file) we can probably offer more specific comments and maybe perform some hum filtering if the audio is amenable to it. Best to choose a quiet section as that is the most severe test of course.
