Recording vinyls with Audacity. Fine speed adjustment? Quality & down sampling? Surface noise or signal/noise ratio? Normalising & L/R balance?

Apologies if this is the wrong section or has already been asked a million times...
But i guess i'll start with my easiest question first:
So i previously recorded 4x vinyls before addressing the over-speed problem of about 3%. (Replaced the belt and modified the drive pulley diameter).
So to avoid having to re-record another 4x times, i'm guessing it would be easier to simply adjust the speed in audacity using the 'change speed' command?
https://manual.audacityteam.org/man/change_speed.html

I'm certain that I WANT pitch to change as well, so i think its the right tool, but i'm not an expert in Audacity. I'm just a little uncertain as to what this does to the sample rate... I'm assuming that decreasing the speed would increase the sample rate? Though since i originally recorded at the maximum rate, would this not be possible? Causing audacity to do some kind of down sampling to make it fit?

Or is this just a fools errand and i should just bite the bullet and spend a few hours to re-record them? If so, would it be best to record at normal 45rpm, or can i get better performance if i record slower at 33.3rpm and then increase the speed to 45 in post? Or am I just wasting even more time? 😅

Though I kind of wanted to avoid re-recording as i'm a little bit time poor right now, but i will need to return this turntable either today or next week.
(Unfortunately i dont have my own TT, plus i'm moving house atm so its kind of my last chance).

But also i kind suspect that constantly playing these records is wearing them out and is introducing more and more surface noise? i can upload some files later today to demonstrate. (Large file sizes)

Thanks :)
 
I only use Audacity to capture analog audio to a file. I use Adobe audition 3 to edit files.
The screen shot you show of Audacity is exactly how you want to do it. In Audition you
can have a tempo change without a pitch change or a pitch change without a tempo
change. This is not what you want for your job. Audition can also change both pitch and tempo
together as Audacity is doing. This IS what you want as it give the same result as turning a
pitch control on the turntable. What you're doing is "resampling" where the PC calculates what
the sample values would be at the new selected speed. The output sample rate will be what it
should be.

https://en.wikipedia.org/wiki/Sample-rate_conversion

What bothers me far more is how the pitch got so far off in the first place. 3% is more than
1/2 semitone. Since you say you changed the pulley diameter did you check if the motor
speed had changed. At this point you've altered the mechanics so correcting the motor
would now end up being slow. A little slow will cause FAR more complaints than a little fast.
I used to repair turntables long ago and almost nobody complained about fast, only slow but
back then "fast" was maybe 1/2 %, not 3 %.

As far as recording 45s at 33, you should change the RIAA curve since the turnover points will
move with the speed change.

Did this help ?

 
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I think that helps... Though I think in my attempt to save some time, its just over complicates it... So I guess I should just re-record it then, and at the correct speed as well. I've checked the platter speed, and it's as correct as I can get it at least...

As for surface noise, this is basically what I'm getting. Is this normal for Vinyl or should it be much better than this?
You can listen to a few snippets from my G drive: https://drive.google.com/drive/folders/1Z3v2QOigsihUV7NnBKESB-o6GM1bsQhr?usp=drive_link
Any ideas on how to address it?
Signal And Noise.png

Noise Levels Between Tracks.png


 
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I agree with pelanj. It is also important to record in 32-bit mode and keep that until all the manipulations you would eventually do with the audio file are done.
Like denoise, declick and so on. Your screenshot looks healty to me.

Hugo
 
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Thanks for the replies:)
I'm glad to know that my noise levels are within 'normal'.

As for the recording post processing, i.e. denoise, declick, normalising etc; is there a reliable trusted guide that i can follow that will give me the best possible results?
I'm just concerned that any modifications i make will just degrade the quality and introduce artifacts, and generally alter the sound into something not of the original artist...
i guess you can say i'm not sure if i should keep all the defects inherent to vinyl, as thats how the artist originally intended to sound... or maybe thats just crazy talk?

I guess the closest visual analogy i could make would be like applying a smoothing filter over retro pixel art. I admit that its all subjective personal preference, and there is always some amount of filtering and noise reduction is needed, but its very easy to way over-do it... So i guess i'll be looking for guides to process them properly... if such a thing even exists?

Thanks again 🙂
 
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Here is how I do it in Audition.
I haven't used Audacity enough to be able to compare if the same possibilities exist, so you'll need to check that.

First, I record both sides of the LP in 32-bit and save it as a .wav file.
Next I do an automated declick. I then substract the audio from the clicks and look and listen to them to see if nothing more then clicks are removed. In Audition this is done with Mix Paste. Big clicks are removed manually. This can be time consuming.

Next I take a sample of the rumble from the lead-in or from rumble between tracks and substract that from the audio. Again I substract the audio from the rumble and listen if no audio was removed.

If all is well, I eventally apply a little noise reduction. That is a tricky part for artifacts are easily introduced. I rather have a little noise over a messed up audio file. So be carefull with that.

Next I convert the sample rate to 44.100 / 16bit and save the file as .flac.
Last I cut the audio in tracks with space between two and four seconds, depending on the type of music and save them to individual tracks.

This as a rough guide. Experiment, listen to the results and tweak settings as you see fit.

Hugo
 
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As for L/R balance and normalising, the balance should be perfect the moment you start recording.
Cartridge azimuth has to be correct and preamp and soundcard should give equal outputs.
If needed, I normalise the complete track to -0.1dB before cutting the file into individual tracks,
but I always try to record at something like -3dB to leave some headroom.

Hugo
 
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I would not use any of these alorithms. You can easily hear artifacts when you want to change speed and keep pitch. It is a bit better if you change the pitch with the speed. I would avoid both of you can just re-record.
Normally I agree with you but what do you do with a recording that is off speed?
"Carry On" by Crosby Stills and Nash always bugged me either on the LP or CD.
When I bought the CD and ripped it I took it into Adobe Audition and tweaked the
pitch slightly. There are no artifacts when changing pitch and tempo together. Some
of the audio on TV programs and movies have had the pitch tweaked to conform the
program length. It's much easier to change pitch than video speed.

 
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When it comes to analogue source material, the speed and pitch always go together that is, increasing / decreasing speed also does the same to the pitch. Using this knowledge, it is fairly easy to restore the pitch / speed by altering the sample-rate of a digital recording. A step-by-step procedure would be:

  • Mark and copy the erroneous portions of the recording to separate files. Number them accordingly if required. You could identify speed errors using variations in sample count / time-interval between successive beats / peaks within the music.
  • Adjust the sample-rates of these individual portions until they all have the same pitch / speed as the reference material.
  • Resample the pieces (preferably upward) to a standard rate like 44.1k, 48k, 96k or 192k with as high an accuracy as possible.
  • Manually join the re-sampled pieces (in the right order / numbering) to get back the corrected recording at the new sample-rate.

The resulting audio has minimal artefacts when compared to the unnatural method involving separate pitch & speed adjustments. Unfortunately, it maybe very difficult to carry out the above if the speed varies too much / too quickly.


EDIT: Please note that some audio editing software have a 'wow and flutter' removal function built into them. Never used them and not sure about Audacity.
 
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