Sign in to follow this  
Followers 0
Teasing the Korean

Digitizing Mono LPs

12 posts in this topic

Historically, whenever I would digitize a mono LP using a stereo stylus, I would always do the transfer in mono.  This is because when you sum a stereo signal, if everything is in phase, the center increases in volume by 6.02 dB relative to what is on the sides.  The sound of the stereo stylus travel is out of phase, and it virtually disappears when you sum to mono.  Also, left/right anomalies such as inner groove distortion or minor clicks are reduced in volume by 6.02 dBs.

But lately, I have been playing around with transferring the mono albums in stereo, and then using Audacity's "isolate center" feature.  This has virtually the same effect as summing to mono, and may result in an even better signal-to-noise ratio.  

I'm curious to know if anyone has tried this Audacity feature, and how it has worked for you.  

Share this post


Link to post
Share on other sites

Have not tried, but will do next time. For many years, I have (without reflecting much over it) recorded mono LPs in stereo and then used only one channel - the "better" one if there is a difference - for the final audio file. 

Share this post


Link to post
Share on other sites
On 2021-10-31 at 4:46 PM, Teasing the Korean said:

But lately, I have been playing around with transferring the mono albums in stereo, and then using Audacity's "isolate center" feature.  This has virtually the same effect as summing to mono, and may result in an even better signal-to-noise ratio.  

I'm curious to know if anyone has tried this Audacity feature, and how it has worked for you.  

I just tried this when I transferred an old Savoy album with Frank Wess and Jerome Richardson, 'Flutes and Reeds'. It worked really well! The noise level was reduced substantially with no audible artifacts that I have been able to detect so far. Will proceed immediately with Cal Tjader's 'Along Comes Cal'. Now, it makes me want to get only mono versions for everything I want to transfer from vinyl!

Share this post


Link to post
Share on other sites

Here is an update. I noticed that on sections with pure groove noise (no music signal), the noise itself is heavily reduced, but there is a kind of "swirling" artifact if use 1,0 for the "strength" value. Normally this would not be a problem since I cut between the tracks anyway, but for a very long and quiet fade-out it seemed to interfere slightly. When I applied a 200 Hz high-pass it sounded good enough not to be a problem.

Share this post


Link to post
Share on other sites
42 minutes ago, Daniel A said:

Here is an update. I noticed that on sections with pure groove noise (no music signal), the noise itself is heavily reduced, but there is a kind of "swirling" artifact if use 1,0 for the "strength" value. Normally this would not be a problem since I cut between the tracks anyway, but for a very long and quiet fade-out it seemed to interfere slightly. When I applied a 200 Hz high-pass it sounded good enough not to be a problem.

Thanks for this!  I have transferred a few mono LPs using isolate center, but I have not noticed the effect you mention.  I will listen more closely.

1.0 is the default setting.  If I notice the artifact, I will try pulling back some.  

Still, I'm guessing the artifact would be less of a distraction for me than the surface noise.

Share this post


Link to post
Share on other sites

Yes, I will experiment some more as well. I went down to 0.8 for "strength", but it seemed to me that the high-pass had a better effect. I suppose that the amount of rumble from the turntable setup might affect to which degree this would be a problem. In any case, the end result is still much better than anything I have tried before, so thanks for bringing this up! The stereo vinyl rips will suffer in comparison, so yet another reason for going mono. :)

Share this post


Link to post
Share on other sites
9 minutes ago, Daniel A said:

Yes, I will experiment some more as well. I went down to 0.8 for "strength", but it seemed to me that the high-pass had a better effect. I suppose that the amount of rumble from the turntable setup might affect to which degree this would be a problem. In any case, the end result is still much better than anything I have tried before, so thanks for bringing this up! The stereo vinyl rips will suffer in comparison, so yet another reason for going mono. :)

I should add here that I have been very happy with the few transfers I have done using "isolate center."  I have not analyzed the results with headphones or waveforms, but listening on the stereo, they sound very clean. One of them you would think may have been from the master tapes.

Share this post


Link to post
Share on other sites

Posted (edited)

Interesting.  After joining the forum recently and finding this thread, I just started using this Audacity feature on some noisy 2-track files of mono recordings that I have.  So far I am impressed.  It's much harder for me to find residual "clicks" to repair, but they are much less audible too.

I have wondered about using a strategy like this before, but usually in the context of a stereo recording.  If I own 2 copies of a stereo record (usually because the first one was rather noisy), I'd like to be able to digitally remove anything in the files that isn't on both recordings.  In this case, though, you'd be wanting the 2 left channels and 2 right channels to "isolate" separately.  Then there is the problem of getting two recordings to sync up exactly with speed, amplitude and start.  And then maybe you'd have to recombine your finished left and right tracks, again synced exactly!  I don't know if Audacity could do that.

Edited by may1620

Share this post


Link to post
Share on other sites
2 hours ago, may1620 said:

Interesting.  After joining the forum recently and finding this thread, I just started using this Audacity feature on some noisy 2-track files of mono recordings that I have.  So far I am impressed.  It's much harder for me to find residual "clicks" to repair, but they are much less audible too.

I have wondered about using a strategy like this before, but usually in the context of a stereo recording.  If I own 2 copies of a stereo record (usually because the first one was rather noisy), I'd like to be able to digitally remove anything in the files that isn't on both recordings.  In this case, though, you'd be wanting the 2 left channels and 2 right channels to "isolate" separately.  Then there is the problem of getting two recordings to sync up exactly with speed, amplitude and start.  And then maybe you'd have to recombine your finished left and right tracks, again synced exactly!  I don't know if Audacity could do that.

It would probably be easier to combine various chunks of the tracks in question, for example, the first 32 bars from one record, the solos from another etc.  Of course, it depends on both the condition of the LPs and the degree to which you want to drive yourself crazy seeking perfection.

Welcome to the forum!

Share this post


Link to post
Share on other sites

Posted (edited)

Hi,

Just checking back in, as I'm now had a chance to use this Audacity procedure on a more few recordings, and it's really quite remarkable.  I have thus far just left the "Isolate Center" setting on default, 1, 120, 9000.

Do I understand correctly that what the software is doing, when applied to a mono record recorded in 2 tracks, is that it analyzes both tracks and preserves only what is present simultaneously on both tracks?  That is, finding what is different between L and R and then leaving it out?  Some of the larger surface pops seem to be still present, but much smaller/softer.  What are we losing from the recording when we do this?  Do I have to use a stereo cartridge or should I use my mono cartridge but just have Audacity record in stereo?  Trying to refine my technique a bit before going back to re-record some of my favorite mono recordings.  Thanks.

Edited by may1620

Share this post


Link to post
Share on other sites
1 hour ago, may1620 said:

Hi,

Just checking back in, as I'm now had a chance to use this Audacity procedure on a more few recordings, and it's really quite remarkable.  I have thus far just left the "Isolate Center" setting on default, 1, 120, 9000.

Do I understand correctly that what the software is doing, when applied to a mono record recorded in 2 tracks, is that it analyzes both tracks and preserves only what is present simultaneously on both tracks?  That is, finding what is different between L and R and then leaving it out?  Some of the larger surface pops seem to be still present, but much smaller/softer.  What are we losing from the recording when we do this?  Do I have to use a stereo cartridge or should I use my mono cartridge but just have Audacity record in stereo?  Trying to refine my technique a bit before going back to re-record some of my favorite mono recordings.  Thanks.

You would need to use a stereo cartridge for this technique to work.  Your assessment of how it works is correct.  Yes, a loud pop that is in the center will not be removed.  This technique basically works best on mono records that are in reasonably good shape.  As far as what is lost, you are removing only left-right anomalies such as small ticks and pops, stylus travel noise, and inner groove distortion.  You should not be removing any of the music, because the music on a mono record is by default centered. 

Let me know how things continue to go!

Share this post


Link to post
Share on other sites

Thanks, stereo cartridge does make sense of course!

Share this post


Link to post
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
Sign in to follow this  
Followers 0

  • Recently Browsing   0 members

    No registered users viewing this page.