Nancy Street - Music - Digitising Vinyl

Since 1998 I have been digitally recording old vinyl records and converting them to compact discs. I use the software application CoolEdit to capture the raw recordings and filter (remove) background noise and clicks and pops. In September 2003 I upgraded from CoolEdit 2000 1.1 to CoolEdit 2.1, which has been taken over by Adobe and renamed Adobe Audition.

I'm often asked how I produce such clean results from my digitised vinyl records, so I thought it would be a good idea to document the process and hopefully help and inspire others to embark upon this most satisfying hobby.

It's fascinating to capture a vinyl recording and look at the raw waveform where you can literally see the music. One of the first things you will notice is how dirty and noisy vinyl records are. Two types of noise are usually obvious:

Background Noise - You will soon learn that the "silence" at the start and end of records and between tracks is not very silent at all. The background noise in records often looks like a jiggling wave or a series of waves-within-waves which match the rotation of the record. This background noise is often overlooked because it consists mostly of frequencies out of the normal range of sensitivity for our ears, but if you turn up the volume on this noise will probably hear a mixed hissing or rumbling noise perhaps in the form of a whoooosh-whoooosh as the record rotates.
Clicks/Pops (transients) - The curse of vinyl...clicks and pops (technically called transient noise). You will see them in the waveform as sharp spikes. They tend to be hidden in loud music, but they can be incredibly intrusive and annoying in quiet recordings. Delicate classical music can be the worst victim of clicks and pops.

CoolEdit and similar products are capable of removing both types of noise, and as long as you use sensible filtering options you can be quite sure that the original recording will be totally untouched. This is the miracle of digital filtering.

I find it hard to believe now that before the age of compact discs we used to put up with so much noise in records. Even if you had the most fabulous high-tech turntable and Hi-Fi system, there was a limit to how much quality could be pulled out of the grooves of records. You could keep records surgically clean to avoid clicks and pops, but it was almost impossible to remove the background noise. I think it's a scientific curiosity that the primitive system of encoding sound in bumps in plastic grooves lasted for so long (about 100 years) before it died about 10 years after the arrival of the compact disc in 1981.

I have noticed that the only visible difference between very expensive records and typical commercial ones is the nature of the background noise. As a general rule, the expensive "digital masters" and "special release" records tend to have a background noise that is slightly lower in volume and more regular. However, the difference is not very startling.

A full list of records in the Nancy Street library can be found in these pages: 12" Vinyl LPs, 7" Vinyl EPs and 78 rpm Records. The Compact Disc list includes CDs which have been created from digitised vinyl, they are identified by a V in the Flags column.

I'm going to describe how I convert vinyl to CDs using the software and hardware that I have here at home. Not everyone will have the same setup as me, but I hope the description will be general enough so that you can translate the procedure to your environment. The most critical steps happen inside the software that captures and filters the music. I personally use CoolEdit Pro 2.1, but I know there are many competing products such as Sound Forge and the wave editor built into Ahead Nero.

The process is split into the following sections:

The Hardware
Setting Levels
Getting the raw recording
Delete leading and trailing "junk"
Eliminate Clicks (Transient Noise)
Manually fix remaining clicks
Filter Background Noise
Splitting and saving the tracks

Start with a good turntable with a good stylus. I'm using a 25 year old Akai AP-B1 turntable with a Goldring D 1008SR stylus (which I have to drive halfway across town to buy). The turntable plays through a 1977 vintage Marantz 3250 Pre-amp and the Tape Monitor Out feeds into the Line-In on a Sound Blaster Live card in my PC. The audio equipment and its history are described in great detail in the Hi-Fi page.

I have read complex discussion about what sort of turntable to use and what sort of sound card to use for the digitising process, but I suspect it may be partly a pointless debate due to the law of diminishing returns. There can be little doubt that better equipment will produce better results, but there is so much noise in vinyl records that the most expensive turntables and sound cards will not help break through it.

I was surprised to find that the background noise from my audio equipment is an inaudible pulsating signal that hovers around -65dB. Some experiments show that the noise of the turntable is too low to be measured, which surprised me, as it wasn't a very expensive turntable and I thought the noise of the rotating turntable would be significant. The background noise in the best quality record I have seen would completely drown any noise from the electronic equipment and turntable.

In any case, when done with care, the digital filtering process will utterly remove any background noise from the recording, including circuit noise, turntable rumble, and noise present on the master tapes that made the record. This leads me to conclude that although good equipment is important, going beyond a certain quality level will not help the digital filtering process. I have concluded that it's more important to make sure your turntable is balanced and performing well before wasting time and money on expensive equipment.

The "computer room" in June 2007 showing the
Marantz Hi-Fi stack on the mid-left.

Open a new waveform and select 44.1KHz sampling rate as stereo 16-bit. This corresponds to how music is recorded on compact discs.

Figure 1 : New File Waveform Options

I play a sample of the vinyl record that is probably around the loudest part so I can set the recording level in CoolEdit. In CoolEdit you use F10 to toggle the Monitor Recording Level option. Make sure you are showing the Level Meters (menu View | Show Level Meters).

Figure 2 : Monitoring the recording level

The recording level can possibly be set via the volume controls on your Hi-Fi equipment, in your recording software, or in the operating system. It's important that the loudest part of the recording just reaches a "sweet spot" that approaches but doesn't exceed the 0db limit. You can adjust any small volume errors later in software, but it's important to get a good raw recording first. This is no different than the way it used to be back in the days of tape recorders when (I hope) you would try to get a nice level on the VU meters.

NOTE -- The vinyl sample I will be using in this tutorial is the song Banquet by Joni Mitchell, Side A Track 1 of the 1972 album titled For The Roses. I picked this song at random and I have no memory of ever hearing it previously.

Start recording in your software. With surgical precision drop the stylus onto the start of the leading spiral of the record. If you miss the leading grove or the stylus jumps, don't worry, just pick it up and try again. The silent gaps or failed attempts can be cut out of the recording later. It's vital that you get as much of the leading "silence" as possible, as this will be used later to analyse the noise and filter it out. The leading "silence" is not actually silence of course, it contains the background noise that is a mixture of turntable rumble, clicks and pops, electronic circuit hiss and possibly noise from the original recording studio. This "noise" must be captured so it can later be analysed and removed.

Don't bump the turntable or anything that is connected to it, as this will pollute the recording in ways that are irritating and difficult to remove later. I have personally found that vibrations from the washing machine at the other end of the house can interfere in the recording, and so can a car starting or stopping in the driveway of our house.

Play and record continuously and capture all the tracks that you want in one recording, even a whole side of an LP. The individual tracks can easily be chopped apart and saved separately later. It's easier to digitally manipulate one large file than lots of smaller ones. In this exercise I will stop recording after the first album track.

Stop recording and you should have captured one large raw digital waveform, looking something like this example:

Figure 3 : A raw recorded waveform of LP Track 1

Figure 4 below shows a zoom-in to the leading 11 seconds of the raw recording of the from the previous step. Here's what you can see in the selected part of the waveform:

1.1 seconds of silence before I put the stylus down.
A small bump at 2.7-2.8 seconds where the needle bounced.
Leading "junk" (with some spikes in it) from 2.8-4.4 seconds.

Following the selected part is the following:

Realistic leading noise which probably represents the real background noise from 4.4-9.8 seconds.
The music starts at about 9.8 seconds.

The groove at the far outer edge of vinyl records is only used to capture the stylus as it is dropped into the record and it's usually full of weird "junk" noise that has no relationship with the rest of the record. I prefer to identify the leading "junk" and delete it before we start cleaning. Often the "junk" noise quietens rapidly and then blends into the real background noise of the record, so it takes a bit of practice to listen carefully and watch the wave to find the point where the "junk" vanishes. Delete from the start to this point.

In the sample recording shown in Figure 4, by listening and looking carefully I could tell that the leading "junk" which appears at the start of the record seems to settle down and become regular at about 4.4 seconds. I know that the highlighted part of the waveform is total "junk" that can be deleted. The change from "junk" to normal background noise is quite subtle, but you should be able to hear and see it with practice. In some noisy records it's quite obvious simply by looking at the wave to see where the "junk" quietens down.

After deletion I am left with about 5.4 seconds of leading noise that probably represents the real background noise of the recording. This background noise usually has a regular wave pattern. This background noise will later be analysed and removed from the whole recording.

Figure 4 : A zoom into the leading 11 seconds of the raw recording

More "junk" will probably appear at the end of the recording. By looking at the waveform and/or listening to it, it is normally very easy to locate the point where the music stops and we are left with nothing but background noise again. You can delete from this point to the end.

Figure 5

While playing the record I could tell that although there are dozens of spikes, the recording quality does not contain any terrible continuous "crackling" that is usually found in very old records. So we seem to have a reasonably good quality recording with some random clicks which sound quite crisp and short. Figure 5 (inset right) shows a deep zoom into a single click in the raw recording. Clicks can be the worst pollution in vinyl records, so this noise will be removed first.

We must now use the CoolEdit Click/Pop/Crackle Eliminator Plug-in to analyse the clicks and remove them. This noise reduction plug-in is not a standard part of CoolEdit 2000 and must be downloaded from their web site. CoolEdit Pro 2.1 has the plug-in as a standard component.

Select the whole waveform (Ctrl+A) and bring up the Click/Pop/Crackle Eliminator dialog box. I have cleared the Smooth Light Crackle option as there doesn't seem to be any in the recording. The Sensitivity can range from 10-20 and the Discrimination can range from 4-40. I don't have time to explain in detail what these settings are, I recommend you read the Help on this facility, and read it very carefully as it's quite complicated. In a nutshell though, the lower the values, the more aggressively the eliminator will find and remove clicks. For this waveform I have chosen 14 and 18 respectively, which are slightly aggressive, but I didn't want to go any lower just in case it started mistaking real music for clicks. After some experience you will probably be able to make excellent guesses for the Sensitivity and Discrimination values based upon how the raw waveform looks.

Click Auto Find All Levels to begin analysis of the waveform, which might take a few minutes for a whole LP side. Figure 6 show the dialog box after the analysis has completed. The Detection graph will be adjusted to represent filtering levels according to what was found during the analysis.

Figure 6 : After Auto Find All Levels

Click OK to begin the elimination process, which might take over an hour for a full LP side with very aggressive settings.

Once the eliminator has finished, most of the clicks in the waveform should be gone. It's unlikely that they will all be gone, as experience has shown me that some seem to leak through, especially the spikes that are very wide.

If only a small number of clicks remain visible, then it's probably easier to fix them manually using the Fill Single Click Now facility as described in the next section.

If large numbers of spikes remain, then something has gone quite wrong with the settings and you may want to undo (Ctrl+Z) and retry the elimination with new settings after reading the help carefully.

Figure 7 shows the waveform immediately after the Click/Pop/Crackle Eliminator has finished. All of the obvious spikes have been removed, but when playing the recording a few small clicks can be heard in the quieter parts.

Figure 7 : After click/pop elimination

Now you have to decide how much manual click/pop elimination you want to perform. I have some general rules:

Is the music mostly high-volume?

If Yes, then any remaining clicks will probably be drowned in the music and there's little point in finding them. In this case I just check there aren't any obvious clicks visible.

Does the music contain quiet parts?

If Yes, then I will zoom down into the quiet parts of the waveform looking for small clicks. I usually play the quiet parts and listen for clicks.

Is the music rare or precious?

If Yes, then I will zoom into the waveform and play it from start to end and listen carefully for any clicks that were missed. This is time-consuming of course, but if the music is precious then the time is worth it. Each time I hear a possible click I will immediately stop play and zoom deep down into the waveform until I can see the flaw in the wave. After some practice you will be skilled in zooming in and scrolling through the wave, recognising tiny transients that don't match the surrounding waveforms. Learn the keyboard shortcuts for zooming and panning to save time during this step. A wheel-mouse really speeds-up the process of zooming in and out.

Figure 8 : Zoom into a single click

Figure 8 shows how I have zoomed far down to expose a small click I saw in a quiet part of the waveform. Bring up the click/pop/crackle eliminator dialog and click Fill Single Click Now. The wave should magically smooth itself over the click. If you're not happy with the results, use Ctrl+Z to undo the action, select a different area around the click and hit F3 to retry. It takes a bit of practice to know how much to select either side of the click to make it vanish.

You can use Page-Up and Page-Down to scroll through the waveform looking for clicks, or you can zoom in and out looking for them, or you can play the wave and listen for them. It depends how fastidious you want to be.

Remember: If there more than a handful of big clicks remaining, or if you find there are large numbers of small clicks remaining, then something has gone seriously wrong with the main elimination process. Rather than waste time removing dozens (or hundreds) of clicks manually, I would start Stage 5 all over again and carefully chose the elimination options after reading the Help carefully. Some experimentation might be needed.

By now all of the clicks and pops in the waveform should have been removed mostly automatically, with perhaps a bit of manual help. Now we are ready for the most beautifully satisfying and effective part of the digitising process: the filtering of background noise.

Figure 9 returns to a zoom into the lead-in of the recording after the junk has been trimmed off and clicks have been removed. I have selected about 5.3 seconds of the leading part of the waveform, just before the music starts. This selected part contains the real background noise of the record. It's probably a mixture of noise present in the vinyl groove, the hum of the Hi-Fi electronics and the noise from the original master recording. This noise will be analysed by CoolEdit, then digitally extracted from the whole recording. It is this miracle of signal processing and mathematical algorithms that produces the fantastically clean final recording from the original vinyl.

Do not accidentally select any music, or it will be considered as noise and removed from the recording, which can produce bizarre sounding results. You should play the background noise selection and listen carefully to be totally sure that there is no music present, just background noise. If the music fades-in very slowly, then it's very important to listen and check you haven't sampled some of the music by accident.

Figure 9 : Sampling the background noise

Bring up the Noise Reduction dialog and click Get Profile from Selection. Figure 10 shows the dialog after it has analysed the noise.

Figure 10 : After Get Profile from Selection

Close the dialog and then select the whole waveform (Ctrl+A). Reopen the Noise Reduction dialog, set the Noise Reduction Level to 90 and click OK. The sampled noise will now be digitally filtered out of the whole recording, a process which might take several minutes for a whole LP side.

The closing, selecting, and re-opening of the dialog is a bit tedious, but if you forgot to do it then you'll just clean the bit of the waveform you previously selected, which is the leading part.

Figure 11 : After background noise reduction on the 7" single

Figure 11 shows the whole waveform after Noise Reduction is complete. You can see that all of the background noise has been removed, leaving only flat silence at the start and end of the recording. Assuming that you chose your background noise sample carefully and did not accidentally include any of the music, you can be sure that the original recording is perfectly preserved. It is quite possible that you now have a recording that is actually better than the original master recording made by the studio. This is because any tape hiss present in the original tape master will also have been removed. Even if the original recording accidentally included the sound of the studio air-conditioning, then this will also be removed.

In my example I only sampled a single classical LP track and one side of a 7" single, but I typically record a whole LP side at a time and finish-up with a 20 minute duration waveform with half a dozen songs that is around 300MB in size.

In CoolEdit you can cut-and-paste the individual tracks out of the whole waveform into new ones and save them separately. Just repeat Select and Cut, File New, Paste and Save until all tracks are saved. As I do this I trim off almost all of the leading and trailing silence between the tracks, this because when the individual WAV files are burnt to a compact disc they will have a default 2 second gap between them. There is no need to keep the old vinyl record groove gaps when they will have a new gap added on a CD. There are free programs available that automatically split files into separate tracks, but I prefer to do the job manually.

Here is the start of the Joni Mitchell song after the full cleaning process:

banquet.mp3
Duration: 00:23, Format: 112KB/sec MP3, Size: 313KB

To demonstrate how effective the cleaning process can be, I include here a full recording of Howard Shelly playing Rachmaninov's piano prelude No.9 in Eb minor. This sensitive classical recording originally contained a low rumbling background noise and dozens of intrusive clicks and pops. You will hear that the filtered results are crystal clear.

prelude9.mp3
Duration: 01:47, Format: 112KB/sec MP3, Size: 1.43MB

For many years, this appendix contained a sample of the waveforms and sounds of cleaning a 7" vinyl single of the theme from The Aunty Jack Show, but then I received the following rather terse email:

From: XXXX@aol.com
Sent: Sunday, 8 April 2007 20:51
Subject: digitising vinyl

I was looking for some advice on digitising my vinyl collection and came across your page

http://www.orthogonal.com.au/music/digivinyl/index.htm

Although very interesting and informative, I find your before and after samples of the cleanup show just how poor the results of 'cleaning' old records can be. Sure you removed all the noise from the recording, but it was also robbed of high frequencies and the bite and emotion of the recording was lost, making it sound more synthetic. Advising people to set noise reduction to high is just going to give a lot of people inferior quality recordings.

I agree perhaps that the vinyl I used for my original sample was such terrible quality that it was not a good example, as rather aggressive noise reduction settings were required to achieve reasonable results. I would never advise people to "set noise reduction to high", because you will lose high frequencies and possibly get strange sounding artifacts like "gurgling" background noises. The art of noise reduction is finding the delicate balance point where noise is reduced without degrading the original to an unacceptable level. As I explained earlier, finding this balance requires practise and a good ear.

As a result of the email, I have replaced the Aunty Jack sample with a better one taken from the Deutsche Grammophon 1984 recording of Le Sacre du Printemps (The Rite of Spring) performed as a piano duet by Güher and Süher Pekinel. This record has been a prized part of my collection since the early 80s, so when I finally digitised it in April 2007 I thought it would be a good example of the magic of digitising vinyl. This record is a great example because it has such an enormously wide dynamic range. The sample I have chosen is the start of side B of the record where the pianos are so quiet that they are almost lost in the background noise. The sample waveforms have been amplified by 300% to exaggerate their shape. Click the icons to listen to 36 second 536KB mp3 (128kb/sec) audio samples. The first 6 seconds are the lead-in, which is silent in the cleaned version and amazingly noisy in the others.

1. The "raw" waveform	2. The "cleaned" waveform	3. The "noise" extracted from the "raw" waveform