Development [LWN.net]

Digitizing Vinyl Records with Audacity

By Forrest Cook
October 28, 2008

The Audacity sound editor is an excellent application with many uses. Your author recently started working on a long-term project to convert the better parts of his ancient vinyl phonograph record collection to FLAC files so that they could be added to his digital audio library. Audacity was chosen to do the audio recording and processing work.

Prior to undertaking such a project, one must first assemble the appropriate equipment. An older desktop computer with an Athlon 2500 processor and 500MB of RAM was used for the computing platform. Besides a sufficiently powerful CPU, the second most important piece of hardware is a decent sound card. An M-AUDIO Delta 44 was chosen. Standard sound cards should also work, but the Delta 44 has higher quality A-D converters that are mounted external to the computer for lower noise. The Ubuntu Studio distribution was used on the machine, although any current Linux distribution should work.

The turntable is an ancient Technics SL-D3 and a Pioneer SX-780 receiver is used as the phono preamp. One of the Tape Record Outputs from the Pioneer receiver is fed into the Delta 44 sound card with an appropriate set of adapter cables. The turntable's tracking weight, anti-skid settings and platter speed should all be adjusted appropriately. One of the new USB turntables could probably be used here if you don't already have access to the legacy hardware.

The Audacity sound editor needs to be set up by entering the Edit->Preferences menu, the audio quality was set to 44,100 Hz sampling at 16 bits (standard CD quality). Depending on your needs, other sample rates can be used. One of the more important configuration steps involves making sure the Software Playthrough button in the Audio I/O preference window is deselected. On this particular machine, enabling Software Playthrough results in audible sample loss on the recording. Audio monitoring is done through the Pioneer receiver. The audio meter should be enabled on the main Audacity window and the GNOME ALSA sound mixer is used to set the sound card input levels. The machine is now ready to record.

It is a good idea to make a few test recordings on various album tracks to set the sound card's input level adjustment. A loud track should be played and the input level should be adjusted to achieve fairly high readings on the meter without any clipping.

Unless you only need to extract one track, it is best to record an entire album side in one pass. Recording should be enabled prior to setting the needle on the record, and disabled after the needle has been lifted. Be sure to use an appropriate record cleaner on the disc to get rid of any dust particles.

When an album side has been successfully recorded and the levels look reasonable, it is time to do some trimming. Listen to the beginning of the recording with the volume up a bit, At some point the sound will probably begin with a fade in. Select the audio from the beginning of the recording, past the initial pop from the needle landing in the groove, and ending a few seconds before the first track starts. Delete the selection with Edit->Delete. Next, select from the new beginning to where the sound begins. Use Effect->Fade In to make a smooth transition from quiet to the beginning of the audio. Perform a similar edit at the end of the album side. Delete everything from a few seconds beyond the last sound to the end of the recording and put a Fade Out at the end of the side.

If your album has a few clicks and pops, now is the time to remove them. Select the entire recording with Edit->Select->All and de-click with Effect->Click Removal. The default click filter settings seem to work fairly well.

The next step involves putting labels at the beginning of each song, assuming the album's material is not one long track. First, create a label track with Tracks->Add New->Label Track. Hit the << rewind button and type Control-B, this puts a label at the beginning of the recording. Move through the album side and put more labels at the middle of each song transition. It is a good idea to zoom in and put the label on a wave zero-crossing point to prevent clicks at the beginnings of individual tracks. If you zoom in, you can often see a change in wave patterns that is left over from the master tape splice. The recording should now look something like the first frame of the Audacity Images.

It is a good idea to listen carefully to the entire recorded album side. If the recording has any obnoxiously loud clicks and pops that weren't removed with the Click Removal step, Audacity can smooth them out. To smooth out a click, locate the offending waveform by playing and pausing, then zoom in multiple times until the click is visible. Select a small region around the click (< 128 samples) and use Effect->Repair to smooth out the waveform. Zoom out and play the area where the click removal was performed to verify the operation. Audacity is very forgiving, if you don't like the results of the click removal or make another type of mistake, Edit->Undo will reverse most operations. An example Repair operation is shown in the Audacity Images.

At this point, it is time to split the album side into individual audio files. Select File->Export Multiple, chose the desired export format such as WAV, select Split files: based on labels and Name files: Numbering consecutively. Click the Export button and click Audacity will render the individual track files. Audacity can create .mp3 and .flac files at this point, or that can be done at a later time. At this point, you exit Audacity and save any edit information if you think you will need to work on the recording later.

The same operations are performed on the B-side of the record. Your author likes to use a short BASH script to rename the Audacity-generated file names to his own name scheme. The track files are all grouped together in one directory, converted to FLAC format with the command FLAC *.wav. A meta-data text file is created with digitizing notes, track titles and any other information that you wish to save. Lastly, all of the files are played one more time to verify that there are no problems. The original album side tracks can now be safely deleted to reclaim some disk space.

With enough editing effort, it is possible to make a digital copy of a vinyl record that sounds better than the original. Performing all of the above steps on a large collection of albums is a big undertaking, but the reward comes in turning a hard to play discrete music library into an easy to play digital library.

For furthur information on this topic, see the followup article.

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