Recording 78rpm records

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Grabando grabaciones a 78rpm


This tutorial outlines the steps that are needed to process the recording of 78rpm records with Audacity:
  • Ideally use a turntable with 78rpm and adjustable speed - though you can use lower speed dubbing.
  • Use a proper 78 stylus - you may want a separate headshell/cartridge.
  • Clean your records thoroughly.
  • Audacity setup - use the defaults: 32-bit float sample format and 44100 Hz Project Rate
  • Processing to adjust equalization and remove noise - and review results.
  • Export to WAV/MP3 in the normal way.

Workflow overview

  1. Clean the records
  2. Recording capture with Audacity
  3. Export a WAV as a raw master backup
  4. Remove any DC offset that may be present
  5. Apply the correct equalization (whatever that may be)
  6. Invert the RIAA equalization
  7. Correct the speed via the Change Speed effect
  8. Filtering to remove high and low frequency noise
  9. Clean up clicks and other random noise
  10. Fade in/out the track beginning/end
  11. Volume adjustments - normalization and compression
  12. Review and Export as WAV, MP3 or whatever
  13. Backup (you don't want to lose all this valuable work)

Use a special stylus or cartridge

You should not use a normal stylus (needle) to play 78's. The grooves on a 78 are significantly wider and deeper than the grooves on an LP, so a normal stylus will bottom out in the grooves and also bounce from side to side in louder passages. This will result in:

  • noisier, more hissy transfers
  • far less accurate reproduction of the music
  • damage to the stylus which will then impair its further use for LP's

Check the website or manual for your turntable to see if the manufacturer supplies a special 78 rpm stylus or cartridge. If not, search the web for "78 rpm stylus". A typical good starter saphire stylus size is 3mm, but watch how many sides you play as the stylus does not last as long as a diamond one. Typical groove widths on 78's prior to the 1940's range from 2.5mm to 4mm, there is wider variation with recordings from the 1920's and older.

Use a separate catridge
If you can afford it, use a separate cartridge from the one you use for your LPs. You need one which will support tracking at the heavier 4 or 5 gram weights that most 78 rpm recordings need. Ideally you should consider more than one stylus width if you are playing really old shellac records, because there was no standardisation of groove dimensions until late in the 78 rpm era. Again, search on the internet for advice.

Use a spare headshell
The safest way to swap between stylus types (if you are doing this often) is to use a separate headshell and cartridge. This way you will not be continually swapping the stylus on your cartridge - a risky procedure.

Workflow

Cleaning the records

Try to clean the 78s as thoroughly as possible before recording. This will save you time later as cleaning clicks/pops is hard work if you do it manually.

Do not use alcohol-based solvents on the shellac, use only water or water-based cleaners. You can use a bit of washing up liquid on a piece of velvet and warm water. Give them all a wash, in cool not hot water, and place them in the dish rack - then change the water and rinse thoroughly - finally rinse off with distilled (de-ionized) water, then drain and dry off with a dry piece of velvet.

Avoid wiping with kitchen paper or similar, as these are both abrasive, and can leave fibres stuck in the grooves. If you are in a hurry, placing the record on a piece of kitchen towel can absorb the majority of the distilled water, but avoid wiping the record.

Fairly obviously, do not play or record warped, cracked or badly chipped records. With a certain amount of patience, problems such as this can be repaired.
Warning icon You should never attempt to play a shellac disc when it is wet.

Capture

Work with Audacity set to a project rate of 44100 Hz and 32-bit sample format (these are the default quality settings). Working with 78s you are likely to be doing a lot of processing and you will need the headroom that 32-bit provides.

Record both sides of the 78 into the project prior to doing the processing. You can either Stop the recording after the first side using the The Stop button button or Transport > Stop and then use Transport > Append Record (or use SHIFT + R) to restart recording when you are ready. Alternatively you can pause by pressing the The Pause button button (or use Transport > Pause) at the end of the first side and then press the The Pause button button again once you are ready to record the second side. After recording you may find it helpful to zoom out to display the entire recording in the Audacity window.

You may prefer to work with a single side at a time as the noise levels may vary from side to side.

Export a WAV as a raw master backup

Export a single WAV for this recording at 32-bit float (not 16-bit).

To set Audacity to do this, in the export dialog click on the Other uncompressed files option in the export dialog, then click on the Options... button and select WAV (Microsoft) and 32-bit float. Once that setting is made you can select the file and folder location to export to and then click on the Save button to export the audio file.

Retain this WAV file as a maximum quality "raw capture" file that you can import back into Audacity later to start over (if you damage the project while working on it).

Remove DC offset

DC offset can occur at the recording stage so that the recorded waveform is not centered on the horizontal line at 0.0 amplitude. If this is the case with your recordings, see the Normalize page for how to use Normalize to remove DC offset and how to check if your Windows sound device can perform this correction automatically.

Equalization

When recording 78 rpm's, there is a problem that the pre-amplification built into any consumer-level pre-amplifier or USB turntable will be designed for vinyl records made from the 1950s onwards. This is because the pre-amplification not only provides the necessary amplification for the cartridge signal that is sent to Audacity, but applies what is known as "RIAA playback equalization" to it. This equalization is essential when playing records made from the 1950s or later, as it cancels out the high frequency biased "RIAA recording equalization" that such records are cut with, making them sound normal again. The problem is that most 78 rpm records were not cut with such a strong high frequency bias. They therefore sound dull if played through modern equipment that applies RIAA playback equalization.

So, to make a fully professional job of transferring your 78 rpm records, you should open Effect > Equalization in Audacity immediately after recording, and apply the inverse of the RIAA playback curve (see the next section). This will cancel out the unwanted RIAA equalization, after which you can apply one of the 78 rpm playback curve presets supplied with the effect. Note that the 78 rpm curves are generic. In practice, many different equalizations were used according to the record label or even the recording engineer. See 78rpm playback curves in the Audacity Wiki for a list of known equalizations used by different manufacturers of 78rpm records.

Inverting the RIAA curve

You can select the "RIAA" curve, then use the Invert button to invert it. Then apply that equalization to the recording

The Invert button provides other opportunities for correcting inappropriate equalization. For example, if you were recording an acoustic record on equipment that could only reproduce one of the listed "78" or "RCA" curves meant for electrical 78's, you could invert that curve, then apply the very different "acoustic" curve. The result would not be ideally accurate, but far better than not changing the equalization at all.

Lower speed dubbing - 33 1/3 or 45rpm

If your turntable does not have the facility to play records at 78rpm, you can use Audacity's ability to change the speed of recordings to record your 78 rpm records at either 33 1/3 rpm or 45 rpm. Since you are playing the disc slower than normal, tracking should not be an issue. The top frequency on a 78 will be around 8 kHz, and playing it slower will lower that to about 4.6 kHz.

Gale: On reflection, is the below div in the best place? Perhaps it should be in "Note on actual speeds"? There are several cases a) record really is a later electrical disc meant for 78 rpm but the fixed speed t/t is actually going at 75 rpm. b) Fixed speed t/t correctly goes at 78 rpm, 33 1/3 or 45 rpm but we have an 85 rpm record. In all these cases don't we need the formula to decide the change speed percentage to apply?
If your turntable doesn't have a strobe or speed adjustment, you can measure the playback speed in revolutions per minute (RPM) very accurately thus:
  1. Record the leadout of the final groove and select the distance between the recorded clicks in the Audacity waveform
  2. Measure the time taken for 10 consecutive revolutions (you can measure to 1/1000 of a second by zooming in on the waveform)
  3. Divide that time by 10 (for example, if you measured 8 seconds, dividing that by 10 gives you a resultant value of 0.8)
  4. Divide the resultant value into 60 (in our example, 60/0.8 gives us the answer that the record was playing at 75 RPM)

Record the track into Audacity at your chosen speed and then simply select all the track by clicking in the Track Control Panel and click Effect > Change Speed. In the "From" box choose the speed you played the record at (for example, "33 1/3" or "45") and in the "To" box choose the speed you want to convert the recording to (that is, the speed it should be played at according to the label).

Note that you should reverse the RIAA equalization before changing speed - now the transfer is "flat". Then change the speed. Then apply the "proper" 78 rpm equalization (whatever that may be). So the workflow steps for this part of the process are:

  1. Record the 78 at 45 or 33 1/3
  2. Apply the Inverse RIAA EQ (to make it like a "flat" recording)
  3. Change the speed to 78rpm
  4. Apply appropriate EQ for what the 78 was recorded with

Note on actual speeds: With the early clockwork turntable mechanisms the rotational speed was rather approximate and manufacturers produced records in the 70 to 90rpm range with 78 being the most commonly accepted “standard”. Many discs had the speed stamped on the label and they depended on the early players which had a speed control. With the introduction of the synchronous AC motor, for detailed technical reasons, the standard was changed to 78.26 rpm. See this website for details: http://www.videointerchange.com/vintage_78s.htm

Stanton T-series USB turntables still offer 78rpm working, and helpfully they have a wide speed adjustment range. If you know exactly what speed your records should spin at you can find a strobe disc on the Internet and print one out with exactly the right spacing of bars. One example site is: http://www.78rpm.com/rescat/strobe_info.htm.

Filtering & noise removal

Noise on 78's is complex, and relatively high in level. You will need to try to reduce some of the different types of noise in separate passes.

Noise removal

Over the years your 78s will undoubtedly have received scratches and wear, which will result in clicks, pops and crackle. Audacity does have tools for click removal and noise removal - but there are better tools than Audacity for removing these, although "Effect > Repair" works extremely well for removing single clicks.

Some of these tools do cost some money but most have free-trial periods. Goldwave is often recommended by Audacity users, as are Brian Davies' ClickRepair and DeNoise packages.

Filtering

  1. Make sure you have set the Audacity Default Sample Format in the Quality Preferences to 32-bit float (the default) because you are probably going to do a fair bit of processing, and some of the filters appear to work better with 32-bit input.
  2. Then run Effect > Low Pass Filter to remove high frequency noise - set the cutoff frequency to suit the vintage of the record. For recordings from the 1940s or later set the cutoff frequency at 9 kHz or 10 kHz; for electrical recordings (1926 to 1939) about 8 kHz, and acoustic recordings (before 1926) about 7 kHz. Use a rolloff of at least 12 dB per octave; 24 dB per octave could probably be better. Listen to the result to make sure the sudden cutoff of high-frequency noise does not sound too artificial.
  3. Then deal with the low frequency noise - select a "noise sample" from the current audio track (that is, a section of the recording that is surface noise only) and copy it to a new track. Use Analyze > Plot Spectrum to see the frequency content of the noise. Use the low pass effect on this noise sample to isolate the lower frequency noise, (for a very rough and ready setting, try a rolloff of 12 dB per octave at a cutoff frequency of 1000 Hz). Then open Effect > Noise Removal, select the low-passed noise sample and choose "Get Noise Profile". Finally, select the original track, open Noise Removal again, choose the slider settings and run the effect.

An alternative, simpler, method for dealing with low frequency noise is to use Effect > High Pass Filter to filter out frequencies below 20 Hz. It's amazing that the waveform can display these sub-sonic frequencies, usually deficiencies in the cutting lathe during the original recording session.

Click Removal

Remove any clicks and pops from the recording using Effect > Click Removal

Alternatively you can use third party software as discussed above.

Fade In/Out

You may wish to more cleanly Effect > Fade Out the track end and Effect > Fade In the track beginning. Normally the fade out should be longer (typically a few seconds), and the fade in, if required, quite short (typically a fraction of a second).

Consider using Effect > Studio Fade Out instead of the linear Fade Out. It applies a more musical fade out to the selected audio, giving a more pleasing (more "professional studio") sounding result.

You may also get a more musical fade-in by applying Effect > Fade In multiple times to the selcted audio; three times is a good guideline. This will produce a shaped, curved, fade rather than a linear one.

Normalization & Compression

As a final step you may wish to adjust the loudness of you recording.

Normalize

You can use Effect > Normalize to bring the maximum volume of your recording to a specified level - we would suggest to around -3.0 dB. Audacity's Effect > Amplify can also be used for the same function. Normalize has the advantage that it can be optionally set to adjust for channel imbalance.

Compression

As a final step, to increase the perceived loudness and density of the recording, more advanced users can perform compression on the recording. You can use Audacity's Effect > Compressor to do this.

There are also some alternative free compressors available as separate downloads which work well with Audacity.

Review & Export

Then review the track to decide if any further treatment is required, or if you need to restart from scratch. If you are happy with your work than your project is ready for Export to WAV and/or MP3 and similar.

Backup

Don't forget to backup your finished audio files as you will not want to lose all that hard work; ideally at least two separate copies on separate media. You may wish to consider also backing up your original capture masters as WAV files, then you can always come back to the raw recording later and re-process it if you need or want to.

Don't expect miracles with badly worn records. The process can be very frustrating and the results can be disappointing. Avoid aggressive denoise. The artifacts are usually worse than the noise. Some users like to leave a little surface noise in their transfers (they are 78s after all!). Declick and equalization are the most important steps in the process. Learn to read the waveform. Sometimes an equalization can increase the amplitude of some frequencies to a clipping level, so consider reducing the amplitude slightly before equalization.

Links

|< Tutorial - Copying tapes, LPs or MiniDiscs to CD

>  See also tutorial on: Sample workflow for LP digitization

  • See 78 rpm playback curves on our Wiki for an extensive list of 78rpm playback equalisation curves and a Nyquist plugin that can generate XML files from these curves for use in Audacity's Equalization effect.
  • Brian Davies offers a free Equalizer program that simultaneously applies the proper Inverse RIAA curve, corrected for the different playback speed, and a choice of 78 rpm EQ curve.
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