Does analog media force a dynamic on music? or Does Analog Media increase the dynamics?

Previously in the dynamics of music, we saw the difference between the dynamics of the medium and the dynamics of the music, as well as the effects of dynamic compression on the music in terms of distortion.
Today, we will approach another aspect, that of the impact of the dynamics on the recording on tape or vinyl.
The subject seems simple, we transfer the digital file on tape or vinyl and this one is reproduced with no or few modifications.

Before the arrival of digital, recording and mastering was done on tape, mastering was also done on tape and finally, the vinyl was cut.
With the gradual rise of digital technology, our methods of recording and editing music have adapted, sometimes incorporating a mix of digital and analog techniques.

Then came the full digital era, accompanied by the loudness war, meaning the desire to have a strong and powerful sound. As we could see in the previous article, the digital being capped with the 0 db, we can’t just raise the level, we have to raise the average level by crushing the peaks. This is the role of brickwall limiters.
This is an operation that can drastically reduce the dynamic range to DR5 or even DR3 for some tracks, but which is only possible at these extremes in digital.

If we try to transfer this music processed in full digital to an analog medium, we will realize that analog does not always like digital processing, and in particular the limitation of the dynamic range of the brickwall type. This is what we are going to experiment with in the examples below.

Digital to digital

Before analyzing the result of a transfer process from a digital master to an analog medium, we will define a digital reference that will be used for the rest of the test.

Using the example of the song So Far Away by Dire Straits, which has a DR (Dynamic Range) of 19, we will build a test file that will contain the same sound extract that we will reproduce by applying a dynamic range limitation that will cover several values from DR19 to DR7. This will allow us to measure the effects of dynamic range via different media.
To allow for more consistent testing, each sample is adjusted to have the same sound level, i.e. -20 LUFS.
Comparing the waveforms below with different levels of DR, we notice that as the DR decreases, the waveform becomes flatter and flatter, losing the peaks and details that characterize a high-quality waveform. This lack of detail usually results in a loss of clarity and sonic depth, making the music less enjoyable to listen to.

Duplicating this file digitally does not change the result of the compression and therefore the DR.
We can therefore define a curve representing the DR of the initial file on the horizontal axis and the DR of the final file on the vertical axis. As the copy of a digital file does not modify the file, a DR6 remains a DR6, as a DR17 remains a DR17, one thus has a line which connects the whole of the points. This line will be used as a reference. If during the transfer on an analog support one moves away from this line, that will mean that the dynamics were impacted by the analog support.

Digital to vinyl

Let’s start with the vinyl and the 8 DR values. After cutting and reading the vinyl we obtain the following curves:

We can see that the DRs are not identical to the original, especially for the lowest DRs. The values in the digital file went from DR19 to DR7, and after playing the vinyl, we get DRs from DR17 to DR10.
To see the difference, we plot the brown curve which represents the result of the measurements for the vinyl, with horizontally the DR value of the digital master file, and vertically, the DR read after the vinyl was burned. We can see that the vinyl has a DR that does not go down to DR7, and that it always remains above DR10 for the lowest values.

What happened?

Vinyl is an analog equipment that uses mechanical and electromagnetic properties for cutting and playing.
These mechanisms produce an phenomenon that has an impact on the way the sound signal level varies.
The Brickwall compression brings very strong limiting constraints, so strong, that the vinyl is not able to follow them.
The vinyl thus modifies the signal because it cannot follow the digital signal. This creates a new artificial peak where the original peaks have been the most planed.
The vinyl will therefore recreate dynamics, which is in fact distortion.
What to do to avoid this problem? You simply have to have a master that respects the functioning of analog with a DR of at least DR10.
Otherwise, it’s a double punishment. The dynamic limiter generates distortion as it has been shown here and the cutting of a compressed track will also generate additional distortion. We thus cumulate two phenomena of distortion by not respecting the analog constraints specific to the vinyl disc.
If we make a vinyl master with a DR higher than DR10/DR11 we reduce this phenomenon.
Another conclusion is that the measurement of the DR of an analog medium does not allow us to deduce the DR of the master that was used, especially for masters with a low DR.

Digital to tape

Another analog reference medium is magnetic tape. We realize the same test by recording on an analog tape with a TEAC A-3440 tape recorder and a RTM (Recording The Master) SM900 tape at 38 cm/s (15ips).
The digital file containing the same song with different DRs is recorded and then played back. The result of this playback has the following waveform:

We can see that the DRs are not identical to the original, especially for the lowest DRs. The values in the digital file went from DR19 to DR7, and after playing the tape, we get DRs from DR18 to DR10.
To see the difference, as for the vinyl, we plot the blue curve which represents the result of the measurements for the tape, with horizontally the DR value of the digital master file, and vertically, the DR obtained after the tape is played. We can see that the tape has a DR that does not go down to DR7, and that it always stays above DR10 for the lowest values.

Similar results for vinyl and tape

Vinyl or tape gives a similar result. To better understand this, we group the vinyl curve in orange and the tape curve in blue on the same graph.
The two curves are similar with an inability of analog media to accept a digital master with DRs below 10 without significant impact.
For the highest values (above DR14), we lose some dynamics, but this will have a smaller impact on the listening experience because of the high DR value.

The graph below represents a zoom on the 4 lowest DR values from DR10 to DR7 corresponding to the values of the digital file. We can see that the level limitation present on the digital file does not exist anymore, and that peaks have appeared for the vinyl and the tape due to the operating principles of vinyl cutting and tape recording process.

Conclusion

These examples demonstrate the importance of considering the characteristics of the analog medium when recording music that has been digitally mixed and mastered. Digital technologies allow a wide range of processing that may not be compatible with analog equipments.
To make this test, we used the same song with the use of a Brickwall limiter to get the different DR levels, which allows to better understand the waveforms of the different media. But, to be more exhaustive, the test was also done with other pieces of music of different styles, which gives in all cases a similar result with a minimum DR below which the vinyl or tape can not go down.
This shows the importance of creating a specific master for vinyl or tape which must preserve the dynamics to be perfectly retranscribed on the analog support, otherwise, we just degrade the original signal and the sound quality is not guaranteed anymore and we leave the world of high fidelity.

So we can wonder about the quality of the master of some vinyls that have a low recording level and a DR around DR10, was this vinyl made from a master compressed in dynamics, or is the music really like that?

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