Stephanie G. Mathis Ever since the advent of the compact disc and the widespread consumer access to digital audio that it brought, people have debated whether digital audio could ever adequately replace its analog predecessors.
The discussion about digital audio formats has intensified as the number of downloads and streams has grown. Many “purists” who are diehard analog fans lament the lack of soul in digital audio formats.
But I am not here to argue for or against the purists. Let’s instead explore the requirements for a scenario where digital sound would be equal to analog sound or even surpass it. The answer to “Could analog audio ever be outperformed by digital?” is actually twofold.
Hold on to your hats because we’re about to delve into the worlds of math and sciences!
Continuous vs. discrete signals
It’s crucial first to understand the differences between digital and analog sound.
Analog Sound uses a constantly changing audio signal. This means that the pressure variations fed to a loudspeaker from its signal are (at least in theory) an exact replication of the original sound.
Digital Sound is composed of discrete audio steps that are changed quickly enough to give the impression of a continuous sound when sent to a speaker. It is similar to how a video is created from a sequence of still images, which are cycled quickly enough to create the illusion of motion.
In effect, digital sounds attempt to approximate the continuous sound of analog. If the discrete digital steps are changed frequently enough and the levels of the steps are close enough together, the resultant approximation can be as close as our ears and brain will believe to an analog continuous signal.
Signal Resolution
Sample rate is the speed at which discrete steps are cycled in a digital audio signal. The total number of possible steps is known as the bit depth. This determines the difference in levels between each step.
For example, a CD audio file has a sample rate (Hz) of 44,100 Hz. (Hz is Hertz, the unit used to measure how often an event occurs each second.) This means that it creates 44,100 audio signals every second.
Analog media
Consider the vinyl record, analog’s most popular format. Vinyl records have certain material properties that determine their behavior, capabilities, and limitations, just as a turntable or record player has its abilities and limitations.
Vinyl records are usually made from semi-rigid PVC or polyvinyl chloride. The grooves are carved with an analog signal, which deforms the PVC in response. The needle on a record player is used to “read” the microscopic deformations and reproduce the original signals that created them.
Vinyl material PVC has a minimal size associated with its molecular and crystalline structure. This means vinyl’s deformations within record grooves are limited by its physical properties. Therefore, it is not able to create a perfect continuous signal but only an approximate version of it, limited by the vinyl material’s properties.
The vinyl chloride monomer, also known as the chloroethene molecular structure of PVC, is the minimum size for a groove in the record.
Vinyl records with high-resolution signals
Vinyl records are made from PVC, which has a density of around 1.3 grams/cubic centimeter. Vinyl chloride monomers (one molecule chloroethene) have a mass around 1.07×10 22 grams. This means that there are approximately 12.1×10 21 chloroethene molecules in a cubic centimeter space of vinyl LPs. We can estimate that the smallest piece of material, which is one molecule in thickness, has a thickness of 4.4×10 8cm.
The groove on a vinyl disc can be cut up to a maximum width of. 008cm, where one half is associated with the left and the other with the right channels. The needle can detect a maximum change in position for each channel up to. 004cm.
The maximum number of molecular slices that we could remove to achieve the maximum change in groove size for each channel is 91,000. This is the same as bit depth in digital audio signals.
The groove length is approximately 45,000cm on each side. If the groove is filled to its fullest, it will take around 1400 seconds to play back at the correct speed.
During the playback of a side of LP, the needle passes over approximately 730 million individual chloroethene molecule molecules per second. This is the same as the sampling rate in digital audio signals, which tells us how close we can get to the audio signal’s original change in time.
Signal resolution and comparison
With some estimation methods, we can see (oversimplified but still valid) that a vinyl recording produces the same discrete sound approximation as a digital audio signal with at least 16-bit depth and 730 MHz sample rate.
Don’t get too excited yet. You can’t just convert all your digital MP3 and WAV files to 17-bit audio files with 730MHz and claim that they are as good as vinyl. To meet this standard, your approximation must maintain its highest resolution, whether it is analog or digital.
The majority of analog equipment can do this, but most digital equipment cannot. As soon as you use a digital technique that is less accurate than LP minimum standards, the accuracy of the approximation will decrease. Up-conversions to higher resolutions will reproduce your most accurate approximation from your production process.
Even though 24-bit and even 32-bit digital recordings can be easily obtained today, they are still far inferior to the bit depth of vinyl. The best digital recording gear available to the majority of people today only has a sample rate of up to 192kHz. This is nearly 4,000 times slower than the sample rate vinyl would require.
The answer to our first question is yes, digital sound can perform better than analog sound. Modern digital sound has greater technical potential in terms of bit depth but falls short in sample rate.
Analog flavor in the production chain
Second, how does the product sound? Let’s say that in the future, the technology will allow digital audio to reach the 730MHz sample rate or higher we calculated, which is required to match vinyl’s effective sample rate. Would digital audio sound better or worse than analog at that point if digital audio had the potential to match or exceed analog audio’s technical potential?
In order to answer this question, it is important to understand that the sound of vinyl comes from the analog equipment used for recording and mixing and the sonic flavor.
In recent years, digital modeling has improved dramatically and is now capable of matching many classic analog sounds that people like. The technology must also allow the maximum resolution of sound to be maintained throughout the entire process.
It would appear that digital audio could meet or surpass the technical performance of analog sound, both in terms of sound quality and sound preference, if it can achieve and maintain the same resolution for the entire production cycle and if analog gear or digital models of analog gear are used to create the desired sound flavor.
Practicality
Imagine the entire process in digital format, at or above the technical standards that match analog, and using analog modeling effects. The size of a digital file at this level for a three-minute recording would be nearly 18,000 times larger than a CD-quality WAV of the same duration. This means that a single short song could have a file size of over 500.
Vinyl is still the best option despite the massive file size problem and the fact that digital sampling rates are far below the standard analog sound.
It’s only a question of time before digital sound surpasses analog sound.
