In the vinyl vs CD debate, I am often asked why vinyl sounds so good and why compact disc (CD) was created, if vinyl was a better medium in the first place? To put this another way – the question might be: “Vinyl vs CD – is vinyl higher resolution?”
This is not a simple question to answer, there is a great deal to consider. What makes a great medium? What makes a better medium? A bad record played back on a bad turntable sounds bad, full stop. But the potential is there with vinyl, with good pressings and great playback equipment, to sound superb, better than CD, better than any MP3 can ever sound and better than even high-res digital. Even with my super-specced up Musical Fidelity Tri-Vista Class A Tube DAC, a good vinyl pressing of the same recording will often sound better – smoother, more relaxed.
Note that we need to consider what metrics we are using. I’m specifically talking here about resolution, NOT noise, or pitch accuracy. Based on those two metrics, CD has the edge and everyone in audio knows that. But one can make a strong argument for the fact that resolution of fine detail, of nuance and of subtle micro-dynamic and high frequency information that is lost in the digital sampling process, is more important in realistically reproducing music.
You might think of resolution as the ability to discern fine detail, to accurately portray two sounds of slightly differing levels. The simple answer is that, as a medium, vinyl is capable of higher resolution than CD, but we need to examine this in a little more detail.
Looking at bit depth first, CD has a technical resolution of 2 levels, 0 or 1, raised to the power of 16, the number of bits in each digital word and the bit depth specified in the Red Book standard. This gives us 2^16 or around 65,536 possible amplitude levels for any sample. Simply stated, any tone can have 65,536 volume levels.
Sample rate determines the number of times the digital system captures a waveform, per second. For CD, this was set at 44,100 samples per second. This means that continuous tones in real music are chopped up 44.1 thousand times a second and joined together.
Think about bit depth and sample rate – both are finite and limited to a set number of steps or samples, in a given time or for a given sample. Analog systems are not limited in this way at all. Vinyl for example has an infinite number of possible volume levels, within the dynamic range of the medium. Likewise, there is no sampling of waveforms in analog playback, hence high and low-frequency waveforms have the same amount of detail possible in them.
Think for a moment about a high frequency signal, like the sound of a cymbal being hit. This sound will have a range of harmonics and overtones that extend either side of the fundamental. Some of these harmonics will extend to over 20 kHz. Vinyl replay systems allow for the playback of frequencies over 20 kHz, whereas CD does not. This is due to the limitations imposed by the 44.1 K sample rate.
More importantly than the limitation in high frequency response, the 44.1K sample rate means that a 20 kHz signal will be sampled approximately two times per waveform! If you look at the complex shapes and curves of a sine wave for example, you will quickly see that no two points or samples on this waveform are going to allow you to accurately represent it during playback.
This is a fundamental and acknowledged limitation in the resolution of compact disc. This may also explain why most of the criticism of the Red Book format seems to be around high frequency performance, hardness and glare.
There is no escaping that 16 bit 44.1K digital was the best they could roll out in 1982. These days however, 32 bit, 384 kHz digital is where we are at, in terms of playback. The problem is finding sources – recordings and masters – that have that amount of detail in them. They are virtually non-existent. Unless you have the analog master tape of course. Then you have a source with resolution higher than even 32 bit 384 kHz digital. Can you see where this is headed?!
So, CD is technically less resolving of fine level detail and high frequencies than a good vinyl system, but herein lies another caveat. Vinyl is capable of superb technical performance in some areas, but is itself limited in others.
Typically pitch and speed accuracy of vinyl playback is an order of magnitude worse than CD. Turntables suffer from additive speed inaccuracies, meaning that off-centre records and pitch issues with the mother and stamper vinyl are added to playback inaccuracies caused by the record player itself.
Dynamic range of vinyl cannot compete, on paper at least, with that of compact disc. Vinyl offers a usable dynamic range – the difference between the softest and loudest sounds that can be accommodated within the medium – of around 70 dB. Compact disc offers a dynamic range of around 90 dB. The scale is logarithmic, so 20 dB more is not 20% more, it’s much, much more!
Compact disc also offers a technically flatter frequency response which is not subject to the resonances and wiring effects of magnetic cartridges of a turntable. There is also much less distortion, again on paper, than vinyl systems are capable of. The CD player itself theoretically introduces much less in the way of noise and distortion than a record player does.
AND YET, we have the curious situation where, given identical recordings, made from the same master, played back from vinyl and CD pressings from the same era, the vinyl recording very often sounds better! Isn’t this interesting? The conclusion one must reach is that, despite the shortfalls in dynamic range, pitch accuracy and distortion, vinyl’s inherent higher resolution is the key to why it sounds better.