LP Records aka "vinyl" - fact and fiction

Some common misunderstandings and misconceptions clarified or debunked.
Analog vsdigital, record vs cd, valve (tube) vs solid state (transistor) and so on.
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LP Records aka "vinyl" - fact and fiction

Post by superphool » Sat Aug 24, 2019 7:10 pm

Records - LPs or "vinyl" as the present fad names them - are and have always been a very contentious issue quality-wise, especially when the quality of these is compared to the quality of CDs and other digital recordings.

This is probably the single commonest audiophile analog-vs-digital argument.

In reality, there is no contest - from a purely technical perspective, CD audio is simply better. Newer digital audio formats can be much better still.

Note that in our articles we stress the technical, objective, view. Subjectively, what "sounds best" is as always a matter of personal taste, and especially with LPs, the overall preparing, handling and finally placing the stylus on the disc is as much part of the overall experience as the sound.

The arguments for and against each type of media:-

Analog discs - LPs aka vinyl:

A groove representing a sound waveform is the earliest type of sound recording, and from the earliest purely mechanical foil or wax cylinder systems, through Bakelite discs and on to vinyl LPs, the process went through a phenomenal amount of development, with pinnacle being a disc and stylus system that under the proper conditions could reproduce frequencies into the far ultrasonic range, vastly above human hearing.

LPs, played on really good equipment, are pretty good; compared to the first stylus-and-groove systems they are amazing - but they are not perfect.

The low-end frequency response is limited by the playback arm having to follow the disc surface by its own weight and inertia.
As frequencies get lower, the whole arm moves with the groove rather than the stylus moving relative to the arm.

The surface of the plastic within the groove is not absolutely perfect and free from imperfections.
That means there is some (admittedly very low) level of background noise with even the best and most expensive turntable, arm, cartridge and stylus combinations.

Rumble, wow and flutter:
If the bearing system of the turntable is anything less than perfect, mechanical noises can be transmitted from that through the disc and picked up by the stylus, resulting in unwanted noises.

Any imperfections in the mechanical drive that rotates the turntable will cause the playback pitch to vary in proportion to the speed error - causing "flutter".

Likewise, if the disc centring is not perfect about the rotational axis of the turntable, the pitch of the playback will vary up and down with each rotation of the turntable - known as "wow".

Digital - CD quality audio:

The original audio is converted to digital (a stream of numbers) by "sampling" the audio waveform 44,100 times per second, or some multiple of that.

It is converter to 44.1 KHz with 16 bit samples (giving 65,535 different possible voltage levels for each sample on each channel), has extra data added to allow for some level of data error correction if a disc is less than perfect, and finally stored as tiny pits in a metal layer within a CD.

When played back, the CD player converts the recorded data back to the 16 bit, 44.1 KHz, stereo, audio format.
There is no compression or data loss involved in the overall system, unlike such as MP3 or Bluetooth digital formats, which use "lossy" compression.

The digital audio is finally converted back to analog, either in the CD player itself or in an amplifier or computer etc. that is is connected to via a digital link.

As the reconstruction from digital is a kind of "join the dots" process with the sampled values being sent out sequentially and the resulting steps smoothed out by filtering out anything above around 20 KHz, the reproduction of the original analog signal that was digitised is not quite perfect.

That is a key claim of LP / vinyl fetishists, why LPs are supposedly better.

However: The noise level inherent in the mechanical reproduction system has a theoretical best-case limit of around -70 db compared to the maximum signal level the disc can reproduce; with real world equipment this is considered to be somewhere from -55 to -65 db at best.

The distortion cause by digitising and then reproducing the analog signal with CD Quality" digital audio is roughly -96 db, compared to it's maximum signal level.

So, the digital distortion is far, far lower level than the analog disc noise. CD gains around 35 - 45 db better signal-to-noise ratio.
And, the low frequency response is really only limited by the amplifier and speakers used to reproduce the audio; the CD standard has a flat frequency response down to 20 Hz, rather better than typical LP disc & turntable combinations.

And note that the CD Audio standard is now around 40 years old. Newer digital audio standards use more bits per sample, so even better signal to noise and lower distortion resulting from digitisation, plus higher sample rates, giving possible frequency response far beyond what any LP system could ever achieve.

Many Blu-Ray movie discs use digital audio standards far beyond CD quality and quite a few music albums have been released as Blu-Ray audio discs.

For more and independent information on LPs / vinyl vs CD audio, see the Vinyl myths page on the Hydrogen audio site here:
http://wiki.hydrogenaud.io/index.php?ti ... hs_(Vinyl)

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