This can involve anything from turntable-based, vacuum equipped, professional cleaning machines that use proprietary chemical formulations and cost four figures, to improvised methods involving home-made equipment and/or cleaning solutions consisting of isopropyl alcohol, distilled water (unpurified tap water should not be used, as it will probably leave limescale deposits on the record surface) and a surfactant to aid drying.
More often than not, a magnetic cartridge and stylus combination is used because of its superior sound characteristics and signal-to-noise ratio over other pickup systems.
The output of a magnetic cartridge is of a very low volume (typically ≈5mV) so the signal must be amplified with a preamplifier to bring it up to line level before being routed into the line-in jack of a computer's sound card.
[1] The software used to process the resulting digital files ranges in price from thousands of dollars to freeware.
Moreover, some applications are designed for easy fast processing with the push of a few buttons, and others require a time-consuming but perhaps more exact manual approach to editing out damage.
First, there is the constant background noise that goes on through the entire recording that is the result of the sound the stylus makes in the groove when no music is playing, plus whatever subtle drones are generated by the electronics involved (such as turntable rumble or 50/60 cycle hum).
The software must filter this kind of click-pop damage conservatively, because a click or a pop can look very much like a legitimate percussive effect, such as a light snare drum rim-shot.
These residual clicks may then be corrected by attenuation (reducing or muting the volume of the anomaly), interpolation (replacing the waveform "spike" with a less offensive section, either a straight line—linear interpolation—or a calculated facsimile deduced from what the wave looks like on either side); substitution (replacing a damaged waveform segment with a similar section from elsewhere); channel substitution (where damage occurring in only one channel of a stereo waveform is replaced by a similar good segment in the other channel); and simple deletion, which is usually not noticeable for small samples.
How the records are handled and the equipment on which they are played as well as the manufacturing process and quality of original vinyl have a considerable impact upon their wear.)
However, anyone can do this using a standard record player with a suitable pickup, a phono-preamp (pre-amplifier) and a typical personal computer.
Once a recording has been digitized, it can be manipulated with software to restore and, hopefully, improve the sound, for example by removing the result of scratches.
Paper sleeves deteriorate over time, leave dusty fibers, and produce static that attract dust.
100% poly sleeves produce less static (thereby attracting less dust), are archival, and are thinner by nature so they minimize pressure on the LP jacket seams.