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Overview

I've spent the last several years putting together enough material for a vinyl LP. By last December (2018), I had all of my songs mixed and sent them to a mastering engineer who prepared them for vinyl. The mastering engineer will roll off very low and very high frequencies, remove digital limiters (which make the songs louder for digital media), remove sibilance, and create two final audio files - one for side A and one for side B. Next, I sent the vinyl masters to a lacquer cutter, who transfers the master tracks to a acetate coated, aluminum disc by literally cutting a wave form into a virgin lacquer disc, which looks like a very thick and heavy 33" record. The lacquers (one for each side) are sent to a pressing plant, where they are converted to a pressing disc (essentially a negative of the lacquer) from which the final records are pressed.

Quality Control In The Vinyl Production Process

Quality control starts in the recording phase. Microphone placement, microphone level (or loudness), and background noise are factors the sound engineer controls to obtain the purest, sweetest tones from all instruments. Further, in most modern studios, audio (or, program material) is recorded in digital format. Sampling rate and bit-depth must be sufficient so as to "fool" the listeners ear into hearing a continuous playback waveform. Commonly, 24 kHz sampling rate is recommended with the greatest bit-depth possible (which is generally 12 or 24 bits). I used an Audio Technica AT-2020USB with a sampling rate of 16 kHz into an iPad. Garageband on iPad saves at 12 bits. However, the bit depth was increased via the desktop version of Garageband.

After program material is recording, a producer or mixing engineer takes the raw tracks and creates a pleasing and cohesive song. In practice, this is done through editing, adjusting EQ, panning, and adjusting effects, such as reverb. The mixing engineer also produces a final version of the song (also called a "bounce") ensuring that there is no "clipping" (distortion due to a song being too loud), and that the EQ, volume, and panning of the instruments suits the final media format. For example, on vinyl, high frequencies (such as "s" sounds and cymbals) can easily cause distortion, while low frequencies can cause skipping if they are not in phase (that is, low frequencies should be panned in the mix together). Finally, the producer or mixer arranges the songs so that the length of time of each side does not exceed the vinyl format. The songs on "On The Edge Of Eternity" were all de-essed to reduce sibilance. I further used a low cut filter at 40 MHz. I also rolled off the high frequencies. In short, the mixing was done with the vinyl media in mind.

The mastering engineer typically creates a digital master first, followed by a vinyl master, if needed. Digital formats today exploit limiters and compressors to make the program material as loud as possible. However, vinyl has strict limits to the volume of program material. Cut into the groove of the vinyl is a literal representation of the sound wave. In mono mixing, volume is represented by the lateral (inside to outside) swing of groove. If volumes are too loud, the needle swings too much and has a greater probability of mistracking, or jumping out of the groove (a.k.a., skipping). I used MysteryRoom Mastering for digital and vinyl masters.

The lacquer engineer has a great amount of control over the final process. She takes the program material and translates it into a wave form that will fit onto one side of the record without mistracking. Since the wave form is physically represented on the album, controlling its playback is done through physical dimensions: the depth of in-out wave swing, the depth of the groove, the amount of uncut record between the grooves (called pitch). By adjusting the wave amplitude (the in-out swing), she  ultimately controls how much program material can fit on one side of the record. The groove depth affects how well a needle tracks, or sits in the groove. I used Well Made Music for lacquer mastering.

In the pressing phase, the engineers create a master from the lacquer and press. They also listen to the first pressings and subsequent pressings at regular intervals. This ensures the master is not degrading. At this step, problems with the playback typically mean an earlier step was incorrect and one must go back in the process to correct it. Gotta Groove Records pressed the records.

Quality assurance does not end once the record is made. Vinyl is susceptible to warping. Thus, storage can degrade the audio quality. Dirt in the grooves causes random noise (clicks, pops, and static). Finally, the turntable itself can cause mistracking.  After all, the needle itself is literally scraping the surface of the record. If the forces are not balanced, the needle can damage the groove. For example, too light of a tracking force (downward pressure) and the needle will jump out of the groove at the slightest disturbance (insufficient tracking force becomes more problematic with stereo rather than mono, since the needle moves both side to side and up and down for to encode stereo). Also, too much lateral force (outside to inside force, called skate) will cause excessive skipping. Mid to high quality turntables allow the user to control the downward force and lateral (in-to-out) force of the needle. For best sound reproduction, and to prevent records from wearing, a turntable must be properly calibrated. Other factors, such as needle shape, affect sound reproduction, but should generally not damage a record on a properly calibrated turntable.

Mistracking With "On The Edge Of Eternity"

On some turntables, specifically less expensive models (such as Crosley styled, suitcase players, or potentially other turntables without adjustable tracking force and anti-skate), this album may not track correctly. Essentially, the audio will skip. I spent almost two months investigating the problem with my mastering, lacquer, and pressing vendors. The exact reason of the mistracking is not known. However, in the investigation, I believe some were ruled out. Further, the issue is not seen on properly calibrated turntables. In short, I think the problem could be due to the loudness of the master lacquer. A louder master causes more side-to-side movement of the needle, perhaps more than a cheap turntable can handle. Of course, that is only a guess, though it is hopefully educated.

In the end, some mysteries are not to be solved...