User:Mjb/Most vinyl contains digital recordings
Did you know?
Vinyl records mastered since c. 1978 may not be fully analog.
I occasionally hear or read someone saying they love vinyl because the music on it is fully analog. But that's not always true.
Since the late '70s, even if the music was recorded and delivered to the mastering house entirely on analog media, there's a good chance digital gear was used at some point in the mastering chain.—That is, the audio signal stored in the groove of most records is likely to have been converted from analog to digital and back as an inevitable part of the cutting process.
On early, manually controlled lathes, any adjustments to the way the groove was being mechanically cut were made by the engineer as needed, turning dials and flipping switches based on notes prepared ahead of time. On the newer lathes this was partially automated: the control system "reads ahead" so it knows what's coming and it makes certain adjustments automatically. To do this, the control system is fed a live audio signal (which could be analog or digital, doesn't really matter), while the cutting head itself gets a delayed version of that signal, half a record rotation behind.
Some control systems were fed both signals by a special tape player with two heads (e.g. the Studer A80), but once digital technology became available around 1978, a typical lathe control system used a single-head player (or whatever analog source you wanted to use). A PCM converter digitized that audio and fed it to a digital delay unit to generate the delayed signal. The cutting head ultimately received an analog version of the delayed signal, as produced by a DAC in the delay unit or immediately after.
In the '80s, a normal setup included a Sony PCM-1610 to do the digitization, and a Studer DAD-16 or Ampex ADD-1 to do the delay. (This was an upgrade from the first 14-bit Studer models!). These operated at 16-bit, 48 kHz maximum. Those old converters also had quirks & flaws, so 16-bit performance was not always easily achieved, but it was still considered an improvement over analog. Converter technology and performance did not stabilize until the mid-1990s, by which time the lathe and control system manufacturing was dying out; any improvements to a particular mastering house's control systems since then are most likely customized just for them.
There is also the question of what recording was being fed to the control system. Very likely it was a sonically processed production copy made by the mastering house. The processing may have been done in the digital domain, or the destination may have been digital. No guarantees.
Well into the '90s, before DAT and CD-R became affordable and commonplace, recordings which weren't on analog reels were typically delivered to mastering houses on digital videotape. Ideally these masters, as well as whatever digital production copies may have been made, would all be at 16/44.1 or 16/48, and no conversions would have been done where not necessary. However, the PCM adapters used in the recording of these tapes were sometimes run in a 14-bit mode so that more of the bandwidth on the videotape the audio was stored on could be used for error correction.
In my opinion, in the '80s and beyond, it is safe to assume that the mastering houses under contract to the major labels routinely used digital gear at some point in their mastering chain. Any lacquer cuts made during that time are unlikely to be fully analog. There are some engineers who do not use delays—e.g. Mike Marsh prefers to make adjustments manually, as he mentions [ http://www.mikemarshmastering.co.uk/vinyl_info.shtml on his website]—but he is probably an exception rather than the rule.
References
- a 1985 profile of Europadisk
- The cutting process as described by Denis Blackham in the book Island Records 1962 - 1977
- Studer DAD-16 manual which has specs and diagrams
- discussion of '80s PCM converter flaws
- https://www.lathetrolls.com/viewtopic.php?f=11&t=4494#p27575
- http://www.preservationsound.com/?p=7690
