Not a complete discussionEdit
This article does not discuss Dynagroove in depth. As Dynagroove was a major attack on the very concept of high-fidelity sound reproduction, it needs a more-thorough description and discussion.
There are two obvious errors, as well. J Gordon Holt was never an audio engineer (unless you consider being a serious and experienced live-recordist being an engineer). He also retracted his criticism of Dynagroove's pre-distortion, based on RCA's claim that, though the distortion was optimized for a 0.7 mil spherical stylus, the correction did not increase distortion with elliptical styli.
This article should include (or have a link to) Gordon's complete anti-Dynagroove article, which is one of the all-time great pieces of audio journalism.
Mechanics of Dynagroove...Edit
As William mentioned above, this article could use a more in-depth description of how Dynagroove worked (but fortunately, it now has a link to Mr. Holt's famous article), because I'm really wondering how the low-level "mechanics" of Dynagroove worked.
For example: did the computers (or as RCA called them, "electronic brains", IIRC) used in the process actually digitize, analyze, process, and output the audio using software algorithms in conjunction with A/D & D/A converters, or was it a more simpler & passive process, such as the Dynagroove computer only controlling an outboard audio equalizer or filters operating in the analog domain? The former would be a feat that would practically be black magic considering 1963 computer technology, but then again, RCA seemed to have unlimited funding for new developments back then due to their corporate success, not to forget that RCA was also in the computer business at that time also.
As for the latter, I'm assuming the computer still would of had to do some analysis of the audio itself, whether by digitization/sampling or other means... Just the feat of signal sampling/acquisition was a feat that computers were barely beginning to do upon Dynagroove's debut (the Lincoln Labs TX-0 machine of that same era is the only one I know of upon Dynagroove's introduction that could fully do such, in fact, it was the TX-0's data acquisition features that led Dr. Thomas Stockham to perform some of the very first digital audio experiments on that same computer)... misternuvistor (talk) 10:50, 8 August 2009 (UTC)
- Dynagroove comprised a number of processes, only a few of which did anything to enhance the fidelity of the recording and its playback. The "good" things included the use of 30ips recording, and the pre-distortion of the groove to compensate for playback with a stylus of a finite radius (0.7 mil). The "naughty bits" were the use of compression, and worse, dynamic equalization (that is, a screwing-up of the original flat response) so that playback would be vibrant and alive at the low listening levels at home, especially during climaxes.
- A computer does not have to digital. Analog computers were in common use until digital computers got fast enough to make sampled-data modeling of physical systems practical. Any electronic device that performs modification to or calculation on a signal could be considered a "computer", and that's what RCA was using. Practical, reasonably priced DSP for audio applications was at least 15 years in the future. WilliamSommerwerck (talk) 14:53, 26 June 2010 (UTC)
- YES. tixo was a DIGITAL computer. Analog computers were well-known in the 1950s and 1960s and could handle multiple analog inputs and outputs -- they were used on spacecraft and many other realtime tasks such as chemical process control, missile tracking, etc. Nobody in 1963 had anything that could have handled processing of digital audio. If they had, they could have trumped Sony/Philips on the CD by 20 years! Hehehh. — Preceding unsigned comment added by 188.8.131.52 (talk) 11:10, 11 January 2015 (UTC)
Cutting Lathe Disk -> Electroplated Mother Master -> 2nd negatives -> Electroplated Metal Stamping MastersEdit
This is misleading, wrong as stated: "modify the audio signal fed to the recording stylus (chisel-shaped) of a phonograph record to make the groove shape". I'll change it to "modify the audio signal fed to a cutting lathe with a chisel-shaped cutting stylus, to make the recording from which production LPs would ultimately be pressed (hot-stamped)."
Does this help? ". . . to modify the audio signal fed to a cutting lathe with a chisel-shaped cutting stylus, to make the master disk from which production LPs would ultimately be pressed (hot-stamped). The intent was to boost bass on quiet passages, and reduce the high-frequency tracing burdens (distortion) for the less-compliant, "ball" or spherical-tipped playback cartridges then in use. With boosted bass, tracing demands could be reduced in part by reduced recording levels, sometimes supplemented by peak compression. This added top-end margin permitted selective pre-emphasis of some passages for greater perceived (psychological) brilliance of the recording as a whole. As in any compander (compression-expander), the program material itself changed the response of the Dynagroove electronics that processed it. But, because the changes were multiple (bass, treble, dynamic range) and algorithmic (thresholds, gain curves), RCA justifiably referred to the analog device as a computer." I hope others will also find time to contribute and extend this.
If I recall correctly, these technical improvements were all in place before RCA introduced Dynagroove:
- heated stylus (universal)
- high frequency pre-emphasis -- equalization -- so permit de-emphasis and surface noise reduction on playback. The curves were hotly contested -- AES, COL, RIAA. RIAA won out in the end.
- variable speed motors for radial advance to make variable-pitched grooves; the audio signal controlled the motor speed. This made the LP play longer by putting quiet grooves closer together. An advance tape playback head on the master tape gave the pitch control system advance warning, to overcome mechanical inertia.
- electronic bass cut to prevent large needle excursions (universal)
- half-speed, halved-frequency mastering for better high-frequency resolution (optional)
Dynagroove consists of a wider variety of signal pre-processing than extant RIAA equalization, based on listening to the master tape as it plays to affect the cutting lathe in more ways than variable pitch.
Nothing in this article discusses the fact that Dynagroove releases were pressed on a harder vinyl than typical later-Sixties releases. The "wooden" sound mentioned in connection with conical styli (often old osmium-tipped mono ceramic cartridges found on cheaper "hi-fis" from the 1950s) didn't carry over to the later elliptical or biradial styli common in the 1980s, and the vinyl was pretty darn durable compared to the completely-unrelated "DynaFlex" records released in the 1970s, which were necessarily on softer vinyl. All these years later, DynaGroove releases clean up better and sound remarkably brilliant even after more than fifty years, where other mass-market releases from the same time period haven't aged as well. It's worth discussing. — Preceding unsigned comment added by 184.108.40.206 (talk) 11:02, 11 January 2015 (UTC)