Talk:Dynagroove

message: 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.
WilliamSommerwerck (talk) 13:46, 1 January 2008 (UTC)
thread_title:  Not a complete discussion 

message: 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. 
This isn't the scholarship we need; I'll try to get back to this.  I hope others can find time to fulfill the other good suggestions above. 
Jerry-VA (talk) 20:37, 4 February 2014 (UTC)
thread_title:  Cutting Lathe Disk ->  Electroplated Mother Master -> 2nd negatives -> Electroplated Metal Stamping Masters 

message: 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 108.51.203.80 (talk) 11:02, 11 January 2015 (UTC)
thread_title:  Harder vinyl