Hello There,
Is anyone out there familiar with RCA's Dynagroove of the 60's??????
What was going on and can it be somewhat compensated for when listening to a Dynagroove disc. ?????????
Thank you
ormandylives
-
ormandylives
- Posts: 7
- Joined: Tue Mar 04, 2008 3:08 pm
- Location: Massachusetts
RCA's Dynagroove..What was it ?? Why did it sound awful
Hello There,
Is anyone out there familiar with RCA's Dynagroove of the 60's??????
What was going on and can it be somewhat compensated for when listening to a Dynagroove disc. ?????????
Thank you
ormandylives
-
Perisphere
- Posts: 39
- Joined: Thu Nov 10, 2005 9:53 pm
- Location: Mountain Home, Arkansas
Dynagroove was designed to do two things: Overcome the dynamic range limitations of domestic console stereos of the era (it was introduced in c.1963) through manipulation of the frequency balances of sounds depending on the dynamics and loudness of them (somewhat compressing bass and midrange more than the top end) and reducing inner-groove distortion (by way of introducing a degree of distortion opposite in polarity to the pinch distortion that inner grooves suffer from worse than any other).
AFAIK these processes were introduced at the disc cutting stage. I think the first processing (the dynamics stuff) was discontinued around 1967. The latter is what must be what was used for some years afterward where Dynagroove is mentioned on the backs of some RCA LP sleeves into 1968, even though it was not shown on record labels after the introduction of the orange labels. (The first album from Brotherhood, RCA LSP 4092, was originally issued on orange labels, but has a small Dynagroove blurb on the back of the sleeve, for example.)
The pre-distortion was designed with the limitations of conical styli in mind.
Hope this helps!
AFAIK these processes were introduced at the disc cutting stage. I think the first processing (the dynamics stuff) was discontinued around 1967. The latter is what must be what was used for some years afterward where Dynagroove is mentioned on the backs of some RCA LP sleeves into 1968, even though it was not shown on record labels after the introduction of the orange labels. (The first album from Brotherhood, RCA LSP 4092, was originally issued on orange labels, but has a small Dynagroove blurb on the back of the sleeve, for example.)
The pre-distortion was designed with the limitations of conical styli in mind.
Hope this helps!
The RCA Dynagroove process was originally intended to describe the signal processing that was newly developed. The name Dynagroove later came to imply the changed record profile and record weight which were originally termed "Dynaflex". Yes, as has been mentioned here already, Dynagroove was primarily a "predistortion" of the signal sent to the cutter. This was done by the use of an analog computer (remember this was 1963, before digital computers were commonplace or fast enough to do this work) which was called the "Dynamic Recording Correlator" or DRC. RCA Broadcast Division in Camden, NJ manufactured the DRC to a design developed by RCA's Princeton research laboratories (known then as the David Sarnoff Research Center, or DSRC) from a design by Dr. Guy Woodward. If any of you is interested in the details of this contraption, you can read the paper written about its development and published in the Journal of the Audio Engineering Society (JAES). It will be in their archives from sometime in the early 1960s.
Essentially, the DRC was a device that computed the deformation of the waveform which occurs when a rounded playback stylus traces the groove cut by a sharp-edged cutting stylus. This distortion is well-known as "tracing distortion" and is documented in a number of technical papers in the professional audio press and journals. In the early 1960s, the elliptical or bi-radial stylus (which significantly reduces tracing distortion) had not yet been re-invented. Edison (of course, who else?) had invented it for the playback of his 2-minute wax cylinders around 1900, but it was forgotten about until about 1964 or so when several european cartridge makers, notably Ortofon, began supplying them with their top-end cartridges. So the conical stylus was the only shape in use when the DRC was envisioned. The DRC operated in real time and could be tuned or adjusted to simulate the distortion of varying scanning radii from 0.6 mil to 1.0 mil which were commonly in use then. Feeding a clean signal into the DRC would result in a distorted output which looked like that obtained by a conical stylus of the specified radius while playing a record. Because tracing distortion is a function of signal wavelength and linear groove velocity, the amount of distortion increases with decreasing record diameter and increasing signal frequency. So the DRC had a linkage to the recording lathe that measured the cutting diameter and adjusted the distortion algorithm to increase the distortion as the diameter got smaller. By taking the output of the DRC and applying it REVERSED IN POLARITY to the cutting amp, the cutting stylus cut the distorted waveform such that when it was played back by a conical stylus, the recorded distortion cancelled out the physical tracing distortion of the playback stylus and a "distortion-free" waveform was obtained from the pickup cartridge. The DRC was usually operated connected to the cutting amplifier, although a few examples of tape backup copies were made from the DRC output to be used for extra takes and recuts in cutting rooms that were not equipped with the DRC.
This system actually worked, although probably not as good in practice as it did in theory. It very much depended on the shape of the playback stylus which is pretty unpredictable in the homes of the typical record listeners - sylus wear, improper shape to begin with, etc. But when everything was working right, reductions in distortion were significant. Those of you who haven't actually looked at the output of a phono cartridge playing back a 5kHz sine wave probably will be shocked to find out that it's pretty ugly looking and the harmonic distortion is something like 10 or 20 percent when using a conical stylus at small diameters. This distortion could be reduced to about 2 to 5 percent or so with the use of the DRC.
The problem experienced today when playing back real Dynagroove records made in the early 1960s is that most people are now using elliptical or bi-radial styli with scanning radii of between 0.1 mil (micro-line) to 0.4 mil. This is the wrong scanning radius for these records and results in producing much more distortion than if the record were played with the 0.7 mil radius for which it was cut. The other problem is trying to decide which "Dynagroove" records were actually cut with the DRC. The DRC proved to be unstable and was difficult to keep adjusted, so the mastering rooms at RCA stopped using it after just a few years. Also, the elliptical styli had just come out right after the debut of Dynagroove records, and the need for the DRC was largely eliminated by the use of the new styli. So the DRC was used only for about 3 years or so. But RCA records continued to advertise the term Dynagroove for many years after the use of the DRC was terminated - those records are NOT actually Dynagroove and should be played with the same equipment as for any other records. There is no way to tell which records were actually mastered with the DRC except to ensure that the pressing was made around 1963 or 64 - there is no secret DRC code imbedded in the matrix number or any other way to tell if the DRC was used aside from looking at the master disc production sheet. If the record remained in the catalog for a number of years, chances are good that it was remastered without the DRC even though the label and jacket art were not changed and still called the record Dynagroove.
Essentially, the DRC was a device that computed the deformation of the waveform which occurs when a rounded playback stylus traces the groove cut by a sharp-edged cutting stylus. This distortion is well-known as "tracing distortion" and is documented in a number of technical papers in the professional audio press and journals. In the early 1960s, the elliptical or bi-radial stylus (which significantly reduces tracing distortion) had not yet been re-invented. Edison (of course, who else?) had invented it for the playback of his 2-minute wax cylinders around 1900, but it was forgotten about until about 1964 or so when several european cartridge makers, notably Ortofon, began supplying them with their top-end cartridges. So the conical stylus was the only shape in use when the DRC was envisioned. The DRC operated in real time and could be tuned or adjusted to simulate the distortion of varying scanning radii from 0.6 mil to 1.0 mil which were commonly in use then. Feeding a clean signal into the DRC would result in a distorted output which looked like that obtained by a conical stylus of the specified radius while playing a record. Because tracing distortion is a function of signal wavelength and linear groove velocity, the amount of distortion increases with decreasing record diameter and increasing signal frequency. So the DRC had a linkage to the recording lathe that measured the cutting diameter and adjusted the distortion algorithm to increase the distortion as the diameter got smaller. By taking the output of the DRC and applying it REVERSED IN POLARITY to the cutting amp, the cutting stylus cut the distorted waveform such that when it was played back by a conical stylus, the recorded distortion cancelled out the physical tracing distortion of the playback stylus and a "distortion-free" waveform was obtained from the pickup cartridge. The DRC was usually operated connected to the cutting amplifier, although a few examples of tape backup copies were made from the DRC output to be used for extra takes and recuts in cutting rooms that were not equipped with the DRC.
This system actually worked, although probably not as good in practice as it did in theory. It very much depended on the shape of the playback stylus which is pretty unpredictable in the homes of the typical record listeners - sylus wear, improper shape to begin with, etc. But when everything was working right, reductions in distortion were significant. Those of you who haven't actually looked at the output of a phono cartridge playing back a 5kHz sine wave probably will be shocked to find out that it's pretty ugly looking and the harmonic distortion is something like 10 or 20 percent when using a conical stylus at small diameters. This distortion could be reduced to about 2 to 5 percent or so with the use of the DRC.
The problem experienced today when playing back real Dynagroove records made in the early 1960s is that most people are now using elliptical or bi-radial styli with scanning radii of between 0.1 mil (micro-line) to 0.4 mil. This is the wrong scanning radius for these records and results in producing much more distortion than if the record were played with the 0.7 mil radius for which it was cut. The other problem is trying to decide which "Dynagroove" records were actually cut with the DRC. The DRC proved to be unstable and was difficult to keep adjusted, so the mastering rooms at RCA stopped using it after just a few years. Also, the elliptical styli had just come out right after the debut of Dynagroove records, and the need for the DRC was largely eliminated by the use of the new styli. So the DRC was used only for about 3 years or so. But RCA records continued to advertise the term Dynagroove for many years after the use of the DRC was terminated - those records are NOT actually Dynagroove and should be played with the same equipment as for any other records. There is no way to tell which records were actually mastered with the DRC except to ensure that the pressing was made around 1963 or 64 - there is no secret DRC code imbedded in the matrix number or any other way to tell if the DRC was used aside from looking at the master disc production sheet. If the record remained in the catalog for a number of years, chances are good that it was remastered without the DRC even though the label and jacket art were not changed and still called the record Dynagroove.
Collecting moss, phonos, and radios in the mountains of WNC
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Dr. Groove
- Posts: 23
- Joined: Fri Jul 04, 2008 2:25 pm
I bought an RCA record around '72 and the sleeve advertised the record as dyna-something, I forget. I thought it was dyna-flex but I guess that wasn't it. The sleeve info talked about how superior it was to regular records. I found it rather flimsy. If you held the record horizontally between your hands, it sagged a bit.
The other problem was that certain songs would skip. Not all of them but certain of them I couldn't play. Granted, it wasn't the greatest turntable but it was good enough. None of my other records did that.
The other problem was that certain songs would skip. Not all of them but certain of them I couldn't play. Granted, it wasn't the greatest turntable but it was good enough. None of my other records did that.
"A dog don't want a bone. That's why he buries it." --James Brown
As I mentioned above, "Dynaflex" was the term used to designate a new physical record profile and weight that RCA introduced in the 1960s, although it came to be confused with the term Dynagroove which originally was meant to describe the new electrical processing of those records. Prior to this time, most 12 inch vinyl LP records were made with a weight of about 115 - 120 grams or so. The profile, that is the cross-sectional shape you would see if you cut the record along its diameter, was not standardized among manufacturers but was generally flat. Some makers had introduced profiles that were thinner in the music area and thicker at the "bead" (the outer rim) and thicker at the "hump" (the label area), with the bead and the hump being the same thickness. In fact, RCA had been making such a profile that they called "Gruv-Gard" prior to introducing the Dynaflex profile. The benefit was that the music areas would not scrub and scuff against each other when records were stacked on a record changer.
Dynaflex was essentially an exaggerated Gruv-Gard profile that was even thinner in the music area. It also incorporated a "ramp" which was a taper from just inside the bead to a very thin section at about the 10.5 inch diameter, whereupon the taper reversed to a thicker section just before thickening abruptly at the hump. The purposes of this new profile were two: The record was deliberately intended to be floppy so that any warpage which might get introduced into the record by improper storage would be less consequential during playback since the floppy record would just droop and conform to the shape of the turntable platter. The second benefit was cost - the Dynaflex profile resulted in a record which weighed about 95 grams, a savings of about 20 percent in vinyl cost and weight. At the time, the record industry was trying to reduce the manufacturing costs of the LP and this was a substantial savings.
An unintended consequence of the Dynaflex profile was the increased likelihood that the record could turn out with its center of gravity considerably removed from its hole if the profile wasn't very carefully controlled at all angles around its circumference. This was because of a greater percentage of its weight being concentrated at the bead. This became a problem with the German Dual and Miracord record changers which were very popular in the 1970s and which employed the "umbrella" or "tripod" stacking spindles. When the records were sufficiently off-balance, the record or the stack of records would tilt over on the spindle at a noticeable angle because they were supported only at a small area around the hole - these changers did not employ a stack stabilizer arm which was common in US-made changers. This resulted in faulty changer operation with the tonearm banging into the record stack if it tilted down too far or the records not dispensing properly from the spindle. The RCA Records manufacturing plant was forced to hold the tolerances of the press dies (the large steam-heated molds that hold the stampers) as well as the stamper thicknesses to very close dimensional tolerances to ensure a uniform thickness around the bead of the record. But the Dynaflex profile eventually got a bad reputation mostly by its flimsy appearance which consumers misunderstood as being "cheap". The consumers didn't understand that the floppy record actually performed better when lying on a flat turntable than thicker records which aren't fully supported by the platter due to minor warpage that may be in them. When fully supported, the record was better damped and didn't have the propensity toward mechanical "ringing" that slightly warped thicker records can have when not fully supported at their bead. Regardless, the customers shouted down the Dynaflex profile, and RCA returned to a variation of the Gruv-Gard profile with a 115 gram record for the last 15 years or so of their manufacturing operation.
Dynaflex was essentially an exaggerated Gruv-Gard profile that was even thinner in the music area. It also incorporated a "ramp" which was a taper from just inside the bead to a very thin section at about the 10.5 inch diameter, whereupon the taper reversed to a thicker section just before thickening abruptly at the hump. The purposes of this new profile were two: The record was deliberately intended to be floppy so that any warpage which might get introduced into the record by improper storage would be less consequential during playback since the floppy record would just droop and conform to the shape of the turntable platter. The second benefit was cost - the Dynaflex profile resulted in a record which weighed about 95 grams, a savings of about 20 percent in vinyl cost and weight. At the time, the record industry was trying to reduce the manufacturing costs of the LP and this was a substantial savings.
An unintended consequence of the Dynaflex profile was the increased likelihood that the record could turn out with its center of gravity considerably removed from its hole if the profile wasn't very carefully controlled at all angles around its circumference. This was because of a greater percentage of its weight being concentrated at the bead. This became a problem with the German Dual and Miracord record changers which were very popular in the 1970s and which employed the "umbrella" or "tripod" stacking spindles. When the records were sufficiently off-balance, the record or the stack of records would tilt over on the spindle at a noticeable angle because they were supported only at a small area around the hole - these changers did not employ a stack stabilizer arm which was common in US-made changers. This resulted in faulty changer operation with the tonearm banging into the record stack if it tilted down too far or the records not dispensing properly from the spindle. The RCA Records manufacturing plant was forced to hold the tolerances of the press dies (the large steam-heated molds that hold the stampers) as well as the stamper thicknesses to very close dimensional tolerances to ensure a uniform thickness around the bead of the record. But the Dynaflex profile eventually got a bad reputation mostly by its flimsy appearance which consumers misunderstood as being "cheap". The consumers didn't understand that the floppy record actually performed better when lying on a flat turntable than thicker records which aren't fully supported by the platter due to minor warpage that may be in them. When fully supported, the record was better damped and didn't have the propensity toward mechanical "ringing" that slightly warped thicker records can have when not fully supported at their bead. Regardless, the customers shouted down the Dynaflex profile, and RCA returned to a variation of the Gruv-Gard profile with a 115 gram record for the last 15 years or so of their manufacturing operation.
Collecting moss, phonos, and radios in the mountains of WNC