Stylus speed inside the groove

sombunya · May 21, 2013

I was perusing another forum and the subject of stylus speed, inner groove distortion etc. came up. A person mentioned how the stylus travels faster through the groove on the outer tracks than it does on the inner tracks. Being the simple person I am I asked why a 5 minute track isn't the same groove length on the first track of a 12" LP as it is on the last, or inner most track, assuming one could straighten out the groove and measure the length. I linked to this forum, cartridge setup, null points etc. but no one there seemed too interested.

Then I started thinking about it. Obviously the circumference is greater on the outside than the inside.

So, simply stated, does the outer portion of the groove sound better than the innermost part?

JackD201 · May 21, 2013

Actually I believe it is the reverse, it speeds up on the inner tracks. I could never really notice pitch becoming "off" but when beatmatching (DJing) I often find myself playing catch up with the track that's ending by riding the pitch control on the deck playing the incoming song ever so slightly.

Theoretically the outer grooves should sound better but in practice, if an arm and cart are set up properly, you won't notice much of anything. With classical music, you tend to get the exciting stuff at the end of the sides. I've never had any problems with the arms and carts I use.

KlausR. · May 21, 2013

JackD201 said:
Actually I believe it is the reverse, it speeds up on the inner tracks.

Linear groove speed at the outer groove is about 51 cm/s, at the inner groove about 23 cm/s. Recorded wavelength, that is the crest-to-crest distance of the groove modulation, gets smaller in the inner groove, for 10 kHz it's about 50 microns at the outer groove, about 24 microns at the inner groove. A 18 micron spherical stylus like in Ortofon SPUs might have tracking problems when recorded levels are high.

Klaus

garylkoh · May 21, 2013

Following up on Klaus' post.....

When the wavelength of the signal created by the groove modulation is equal to the stylus size, it just skips over the groove, hence the larger the stylus size, the lower the resolution and detail. Thus an 18 micron spherical stylus will just skim over a 12kHz track in the inner grooves and produce silence.

This is called the extinction frequency, and it is there with tape machines too.

Tape heads often have a gap size on the scale of 10 micron. Given tape speed of 15ips (38 cm/s), scaled accordingly, a tape head reading tape at 15ips has about the same resolution as a 18 micron spherical stylus at the inner grooves of an LP. Whenever I look at a cartridge, one of the most important aspects to me is the contact area and profile. With a tape machine, it should be the gap width of the head.

This is just the physics of it. I don't intend to imply that vinyl is better than tape or vice versa.

Groucho · May 21, 2013

What is Diameter Loss?

Problems that occur from “Diameter Losses” have been around since the beginning of the phonograph disc. The most common observation is when you compare the tape to the disc. You will notice less high frequencies as you approach the inner diameter. This is because the length of the groove speed passing under the stylus is in direct relation to the radius of the disc at that time. The beginning groove speed on a standard LP is approximately 20 inches per second. The turntable speed remains constant so groove speed decreases as the playback stylus approaches the inner diameter to approximately 8.3 inches per second at its minimum closing diameter. “Cutting Losses” and “Tracing Losses” become worse as this happens. Cutting Losses occur due to the width of the burnishing facets of the cutting stylus. The combination of high frequencies and reduced groove speed at the inner diameter results in some self erasure. Tracing Losses occur due to the failure of the playback stylus to accurately trace every groove undulation. The stylus will often take shortcuts and miss very small sections of the groove.

http://www.saemastering.com/VinylMasteringFAQs.php

NorthStar · May 21, 2013

I have always been under the impression (belief) that the inner (ends) of an LP (and R2R tape) sounds better that its outsides (beginning).

Speed: it turns faster, more accurately reproducing the music?

Bruce B · May 21, 2013

NorthStar said:
I have always been under the impression (belief) that the inner (ends) of an LP (and R2R tape) sounds better that its outsides (beginning).

Speed: it turns faster, more accurately reproducing the music?

The speed of an LP is RPM, so it's nonlinear. The distance traveled by the stylus is different from inner to outer groove.
The speed of tape is in inches per second, so it's linear. At the beginning or at the end, the distance is constant. The tape sounds the same if it's inside the the reel or outside!

NorthStar · May 21, 2013

And why are 45s (RPM) sound better than 33 1/3 LPs?

And for R2R tapes; linear mechanism, does turning faster at the inner edges of the tape sound better than turning slower at the tape's outer edges? ...Like more stability in reading less imperfections; similar to the wheels of a car.
...Slow and you feel all the bumps of the road, fast and you fly smoother. ...You know what I mean.

Johnny Vinyl · May 21, 2013

NorthStar said:
And why are 45s (RPM) sound better than 33 1/3 LPs?

And for R2R tapes; linear mechanism, does turning faster at the inner edges of the tape sound better than turning slower at the tape's outer edges? ...Like more stability in reading less imperfections; similar to the wheels of a car.
...Slow and you feel all the bumps of the road, fast and you fly smoother. ...You know what I mean.

I think Bruce said the opposite insofar as tape is concerned. There is no "diameter loss" with tape since it travels at a constant speed.

The earlier link provided for LP's with a 33.3RPM cycle says that the outer groove starts around 20IPS, but is reduced to something like 8.3IPS for the inner most groove.

microstrip · May 21, 2013

Bruce B said:
(...) The tape sounds the same if it's inside the the reel or outside!

Bruce,

It is true on our A80's and other constant tension tape machines. On cheaper machines, golden year audiophiles will be able to find some differences in pitch due to tape micro-stretching differences between start and end of the tape!

microstrip · May 21, 2013

John72953 said:
(...) The earlier link provided for LP's with a 33.3RPM cycle says that the outer groove starts around 20IPS, but is reduced to something like 8.3IPS for the inner most groove.

This horrible continuous variation of linear speed can spoil listening pleasure and perhaps induce headache or even nausea. It is why some serious audiophiles still listen to phonograph cylinders. At GBP 16 for 2 or 4 minutes it is not more expensive than the TapeProject tapes, although the catalog is limited and not typical audiophile music, but still expanding.
http://www.phonographcylinders.com/index.php

Groucho · May 21, 2013

I have long since abandoned vinyl as my source of choice, but I clearly remember the difference between the fresh loveliness of the outer tracks and the dried-out grottiness of the inner ones. However, at the time I was unaware that the track sequencing was also influenced by this 'feature' of vinyl rather than strictly artistic reasons.

If you've ever noticed how a number of classic records often had a really mellow or somewhat anticlimactic song at the end of each side, this is why! When vinyl was the main release format, records were sequenced to put the songs with the most high frequency content, or often, just the more important songs nearer to the outsides of each side. So consider putting your most blistering tracks towards the outside when sequencing for vinyl!

http://www.chicagomasteringservice.com/vinyl.html

Interesting that some genres of album may not allow such flexibility in the track sequencing, so the most important music may end up stuck in the dessicated crunchiness of slow-moving vinyl.

(In contrast, tape speed is constant, being regulated between capstan and pinch roller, so quailty is independent of position in the reel.)

Bruce B · May 21, 2013

Groucho said:
Interesting that some genres of album may not allow such flexibility in the track sequencing, so the most important music may end up stuck in the dessicated crunchiness of slow-moving vinyl.

That's why some classical LP's were cut from inside to out so that the big crescendo at the end had the best fidelity!

Andre Marc · May 21, 2013

Bruce B said:
That's why some classical LP's were cut from inside to out so that the big crescendo at the end had the best fidelity!

I think Inner Groove Distortion is a great name for a band!

Groucho · May 21, 2013

Bruce B said:
That's why some classical LP's were cut from inside to out so that the big crescendo at the end had the best fidelity!

I never heard of that before!

Found this in Wikipedia:

Inside-to-outside recording

Almost all analog disc recordings were recorded at constant angular speed, resulting in a decreasing linear speed toward the disc center. The result was increased "end-groove distortion" toward the center of the disc, particularly on loud passages. Since classical music tends to start quietly and mount to a loud climax, it was frequently suggested that it would be better if recordings were made to play from the center of the disk outward. A few such recordings were made, but the domination of record changers, and the fact that symphony movements are not uniformly twenty minutes long, made these recordings no more than curiosities.

https://en.wikipedia.org/wiki/Unusual_types_of_gramophone_records

NorthStar · May 21, 2013

Groucho said:
I have long since abandoned vinyl as my source of choice, but I clearly remember the difference between the fresh loveliness of the outer tracks and the dried-out grottiness of the inner ones. However, at the time I was unaware that the track sequencing was also influenced by this 'feature' of vinyl rather than strictly artistic reasons.

http://www.chicagomasteringservice.com/vinyl.html

Interesting that some genres of album may not allow such flexibility in the track sequencing, so the most important music may end up stuck in the dessicated crunchiness of slow-moving vinyl.

(In contrast, tape speed is constant, being regulated between capstan and pinch roller, so quailty is independent of position in the reel.)

You're into CD/SACDs now? ...The speed of a CD/SACD also varies according to the outer and inner circles (rotations).
- Spins faster at the beginning.
* More jitter at the beginning, or at the end of a "digital" CD?

R2R tape machines: motor's speeds, can they affect the sound quality?

Bruce B said:
That's why some classical LP's were cut from inside to out so that the big crescendo at the end had the best fidelity!

Bruce, do you mean that you start those LPs from the inside instead of the outside???

_____________

A Linear Drive tonearm; better and more accurate than a straight and/or S shape tonearm?
...Because on how the stylus is inserted/travelling between the walls of an LP's grooves.
Also, a linear drive tonearm is more accurate in the inner grooves of an LP because of the angle of the stylus between the walls?

____________

Less mechanical noise/nuisance/alteration of the music from hi-res music download in our computer's drives than CD transport's mechanism, turntable's motor and belt friction and cartridge's resonances and rumble and tics and pops, and R2R tape recorders with motors and tape friction over the heads plus belts?

Bruce B · May 21, 2013

NorthStar said:
Bruce, do you mean that you start those LPs from the inside instead of the outside???

That is correct. Back in the day when you could cut your own records, that's the way it was done as well. I've had a few in here to digitize. Weird...

NorthStar · May 21, 2013

Albums are non-linear; concentric and spiraling like a tornado (outside in). ...But now that tornado is spiraling from the inside out!
I've never seen albums like that of my entire life, and I can only recall very briefly of hearing about it (reading it in an audio mag). WoW!

* Tapes; can they be start from the end and rolling towards the beginning?
** CDs?

Bruce B · May 21, 2013

NorthStar said:
* Tapes; can they be start from the end and rolling towards the beginning?
** CDs?

Yes, but you might hear that "John is Dead"... Think of the "auto-reverse" deck... it goes to the end.. and kicks into reverse and plays the other way.

And CD... unlike the LP, it actually starts from the inside and reads to the outside.

rockitman · May 21, 2013

Fortunately with today's better engineered arms and carts, inner groove distortion is a non issue as long as you are precise with the setup.

Stylus speed inside the groove

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