Combating Distortion In Vinyl

[Superdisc]

COMBATTING DISTORTION IN DISC RECORDING

The disc record is a strange medium and needs some help to get a good master. The amount of distortion you get on playback is directly related to the bandwidth of the recorded audio. The groove speed is slowing down from the beginning of the record (the rpm is constant but the diameter you are recording on is diminishing). The outer groove can be about 250 percent faster than the inner grooves.

Almost all of the distortion comes from a thing called Tracing Distortion which is caused by trying to play back a groove made with a triangular cutting stylus by using a round (or rounded) playback stylus. As the groove get shaper (because of level or dimishing wavelength) you get more tracing error and more distortion. The distortion on the inner grooves increases more than 100%.

So the inner bands are more distorted - often right where the crescendo is. stike

How do you handle this as a Disc Mastering Engineer? How can you modify the digital file you are going to send out to be disc mastered to help this situation?

PHYSCOACOUSTICS TO THE RESCUE

When you turn music up people can plainly hear that, but when you turn it down, it's less noticable. Physcoacoustics!

One way I've reduced this problem is by gradually decreasing recording levels as the disc goes to the center. Start at about 4 minutes for a 20 minute side and decrease the recording level by 1/2 dB every 4 minutes. People won't notice and people won't complain.

You've just reduced your inner-band distortion by 23% - well on the way to getting a clearer master.

Take Care

Bob Dennis

PS: Question? is ANYONE interested in this stuff?

[Doc Mixwell]

Originally Posted by Superdisc

PS: Question? is ANYONE interested in this stuff?

I sure am!

[Adam Dempsey]

And another reason to have your project mastered properly for the format at hand & not submit a CD master for pressing vinyl, though it's really in the hands of the cutting engineer & the particular lathe.
Yes at one stage it was fairly common to have the the softer tracks towards the end of a side.
Best we can do in pre-mastering is encourage adequate side lengths, keeping away from the inner grooves and, where possible, avoid 7" if you're really after hi fidelity.

Originally Posted by Superdisc

Almost all of the distortion comes from a thing called Tracing Distortion which is caused by trying to play back a groove made with a triangular cutting stylus by using a round (or rounded) playback stylus.

Is also the reason to avoid using microgroove 78rpm needles on older (non microgroove) 78's. A very common mistake. fwiw..

Mastering for cassette tapes posed similar limitations (HF saturation, S/N ratio and, to a lesser extent, side length evenness).

[Superdisc]

Originally Posted by Boomshanka

And another reason to have your project mastered properly for the format at hand & not submit a CD master for pressing vinyl, though it's really in the hands of the cutting engineer & the particular lathe.

I regularly master for a European record company for vinyl release. If the mastering engeer doing the job understands it has been premastered, they don't make tese kind of changes on their own.

Yes at one stage it was fairly common to have the the softer tracks towards the end of a side.
Best we can do in pre-mastering is encourage adequate side lengths, keeping away from the inner grooves and, where possible, avoid 7" if you're really after hi fidelity.



Is also the reason to avoid using microgroove 78rpm needles on older (non microgroove) 78's. A very common mistake. fwiw..

Mastering for cassette tapes posed similar limitations (HF saturation, S/N ratio and, to a lesser extent, side length evenness).

Your point is well taken, but now that vinyl releases are competing with CD's, many releases are 20 minutes + At those lengths the mastering engineer will be moving those grooves closer than you would like.

Hmm.. "78" needles sill exist


Take Care

Bob Dennis

[Adam Dempsey]

Originally Posted by Superdisc

Your point is well taken, but now that vinyl releases are competing with CD's, many releases are 20 minutes + At those lengths the mastering engineer will be moving those grooves closer than you would like.

You can't change the laws of physics - again, education and taking on an experienced mastering engineer's advice is key. If they want the best possible end product.
Still, as you'd know, 20 mins or slightly more per side is fine for a 12" 33rpm, other than for a loud hip hop cut (too often coming from a pre-clipped and hence sonically sacrificed master anyway).

[turtlerock]

without overcomplication or oversimplifing the issue, and having cut well over 5000 vinyl records myself
tracing simulator distortion is not a problem or noticable on MOST music.
because the neumann system actually works .

stuff like solo piano , violin , nylon acoustic ... pure wave form stuff it is not so good at and then the system shows it flaws and more so with really long sides , so as a cutting engineer you make the decision .. do i turn the t.s off on this one ...?

i would turn it off at least once a week , but the other guy that cut with me on the other shift NEVER turned it off

my advice is keep the sides as short as you can and let the guy that drives the lathe worry about the distortion or lack there of from the tracing simulator.
i do not make vinyl masters nowadays with any concern for the T.S

[Paul Gold]

Originally Posted by turtlerock

tracing simulator distortion is not a problem or noticable on MOST music.
because the neumann system actually works .

I thought he was talking about tracing distortion.

i would turn it off at least once a week , but the other guy that cut with me on the other shift NEVER turned it off

I've never used one but I was under the impression they were very rarely used because at the levels most sides were cut at the T.S. caused more problems then it solved. I would like to hear your experience with it.

[dcollins]

Originally Posted by Paul Gold

I thought he was talking about tracing distortion.



I've never used one but I was under the impression they were very rarely used because at the levels most sides were cut at the T.S. caused more problems then it solved. I would like to hear your experience with it.

Doing the tracing simulator in DSP might be slightly interesting as, iirc, you have to create X^2 (30dB dynamic range becomes 900, etc).

Istr people leaving it off, though.


DC

[dcollins]

Originally Posted by turtlerock

without overcomplication or oversimplifing the issue, and having cut well over 5000 vinyl records myself
tracing simulator distortion is not a problem or noticable on MOST music.
because the neumann system actually works .

stuff like solo piano , violin , nylon acoustic ... pure wave form stuff it is not so good at and then the system shows it flaws and more so with really long sides , so as a cutting engineer you make the decision .. do i turn the t.s off on this one ...?

i would turn it off at least once a week , but the other guy that cut with me on the other shift NEVER turned it off

my advice is keep the sides as short as you can and let the guy that drives the lathe worry about the distortion or lack there of from the tracing simulator.
i do not make vinyl masters nowadays with any concern for the T.S

Doing the tracing simulator in DSP might be slightly interesting as, iirc, you have to do X^2 (30dB dynamic becomes 900, etc) but I wonder how much difference it would make?


DC

[Bob Weston]

We've never used the Neumann tracing simulator.

On a long side, I'll often turn down the last 2 or 3 or 4 songs in 1/4dB steps. I think this is a pretty common solution. I can get a louder cut / longer side / and lower inner groove distortion by doing this.

bob weston
chicago mastering

[Superdisc]

Originally Posted by Sounds Great

Are you sure? You want to decrease the playback volume of the record as it goes on? Unless the songs and song order are figured in, how could you not notice?

A 3 dB change, according to texts, is a "small but noticeable change" and is true for casual listening.

A 1 dB change is noticeable in critical listening, especially if it an upward change (less noticable if a downward change)

a 1/2 dB change in level (not EQ), especially downward is, for all practical purposes, undetectable.

The total change in level was limited to 2 dB so that it wasn't evident. The ear actually physically adjusts (over time) to different levels to hear softer sounds better and louder sounds without damage - so a gradual change of less than 3 dB over 20 minutes goes unnoticed.

And would this really have any effect on the audibility of the distortion?

HUGE difference

I would think a better way would be to use time management and add groove width as you went along.

Sorry, groove width/depth doesn't affect this - the stylus always rides the same distance up in the groove regardless of depth of cut (not considering tracing distortion). The sylus rides the same way in the groove independent of how deep the cut is made. [deeper groove = wider groove]

Take Care

Bob Dennis

[Superdisc]

Originally Posted by turtlerock

without overcomplication or oversimplifing the issue, and having cut well over 5000 vinyl records myself
tracing simulator distortion is not a problem or noticable on MOST music.
because the neumann system actually works .

You certainly can trust Neumann's engineering. I exclusively used their lathes and cutting systems, but "retired" from disc mastering before this came out.

In general, you would not want to overcompensate with this because different playback styli would give you different results (eliptical vs. mild elptical, vs. "standard") You want to compensate for the best playback systems and then it would help all playback systems.

Maybe if I had stuck around long enough (I retired around 1980) I wouldn't suggest as much lowering of level on the inner bands - somehow I think I still would though.

Good Pointstike

Take Care

Bob Dennis

[Superdisc]

Originally Posted by Bob Weston

We've never used the Neumann tracing simulator.

On a long side, I'll often turn down the last 2 or 3 or 4 songs in 1/4dB steps. I think this is a pretty common solution. I can get a louder cut / longer side / and lower inner groove distortion by doing this.

bob weston
chicago mastering

Thanks for your post.

I miss the 0.2 dB per step attenuators that we used at Motown - My later setup's had 1/2 dB per step attenuators.

Take Care

Bob Dennis

[Paul Gold]

Originally Posted by Bob Weston

On a long side, I'll often turn down the last 2 or 3 or 4 songs in 1/4dB steps.

I don't do this. I find a 1dB difference is the least amount that makes a significant difference in the last 1/8th of the disk surface. I level match for best flow and I don't like to mess with others masters. Sometimes .5dB sounds like a lot and greatly impacts the feel of the record. I rarely do a shootout for a side. If I did I might resort to this but otherwise I think it is a cheap trick. Like a lot of things with cutting, by the time you do enough to make a significant difference it's too much, so do nothing.

I don't know when the Tracing Simulator became commercially available. I know my VMS66 is pretty close to a prototype. There are number of extra holes on the back. It has the switch assembly for the tracing simulator on it. The switch assembly I have is of a different design than found on later VMS66's and all the VMS70's I've seen. Neumann at least knew what was coming in 1966. I'm pretty sure it became available in 1974 when the SAL74 was released.

[Bob Weston]

Originally Posted by Paul Gold

I think it is a cheap trick.

Cheap trick? Paul, I LOVE Cheap Trick. They're awesome!

-b

[Paul Gold]

Originally Posted by Bob Weston

Cheap trick?

He's a *****.

[Paul Gold]

Huh? It's a song title by the above mentioned super rad band.

[Axon]

Does anybody have a schematic or a block diagram of the Neumann simulator? I don't remember it being discussed in JAES.

[turtlerock]

i have a T.S circuit somewhere but i sold my lathes with a sal 74 rack last year

the reason i didnt want to get real technical about its use is it is actually just an on off switch- no real tweeking to be done , it adds a certain percentage of out of phase distortion , calculated to amount of tracking distortion that should be evident on a time and pitch basis thus "cancelling the playback distortion"

considering the lathe cuts an overhead path and most turntables playback on an arc so the contact of the needle in the groove is naturally worse on one wall . without worring about the different sytlus geometries etc etc neumann figured they had the solution

i used the T.S on the sal rack on a vms 80 and a vms 70 for ten years day in day out .

we get our cuts done at abbey road nowdays and the T.S is part of that process
so i just leave it up to the cutter to make his mind up what to do about this stuff

i am no heavy techbod or a tracing simulater advocate for that matter !
just adding my two cents worth from the experience bank

[turtlerock]

oh by the way paul , of course you are right he was talking about tracing distortion

i was just adding my bit about the T.S because i assumed it was the common used solution to this problem !

[Axon]

So I just answered my own question: Development and Application of a New Tracing Simulator. JAES Volume 19 Issue 2 pp. 108-114; February 1971. Looks like I have some reading to do.

This, of course, drags up a more uncomfortable question: How similar is the Neumann tracing simulator to the Dynagroove scheme?

[Superdisc]

Originally Posted by Axon

So I just answered my own question: Development and Application of a New Tracing Simulator. JAES Volume 19 Issue 2 pp. 108-114; February 1971. Looks like I have some reading to do.

This, of course, drags up a more uncomfortable question: How similar is the Neumann tracing simulator to the Dynagroove scheme?

Now that I've seen descriptions of the Neumann TS, I don't think I ever would have used one for the following reasons:

1. I absolutely avoid any device that has only two states (on/off) cause the factory programs only work well occassionally. (always true, in my experience).
2. For the last 14 years of my disc mastering days (1966 - 1980) I exclusively mastered half speed.

Take Care

Bob Dennis

[Joemamma]

Hey,

I just got a test vinyl back from a vinyl pressing plant.

It's hiphop, pretty loud, and 20 min sides.

There is a slight distortion on the last song of side b, but other than that, it sounds really good!!
The distortion is very mild (I can hear it slightly on the vocals).

Does this sound okay, something I should be satisfied with, considering the material (side lengths, genre, loudness)?

[bob katz]

Originally Posted by Joemamma

Hey,

I just got a test vinyl back from a vinyl pressing plant.

It's hiphop, pretty loud, and 20 min sides.

There is a slight distortion on the last song of side b, but other than that, it sounds really good!!
The distortion is very mild (I can hear it slightly on the vocals).

Does this sound okay, something I should be satisfied with, considering the material (side lengths, genre, loudness)?

Let me put your post to my ear. Hmmm... sounds good to me. But seriously, it depends on your tolerance level for distortion. It's not unusual though to have a hip hop vinyl come back with a little distortion here and there in this competitive world. And the last song is probably subject to inner groove distortion, so it could be your turntable is not perfectly aligned. Did you align your cartridge with the two-point alignment protractor?

BK

[Joemamma]

Thanks for the reply!
I don't know that much technical stuff about turntables. I just heard the test print on a Technics 1210 turntable. Maybe I should try listening to it on another record player.