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Cutting Engineers
Old 1st March 2014
  #1
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🎧 5 years
Cutting Engineers

Can someone point me in the direction of (or write) a short explanation of why a test pressing might skip? What causes a lift, overcut.......?
Lateral info is stereo and vertical is common, right? Stereo bass causes swings and out of phase bass causes lifts?

Simply stated, easily understood by client if you can.

Thanks,

Knob
Old 1st March 2014
  #2
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Greg Reierson's Avatar
 
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Lateral is the sum (L+R) and vertical is the difference (L-R). Lots of things can cause skipping or miss-tracking. Excessive lateral or vertical energy can cut a groove that the stylus can't track. The cartridge has a lot to do with it. Think Ferrari vs. Buick. The better the design the more likely it will stay in the groove.

A loud kick with a strong attack can do it. That's a lateral motion where the groove jumps sideways too fast for the cartridge to follow and it jumps out of the groove.

Out of phase LF energy can do it. That's a vertical motion where the stylus will jump up out of the groove like a ramp. It will look like an hourglass shape under a microscope. If it's really bad and the cutting guy doesn't catch it, the cutting stylus can actually lift off the lacquer and the groove will completely disappear.

Another form of skipping is caused by excessive HF energy where the stylus bounces across the top of a very complex groove, turning SSS into SHSHSHSHSH. It usually doesn't skip completely out of the groove but it's still something to watch for.

Overcuts happen when the program is too loud (too much lateral motion) for the given cutting pitch. The pitch computer is supposed to compensate but if driven too hard it can still happen. Tons of records I look at have groove kissing and some overcuts but it's only a problem if the grooves merge to the point of skipping or audible popping.
Old 1st March 2014
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Greg Reierson's Avatar
 
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This is a great illustration of how a groove is cut.

How to pack a stereo signal in one record groove
Old 2nd March 2014
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Paul Gold's Avatar
 
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A warped or dished record can cause skips too. There is no easy answer that always applies. You have to examine the record and draw conclusions.
Old 2nd March 2014
  #5
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Thanks. So an engineer will "monoize" below a given frequency to restrict lateral movement and therefore be able to cut louder?
How does he tame out of phase low end to prevent lifts?
Old 2nd March 2014
  #6
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maybe with the Neumann VAB 84 (vertical amplitude limiter) or eliptical filter...
Old 2nd March 2014
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Do not forgot too shallow of a groove with loud LF information.
Old 2nd March 2014 | Show parent
  #8
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Bonati's Avatar
 
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Quote:
Originally Posted by Theknob ➑️
Thanks. So an engineer will "monoize" below a given frequency to restrict lateral movement and therefore be able to cut louder?
How does he tame out of phase low end to prevent lifts?
What you're talking about is commonly done with a device called an "elliptical equalizer", which sums the channels below a selected frequency. You'll see this sometimes labeled "EE" on older cutting consoles. If you select 75Hz then everything is summed to mono below 75Hz, etc. This limits vertical movement, not lateral. You have it backwards.

Controlling vertical movement might allow a louder cut but don't draw the wrong conclusion and think the equation is simply "mono the bass = loud cut". There are many other factors that play into a loud cut. I have made loud cuts using no elliptical EQ.
Old 2nd March 2014
  #9
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🎧 5 years
So EE is used to control vertical.
To control lateral (to pack in more lines for a long side) cut low end
and /or lower level.
I imagine it's easier to see lifts and correct them than to judge that a lateral swing will or wont track.
Old 2nd March 2014 | Show parent
  #10
Gear Nut
 
🎧 5 years
Quote:
Originally Posted by Theknob ➑️
I imagine it's easier to see lifts and correct them than to judge that a lateral swing will or wont track.
Yes, this is why a test is cut first on the problem areas. It's always a good idea to get a reference disc cut before metal work.
Old 2nd March 2014 | Show parent
  #11
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Quote:
Originally Posted by bonati
Controlling vertical movement might allow a louder cut but don't draw the wrong conclusion and think the equation is simply "mono the bass = loud cut". There are many other factors that play into a loud cut. I have made loud cuts using no elliptical EQ.
Truth. Run time of each side and frequency content of the program material (not just low-end phase coherence) are other important factors. Every record is different so treatments will vary from cut to cut.

Quote:
Originally Posted by petermontg
It's always a good idea to get a reference disc cut before metal work.
I also encourage clients to get a reference disc.
Old 2nd March 2014 | Show parent
  #12
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🎧 15 years
Quote:
Originally Posted by adamgonsa ➑️
Truth. Run time of each side and frequency content of the program material (not just low-end phase coherence) are other important factors. Every record is different so challenges and solutions will vary from cut to cut.

I also encourage clients to get a reference disc.
Our cutting engineer, Kevin, wants to make test cuts mandatory. We've made it so cheap that it's almost a no-brainer. It's been really good for QC. Funny though, in the old-phase of cutting for us (5 years ago to 39 years ago) we hardly ever made reference cuts.

BTW we've been using Brainworx's BX-Control for an elliptical filter and it's been working great.
Old 2nd March 2014 | Show parent
  #13
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Quote:
Originally Posted by grandmasters ➑️
BTW we've been using Brainworx's BX-Control for an elliptical filter and it's been working great.
I'd add that this tool is best used by the guy cutting the lacquer. Less so by the guy sending the files to him.

Paraphrasing something Paul said long ago, "If you want it to cut easily, remove the LF side energy (mono the bass). If you want it to sound good, let me take care of it."
Old 3rd March 2014
  #14
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Bonati's Avatar
 
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I think what we're all basically saying is "get a ref cut". Also, "don't shoot your low-end in the foot by doing something to the bass you don't understand."
Old 3rd March 2014
  #15
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🎧 5 years
Does a 12' ref really represent the test pressing or is it only to cover the engineers butt so he can blame the pressing plant if there are problems?
After all, there are quite a few opportunities for things to go wrong once the lacquer leaves the mastering house, right?
Old 3rd March 2014 | Show parent
  #16
Gear Nut
 
🎧 5 years
Quote:
Originally Posted by Theknob ➑️
Does a 12' ref really represent the test pressing or is it only to cover the engineers butt so he can blame the pressing plant if there are problems?
After all, there are quite a few opportunities for things to go wrong once the lacquer leaves the mastering house, right?
The ref is a playable lacquer, a dub. Once notes are made, it will more or less cut the same to lacquer.

Covering their ass, in a way yes, but more importantly it shows if there is a problem before metal work. If the problem shows after metal work you have to start the chain all over again and begin the process of assigning blame for the problem. It can fray tempers if the other person thinks it's the others problems and really slow things down.

In the long run it's a product control step that should be taken every time. As well as the Test pressing.

Does it sound the same as a test pressing? not a 100%. The trick to Galvanics is to gather as little surface noise as possible during the process. You might get none, which is rare and then again you might get a couple db.

If it's damaged in shipping it's the shipping companies problem. They are well packed/protected for shipping. The only thing that changes after the cut is the groove will "relax" after the first hour or so.
Old 3rd March 2014 | Show parent
  #17
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🎧 15 years
Quote:
Originally Posted by Theknob ➑️
Does a 12' ref really represent the test pressing or is it only to cover the engineers butt so he can blame the pressing plant if there are problems?
After all, there are quite a few opportunities for things to go wrong once the lacquer leaves the mastering house, right?
We suggest it because then they have something other than the CD master to compare the test pressings to.
Old 3rd March 2014
  #18
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🎧 5 years
Cutting lacquers must be a tough way to make money considering all the things that can go wrong once the masters have left the facility.
Also, what if there is one little bit of sibilance that the customer is unhappy with at 2:45 on track 5 Side A? You have to redo the whole side right?
Find and address the anomaly, another 14 inch lacquer (and ref too?), set up and cutting time, shipping charges, plating, pressing................
Who pays for all this work and material?
Old 3rd March 2014
  #19
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Are you been charged for a recut and plating?
Old 3rd March 2014 | Show parent
  #20
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Paul Gold's Avatar
 
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Quote:
Originally Posted by Theknob ➑️
Cutting lacquers must be a tough way to make money considering all the things that can go wrong once the masters have left the facility.
It's not for the faint of heart. You risk damaging the lacquer by playing it so most don't. That means that without an acetate the first time anyone hears it is the test pressing. You have to know it's a good cut.

There are actual consequences to doing a bad job. You can loose money. Not the money you would have made but actual real money. Parts and shipping are expensive.
Old 4th March 2014 | Show parent
  #21
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dietrich10's Avatar
 
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Quote:
Originally Posted by Theknob ➑️
Cutting lacquers must be a tough way to make money considering all the things that can go wrong once the masters have left the facility.
Also, what if there is one little bit of sibilance that the customer is unhappy with at 2:45 on track 5 Side A? You have to redo the whole side right?
Find and address the anomaly, another 14 inch lacquer (and ref too?), set up and cutting time, shipping charges, plating, pressing................
Who pays for all this work and material?

Good communication with clients can go a long way as well.
Old 8th March 2014
  #22
Gear Nut
 
🎧 10 years
I've been following the various threads here and elsewhere regarding LF mono crossover and "elliptical" equalizers for vinyl mastering and wanted to share with you some recent findings from a circuit design standpoint.

I got involved in this due to a lot of questions about using MS to provide this function. Encoding L and R into M and S and HP filtering Side gives you mono below the cutoff frequency...

In fact, it gives you reduced separation above the cutoff frequency (several octaves above in fact) because the slope is 6 dB octave. Because it's a subtractive process, it is similar to a derived filter and the slope will be 6 dB octave regardless of the HP filter order. Rod Elliot has an excellent discussion on that. See: Subtractive Crossover Networks

Because the Side component is filtered out below a certain frequency, that information is lost. This may be a good thing or a bad thing depending on its artistic value to the particular track. From a vinyl mastering viewpoint this information can create problems due to its vertical mechanical vector which is non coincidentally the subject of the OP.

I also looked at the Neumann Elliptical Equalizers EE70 and EE77. The first thing that threw me was the word "elliptical." As I quickly learned there's a difference between an Elliptical EQ and an Elliptical filter. The first describes an oscilloscope (vectorscope) and/or vinyl land pattern specific to disk mastering, the second is a filter topology completely unlike the EE70 or EE77.

Examination of the EE70 and EE77 schematics show very simple ways to blend LF difference information by bridging a reactive component - in the E70 an inductor bridging across Left and Right working against series resistors - or in the case of the EE77 a resistor bridging Left and Right shunting two reactive series capacitors. Both are 6 dB per octave. They also remove Side via subtraction.

In practice the EE70 and EE77 do the same thing as filtering Side in an MS matrix.

An interesting analog for what the EE70 and EE77 do is what happens when a speaker is bridged across the "+" outputs of a power amplifier. What you hear is Side or L-R. Switch the source to mono and everything disappears.

The EE70 and EE77 shunt LF Side information via summation of L and R below a certain frequency to reduce Side but they do not necessarily blend L and R. If L and R have the same polarity and are stereo by virtue of simply being panned, (fully correlated) then they will fold down to mono about as accurately as the pan-pot law is to constant power. But if Side has elements that are uncorrelated or completely out-of-polarity, than those elements get subtracted from mono when EE'd. By definition, a fully "different" signal is one that is completely opposite of itself, i.e. reversed polarity. A reversed polarity or fully uncorrelated signal added to itself subtracts.

I've also looked at some of the modern EE's all of which that I've found are 6 dB/octave.

What I discovered is that the Nuemann VAB84 works completely differently. One obvious aspect of the VAB84 is that the filter moves to dynamically limit vertical modulation. As it turns out that is not, IMHO, its most unique attribute. Neumann said it with such brevity - one sentence - that it's uniqueness has been overlooked in these and other pages.

"Flank signal components are simultaneously transferred to the other channel."

What the VAB84 does is entirely different. Rather than subtract side it folds Side into Mono by steering.

For whatever reason GearSlutz will not let me embed an image but you can find a block diagram here:
http://www.waynekirkwood.com/images/...ix_Block_1.jpg

The VAB84 exploits a unique property that I've found occurs with MS. If L and R are encoded into M and S and re-encoded back into L and R a strange thing happens if the polarity of Side is "accidentally" reversed: L and R swap!

By making the polarity of Side Inverted with respect to L and R at some frequencies but not others it is possible to "steer" R into L and L into R. That's what the VAB84 does that makes it unique compared to the EE70, EE77 and MS processing. Side information is not lost: It's folded or steered into mono, not subtracted from it.

There is another advantage to the VAB84 topology that Neumann didn't exploit. The filter order can be >6 dB octave. I've constructed both a 12 dB/octave and an 18dB/octave "elliptical equalizer." IMHO this is a huge advantage allowing a far more aggressive lateral crossover without mucking up the midrange.

There are other reasons not related to vinyl to have some applications for an EE. I'll save those for later.

Whether or not this information is useable and ultimately provides a tool I'll leave up to you guys....I'm just a circuit designer.

You can follow the thread here: Pro Audio Design Forum • View topic - Using the Precision MS Matrix for Mono Crossover LF Blending

Maybe some day GearSlutz will let me post an image. In the meantime I hope I've provided some food for thought.
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