Scott Hull on Vinyl, Part Eleven

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All About Deadwax and the Origins of the Independent Mastering Studio

Record Store Day may be past, but the vinyl keeps spinning. Welcome back for a “bonus round” of vinyl trivia! It’s time to talk about “deadwax.”

If you look at your records very closely you will see a variety of symbols cut into the lead-out or terminal groove. This area of the record is nicknamed the “deadwax.” The numbers in the deadwax go by a lot of different names. These are the main ones:

The Scribe Number: the cutting engineer uses a sharp pointed tool to cut the numbers and letters into the lacquer.

The Matrix Number: essentially a “part” number. It’s called “matrix” because the metal parts that are made at the plating plant are referred to as a matrix. It’s an older term from the molding industry.

The Catalog Number: reflecting the record label’s catalog system.

Other marks and symbols are sometimes in the lead out area of the disk. The technical ones can tell you a little something about the quality of the pressing. But to understand their significance you need to know a little more about the history of the mastering process.

Masterdisk Deadwax

In the 50’s and 60’s, lacquers cut for a major label project were cut by a technician. Literally he was a white-coat lab tech. They might not have known much about the music (of course some would have known more than others) but they weren’t there to change anything. Their job was to take the tape and cut it on the masterlacquer disk. Hence “mastering.”

If there was a technical problem, like the record skipped or distorted too much, they would either turn the level down or apply a filter to the highs or lows to allow the disk to be cut. Also during this early vinyl age, when an artist and producer went into the studio to record a song they could only hear the master when it was played in the studio. No one privately owned master playback decks — they were as large as a washing machine. A few people had low-speed 1/4″ analog tape decks at home, but for the most part they could only listen to their work when it was cut onto a lacquer.

Most recording studios and all labels had a mastering room. In the mastering room tapes from that day’s sessions would be transferred to record. These weren’t for mass production — they were take-home references. That was how the producer could listen to the final mix outside of the studio. That’s also how the label would hear the record. And the mastering engineers in these rooms, most of them anyway, were not known for taking extra care with these “dubs.” They were just like cassette copies, made so that the music could be more portable. Occasionally you will find some of these in the collectors market. They are often called acetates (though they stopped making them from acetate years prior).

But as the music business evolved an interesting thing happened. People began to notice that records cut by certain mastering engineers not only sounded better, but they were less likely to skip. And — most importantly — they SOLD more copies. So now not only did you need a great song, producer, band and studio, you needed a killer recording and mix engineer and the right mastering engineer, too.

This was truly the golden age of mastering. I got to see the last 10-12 years of it and it was remarkable. Independent mastering studios popped up in every major music market. And even though the major labels all had their own mastering studios and engineers, they would always send their important projects to Masterdisk, or Sterling Sound (both in NY), Kendun or The Mastering Lab (in LA) or other notable houses in Nashville, London, etc. Forgive me because I am leaving a lot of names out, but you get the idea that this new independent mastering business was off and running.

Album art for Sting Nothing Like the Sun

Some labels devoted enough resources to their engineering departments to make high quality cuts. CBS, A&M, Capitol, Atlantic and others had great engineers and some of the best equipment, but their livelihood rarely depended on being the BEST. Whereas the independent mastering engineer was constantly in competition for any new release. There even used to be “shoot-outs” (and still are, often). A record company or producer would make a few copies of the master tape and send one song to different mastering studios. When the different lacquers came back, they would then compare the results, and only one engineer would win the job. It wasn’t about price: they were looking for the sound.

Artists and producers would come from all over the globe to work with their favorite mastering engineer. My mentor, Bob Ludwig, had a very consistent relationship with Hugh Padgham from the UK. Hugh produced many wonderful recordings, but the projects I remember best records by The Police, Genesis, Sting and Phil Collins. The production team would finish their mixes in England and that night would fly “across the pond” on the Concorde. They would master their record with Bob that day, and that night, with reference disks in hand, they would return on the Concorde. Wow. And it had to be perfect.

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Scott Hull on Vinyl, Part Ten

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How many grooves are there on a typical record?

The RIAA (Recording Industry Association of America) set all the parameters for the dimensions of the modern vinyl record. The parameters needed to be made consistent so that player functions would all work. So, as a mastering engineer, I need to know that the final locked groove on an LP (33 1/3 rpm) must be at a diameter of 3.875″ (give or take 1/32″). And lots of other details. (See the disk diameter chart from the RIAA, below.) Lets look at the parts of the disk surface.

RIAA diagram illustrating the surface of an LPThe Safety Groove

The outermost grove is automatically cut a little deeper and wider than standard, and its purpose is to catch the needle if it’s manually placed on the record too near the outer edge. If you let the cartridge bounce off your turntable it will almost always cause some damage to the delicate stylus/cartridge.

The Lead-In Area

The lathe carriage — the part of the cutting lathe that moves the cutting head across the surface of the disk — moves at a fast rate in the lead in. There is some blank area there on the disk that must not have audio recorded. The reason for this is that automatic record changes would not always drop the needle precisely. The grooves in the lead-in and the safety groove did their best to keep the needle on the record.

The lathe carriage, driven by the lead screw, then slows down to standard pitch for about 3 seconds. Then and only then is audio supposed to begin. From this point on, the pitch of the grooves (how far apart they are) is controlled by the computer in the lathe. The pitch drive computer listens to a preview audio signal that comes 1.8 seconds before the audio. It’s that far ahead because that is about how long it takes the record to make one revolution at its outermost diameter. Between songs we press a “spiral” button which advances the carriage quickly for just a moment. This creates the visual band between the songs so you can see where to place the needle.

This part gets pretty technical…

Lets look at the process of cutting the groove in the first band of an album. And let’s assume for simplicity that the grooves of the left channel face towards the center of the record and the grooves of the right channel face the outer edge of the record. A modulation on the left channel moves the groove into the “virgin” area of the disk that has yet to be cut, while a modulation on the right channel moves the groove into the part of the disk that has already been cut. So to keep the grooves from colliding, the computer has to calculate how it has to turn the lead screw to avoid cutting over a previously cut groove. This happens very fast, and it’s hard to see with the naked eye, but we can monitor the progress of the groove by watching a meter on the front of the lathe. It’s calibrated in Lines Per Inch (lpi) (see photo below).

This, logically, is the number of grooves (lines) that are cut in an inch of the lateral record surface. The computer then has to store the left channel information into memory, and add that to the right channel information that is coming up on the next revolution. You see, the collision that has to be avoided is between the left channel of the first grove and the right channel of the second groove. If you make a little drawing of a disk and a squiggly groove you will see what I mean. In real time, the lead screw motor has to turn fast enough so that when the next groove comes around there is enough room to cut the groove and still leave a tiny bit of “land” between the grooves.

Photo of an LPI meterLevel and Duration

Very early lacquer lathes cut at a fixed pitch. There was no computer control. With these lathes it was virtually impossible to cut a 20 minute side of pop music with a reasonable level. It took the variable pitch lathe to cut a better sounding record — as long as you didn’t let the grooves collide.

We align our cutting system with a basic geometry assumption. We adjust the cutting parameters so that a 2 millimeter-wide groove cut with 600 lines per inch should produce no land or open space between the grooves. From that baseline, any audio that is present causes the groove to wiggle and requires that the pitch be lower than 600 lpi. Does this make sense? Ok… More music = fewer lines per inch. So the louder the music the less space to record the audio. There is a direct relationship between level and duration.


A couple other factors cause us to increase the space between the grooves. If we have audio that causes a very challenging groove to be cut, we may need to momentarily increase the land between the grooves (thus lowering the lpi) to give the grooves a little extra space. This is only for insurance, but a good practice when it’s possible. Also there is a peculiar effect when cutting into lacquer. The disk is rather soft, and it’s being cut buy a heated stylus. But what happens after the groove is cut is what is interesting. Being a “plastic” substance, the lacquer partially springs back to it original shape after being cut. Not entirely, of course, but enough to cause the neighboring grooves to be affected. This “spring back” or elasticity can cause audio to “ghost” into neighboring grooves. This is referred to as groove pre-echo and it very hard to deal with when there are soft passages followed by very loud sounds or visa versa. The loud sound can be heard one full revolution before or after the audio actually happens. Sometimes even both. Many of you have probably heard this and probably wondered why echo would have been added in the production. It wasn’t added in the production studio. This groove echo was caused by the disk cutting process itself. To avoid groove pre echo we open up the spacing of the grooves right before any sudden loud passage and right after any loud passage that stops suddenly.

Analog Tape Print Through

There is one more complication. Analog tape recording has a similar effect called print through. This isn’t due to the tapes elasticity, but it’s due to the magnetic properties of the tape. One layer of magnetic tape laying against another layer of tape tends to give off a small portion of its magnetism to its neighbor. The louder sound will “travel” up and down the packed reel of tape. This effect gets worse with age. The longer the layers are sandwiched together the more of the energy is transferred. Fortunately for records, once that master lacquer is plated in the pressing plant, no more echo can happen.

As for the question at the top of this post: as it turns out there are TWO grooves on any record. One on each side. And if you stretched one of them out it would be 1600 feet or about 1/3 of a mile long.

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Scott Hull on Vinyl, Part Nine

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Scott chats with master cutting engineer, Tony Dawsey.

Photo of Tony DawseyThis week I’d like you to hear from one of my master cutting engineers, Tony Dawsey. Tony, like myself, started mastering before there was digital recording of any kind. Well, we’re not that old. But at that time, everything we did was focused on producing the highest quality vinyl records imaginable.

I sat down with Tony and asked him a few questions about vinyl, and about his experience as a cutting engineer. Here’s a couple of short excerpts; I hope you’ll enjoy listening to the full interview below.

What lessons from the early days still stick with you today?

Good isn’t good enough when it comes to perfecting your craft. That’s equalizing somebody’s project or cutting it. A lot of things can go wrong in cutting and you want to make sure none of that happens. You don’t want to cut a 25 minute side with a worn stylus. That’s not cool.

What was your path to cutting your first record?

Well the shipping room was right next to Bill Kipper’s studio, so in between my responsibilities early on, I’d drift in there with him and just watch him. He did a lot of classical music as well as other things. He ended up showing me how to cut vinyl.

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Scott Hull on Vinyl, Part Eight

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This week, a behind-the-scenes look at some of the challenges of producing good vinyl reissues, particularly remastered-from-vinyl releases.

Hey, where did my master recordings go?

Photo of Analog Tape MachineLets look at vinyl from a different angle. Let’s say you made a record in the 70′s or 80′s. You had pretty good success with the record. It might not have been a “top ten” but the fans loved it. Then in the 90′s your record label folded or was sold. Now today your exclusive deal with the label has expired, and maybe even the rights to the songs are back in your hands, and you want to put that old vinyl back into production. Except who has the masters? The original two-track master tapes. They should have been handed over to you, right? But you call and meet and ask around and no one really knows what happened to them. A few are found in a vault that has nothing to do with your old label, but by and large your original recordings are lost.

This isn’t fiction. This happens every day. During the “digital reissue” days master tapes were taken from the libraries, some orphaned at mastering studios, some taken by producers, others destroyed. They should have been returned to the label, but truthfully, few labels dedicated resources to keeping close track of their own masters. This sounds outrageous, but as labels dissolved and sub labels merged and staffs got trimmed, often there was no one left that truly cared about the music. I’m not saying this was all of the major labels, as there are several notable exceptions still working their back catalog with great care.

So what does the band do? They almost certainly hate the way their CD sounds. Unless it was expertly re-mastered with care it’s either going to sound thin or scratchy-bright, or it was made so much louder to “compete” with recently produced CDs that it’s almost unlistenable.

Sometimes a producer or artist will find a DAT recording that was made at the same time as the mixes, but most times it was made with poor quality A/D converters or it might not include all of the main mixes. If the band doesn’t give up entirely, then they start looking at their vinyl collection and think, “well these pressings sound pretty damn good… why can’t we use these to make our reissue?” And to be honest, if you’re careful, this approach works quite well.

First you have to decide if your fans are in love with the vintage vinyl sonically. If you think they are, then you might just hit a home run by re-doing your vinyl so it sounds exactly like the mint pressings. You can then decide if the digital audience would like to have it presented in a more modern sounding format for streaming and download.

Photo of a shelf of analog tape boxesBut there’s quite a lot to getting a really great transfer from a piece of vinyl. As I mentioned earlier in this series, the cartridge has to be set up just so, and the playback curve correct, and the alignment of the phono preamp through the analog chain. The record also has to be ultra clean. If your record is mint and really clean then you’re almost there. Ideally, you have more than one copy of mint original vinyl, so you can transfer multiple pressings. This is so that if you have a “pop” issue or a noisy groove on one of the pressings, you can select the best disk to use for each track. I’ll often switch between copies multiple times within a track to get the best sound. Now, before you cry foul, remember we have the original pressing as a guide. This was exactly what the producer wanted the record to sound like. And if I can give the consumer exactly that same music with a better noise floor – not taking away any of the feel, groove, air, or warmth, then why shouldn’t I do it?

Once I have a high-resolution digital file that sounds like the vinyl, I can start cleaning any remaining clicks and pops. There are several tools for doing this. Some work better than others. To avoid choosing sides, I’ll just say that the one I use is the best. But again, the goal is not perfection. The goal is to make a pressing that sounds just like the original pressing. It’s my opinion that the original pressings will still be valuable collectors items, but with a reissue of this kind, the general fans can enjoy the sound of the vinyl. Even many collectors might enjoy having a “service copy” of a favorite record. This way they can maintain their collection and still play the record for friends and family.

In a Perfect World

Making a re-issue vinyl from the original analog masters is one of the most fun things you can do with non-adhesive tape. When the original sources are first played they sound “like a record.” Right out of the box, you can hear what went into making the original vinyl. My point is that 20 years ago or more, the mastering process was about getting as much of the original master’s sound onto the vinyl as possible. Mastering was more of a craft and less about “post-production.” Mastering now for CD or vinyl often involves extensive editing, complex fades, mixing in auxiliary elements and sometimes even mixing.

Photo of a lacquer being cut on the Masterdisk lathe.Vinyl cut from original analog masters just sounds right. The two were made for each other – literally. And the compression and smoothness from analog tape – when it’s not recorded too hot – makes all of the technical issues of cutting less of a concern. If you ever get a chance to listen to a favorite recording played directly off of the original masters you will be shocked at how wonderful it sounds. Everything that is good about vinyl is realized on the original masters. If you have any – guard them, catalog them, document them and store them safely. No digital archive format will sound exactly like them.

From CD Back to Vinyl

I have been asked on many occasions to take the CD master files and transfer them to vinyl. You might be able to sense me wincing through your screen. Doing this creates lots of issues for me. Technically, a hyper-compressed CD master will have to be lowered in level to accurately track on a record. Now let me explain, it’s not that the CD is such a low quality format. The issue is that the well known CD level wars have left us with a tiny dynamic range, drastically limited bass range and high frequency hash that is very hard to cut without distortion.

But what if our “heritage” band didn’t make vinyl, but only CDs in the 80s. And like our 70′s band they didn’t keep track of their masters. This happens all the time now that digital files and production techniques vary so much. Only the most responsible producers made backup copies of the original masters. And many of the digital formats of the 80′s are disappearing. We may be forced to take the existing CD master and try to make it sound whole again. Sometimes this can be done, but there are no magic tricks. Just hard work with EQ’s and manual level control to mimic what the dynamics might have been before brick-wall limiting. We never get it all back, but with lots of patience we can often find a much warmer, rich, organic feel by carefully processing the digital masters. The craft in this is making it rich with out being muddy, warm without being dull, and to somehow simulate the sense of space that was in the original. Sometimes I have rough mixes or outtakes to compare to. Sometimes it’s just my imagination. But if the mastering was done expertly, it will sound like I was never even there.

Thanks for reading. I hope you are enjoying reading these as much as I’m enjoying writing them.

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Scott Hull on Vinyl, Part Seven

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What’s the condition of your records?

As consumers you know that the condition of the vinyl is very important in determining the quality of the playback. Tics and pops get much worse if the record isn’t stored right, or isn’t cleaned well. Sometimes visible scratches are audible and sometimes they aren’t. And sometime a good cleaning makes a world of difference… and sometimes it doesn’t. That’s because not all of the noise in the playback of the record is a result of the vinyl itself. The entire process from cutting, handling, shipping, cleaning, plating, pressing, cooling and packaging can cause noises to be introduced. But where it all starts is at the cutting stylus. If the cutting system produces a “dirty” groove, then the record will never sound quiet. So we have to scrutinize the quality of our cut on each and every lacquer we cut.

Photo of new, unused lacquers.
New lacquers
Poor groove quality can cause noise to be recorded in the groove due to a variety of issues. Here is just a small list of visible groove abnormalities that show up in disk mastering.

Streaks – If the cutting stylus picks up a tiny speck of debris it can cause the groove to be cut with parallel streaks down one or both of the groove walls. Some streaks are completely inaudible. Others cause bacon-frying static sounds.

Jagged edges – Either the top edge of the groove or the bottom edge of the groove can appear jagged. The first thing to be concerned about when we see a jagged groove is that the stylus may have been damaged. Each sapphire stylus will cut many sides, but if it strikes the aluminum plate or if it cuts over an imperfection on the disk surface, the stylus has to be replaced.

Stylus heat – Most cutting sytems use a small electrical current to heat the tip of the cutting stylus. This helps the stylus glide thru the cut like a warm knife through butter. If the stylus heat doesn’t match the lacquer black and/or the stylus, you get groove quality issuses. Both too hot and too cold are a concern. Both extremes cause hiss and surface noise to increase.

An Aside — First Edition Pressings

If you’re a collector of first edition pressings, you are already aware that they do indeed sound better than later pressings. There are several reasons for this, but the main one is that it takes a lot of effort and extra time and money to cut that first record. Independent mastering engineers and studios usually charge by the hour and are closely supervised by the producer of the record. Every nuance is considered, and for major label releases in the ’70 and ’80s almost no expense was spared to make the best sounding record possible. When a record sold very well, and had to be pressed again (second or third edition pressings), those later lacquers were rarely cut by the original mastering engineer. Each label had its own in-house mastering facility. And while in some rare cases labels spent the time and money necessary to create really high quality masters, the fact is that most did not. These mastering studios were run more like union shops and the managers and engineers were given the task for the day and in general they were not highly motivated to produce the highest quality product. I’m not saying that the engineers were less competent, as many of them had years and years of record making experience. But the equipment and the general quality control were just not as specialized as they were at an independent mastering studio like Masterdisk.

Chip Squeal — There is one more quality control issue that plagues the record making process. A high frequency squeal can be caused by many factors. This noise is the most dreaded of the cutter-induced noises. Sometimes is can sound like a buzz, or a very high-pitched whistle. It’s not loud, but it can clearly be heard in the quiet sections of a classical piece or in the blank sections between songs. It’s very difficult to make it go away and it can really slow down the process.

Photo of used lacquers (scraps)
Used lacquers (scraps)
Many a sane mastering engineer has been thrown into a foaming stupor over this issue. I’ve seen it happen and it’s not pretty. In fact years ago one Masterdisk engineer used to take his personal frustrations out on the poor lacquers themselves. You see, if the lacquer chip doesn’t get picked up by the vacuum, or if there are ANY noise problems with the cut – you had to discard the lacquer and start the process all over again. It’s like glass blowing: your final product was either perfect – or it was scrap. You could tell when this engineer was having a bad day when there was a pile of V-shaped partially cut lacquers sitting in or next to the waste can, or sometimes against the wall outside his room where they landed after being thrown in disgust. He would bend the disks in anger over his knee. It didn’t help the mastering process at all, but maybe it helped him emotionally. Cutting a quality side is indeed part skill, part luck.

This demon goes by many names. Chip squeal, cutter squeal, chip drag and many others. In short, it’s a vibration – usually caused by the stylus skidding through the lacquer instead of smoothly slicing through. It can also be caused by the extraction of the chip. Now this part gets interesting. Chip is the tiny piece of lacquer that is removed from the disk as the groove is cut. The stylus is like a tiny plow or wood gauge that lifts up this hair-thin “line” of lacquer. A vacuum system then takes it to a jar for safekeeping. Safety is actually a concern as this nitrocellulose is extremely flammable.

So as this chisel-shaped stylus is carving up the chip the vacuum has to carefully draw it away from the stylus. If the velocity of the vacuum is too great, or the chip falls on the lacquer, or if the lacquer is too soft or too hard, or the stylus is a little caked with lacquer, or… (you get the point) then you can get a very high pitched squeal recorded into the groove. Remember that each and every motion of the stylus is analogous to the audio. The chip vibrates like a microscopic guitar string and that vibration can cause the stylus to move which creates undesired results on playback.

So if something foreign is added to the groove, it turns into audio when the cartridge plays it back. A scratch, a glob of lacquer, a squeal from chip drag, or even low frequencies transmitted from the building floor up into the turntable platter as it’s being cut. In fact if you stand right in front of the cutter head and speak loudly you will hear your voice played back in the recorded lacquer. That mechanical transfer of sound into the groove was how the original edifone worked. How cool is THAT.

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Scott Hull on Vinyl, Part Six

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Could your turntable could be performing better?

If you’ve been following along this blog since week one, you now have a pretty good picture of how music gets recorded onto vinyl.

This seems like a good time to talk about record players and especially phono cartridges. I won’t even try to tell you what turntable is right for you; there are many factors to consider. But I can say for sure that you really do get what you pay for.

photo of an LP on a turntableNot all records are “challenging” for the stylus. The least expensive cartridges will play back non-challenging grooves just fine. A $30 cart on a $150 table will probably have problems with higher levels and with high frequencies, whereas more expensive cartridges almost always provide much truer playback. But (there’s always a “but”) cartridges and turntables built for DJ use – even though expensive – are not the best at reproducing crystal clear music. It’s because the DJ cart has to be sturdy. It doesn’t give as easily and is weighted more; as a result it can distort on high frequency material. My favorite cart is one that balances all these issues. And since I don’t have an endorsement deal, you’ll have to ask your hi-fi shop what equipment suits your style and wallet best.

It’s interesting to note that the distortion we hear on sibilant vocal “esses” and cymbals is almost always NOT in the cut or the groove of the record. The distortion heard when playing back is a function of the quality of the cartridge, the condition of the record, and how squiggly the groove is. It’s the mastering engineer’s job to find the right compromise between level, brightness and playability. And it is always a compromise.

For example, I was once asked to restore some solo trumpet music. The masters had been lost. The client made transfers at a pro studio from mint vinyl before bringing me the digital files to clean up. The record noise was not the worst issue. The main problem was the horrifically bad ripping distortion on the muted trumpet. By the way, Harmon muted trumpet is a big challenge to cut cleanly as it has tons of high frequency content.

I tried everything I knew to reduce the distortion to acceptable levels, but I wasn’t getting anything I could use. It was a mono recording played back by a stereo cartridge, and I was working on just one channel at a time. But when I played back the stereo transfer, my ear immediately recognized the source of the clipping. What was thought to be peak distortion was actually caused by stereo “splatter.” It sounded like the trumpet suddenly went from mono to stereo and back but only on the bright passages. I knew that only stereo splatter could make that sound. The cartridge they had used for the transfer was unable to track those high frequency waves accurately.

I stopped what I was doing and contacted the client, asking them to send me their vinyl copies so that I could try a transfer myself. They were very hesitant, as they had spent a lot of money already to transfer and clean these recordings. (I forgot to mention it was a multi–disk box set!) But I insisted. When I played their vinyl on my best cartridge it was a beautiful thing. There was absolutely zero distortion. It sounded perfect. I played that same passage back on my cheaper setup and not surprisingly that ripping distortion was back.

Photo of an LP on a turntableSo if you hear sibilant esses and a sort of glassy sheen on most of your vinyl, you probably could use a better or newer cartridge. Also, turntables need to be setup properly to achieve optimal results. Your record store turntable guru can help – or if you want to do it yourself, get this very good DVD: Michael Fremer’s Practical Guide to Turntable Set-Up.

It is often frustrating for our clients and for my cutting engineers when a producer gets their test pressing and doesn’t like what he or she hears. We have to wonder, “How old is their cart? Was it setup properly? Is the stylus clean? Is the turntable causing rumble or interference? Has the turntable been listened to regularly or was it dusted off and plugged in this morning to play back this one piece of vinyl?”

The fact that each turntable and cartridge sounds different makes it very hard to quality control masters and pressings. If you use a very expensive cart and turntable then nearly everything sounds perfect. If you use a very low grade consumer turntable as your measuring stick, then everything sounds distorted to some degree. Somehow you need to determine what level and how bright to make the music.

In my opinion, the best results are achieved by looking at both extremes. Then I try to determine what a typical listener will be using for playback. Then we come up with a compromise that fits our music and our listener.

Yes, it’s more work and costs more money to give a cut this kind of attention. But like I said — you get what you pay for.

(Read all of the “Scott Hull on Vinyl” articles here.)

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Scott Hull on Vinyl, Part Five

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What is the RIAA curve?

The Recording Industry Association of America developed a standard playback equalization curve and required that all LP records and record players manufactured conform to this standard.

graphic description of the RIAA curve

You have probably noticed that you cannot take the audio plugs from your turntable and plug them into an ordinary line input connection on your preamp. Well, you can, but it sounds horrible. The line input connections, designed for tape machines and CD players, do not have the RIAA curve. Every phono pre-amp must have this playback equalization built into it. Since most of you are probably not audio engineers, I’ll try to describe this curve by explaining why it was used.

If you were to cut an ordinary audio source (without the RIAA EQ) into a lacquer at a reasonably hot level you would notice two things. First the bass frequencies, with their long wavelengths, are so big and loud that they cause the grove to make really large squiggles. So large in fact that it would be hard for a cartridge to playback the squiggles. These very large cut grooves would take up a huge amount of space on the disk and limit your playing time to only a few minutes on a 12″ LP side.

The second thing you would notice is that records are noisy. Yeah I know, you already know that. But I mean a vinyl record is REALLY noisy. That audio source played back without the EQ would be mostly scratchy noise and clicks like you’ve heard from an Edison cylinder. The only way the LP works to make pleasing realistic music is for the audio to be pre-EQ’d so that the bass is reduced dramatically, by 20dB, and the treble is increased dramatically, also by 20dB. The original music returns when the opposite EQ is applied by the phono preamp.

See the picture above — this is the playback curve when the bass is boosted back up 20dB and the high frequencies are rolled off. The reduction in bass helps us get the 20 plus minutes per side and the exaggerated treble works as a very effective noise reduction. You see, the audio had it’s treble boosted before it was cut. Then surface noise from the vinyl was introduced on playback. When played back through the complementary filter, the hi end is cut and the surface noise is reduced but the audio returns to it’s original frequency response. Like magic. The resulting bass response of the LP was better than a 78 too – by a lot. And the noise floor was improved.

So that’s why an equalization curve was developed, and why the RIAA standardized it. For more info on this standard see here.

But even that’s not the end of the story. The big treble boost puts extreme stress on the cutting amplifiers; so much so that specially built circuit breakers need to be inline at all times to avoid damaging the (very expensive) cutter head. This high frequency emphasis also causes bright instruments like cymbals and vocals to distort if cut without care.

Listen to this quick before and after. It’s a sample of a track by the artist Danni (produced by Nik Fairclough).

First, here’s the track without the RIAA curve applied.
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This one has the RIAA curve applied.
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You will immediately notice the almost painfully shrill top end and dramatic loss of bass from the RIAA filter. It was never intended that the end user ever hear the RIAA encoded signal — a good thing, because it sounds terrible. This example illustrates just how much the music has to be pre-emphasized to effectively reduce the surface noise of the disk.

That’s it for my crash course on the vinyl groove and the RIAA curve. On to more aspects of vinyl next week!

(Read all of the “Scott Hull on Vinyl” articles here.)

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Scott Hull on Vinyl, Part Four

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One of the most sought after vinyl-cutting systems in the world is the nearly indestructible VMS-70 and VMS-80 cutting systems built by Neumann. The VMS-82 was the last of these produced. I’m thankful to say that we get to use our VMS-82 lathe every day to cut lacquers for clients around the globe. (Fig. 1)

Photo of the Masterdisk lathe
Fig. 1
The actual cutting happens at the cutter head. In this case, the BMW of cutter heads, the SX-74. (Fig. 2)

Though it was initially built in 1974, this design was never dramatically improved. It was capable of cutting with sufficient level and flat frequency response to please nearly everyone.

The head has been removed from the lathe and is sitting upside down for viewing. (Fig. 3)

Now just a little closer look to see the working parts of this little marvel.

Photo of Neumann SX 74 name plate
Fig. 2
The two round “cans” on either side are the voice coils. (Fig. 4) You can also see the cutting stylus: a faceted sapphire glued to a pin that mounts in the tube that connects to each voice coil. Also in the foreground are two fine wires. These carry a small voltage that heats the stylus to an optimal temperature so that it slices smoothly through the lacquer instead of dragging and causing extra noise from a jagged cut.

The drive coils of the stereo cutter head are mounted at right angles. When there is audio in the left channel the left coil goes in and out, just like a speaker does. And when there is audio in the right channel the right coil goes in and out. One voice coil in the cutter head is wired deliberately out of phase so that when a mono signal is cut, as the left coil is moving in the right coil is moving out. Thus, a mono signal cuts a lateral groove that looks like this. (Fig. 5)

Why is this done this way you might ask?

Photo of the Neumann lathe cutter head
Fig. 3
We have go back to mono to find out. Early records, initially 78s and then LPs, were mono. Systems that cut mono records had only one drive coil and it moved the cutting stylus back and forth creating a lateral, constant-depth groove. There was little concern about the depth of the cut so long as it was deep enough to hold the playback stylus in the groove. Then along came stereo. Researchers needed to find a way to carve two channels of audio into a record but make the new technology compatible with mono records and players.

Unfortunately, today’s technology designers don’t put quite so much effort into forward- and backward-compatibility. That’s a soapbox speech for another time.

So what they came up with was to record the mono component of the stereo audio laterally, like on a mono record. Then by adding a second coil and wiring it “out of phase” with the first coil they created depth modulation which records the stereo or side signal.

If I’ve lost you, take a breath and read on; I’ll try to make it clearer.

Photo of Neumann cutter head close up
Fig. 4
Stereo is made up of a left signal and a right signal. OK, that’s simple. But stereo can also be described as the mono component (everything that is exactly the same in both speakers) and the difference component (everything that is different). This is commonly called Middle and Side, or M-S for short. A stereo signal can be converted into an M-S signal and back again with nearly no change at all. FM radio is transmitted in M-S. The middle signal is a strong “full wave” signal and it is this signal that you hear when you are far away from the radio tower. That signal is mono. As you get closer to the radio tower, your radio can tune in the sub carrier signal, which carries the difference (side channel). When you receive a strong enough signal, the FM station now plays back in full stereo because it has BOTH the middle and the side signals. It can be hard to believe, because we commonly think in left-and-right rather than middle-and-side. But it’s true. It’s a matter of physics and alternating current electronics. Are you still with me?

Photo of record groove
Fig. 5
The groove shows us the “difference” signal by it’s depth. So a mastering engineer speaks “lateral” and means the mono aka “middle” signal. And when the engineer says “vertical” he or she is referring to the “difference” aka “side” signals. Got it now? Good.

Once you have a hold of that concept then we can start to talk about why some records seem to make the vocals spitty and sibilant. And why some recordings have to be modified with equalization to minimize out-of-phase bass.

But there is one more thing to understand before we can control our quality. It was a standard developed in the 1950s called the RIAA Curve.

Next week I’ll talk about what the RIAA curve is, why it was standardized, and what steps we have to take to make records sound really good.

(Read all of the “Scott Hull on Vinyl” articles here.)

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Scott Hull on Vinyl, Part Three

Header image for Scott Hull on Vinyl seriesAs disk cutting engineers we are always looking at sound. We have a microscope mounted on the record cutting lathe and we use this scope to determine the quality of the cut and to diagnose problems when they occur. We can also measure the groove width and separation between the grooves. The space between the grooves is called “land.”

Photo of quiet record grooves
Fig. 1
So, What do the squiggles mean? Lets look at the record groove closely. Very closely.

In the microscope a simple quiet groove looks like this. (Fig. 1)

There are four grooves in this picture. Each groove looks like three “lines.” The light from the scope lights up the bottom of the groove and the top edges. This is a picture of grooves cut in a fresh lacquer. It’s a very clean and quiet cut. This groove would make a very good sounding – albeit silent record.

When we add music to the picture this is what can happen to our cute little grooves. (Fig. 2)

We can notice the grooves move back and forth and they get fatter and skinnier.

Other things we can notice are that there are large sways in the groove that look a little like sine wave. These are the bass frequencies. Bass frequencies have large wavelengths and when cut they make the groove move in long sweeping curves. They’re so long I can barely get part of a wavelength in one slide.

Photo of record grooves with music content
Fig. 2
We can also see grooves that have tight little squiggles that look something like fish scales (center). These are the higher frequencies. Instruments like a cymbal or trumpet can make the very tight squiggles like those in the middle groove.

These sharp, high frequency squiggles are something we’re constantly dealing with. The sustained bright “S” sound is a particular challenge. In fact, there are so many reasons why “esses” are problematic I’ll devote a whole blog entry to just that.

The goal is to cut a “bright” groove that can still be played back by a standard quality needle and cartridge. If the movements of the groove are too sharp and bright, not all playback cartridges will be able to track the groove accurately. When a needle fails to track the groove you hear a fuzzy sounding distortion. A stiff DJ cartridge—one that is durable and can stand up to scratching and back cue-ing—will often be too stiff to accurately track all those sharp turns. “Hi-fi” cartridges are designed to have the flexibility to track those turns accurately. The trade-off is that they tend to be very delicate, and expensive.

Photo of record grooves
Fig. 3
In Fig. 3 we have cut some sine wave tones so that we can see more clearly the independent movement of the left and right channels.

This is a really interesting slide. It wasn’t easy to get all four grooves in one picture—and it wasn’t edited together in Photoshop, either!

The first groove on the left is a recording of a 4,000 cycle tone (4kHz) in both left and right channels in phase. Since the signal was in phase, the depth of the groove is constant, and you simply see the sine wave wiggles of the left and right walls. The left wall is the left channel; the right wall the right channel.

In the second groove you can notice that the left wall is straight. The left channel is silent and the right channel is playing the test tone on it’s own. Since the two channels are not identical in this example, the groove gets alternately deeper and shallower. This is because the channels are not in phase and it causes the playback needle to rise and fall. Remember that even though there are two channels of audio, there is only one point where the stylus touches the record. The movement of the groove, left and right, up and down, is completely analogous to the movement of the left and right speakers upon playback.

In the third groove both channels are off. This is our silent groove like the first photo above. And then the last groove has audio on the left channel and the right channel is silent. I love this slide—because it clearly displays what motion is shared by both channels and what is independent motion.

Next week we’ll look closely at the cutter head.

(Read all of the “Scott Hull on Vinyl” articles here.)

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Scott Hull on Vinyl, Part Two

Header image for Scott Hull on Vinyl seriesHow do we listen to CDs and MP3s? We hear them in the car, while jogging, over computer speakers while we blog (as I am now, listening to yesterday’s mastering project, Dave Matthews), and from the tiny little ear buds plugged into our iPhones.

How do we listen to records? We take the record out carefully, and often we’ll clean it. We double check the tone arm balance and anti-skate, we set the first side on the platter, cue the tone arm and sit back and listen,often playing an entire side, maybe even with our eyes shut.

Columbia Phonograph advertisement, Public DomainIt’s no wonder we have a different relationship with our records than we do with our CDs and computer files. The format engages us on many levels. Records have to be stored and handled carefully or the experience is lost. We’re rewarded with better sound when we spend a little extra time with an anti-stat gun or a record cleaner. The playback sounds nearly the same as it did years ago when we fell in love with music. And I haven’t even mentioned the larger graphics and interesting packaging.

So, I guess I am preaching to the choir, right? All of you understand why you are vinyl junkies. You can justify spending hundreds of dollars on a turntable and pre-amp since it helps you love the music even more. That really is wonderful and I hope all of you have had that experience.

We’ve all heard that the younger generation has rediscovered vinyl. I had a client in my room the other day who told me a story about a young man’s vinyl conversion. A son of a friend of this man was a huge Bob Dylan fan. In fact he believed that he possessed every single downloadable Dylan recording and was very proud of the history and folklore, which he knew by rote.

One day my client invited this friend and his son over to hear his very expensive and detailed record playback system. They left the room for a few minutes to talk, as the son was absorbed in listening to a familiar Dylan record. When they returned they saw he had been crying. And he told them that he had never really heard the album before. It was like everything he knew about Bob Dylan was only on the surface. He had heard the songs a hundred times before, but played back on vinyl it was mind blowing.

Next week I’ll get into the geometry of the record groove. It’s deep!

(Read all of the “Scott Hull on Vinyl” articles here.)

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