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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Ask the Engineer: Tim Boyce on Your Unusual Music

Masterdisk Ask the Engineer graphic

Tim Boyce’s specialties lie in world, dance, dub, hip-hop, ethnic, remixed, and other genres, and his production credits include French Montana, SLDGHMR, Deathrow Tull, MSTRKRFT, Nightbox, and RAC. Tim’s creative desire to breath life into a static space allows him to finely tune an album into a living movement, not just a passive listening experience. If you need cutting-edge mastering, Tim’s your engineer.

Scan from COLLECTION OF DANCES IN CHOREOGRAPHY NOTATION (1700) at the Public Domain ReviewQ: My music is pretty unusual. What kinds of things should I talk to my mastering engineer about before mastering?

A: With so many styles of music, and hybrid/fusions happening in both the live and production music scenes, it’s sometimes difficult for a mastering engineer to guess what the artist has in mind. Sometimes it’s obvious what path to take. For example, a ballad or orchestral work has a very different mastering approach than an aggressive club banger. But what about a folk song with traditional instruments (banjo, fiddle, acoustic guitar), synths, and a hip hop rhythm on upright bass? (It happens: I heard it last week, and it was awesome!)

If you’re making new cutting-edge music, or re-defining your sound by trying something new, it’s often best to let your engineer know exactly what you have in mind. Let them know you really want the bass larger than life, even though it might not be the most dominant element of the arrangement. Or that we are experimenting with filters on the banjo to make it sound filthy and really cut through the mix like a dance synth. Your mastering engineer won’t know unless you tell them.

Personally, I love working on music that pushes the boundaries. You should always be able to feel free to reach out directly to your engineer. We’re not mind readers, but we’re all very nice and we want you to be thrilled with how your music sounds. So reach out, and lets talk.

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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

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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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