Bob Ludwig—The Mastering Master Bids Farewell (Part 2) Decades of Digital Devices

Bob Ludwig first worked with a digital recording in 1978. Telarc Records brought a Soundstream machine to Masterdisk, and he cut one of their early classical recordings. From that time forward, Ludwig worked with almost every format and key piece of equipment in digital sound's evolution.

"Soundstream and the 3M Digital system sounded good, early on," he said, but then the Compact Disc was launched, and Sony came to rule the digital roost. "When I was starting out with digital mastering, we had the first Sony systems that were going to be used for CD production. ... I remember thinking to myself when I looked at that machine, ... this is probably one of a dozen A/D converters in New York City right now ... and it wasn't very good."

Ludwig with an early 1980s Sony U-Matic-based digital recorder

The poor sound of Sony's early A/D converters started Ludwig on a quest. "Being that we are a mastering studio and that we are competing with the planet, it is very important to me to have the very best analog-to-digital converter that was around." He noted, "When CDs were invented, millions of dollars were spent developing D/A converters, for CD players. Nobody seemed to care that much about the analog to digital converter."

A big early breakthrough was the dCS 900, which used dCS's Ring technology and drew on Philips' Bitstream concept of a very high-frequency sampling rate with few word-bits, a precursor to DSD. The dCS 900 worked internally at the equivalent of 24/44.1 or 24/48, at that time setting the bar high for digital resolution. Even though that 24-bit data couldn't be stored on industry-standard U-Matic videotapes, low-level musical details and sounds such as tape hiss were finally being successfully converted to bits and bytes. Thus, the 24-to-16–bit dither-down devices used to convert the data into a digital master finally had a high-resolution signal to work with.

Ludwig was convinced: "We were a very good customer of dCS. Every time they would upgrade their converters, ... we bought those new, every single time." Other companies, including Apogee, also greatly advanced the digital state of the art.

Today, Ludwig uses Merging Technologies Horus converters and a Pyramix workstation, but he prefers listening back through a dCS Vivaldi DAC. "It's the cream of the crop, the standard ... . It's a little more euphonic than the stock HORUS. I'm looking forward to the Apex upgrade ... and being delighted."

So have these state of the art converters brought us to the point where output equals input, sound-wise? "Nothing is output equals input, but we are so, so close. It's amazing how sensitive the human ears are. Using the HORUS ADC at really high-resolution and playing it back through the Vivaldi ... even my engineers, if I did an A-B [comparison with the source], would have to settle into it for a long time to hear anything different."

Ludwig noted "A lot of audiophiles say you have to really live with (a piece of equipment) for a while before you can discern the differences, then it becomes rather obvious. That is true in my opinion. It's just amazing how the brain goes."

In the early days of CD mastering, Ludwig used both the Sony and JVC videotape-based systems. When CD-R recorders came out, they cost a small fortune, and Gateway was first in line. They were among the first studios able to provide clients with reference discs during the mastering process. Later, for a time, DAT tapes became ubiquitous in pro audio.

In 1996, Ludwig says, Gateway was the first facility to do a full-HD mastering session. He remembers the date, October 7, the artist, Michel Jonasz, and the album, Soul Music Airlines (footnote 1). "We did that session 96kHz, 24-bit. We used Iomega Jazz drives [as the storage medium] and the Sonic Solutions DACs and ADCs with alpha (pre-beta) software. We had to kick it a lot to make it work, but we did it."

Sony developed the DA-9000 24-bit magneto-optical mastering recorder in the late 1990s (footnote 2), and Ludwig used one in the mastering of the The John Adams Earbox (footnote 3.)

As far as the humble CD goes, Ludwig said quality constantly improved, with pitfalls along the way. He recalls the discovery of so-called "pit jitter" in the late 1990s. He was working on a major pop album. An executive of the label close to the artist was overseeing the mastering process. He finished one song at a time and asked for reference CDRs, which he took home and listened to repeatedly and carefully on his high-end home system. "He got to be finely attuned to the sound," Ludwig said.

When the test-pressed CDs came back from the record company's manufacturing plant, they sounded awful. "It sounded extra sibilant, and it had a narrower soundstage and the bass wasn't as full. I thought, 'What the heck is going on?" Ludwig said. The client was unhappy. Ludwig analyzed the test CD and found it to be bit-perfect to his CD master. The plant analyzed the glass master and found it to be bit-perfect. Yet, test CDs played in a variety of players sounded different—worse—than CDRs Ludwig burned from his master.

The record company launched an investigation. It turned out that the glass-mastering machine, when working at high-speed, was creating slightly ill-defined pits that were then pressed that way onto the CDs. Ludwig explained. "When they're burning the pit, it's a function of how steep the beginning of the pit is." And that depends on the speed at which the CDs are burned. "2× is a little less sharp. 8× is way less sharp. All speeds make pits that are readable and will digitally clone, but [they] have different sounds" when played back in many CD players, at least of the 1990s vintage. The equipment at the plant was upgraded, including improved clocking for the glass-mastering machinery. The artist's CD was glass-mastered at 1× speed, and the production CD turned out OK.

Another vagary of digital sound had been discovered. Ludwig says, an executive from one of the major CD player manufacturers agreed that "pit jitter" was audible but couldn't explain why. To this day, he noted, when an album is glass-mastered and manufactured at several CD plants, test discs often sound different from plant to plant. "Perfect sound forever. Uh, yeah?"

Today, CDs are no longer mastered to balky videotapes or DATs. A modern CD master is a DDP image—a computer file—which is transmitted to the plant including MD5 checksum data for its contents and file structure. The data is verified bit-perfect through the glass-mastering and manufacturing stages. What ends up in the jewel case should sound like the master file.

CD mastering "really improved" when production and mastering in 24 bits became routine, Ludwig says. The higher sample rates common today in recording and production are "icing on the cake," but 24-bit original recordings, and keeping to at least 24-bits during the production stages, is key. In the case of most CDs produced today, the down-conversion to 16 bits happens when the CD master file is authored, nearly the final stage.

When DSD and SACD came along, Ludwig was an early adopter. He invested "a huge amount of money," converting his mastering room to 5.1 surround for hybrid-SACDs and DVD music projects. "We did tons of ... music videos and surround mixes."

"There's no question that well-done 5.1 SACD played through a very good system like I have here can beat the stereo recording as far as what Harry Pearson used to call the absolute sound of an orchestra," Ludwig said. "I do like 5.1. I had a lot of fun doing the Steely Dan Aja album in 5.1," as one example.

5.1 surround mixes mastered by Ludwig include The Band's Music from Big Pink, Frampton Comes Alive, Roy Orbison's Black and White Night (DVD and BluRay), and projects by Ben Folds, George Strait, Roger Waters, Bryan Adams, Eric Clapton, Queen, and Flaming Lips. Of course there were many others.

Surround sound, though, doesn't work for every artist every time. Ludwig remembers a "fragile" album by a female artist, whom he wouldn't name, that "fell apart" in surround-sound because "it was a record that just shouldn't have been pulled apart" and spread out.

Asked what he thinks about "immersive" audio and Dolby Atmos, Ludwig said, "I love the sound of really well-done 5.1 SACDs. I always wished that the full-range LFE channel (footnote 4) was used as a ceiling speaker! I’ve done several SACD’s for Tom Jung, who used it to great effect on some of his DMP releases. I haven't gone down the Atmos route on purpose. I'm happy I'm retiring and don't have to do it." He wasn't joking.

What is it about Atmos—Apple's version at least—that Bob doesn't like? First there's the fact that it is a lossy-compressed format, akin to (though more sophisticated than) MP3 or ACC. "With Atmos, we're going back to a lossy world. ... It screws up the sound in so many strange ways."

Also, "There is no way to remotely guarantee how the listener is going to listen to it." That's a big part of the point of Apple's Atmos. It could be via a pair of Apple's Atmos-supporting earbuds, or a smart-speaker gadget that throws sound around a room, or a real-deal immersive listening space with speakers around the room and on the ceiling. "When it's done really right in a great system, it's impressive. It’s still not lossless high-res, but it can be impressive. But, that is few and far between."

In the case of a hybrid SACD, there is usually a 2-channel stereo layer with its own discrete stereo mix. No such layer exists in the "immersive" formats, including Atmos. Instead, a "binaural" version is "folded down," derived from the multi-channel mix.

In the end, though, Ludwig isn't judgmental about how consumers listen to the music he has mastered. "Music is very healing. Whatever people want to use with music to make them feel better is fine with me."

Footnote 1: See

Footnote 2: See

Footnote 3: See

Footnote 4: The Low-Frequency Effects (LFE) channel is typically connected to a subwoofer and SACD creators typically use it for sounds below 120Hz or so. However, there is no specification that constrains the channel to low frequencies only. Ludwig's concept is to use the ".1" channel for overhead sounds or sound effects, and spread the low bass around the 5 "on the floor" speakers.

doak's picture

BOTH of You guys!!

Bangagong 1's picture

Thank you Robert Ludwig for all of your contributions to the realm of recorded music and setting the bar by which all future recordings of exemplary quality will be measured!! You will be sorely missed but never forgotten!! May your retirement be filled with immense joy!!