Digital Pipelines

Apr 1, 1999 12:00 PM, Jeff Casey

The introduction of the Alesis ADAT in 1992 was a huge step toward the annihilation of analog technology and the development of the all-digital studio. True, digital audio technology had been around for a while at that point, but it really wasn’t until the ADAT and, later, the Tascam DA-88 hit the streets that the majority of musicians began to understand the potential of this technology.

The success of these two machines initiated a quest to improve fidelity in other areas. Soon digital mixers popped up, digital audio workstations gained widespread popularity, digital dynamics processors hit the market, and various digital support gear joined the party.

Today studios on virtually every level can produce an almost entirely digital recording, starting at the sound module/sampler/preamp, going to the console, to the multitrack, through effects processors, and finally to 2-track. Several companies have even started to manufacture microphones and speakers with built-in digital converters, so the digital chain can begin and end right at the transducers. For better or for worse, the all-digital world has arrived.

The mere presence of digital devices, however, does not make a studio completely digital. Sure, the more digital equipment you own, the greater fidelity your recordings will have. But to really capitalize on this technology, you need to have digital connectivity between gear. After all, the signal path is only as strong as its weakest link, and if you’re constantly sending audio through converters, from analog to digital and back again, degradation is inescapable.

Although 2-channel digital transfer formats such as S/PDIF and AES/EBU are a big part of successfully connecting equipment, what really makes the all-digital studio possible is multichannel (that is, more than 2-channel) digital audio transfer formats, specifically ADAT Optical and Tascam’s TDIF. These two protocols have revolutionized the industry almost as much as their respective MDMs have. Today people who don’t even own ADATs or DA-series recorders are using ADAT Optical and TDIF connections to get from one piece of gear to the next. This month, we take an in-depth look at these two formats, the products that use them, and ways of getting from one format to another.

History Lesson

Neither ADAT Optical nor TDIF was originally designed to be what it has evolved into. The initial idea behind each was to provide a way to transfer multiple audio tracks simultaneously between identical MDMs (ADAT to ADAT, or DA-88 to DA-88), not between MDMs and other gear.

Our story begins with Alesis circa 1991 and the development of the revolutionary ADAT. While the company was designing the original unit, the good folks at Alesis realized that they needed to provide a means of transferring audio digitally between two machines. After all, the ADAT was to be a modular recorder, intended to connect with others of its kind; it would be silly if users lost a generation every time they made a backup tape or copied tracks to another machine. Alesis knew all too well that critics would have a field day if it didn’t come up with a solution.

At the time, AES/EBU and S/PDIF were the only widely used digital audio formats, and they could handle only two channels of audio. Obviously, using either one to transfer eight tracks between ADATs would be cumbersome. So Alesis created its own format that was capable of carrying eight separate signals, and ADAT Optical (also known as Lightpipe) was born. I distinctly remember doing a session in 1993 and being amazed to discover that the ADAT could digitally transfer all its tracks from one machine to another at the same time. Wow!

In 1994, Alesis realized that Lightpipe had much potential that was not yet being exploited. The company started offering ADAT Optical connectivity on some of its higher-end synthesizers and signal processors as a way of directly interfacing with an ADAT. Other manufacturers realized that this format could potentially become the de facto standard and wanted to get in on the action. Shortly thereafter, the ADAT Group was formed, consisting of third-party manufacturers working together to build (and capitalize on) the ADAT empire. Today more than 300 companies belong to the ADAT Group, and a good portion of them manufacture products with Lightpipe connectivity.

Over in the competing camp, Tascam wheeled out the DA-88 in 1993, and along with it came the company’s answer to Lightpipe, the proprietary Tascam Digital Interface Format (TDIF). That was around the same time that Alesis began contracting with third-party developers. So did Tascam, and a struggle over digital data formats soon ensued–another battle in the war already occurring between the two companies.(For an interesting retrospective look at the state of MDMs in the early ’90s, check out "Brave New World" in the October 1993 issue of EM.)

Fast-forward five years to 1998. The ADAT and DA-88 have established their places in the annals of audio history, Alesis and Tascam have both expanded their lines of MDMs, and the Lightpipe and TDIF protocols are more popular than ever. Alesis has even created an entire division devoted to developing and promoting ADAT Optical technologies. At this point, Lightpipe connections are certainly more abundant in third-party products than are TDIF connections; that’s probably because ADATs are more popular than DA-series recorders in personal studios. In any event, it’s almost unheard of for a major digital product to be released today without options for ADAT Optical, and very often TDIF, connectivity.

In a moment, we’ll take a look at some of the products that support each format, as well as the many products on the market that change signals from one format to another. But first, let’s take a look at the nuts and bolts of the unique format that spawned a revolution.

Lighting the Pipe

Although Lightpipe and TDIF accomplish the same thing, they do so in very different ways. The ADAT Optical protocol works on a 24-bit NRZ (Non-Return-to-Zero) encoding scheme that sends information along a high-bandwidth fiber-optic cable.

What does that mean in English? Basically, each audio channel can be carried at 24-bit resolution (regardless of whether you’re actually working with a bit resolution that high). The samples from all eight audio channels are organized into a single block of information called a "data frame," each of which contains 256 bits. If you do the math, you’ll discover that this leaves 64 bits that can be used for synchronization and specialized "user" applications (discussed shortly).

This data frame is then sent through a fiber-optic cable by means of a light transmitter (hence the name "Lightpipe") and is received in the other unit by a light-detecting element. A single-sided, 5-volt power supply runs the system. When all is said and done, the receiver’s output produces an exact replica of the signal that was introduced at the transmitter, save for a nominal propagation delay.

Lightpipe cables typically can run up to about 33 feet, although some people have had success with runs as long as 50 feet. By using more expensive glass cable, you can run ADAT Optical cables quite a bit farther, even without special drivers. Alesis claims that it has successfully tested runs up to 100 feet using these specially terminated glass cables.

One of the greatest benefits of an optical format is the low cost of the cables; in fact, they’re so cheap that Alesis gives away a 1-meter cable with every new ADAT. Also, the connections are small enough to fit on a PCI card or digital-mixer card without the need for a breakout box, and the fiber-optic design virtually eliminates the possibility of electromagnetic interference and ground hum.

But the coolest thing about the ADAT Optical format is that after you account for sync bits and various other information bits, four bits are left over in every data frame. Of those, two are reserved for potential future uses to be determined by Alesis (for example, upgrading the system resolution without the need to change formats), and the other two are denoted as "user-definable." This doesn’t mean that just any ADAT owners can simply decide what they want to send through the Lightpipe; rather, these bits are available to designers looking to implement Lightpipe in new products. For example, the manufacturer of a remote-controlled digital mic preamp could use the extra bits to send control messages between the stage unit and the mix position.

The ADAT Optical format is free to anyone who wants to incorporate it into a design; all you have to pay for is licensing the ADAT logo, should you decide to use it to market your product. As I mentioned earlier, Alesis recently created a separate division, Alesis Semiconductor, devoted to the development of Lightpipe. Its mandate is to promote ADAT Optical as the industry standard in digital audio transfer. Whether this will actually happen remains to be seen, but it seems like a good bet. Although the company’s plans for future Lightpipe implementation are still hush-hush, the live-sound industry appears to be the next frontier. The use of Lightpipe in home-theater systems opens up a great many possibilities, so that direction will probably be explored, too. The future looks exciting for the pro-audio industry and consumers alike.

Keep in mind that although the ADAT Optical specification currently supports 24-bit data, not all gear is capable of handling 24-bit digital audio transfers. Some equipment can send and receive only 20-bit information, a limitation of the Alesis controller chips used to implement Lightpipe in certain products. In fact, Alesis’s current crop of ADAT recorders supports 20-bit Lightpipe transfers only.

T-otally DIF-ferent

Tascam was reluctant to provide me with information on the specifics of the TDIF format (something about the folks in Tokyo not wanting us to publish their secrets). I searched the Internet, talked to my engineering friends, and begged and pleaded, but I still came up with squat. Tascam keeps this stuff pretty well guarded!

Here’s what I do know: whereas the Lightpipe format collapses the multichannel digital information into a single frame of data, TDIF uses a multiwire 25-pin D-sub cable that transmits channel information independently, without creating a composite stream. Obviously, these custom cables are a bit more expensive than optical cable–a 3-foot cable retails for $110, and a 16-foot cable will cost you $135–but they can be run farther than their optical counterparts, albeit with more susceptibility to interference.

The Supporting Cast

Of course, this article cannot possibly serve as an exhaustive guide to every product that supports ADAT Optical and TDIF–there are more than 300 companies manufacturing Lightpipe products alone. But I have compiled a list based on data provided by Alesis and Tascam and from new-product information that I gathered at the 1999 Winter NAMM show in Los Angeles. It’s not comprehensive, but I think it’s a good representation of the gear that affects most personal-studio owners. The focus here is on digital connectivity–specifically TDIF, Lightpipe, AES/EBU, and S/PDIF options. (Unless noted otherwise, AES/EBU and S/PDIF I/O refer to 2-channel connections.)

MDMs. Ironically, simply interfacing between two identical MDMs doesn’t seem very exciting anymore. But being able to connect those machines to the wealth of mixers, DAWs, hard-disk recorders, sound cards, synths, outboard gear, and even competing MDMs that support TDIF and Lightpipe certainly is exciting. (Actually, with the advent of onboard digital patch bays, the ability to digitally transfer from one MDM to another is quite cool in itself.)

Lightpipe I/O currently comes standard on the full line of Alesis ADAT recorders, including the ADAT XT20, LX20, and post-production-oriented M-20. ADAT recording is now at 20-bit resolution, but you can set the Type II recorders to produce a 16-bit output signal complete with dither so that they’re compatible with the older ADAT-XT and "blackface" models.

Other MDM manufacturers–not surprisingly, companies that have developed S-VHS recorders based on the ADAT–also offer Lightpipe connectivity. For example, the 20-bit Studer V-Eight offers eight channels of ADAT Optical I/O. If you feel like dusting off a 16-bit Fostex CX8 or RD8, each of those units provides standard Lightpipe ports, as does the Panasonic MDA-1. (The Fostex and Panasonic MDMs are no longer manufactured, so they’re not included in the table "Putting It All Together.")

On the Tascam front, 8-channel TDIF I/O is standard fare on all of the DA-series multitracks, including the DA-38, the DA-88, and the ultrahip DA-98. All three Tascam decks can interface with the AES/EBU format via the optional IF-88AE.

Interestingly, you’ll find no TDIF connections on the discontinued Sony version of the DA-88, the 16-bit PCM-800; there are only eight channels of AES/EBU. Not surprisingly, Alesis doesn’t offer a TDIF option for ADATs, and Tascam doesn’t provide Lightpipe connectivity. Tascam, however, recently released a nifty TDIF/Lightpipe converter, the IF-TAD.

MHDRs. The ability to digitally connect a modular hard-disk recorder (MHDR) with an MDM can be a valuable asset to the personal-studio owner. For example, you might want to use the MDM as your main recording medium, fly tracks out to the MHDR for editing, and then fly them back to the MDM, all the while maintaining sync between the decks. Or you could do all your work within the MHDR and use the MDM just for backup purposes. Many people use a combination of MDM and MHDR simply to double their track count.

Akai, Fostex, and E-mu are leading manufacturers of MHDRs, and all three companies offer Lightpipe I/O options for their units. The Fostex D-90 offers eight channels of Lightpipe I/O as a standard feature, and the D-160 has two Lightpipe ports for interfacing with a 16-track ADAT system. Both 16-bit units offer optical S/PDIF I/O for backing up data to DAT. E-mu’s 16-bit Darwin recorder has an 8-channel Lightpipe option in addition to the S/PDIF I/O that ships with the standard unit.

Akai’s machines offer both ADAT Optical and TDIF connections. The Akai DR8 and DR16 Plus recorders have options for 8-channel Lightpipe I/O, 8- channel TDIF I/O, and 8-channel AES/EBU I/O. Connections for AES/EBU and S/PDIF come standard with both decks.

Roland’s DM-800, predecessor to the company’s popular VS line of production systems, had an option that allowed 8-channel TDIF and Lightpipe connections. So, if you can find a DM-800, it may or may not be outfitted for multitrack digital audio transfer. For those folks who have $24,950 to spend, Otari’s 24-track RADAR II system offers 24 channels of TDIF I/O.

Digital mixers. In any studio, audio is constantly being routed between the multitrack and the mixing console, so maintaining digital integrity is probably more important here than anywhere else in the signal path. That’s why most digital mixers offer an abundance of connectivity options.

The Panasonic WR-DA7’s digital I/O must be configured from scratch by adding expansion cards. It has three card slots, each of which can accommodate an 8-channel ADAT Optical, TDIF, or AES/EBU (hardware switchable to S/PDIF) card. There is also an 8-channel A/D/A card, and the mixer provides switchable AES/EBU and S/PDIF 2-track inputs and record outputs (on XLR jacks). Furthermore, aux sends 1 and 2 employ S/PDIF on RCA jacks.

Sporting just as many I/O options, the Yamaha 02R offers four expansion slots that accept 8-channel Lightpipe, TDIF, and AES/EBU cards. The stock mixer also comes with AES/EBU and S/PDIF I/O. The 02R’s smaller cousin, the Yamaha 03D, offers the same card options but has only one available slot, as does the even smaller 01V. The 03D provides both AES/EBU and S/PDIF I/O, while the 01V offers S/PDIF only. The long-anticipated Mackie Digital 8•Bus (D8B) also has three card slots for adding Lightpipe or TDIF inputs, and it comes standard with AES/EBU and S/PDIF connections.

The Tascam TM-D1000 comes standard, of course, with 8-channel TDIF I/O. The TM-D1000 also gives you two XLR AES/EBU outputs; an optional expansion card adds eight more channels of TDIF plus four channels of AES/EBU or S/PDIF. The Tascam TM-D4000 ships with S/PDIF and AES/EBU I/O and allows you to install up to three 8-channel cards for additional TDIF, ADAT Optical, AES/EBU, or analog I/O. Tascam’s top-of-the-line console, the TM-D8000, provides 24 dedicated TDIF tape returns and inputs that can be configured to accept analog, TDIF, S/PDIF, or AES/ EBU signals.

The Spirit Digital 328 offers 16 channels of ADAT Optical input, 24 channels of Lightpipe output, and 16 channels of TDIF I/O on the base unit, along with AES/EBU and S/PDIF I/O. Similarly, the now-discontinued Korg 168 RC provides 16 channels of Lightpipe I/O and stereo S/PDIF, but it has no TDIF or AES/EBU ports. The 24-bit Roland VM-3100 will have an optional interface box that adds both Lightpipe and TDIF connections.

Finally, for those with fat wallets, RSP Technologies’ Project X ($3,500 for a basic system) can be outfitted with both Lightpipe and TDIF cards, as well with an 8-channel AES/EBU card or several A/D/A cards.

Audio cards/DAWs. Although you’d think that a digital audio workstation is a self-contained environment, in reality it rarely is. Many people prefer to use DAWs like MHDRs, employing them as editing and processing tools rather than as comprehensive recording systems. Others like to back up data to a particular MDM format simply because random-access storage can get to be a bit expensive. And then there’s the fact that any facility set up to work on outside projects should be equipped to handle whatever tape format the client might provide. So even if you use a DAW, chances are you’ll need to connect to other gear.

For the past five years, Digidesign’s Pro Tools system has remained the most popular Macintosh-based DAW for audio production. Pro Tools is a customizable working environment, and to get any I/O with it, you have to buy interface modules. Pro Tools can interface directly with an ADAT system by using the Digidesign ADAT I/O Bridge, a rack-mount unit that provides 16 channels of Lightpipe I/O. Digidesign does not currently make a dedicated TDIF module, but that doesn’t mean you can’t use Pro Tools with, say, a DA-88. You’d just need to have a format converter to translate the TDIF signals to optical or AES/EBU and then fly the audio into the appropriate Digidesign interface (the ADAT I/O Bridge for Lightpipe, or the 888 for AES/EBU). The same, of course, is true for any piece of gear discussed here that doesn’t support a particular format.

A strong entry into the cross-platform DAW market last year was Ensoniq’s PARIS. Like Pro Tools, PARIS offers a customizable I/O system in the form of a modular expansion chassis. The Interface MEC can be loaded with up to nine 8-channel A/D, D/A, or ADAT Optical cards. S/PDIF I/O is standard on the MEC, as well as on most other PARIS interfaces. The A/D and D/A cards both offer 24-bit conversion.

The cross-platform Lexicon Studio accommodates a number of digital formats. As of this writing, two I/O modules are available: the LDI-12T offers two channels of analog I/O and two channels of switchable S/PDIF/Lightpipe I/O, while the LDI-16S provides eight channels of both TDIF and analog I/O. Options are available for the LDI-16S that add eight channels of AES/EBU I/O or eight channels of ADAT Optical I/O.

The PC-based V8 workstation from Digital Audio Labs can use optional PCI I/O cards for interfacing with both Lightpipe and TDIF devices. Multiple I/O cards may be cascaded, and the V8 provides full transport control of ADAT and DA-series recorders directly from software. AES/EBU and S/PDIF I/O options are available as well.

Soundscape’s integrated PC-based SSHDR-1 hard-disk recording system comes standard with eight channels of TDIF I/O and two channels of S/PDIF I/O. But to send and receive Lightpipe signals, you must have an additional I/O module. The company’s Mixtreme PCI audio card provides 16 channels of TDIF; however, you’ll still need an external breakout box to gain access to Lightpipe and other types of I/O. There are three I/O modules that can be connected to either system: the SS8IO-1 (balanced analog/Lightpipe/TDIF), the SS8IO-2 (TDIF/Lightpipe), and the SS8IO-3 (unbalanced analog/TDIF), all of which will be discussed later. TDIF ports are used to connect all Soundscape hardware.

The Otari PD-80 digital audio workstation has options for TDIF and Lightpipe and comes standard with AES/EBU I/O. Otari’s RADAR II system provides TDIF connections on the base unit, and you can gain ADAT Optical and AES/EBU I/O with the assistance of the company’s stand-alone UFC-24 format converter. The Pyramix Virtual Studio from Merging Technologies also offers TDIF and Lightpipe I/O options.

As part of its Soundlink line of products (which includes the 168 RC mixing console), Korg has introduced the 1212 I/O, a cross-platform PCI audio card that offers 8-channel ADAT Optical I/O, as well as 2-channel analog and S/PDIF I/O. More analog I/O channels can be added using the company’s 880 A/D and 880 D/A, both of which can also function as stand-alone Lightpipe-to-analog converters.

Along the same lines, Sonorus offers the StudI/O PCI audio card, which provides two sets of optical I/O parts that can be independently switched between stereo S/PDIF and 8-channel ADAT Lightpipe formats. When used in combination with one of the company’s hardware AudI/O units, the StudI/O can accept AES/EBU, TDIF, and analog signals. SEK’D recently rolled out its Prodif Gold ADAT card, which brings Lightpipe and S/PDIF signals into and out of a PC.

Also taking advantage of the Lightpipe format is Mytek, best known for its high-end mastering converters. Through a joint venture with Sonorus, it has developed the expandable DAW 9624, which consists of a StudI/O card and the Mytek 8X96-series 24-bit/96 kHz 8-channel A/D and D/A converters. In addition, the Mytek units provide conversion to and from AES/EBU and TDIF (optional). The DAW 9624 is yet another great way to bring analog signals into an ADAT system.

One of my favorite devices is the MOTU 2408. This ingenious box can serve either as the front end to a DAW or as a stand-alone audio-format converter. The 2408 supports 24 channels of I/O that can use any combination of its three sets of TDIF ports, three sets of Lightpipe ports, two sets of S/PDIF ports, and eight analog inputs and outputs. A PCI card allows direct connection to either a Mac or a PC for use with a variety of software applications, and you can connect additional 2408s to your system for a total of 72 channels of simultaneous I/O.

Lastly, the cross-platform ADAT Edit package from Alesis simply provides eight channels of Lightpipe I/O on an ADAT/PCR PCI card. It does not come with other types of digital or analog I/O.

Synthesizers. It seems only logical that synths with multiple outputs should take advantage of TDIF and Lightpipe. Well, it’s taken a while, but manufacturers are now coming around. Obviously, Alesis would be foolish not to implement Lightpipe on its synths: in the company’s current product line, the QS7 and QS8 have ADAT Optical outputs.

Korg’s Trinity line of workstations, including the Trinity, Trinity Pro, and Trinity ProX, offer Lightpipe output options. And using the Kurzweil DMTi format converter, you can interface a K2500 with both Lightpipe and TDIF devices. I think we’ll see a lot more of such products in the next few years.

Other gear. Although TDIF and Lightpipe are designed to carry multiple audio channels, they can also serve lesser functions. Several companies have recently started incorporating these formats into their multi-effects processors and preamps.

Currently, you can find ADAT Optical and TDIF outputs on several mic preamps, including the Drawmer 1962 tube preamp, which delivers a 24-bit signal in either format at the output. The Aphex 1788 8-channel mic preamp can also be outfitted to connect with TDIF- and Lightpipe-friendly units (a great solution for live recording).

The Studer D19 MicValve 2-channel mic/line preamp card for the modular D19 series offers ADAT Optical output and 20-bit D/A conversion. The company’s D19 MicA/D for the same series also supports Lightpipe. Alesis’s Q2–a descendant of the Quadraverb, the first non-ADAT machine to employ Lightpipe–provides ADAT Optical I/O, as well.

Digital Labs has pioneered quite a neat device: the first Fiber Optic Patch Panel for ADAT Optical and S/PDIF optical formats. This box allows you to patch digital signals just as you would on an analog patch bay. The single- rackspace panel has eight fiber inputs and outputs on both the front and rear panels. Also included is a Toslink-to-glass connector that allows you to run cable lengths up to a mile.

Confounding Conversion

It’s great to be able to stay in the digital domain throughout the recording and mixing process, but what happens when you need to send eight or more channels from one multitrack format to another, or to analog, or to a completely different digital format such as AES/EBU or S/PDIF? Several companies make format converters, and they come in all shapes and sizes. What follows here is the lowdown on the current crop of useful little boxes that will get you from one format to another.

But remember, it’s not always necessary to have a stand-alone converter to go from format to format. Other devices (especially mixers and DAWs) can often be used to convert signals, provided they offer compatibility with the formats you’re working with.

For example, if you have a Panasonic WR-DA7 with a sufficient number of expansion cards, you can generally get wherever you need to go, be it from Lightpipe to TDIF, Lightpipe to S/PDIF, TDIF to AES/EBU, or TDIF to analog. The same is true of the Yamaha series of digital recording consoles: an 02R or 03D makes a great centerpiece for a studio, simply because of all the I/O options it provides. (For a comparative look at the gear discussed in this article, including the digital formats supported, refer to the tables "Putting It All Together" and "Converters Compared.")

Alesis AI-3. The Alesis AI-3 ($499) is a stand-alone 8-channel A/D/A converter that translates signals to and from the Lightpipe format. The AI-3 provides eight analog inputs and outputs on balanced 1Ú4-inch TRS connectors. The converters are 20-bit with 128-times oversampling and deliver a dynamic range of 96 dB. The front panel comes with signal-present and peak LEDs for each channel, and the unit can be switched between +4 dBu and -10 dBV operation.

Apogee AD-8000. The AD-8000 ($5,995) is a comprehensive 8-channel conversion solution, capable of interfacing with ADAT Optical, TDIF, AES/EBU, S/PDIF, and the analog world. It features eight 24-bit A/D line-level converters that boast a dynamic range of 114 dB.

The AD-8000 outputs the converted signals through Lightpipe (optional), TDIF (optional), or eight channels of either AES/EBU or S/PDIF (selectable). The unit has stereo S/PDIF and AES/EBU inputs as well, and options provide an additional two or eight analog outputs. The AD-8000 can also be used as a multiple-format conversion system to transfer signals between all available interfaces simultaneously. And because all outputs are active at once, the AD-8000 makes a great distribution system.

The AD-8000 features the patented UV22 process for translating high-resolution digital audio to 16 or 20 bits without losing quality. In addition to the standard 44.1 and 48 kHz sampling rates, the AD-8000 locks intelligently to word clock or any digital input, including video (with the optional video synchronization card).

Apogee FC-8. The FC-8 ($549) is a reasonably priced transfer system for moving between TDIF and ADAT Optical. The unit is bidirectional, so the TDIF and ADAT machines can each act as either master or slave, and the FC-8 will simultaneously transfer signals in both directions. Housed in a freestanding enclosure about the size of a DI box, the FC-8 has three LEDs that indicate Lock, TDIF Active, and ADAT Active. In addition to the 25-pin TDIF port and the optical port, there’s a BNC connector that provides word-clock output.

Apogee Rosetta AD. The Rosetta AD ($1,295) is a 2-channel, 24-bit A/D converter that outputs either ADAT Optical, TDIF, AES/EBU, or S/PDIF–all are standard on the base unit. (Apogee is planning a companion unit, the Rosetta DA.) There are also two AES/EBU outputs, so two signals can always be fed simultaneously from the unit. The Rosetta AD features balanced XLR connections and has an impressive dynamic range of 120 dB. Sampling rate on the standard unit is switchable between 44.1 and 48 kHz, but as an option you can also get the Rosetta AD with selectable 88.2 and 96 kHz rates ($1,995). An A/D/A version, the PSX-100 ($2,995), is also available.

Graham-Patten ADAT Interfaces. This line of converters is designed for use with computer sound cards that offer only ADAT Optical connections. Four models are available.

The ADAT-1 ($1,499) converts eight channels of analog audio into a Lightpipe signal. Input connectors are 1Ú4-inch TRS jacks, and level trims are provided for each of the inputs. A/D conversion is 20-bit. Audio sampling and the ADAT output can be internally referenced or synchronized to word clock or to an AES3-ID signal from the reference input. Two versions are available: one that operates at 44.1 kHz and another that works at 48 kHz.

The ADAT-2 ($1,499) is the D/A companion to the ADAT-1. It adds a stereo headphone output with associated volume control to allow monitoring of any channel pair. There is also a sync output providing either a silent AES3-ID signal or word-clock reference.

The ADAT-3 ($899 to $1,299) takes four AES/EBU pairs and converts them into a single 8-channel Lightpipe stream. It has a reference input/output connector and a 9-pin D-sub miniature remote-control connector. The ADAT output can be synched to any one of the main AES inputs or to word clock or a secondary AES3-ID sync signal fed to the reference input. With the ADAT-3 synched to one of the AES inputs, you can also use the reference connector to output word clock. The control connector allows you to individually mute each input pair and identifies which of the main AES inputs is being used as the sync source. Six models of the ADAT-3 are available. The ADAT-3/A0, ADAT-3/A2, and ADAT-3/A4 have AES/EBU inputs on XLR connectors, with zero, two, or four sample-rate converters, respectively. The ADAT-3/B0, ADAT-3/B2, and ADAT-3/B4 have AES3-ID sync inputs on BNC connectors, with zero, two, or four sample-rate converters, respectively.

The ADAT-4 ($899) performs the reverse function of the ADAT-3. Here, Lightpipe signals are converted back into four AES/EBU pairs. The AES outputs are synchronous with the ADAT input, and there is also a sync connector providing a silent AES3-ID sync or word-clock output. Two versions are available: the ADAT-4/A uses XLR connectors, while the ADAT-4/B employs BNC connectors.

Korg 880 A/D and D/A. The Korg 880 A/D ($950) and 880 D/A ($800) are designed for use with either the 168 RC or 1212 I/O to expand the analog I/O of those units via ADAT Optical. However, you can also use these gizmos with any device that supports Lightpipe. Both units offer eight balanced analog connections on 1Ú4-inch TRS jacks, with 18-bit A/D and 20-bit D/A converters.

Kurzweil DMTi. The DMTi ($1,310) is another converter designed for use with a specific product–in this case with the Kurzweil K2500. But it works well as a stand-alone converter for translating between ADAT Optical, TDIF, AES/EBU, and S/PDIF.

On the input side are eight channels of K2500 protocol, eight channels of TDIF or Lightpipe (optional), and two stereo channels of AES/EBU (one of which is switchable to a stereo channel of S/PDIF optical). Outputs include four stereo AES/EBU channels (or three stereo AES/EBU and one stereo S/PDIF optical), eight ADAT or TDIF channels (optional), and eight Kurzweil Digital Stream channels. In order to transfer directly between TDIF and Lightpipe, two DMTi’s are required. Any of the outputs can be synched to an external clock or to 44.1 or 48 kHz internal rates.

Lucid Technology ADA8824. The latest offering from this high-flying converter company is the ADA8824 ($3,295), a 24-bit A/D and D/A interface designed for Lightpipe systems. The ADA8824 changes eight analog signals into ADAT Optical (and vice versa) using delta-sigma converters that yield a dynamic range of 113 dB; special digitally controlled attenuators on the inputs and outputs help the user achieve the greatest dynamic range possible. Connections are made via balanced XLR jacks. There are also eight channels of AES/EBU I/O and an S/PDIF I/O. The 2-rackspace unit features discrete LED meters for each channel.

Midiman Pipeline 858. The Pipeline 858 ($899.95) is an 8-channel, 24-bit conversion system that takes analog signals and outputs them in Lightpipe format (or vice versa). The Pipeline provides balanced and unbalanced analog I/O, selectable word widths, MIDI I/O, word-clock I/O, and selectable internal sample rates of 44.1 and 48 kHz. The Pipeline also features patented BitRazor technology, which automatically encodes and decodes 24-bit audio on two ADAT tracks, turning any ADAT into a 24-bit recorder.

Midiman SAM. The other offering from Midiman is the SAM ($399.95), the "S/PDIF ADAT mixer." It accepts Lightpipe and S/PDIF I/O, providing conversion between the two formats. But with the SAM, you can also mix all eight ADAT Optical signals down to a stereo pair of S/PDIF, using the individual channel gain and pan controls included on the unit.

MusicNet AD24 and DA24. Available from Wave Distribution, the half-rackspace MusicNet AD24 ($749) and DA24 ($549) provide 24-bit analog-to-Lightpipe and Lightpipe-to-analog conversion, respectively. All analog connections for the two units are via XLR jacks, and both support 44.1 and 48 kHz sampling rates. The DA24 also is switchable between 16- and 24-bit conversion.

The AD24 can generate or sync to word clock, while the DA24 only generates word clock. The AD24 features a Calibration mode that keeps the converter’s internal modulators and integrators properly matched. The DA24 includes a deemphasis filter that eliminates the high-frequency boost that is often used with commercial CDs.

Otari UFC-24/8. The UFC-24/8 ($2,595) universal format converter from Otari can transfer up to 24 channels at a time to and from PD, SDIF-II, Lightpipe, TDIF, and AES/EBU formats. (There are 8 AES/EBU channels on the base unit, and it can be retrofitted for 24 channels). You can link multiple units to provide sample-accurate transfer of more than 48 channels.

All outputs (except what’s being used as the source) are active simultaneously, so the UFC-24/8 also makes a terrific distribution system. MIDI I/O is provided for control of routing presets and input-format selection. You can save all parameters of the UFC-24/8, as System Exclusive data, to a MIDI storage device and later recall it.

Prism Sound MR-2024T. The Prism MR-2024T ($2,570) is designed to bring AES/EBU connectivity to Tascam DA-38, DA-88, and DA-98 recorders. The MR-2024T converts between TDIF and AES/EBU or S/PDIF (selectable) and offers some other features aimed at high-quality applications.

The recording mode can be set to eight 16-bit tracks, six 20-bit tracks, four 24-bit tracks, or two tracks at 24-bit and 96 kHz. The MR-2024T tags the tape so that the correct mode is always selected on playback. You can connect a second Tascam machine to the same MR-2024T as a security backup; a monitor selector is provided to determine the playback machine.

The MR-2024T’s synchronization options are versatile. Using DA-88 sync, the transport can run free or locked to video or word clock while the unit provides sync outputs. Alternatively, the MR-2024T can synchronize the DA-88 to an AES3 or S/PDIF input. You can slave up to 16 machines, for a total of 96 tracks at 20-bit or 64 tracks at 24-bit.

Sonorus AudI/O. Sonorus recently introduced a line of converters intended to work as both stand-alone units and interfaces for the company’s StudI/O digital audio card.

First up is the AudI/O AES/8 ($999), which has eight channels of TDIF, Lightpipe (used to network with the StudI/O card), and AES/EBU (switchable to S/PDIF) I/O. The outputs are not simultaneously available, so the AES/8 can’t operate as a distribution device.

Also available are the AD/9624 and DA/9624 ($2,995 each), both high-quality 24-bit/96 kHz converters. The AD/9624 accepts analog signals via balanced XLR connections and converts them to Lightpipe, four pairs of AES/EBU outputs, or TDIF (optional). The DA/9624 takes any of these digital data formats and delivers it as analog signals.

Sonorus’s AD/24 ($799) and DA/24 ($599) are also 24-bit converters, but both are designed to work with digital data only in the Lightpipe format. Analog connections are handled by balanced XLR jacks, and the internal clock runs at 44.1 or 48 kHz. All three units provide word-clock connections.

Soundscape SS8IO-1. The SS8IO-1 ($1,695) provides a means of converting signals between TDIF and Lightpipe, and between either format and analog. The 2-rackspace unit offers eight channels of balanced analog I/O on XLR connectors, which are fed to 20-bit Crystal converters. Simultaneous transfer in both directions is possible. If you’re connecting the system to a Soundscape DAW or audio card, the TDIF port is used to make the connection, so the SS8IO-1 can serve as either an analog or ADAT front end. Word-clock and Superclock RCA jacks are included. The internal sampling rate is switchable between 44.1 and 48 kHz.

Soundscape SS8IO-2. The SS8IO-2 ($349.95) offers many of the same functions as the SS8IO-1, except it lacks analog I/O. The half-rackspace SS8IO-2 can serve as a TDIF-to-Lightpipe converter or as an ADAT interface for a Soundscape mixing system. (If you’re using the Mixtreme audio card, which has two TDIF ports, you could employ the SS8IO-2 as a Lightpipe I/O and use the spare TDIF port for TDIF, giving your system eight channels of each format.) As with the SS8IO-1, data can be transferred in both directions simultaneously, word-clock and Superclock connections are present, and the clock is switchable.

Soundscape SS8IO-3. The third offering from the folks at Soundscape is the SS8IO-3 ($599), which converts between eight channels of unbalanced analog audio and TDIF. This unit is designed to provide an inexpensive analog I/O solution for owners of the Mixtreme digital audio card, but it also serves as a stand-alone unit for converting TDIF to unbalanced analog.

Spectral Translator. The Translator ($995) gives you an effortless way of transferring eight audio channels from one digital format to another. The unit provides compatibility with Lightpipe, TDIF, SMDAI, and Yamaha Y2 devices. An upgraded model, the Translator Plus ($1,495), adds AES/EBU transfer.

The Translator can slave to external clock signals from any of the supported devices. If the selected source is not present, the Translator provides master clock to keep sync-dependent equipment running. A handy bypass mode ensures that you never have to disconnect cables.

Studer D19 MultiDAC. The MultiDAC ($3,175 for a basic system), part of Studer’s D19 line of modular processors, delivers 24-bit D/A conversion from a number of formats. AES/EBU inputs are standard, and there are options for either ADAT Optical or TDIF inputs. Outputs appear on balanced XLR jacks. A monitor output is also included, and you can selectively monitor certain channels or sum all eight channels into a rough submix. This one is a stretch for the personal studio, though: I don’t know of too many that are equipped with a Studer D19 rack.

Tascam IF-88AE. The IF-88AE ($1,245) is a single-rackspace unit designed to bring AES/EBU capabilities to a DA-series multitrack system. It has four XLR jacks that accept AES/EBU signals, in addition to a D-sub jack for TDIF signals. Conversion can take place in either direction, so the IF-88AE makes a decent stand-alone converter for any TDIF or AES device.

Tascam IF-TAD. Lo and behold, Tascam blinked first! The IF-TAD ($199) is a converter designed to connect ADAT Optical and TDIF devices. It has LEDs to indicate data present for each format, as well as a BNC word-clock output. I was floored when I saw the IF-TAD in an Alesis third-party developer catalog. When Alesis and Tascam start advertising each other’s products, you know that times have changed for the better.

Piping Hot

Perhaps we’re getting a little carried away with all this fuss over digital connectivity. With the wide array of options and accompanying confusion, the eternal cynic in me says, "Give me an analog cable...I want a TT patch bay!" But I know those days are numbered, and that’s probably for the better.

The death knell of analog has sounded, and the all-digital world is upon us. We must be prepared for the new millennium, and ADAT Optical and TDIF will play a big role in ensuring that we are. Without a doubt, these two formats will be around long after the ADAT and DA-series decks disappear.

Former EM Associate Editor Jeff Casey is still looking to get a record deal but recently realized that he probably needs to finish producing the record before that will happen.