RME ADI-192 DD Universal Format Converter

Basically, the RME ADI-192 DD consists of three separate eight-channel digital format converters housed in a single rack-space unit. It also contains switchable SRC circuits that allow for both sample rate conversion and clock decoupling at a very high level of accuracy.
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As I keep acquiring new digital recording equipment—without necessarily getting rid of the older gear—I continually run into interfacing and compatibility issues. In fact, I think I've reviewed at least three digital format converters in this magazine over the past 10 years! First, I needed to convert from the now long obsolete Yamaha MEL-2 format to AES/EBU, ADAT ODI and TDIF gear, so the Spectral Translator Plus of the mid-1990s did that for me. I still have three of them. A few years later, I wrote about the Z-Systems 32-32r system (PAR, 4/98) which enabled me to keep 32 stereo channels of AES/EBU gear continually hooked up, and route them at will.

But then, I got into higher sample rate recordings, so the number of channels I needed effectively doubled (at least using the "double-wide" protocol — which came first), so I added another Z-Systems unit, various small M-Audio "necessary boxes" such as the CO3 and their S/PDIF and ADAT ODI 1x4 distribution units. And, of course, I can't forget the TASCAM IF-AE8HR (PAR, 9/01), which enabled me to record four channels of 88.2 kHz material on one TASCAM DA-78HR. I still have many tapes recorded in that format (which is still my "B Machine" backup system when recording sessions directly to hard disk) — often used in pairs, since playback of all eight tracks necessitates syncing up two DA-78s with two format converters in order to record eight tracks.

Finally, we cannot forget the extremely useful Apogee PSX-100 (PAR, 9/01) and Trak2 (PAR, 5/02) converters, because they both manage to do format conversion as well as ADC duties. In fact, it was because I had to commandeer my Trak2 a few months ago — in order to convert four 88.2 kHz channels coming from my venerable TASCAM recorder/converter system into the ADAT S/MUX format necessary to send some French organ music into my FW-1814 M-Powered Pro Tools system, that I finally said, "Enough already with multiple back-to-back-to-back format conversion systems! Surely someone must make a single box now which can do all these conversions at once."

Yes, there is! The answer is the RME ADI-192 DD, a single rack-space unit that does more slicing and dicing than any piece of digital equipment I've ever seen. I can simultaneously connect digital gear with in three formats (ADAT ODI, TDIF, and AES/EBU), and output whichever of the three inputs I select to all three outputs at once. It operates with PCM sample rates up to 192 kHz, and observes the double and quad-wide protocols of S/MUX and S/MUX 4. Not only that (speaking of slicing and dicing), but one can also change sample rates along the way if desired, since it also features an eight-channel SRC circuit — and a fancy high-tech clock generating system to keep everything locked together and free of clicks and glitches.

Features

Fast FactsApplications
Studio, post production

Key Features
Eight-channel triple, 24 bit/192 kHz format conversion between AES/EBU, S/PDIF, ADAT optical, and TDIF in any combination, and simultaneously; eight-channel sample rate conversion

Price: $1,495

Contact
RME/Synthax at 330-259-0308, www.synthax.com, www.rme-audio.com.Basically, the RME ADI-192 DD consists of three separate eight-channel digital format converters housed in a single rack-space unit. It also contains switchable SRC circuits that allow for both sample rate conversion and clock decoupling at a very high level of accuracy. The format conversion between AES/EBU, ADAT ODI and TDIF operates in both directions at the same time. RME's so-called Intelligent Clock Control permits extreme flexibility; the internal clock can operate up to 192 kHz, or the unit can lock to external word clock, or any channel pair of the digital input signals. LEDs of different colors show the present state of incoming and outgoing signals, SRC processing, and the lock and/or sync states.

The unit's front panel is laid out very logically, divided into seven sections with 46 LEDs and nine pushbuttons. (Over on the far right, next to the power switch, is a pair of TOSlink S/PDIF I/O jacks, which can substitute for AES/EBU channels 1-2.) It's really easier to just look at the front panel, and the flow chart in the manual, than it is to describe the elegant switching and routing setup.

The three input formats monitored on the left are sent to the three output source selectors on the right. Their selector pushbuttons give them access to any of the three inputs. Since the three selectors operate independently, one can either send a single input source to all three together, or send each input source to a different output format destination. And, as I said, along the signal pathway, one can select the SRC circuitry to act on one of the three inputs, whose output can then be sent to all three outputs at the new sample rate.

If only one AES input is used, the ADI-192 DD automatically activates "distribution mode," in which the single stereo input will be copied to all AES/EBU outputs. This special mode — active for the low "single speed" sample rates only — is also available when using the front S/PDIF input, and also allows SRC operation.

The rear panel is simplicity itself. Four sets of AES/EBU inputs and outputs, two pairs of ADAT ODI TOSlink-type inputs and outputs, and two TDIF DB25 connectors are arranged logically, as well as the word clock BNC I/O ports, with their associated 75 ohm termination switch (with confirmation LED).

In Use

I unpacked the unit and — having salivated over my downloaded user's manual for what seemed like an eternity while waiting for it to arrive — I was entirely ready to attempt the four channel 88.2 kHz setup I had been doing previously with my tricked-out Trak2. I mounted the ADI-192 DD in the rack out in the studio — a setup I use for tracking when I'm playing piano at the same time. In that rack, the analog-to-digital converters are my Genex GXA8 (PAR, September, 2002), and that unit outputs AES/EBU at all sample rates up to 192 kHz. I hooked four short Mogami AES/EBU cables between the Genex's outputs and the RME's four XLR inputs.

To get into Pro Tools M-Powered (running on my 1.5GHz 12-inch PowerBook), I now use my new M-Audio ProjectMix I/O control surface, so I simply connected a short plastic fiber optic cable between the first of the RME's pair of ADAT ODI outputs (which, in S/MUX mode, transmits channels 1-4) and the PM I/O. I powered everything up, ran the M-Audio control panel and selected S/MUX and fiber optic input, and opened an old four-channel, 88.2 kHz session template in Pro Tools 7.1. The mics were already plugged into my Manley Mic-EQ500 and D.W. Fearn VT-2 mic preamps and powered up, so as soon as Pro Tools booted up the session, and I put it into record on the appropriate four channels, the proper meters started reading, and I knew that RME had gotten everything right. A quick listening test confirmed this; I had the two stereo pairs I was expected. I know from bitter experience that, when bit-splitting isn't working, sometimes one gets mono, sometimes one gets only one channel, or sometimes nothing at all. But if you get good-sounding stereo, you know you're home free.

When using both TDIF ports (main and aux) on the RME unit, two DTRS machines can be connected; receiving Channels 1 - 4 and 5 - 8, respectively, at 88.2 kHz/96 kHz, or Channels 1 - 2 and 3 - 4, respectively, at 176.4 kHz/192 kHz. This mode, previously available to me only on the Digital Audio Denmark 2408 converter (and its successors, built for Merging Technology) is, in fact, the way I recorded several sessions in Europe a couple of years ago, including the 38 DTRS tapes I made in Paris for my Langlais organ music project. This was the material that caused me to seek out the ADI-192 DD in the first place, as detailed in this article's introduction. So, yes, I can now take these tapes directly into Pro Tools with only one device!

If only one AES input is used, the ADI-192 DD automatically activates "distribution mode," in which the single stereo input will be copied to all AES/EBU outputs. This special mode — active for the low "single speed" sample rates only — is also available when using the front S/PDIF input, and also allows SRC operation.

RME's implementation of Bitclock PLL (as opposed to simple word clock PLL) in its "SteadyClock" technology is said to combine the advantages of up-to-date digital technology with analog filter techniques. In fact, RME states that it finally accomplishes the result Digidesign's so-called SuperClock (256 times the WC frequency) was supposed to do, but often failed, due to the limits of high frequency transmission technology, and that regaining a low jitter clock signal of 22 MHz from a slow word clock of 44.1 kHz is no longer a problem.

Here in my studio, I have two very high quality word clock generating and distribution systems — Apogee's Big Ben (PAR, 3/04) and an updated version of the Rosendahl Nanosyncs unit reviewed for PAR in March, 2002 — necessary since I have elaborate recording installations in both my control room, and in the large studio room itself. Both units improve the sound of any source locked to them, and I can now picture a setup in which each of them is locked to the RME ADI-192 DD. Only one of them can be in the same room with it, so I'll just have to experiment which method (AES or WC) works better over the 40 feet or so (as the wiring within the walls goes) distance between my control room and studio equipment rack which contains the Nanosyncs.

RME claims that its eight channel SRC circuit exhibits exceptional conversion quality, formerly available only from synchronous SRC devices. I tested two such devices for PAR (from Weiss Engineering and dCS) back in June, 2000, but no longer have either one available for comparison. I do, however, have a Lucid SRC 9624 (PAR, 5/01), a Kurzweil DMTi (PAR, 6/97) as well as the SRC circuitry built into my various MOTU hardware interfaces, and I can state that the RME ADI-192 DD's asynchronous conversion process sounds much better than anything else I have here in Studio Dufay.

While monitoring the effect of the conversions through my Weiss DAC 1, Mk. II (PAR, 12/05), an extremely accurate high end digital-to-analog converter, I was pretty hard put to tell any difference at all in when upsampling, and when reducing sample rate, I heard only the typical sound of the lower sample rates themselves. Amazing! RME suggests that, since its SRC process is so transparent, it be left on all the time so that its clock decoupling and signal conditioning features would be available on all digital audio bitstreams coming in and out of the ADI-192 DD. I'm tempted to do this, for it virtually guarantees the lowest amount of jitter and a complete lack of clock sync issues.

Summary

PAR's editor doesn't allow any of its writers to use the term "Swiss Army Knife," but if I could, the RME ADI-192 DD would certainly qualify. It is, in fact, the "missing link" (if he'll let me say that) I've been searching for to finally ensure that all my digital audio equipment will play nicely in my studio sandbox. I'm sure it would do the same for any other studio that needs to interface as many (past and present) digital audio formats as I do. Very highly recommended.