Field Test: MOTU HD192 High-Definition I/O Core System
Dec 1, 2003 12:00 PM, By Michael Cooper
MOTU's new flagship DAW I/O box, the HD192 High-Definition I/O, is available as part of a core system ($1,895; reviewed here) that includes the company's PCI-424 I/O card and AudioDesk
The 2U rackmountable HD192 offers 12 line-level analog I/O, AES/EBU I/O (one each), comprehensive Word Clock I/O and high-resolution LED-ladder metering. A single AudioWire port on the HD192 connects to one of four identical ports on the PCI-424 card using a 15-foot FireWire cable; the cable shuttles proprietary- (not FireWire) format digital audio between the HD192 and the PCI-424 card.
The PCI-424 card's four AudioWire ports can be used with any combination of MOTU PCI-based I/O boxes, including the newer 2408mk3 and 24 I/O, and legacy interfaces such as the 1296, 1224, 24i, 308, 2408mkII and the original 2408. Routing assignments are accessible for each box in turn via a drop-down menu in the included MOTU PCI Audio Console software or DP's Configure Hardware Driver window. The four AudioWire ports can accommodate up to 96 I/O when used with four MOTU PCI-based 24-channel boxes, or up to 48 I/O when used with four HD192s. A single ADAT 9-pin sync port graces the PCI-424.
The biggest breakthrough of the PCI-424 system is its integration of hardware with the included CueMix DSP” mixing and monitoring software. The PCI-424 card and CueMix DSP software together provide near-zero-sample-latency monitoring — no matter what buffer settings you use — via the outputs of any connected I/O boxes. (MOTU times the round trip through the PCI mixer at seven samples.) Although this system might forego the need for a hardware-based mixer and/or patchbays for some, I found that it integrated extraordinarily well with my Yamaha 02RV2 digital mixer. Keep in mind that this system only slashes latency for audio signals that are routed directly through the PCI-424 card, as when using DP's Direct Hardware Playthrough mode. It cannot, for example, reduce latency in virtual instruments or for tracks played through plug-in effects. According to MOTU, the PCI-424 system is compatible with all major Mac and PC audio software applications.TAKE ME HIGHER
The HD192 distinguishes itself from MOTU's other I/O boxes in a number of ways. First, it's the company's only 24-bit PCI box that can currently pass 176.4- and 192kHz digital audio, in addition to accommodating 44.1, 48, 88.2 and 96kHz sampling rates. Whatever sampling rate you choose, the HD192's A/Ds and D/As can each carry 12 audio channels. The HD192's dynamic range is specified to be 120 dB (A-weighted), greater than that offered by other MOTU boxes.
Analog I/O is via 24 servo-balanced (+4dBu nominal) XLRs (12 ins and 12 outs) found on the unit's rear panel. Two additional XLRs serve as AES/EBU input and output, respectively. Because the HD192 only accommodates 12 input channels at once, the only way to get a stereo AES/EBU signal into the HD192 is by selecting the AES/EBU input port (using included software) to temporarily replace a chosen pair of analog inputs. However, you don't lose analog outputs when you output AES/EBU signals; you simply choose which analog output pair you wish the AES/EBU output to mirror, and whatever goes out those analog outputs will also be multed to the AES/EBU output. The HD192's AES/EBU output can also mirror any pair of the unit's analog inputs, providing, for example, a convenient 2-bus return path to a digital mixer. The HD192 can resolve to SMPTE timecode arriving at any of its analog inputs, and can generate SMPTE at any standard frame rate and send it (at an adjustable level) out any analog or digital out.
Three BNC Word Clock connectors are on the rear panel. Two are system-wide Word Clock I/O that externally sync the unit's A/Ds and D/As when they're not locked to internal clock or the AudioWire bus' clock. (Only one I/O box in a multibox PCI-424 system can sync directly to external clock. That box then passes Word Clock on to the other boxes via the AudioWire bus.) The third BNC is a Word Clock input that syncs the HD192's AES/EBU I/O, allowing this section to resolve to a different sampling rate than the analog section. Independent AES/EBU I/O sample rate converters let you seamlessly merge audio from the analog and AES/EBU sections. You can even simultaneously operate the HD192's converters, AES/EBU input and AES/EBU output at three discrete sampling rates.
Two dozen 19-segment LED ladders show analog I/O levels for the HD192. These outstanding peak-hold meters are more highly resolved toward the top of their range. At the top of each LED ladder are two red LEDs that indicate digital “overs.” One of these LEDs is relegated to peak level readings, and the other is a dedicated clip LED. I noticed that the HD192's over LEDs routinely lit at levels a hair below that needed to light DP's various clipping indicators.THIS IS YOUR CUE
The HD192 Core System's included CueMix DSP software provides a virtual mixing board (dubbed the CueMix Console), complete with a fader, pan pot, clip LED, and solo and mute switches for each input channel currently in use in your system. CueMix DSP lets you route any combination of inputs to multiple pairs of stereo outputs across all interfaces in the PCI-424 system, without imposing any load on the CPU. This allows you to create as many stereo cue feeds — each having totally independent mix settings — as you have stereo buses in your system. You can name, save, recall and copy/paste different mix setups. Unfortunately, you can't hide inputs in the CueMix Console, making it a bit unwieldy on large projects. [MOTU says a software revision now lets you name inputs for easier navigation — Eds.]
However, DP users don't even need to use the CueMix Console to take advantage of the PCI-424's near-zero-latency monitoring, because DP's Mixing Board window (i.e., all of its virtual faders, pan pots, and solo and mute switches) also control Direct Hardware Playthrough monitoring. The output of DP's Mixing Board combines with that of the CueMix Console.
I used the HD192 Core System on a project in which I simultaneously tracked drums, bass, guitars and keyboards for several weeks, using Digital Performer Version 3.02 running on my dual-processor 867MHz G4 PowerMac. During all tracking sessions, I kept DP's buffer setting at 1,024 samples (greatly minimizing the hit on my CPU and improving stability) and could not perceive any latency in the monitor mix. I routed all musicians' cue feeds in Direct Hardware Playthrough mode using DP's Mixing Board window, never once opening the CueMix Console. I simply routed all audio tracks (both live and prerecorded) to pairs of ADAT Lightpipe outputs on my legacy 2408, which were, in turn, routed to my Yamaha 02RV2 mixer. Now I had the best of all worlds to work in: I could exclusively use premium outboard mic pre's, compressors and A/Ds (including the HD192's A/Ds) to record all tracks, completely bypassing my mixer. In addition, my 02R's “tape” inputs supplied my own monitor mix, and the 02R's aux 5 and 6 faders sent an independent (near-zero-latency) pre-fader mix to the musicians' headphone amp. Furthermore, this setup provided me with access to the mixer's EQ and talkback mic for the cue feeds. Perfect!CONVERTER COMPARISONS
The HD192's A/Ds sound dramatically superior to any other outboard ADCs (including the Apogee AD16) that I've heard in this price range. Upping the ante, my much pricier Apogee Rosetta 96's A/Ds sounded a bit warmer (less edgy) and smoother (exhibiting a flatter frequency response) than the HD192's A/Ds when each converter set was slaved in turn to its own internal clock.
The HD192's D/A conveters presented a flat spectral balance, devoid of the typical peaks and blurriness in the upper bass and low mids that inexpensive converters routinely manifest. Compared to a Benchmark DAC-1, the HD192's D/As exhibited less depth and nuance, and the DAC-1 sounded warmer and fuller. But keep in mind that Benchmark's DAC-1 is six times more expensive than the MOTU unit on a per-channel basis and lacks most of the HD192's potent functionality. Despite this tough comparison, the HD192's D/As add a lot of value to what is already an extremely cost-effective and impressive package.
Considering the HD192's rock-bottom price, any sins of omission are easily forgiven. That said, I wish the unit featured both a headphone output and calibration trims. The HD192's A/Ds are calibrated such that +4 dBu equals -14 dBFS, an excellent level for most tracking applications. However, I ran into headroom problems with the HD192 when tracking drums using preamps and high-sensitivity mics that don't offer pads.THE VERDICT
These are minor issues considering all that the HD192 Core System has to offer vis-a-vis its incredibly low list price: numerous, flexible and expandable I/O; excellent A/D converters and metering; serviceable D/As; onboard sample rate conversion; SMPTE reading/striping; near-zero-latency, multi-bus monitoring; and multichannel computer interfacing (which you don't get with most outboard converters). For discriminating engineers who want to use a highly specified front end to track to a DAW but who can't tolerate any perceptible latency, the HD192 Core System is a dream come true at a much lower price. I'm sold.
Mark of the Unicorn (MOTU), 617/576-2760, www.motu.com.
Mix contributing editor Michael Cooper is the owner of Michael Cooper Recording, located in beautiful Sisters, Ore.