We take a look at the radical new iMac, as well as checking out the OS9 drivers for the Emagic EMI 2/6 USB interface, a device which seems to demonstrate how well USB audio can work.
Emagic's take on USB audio interfacing, the EMI 2|6.
Paul Wiffen

Last March, at the Frankfurt Musikmesse, Gerhardt Lengeling of Emagic told me that the Emagic EMI 2|6 USB audio interface could handle two audio channels in and six out simultaneously over USB and after the problems I had found with two-in, four-out devices for my 'Music on the new Macs' articles (see SOS November 2000-February 2001), I expressed my doubts somewhat forthrightly. At the time, the unit only worked on the PC, but Gerhardt promised that the same level of USB functionality would soon be available on the Mac as well. (Indeed, SOS reviewed the EMI 2|6 in the November 2001 issue, just after the Mac drivers had been released.)
Thanks to UK distributors Sound Technology, I was finally able to personally get my hands on this unit, with its Mac drivers, when I did an audio presentation recently at the MacExpo exhibition in London. On the day of the show, I really only had time to check out the ASIO drivers with stereo-out operation, but once I got back from last December's AES in New York, I had more time to test it, and found myself increasingly impressed with the implementation of the drivers both ASIO and Sound Manager.
Driving the EMI 2|6
First of all, the installer takes care of the setup of both drivers in one go. Most of the USB audio devices on the market either work automatically with Sound Manager (consumer devices such as Apple's iMic) or with ASIO (music-industry solutions from the likes of Tascam and EgoSys). Wherever I have found a unit which allowed use with both Sound Manager and ASIO, the two have had to be set up independently. In fairness, this is usually because the ASIO driver is produced by a third-party company, Propagamma, while the Sound Manager installation is usually an automatic setup with OS9.0.4 or later.
However, it is a welcome change to simply run one installer for both ways of working. But once this is done, there's even more good news. Emagic provide a switch (in the Apple menu or as a desktop alias) between the Sound Manager and ASIO drivers. In most cases, if you need to move from one to the other you need to either enable or disable an extension and reboot the computer. With the EMI 2|6, all you need do is select the item from the Apple menu or on the desktop, temporarily disconnect the USB connection and click OK, then reconnect. This is so much better as a working method than those of any other USB device I have tried.
Under Sound Manager, the EMI 2|6 is automatically recognised, and starts outputting any stereo audio being played back from both analogue and digital outs (S/PDIF) within a few seconds of being plugged in (just as with other USB devices, as this is handled automatically by the MacOS). On disconnection, the audio returns to the Mac's stereo out. If the computer is put to sleep during audio playback (of iTunes or Internet radio reception, for example), as soon as the computer wakes up the audio comes straight back on.
Getting audio into Sound Manager via the EMI 2|6 does require a minimal amount of setup on the part of the user. You have to go to the Sound Control Panel and select the Input tab, whereupon you'll be shown the available sound-input devices. One of these will be listed under USB Audio as External Mic, and simply clicking on this will select the stereo audio from the EMI 2|6. Whether the input audio comes from the EMI's analogue or digital input is decided by the setting of the hardware switch on the front of the unit, but if no S/PDIF input signal is connected the analogue input is used, regardless of the position of the switch. The choice of internal or external clock (which you would need if your source device was not able to receive wordclock input via S/PDIF, as in the case of most DAT machines and CD players) is also made via a switch on the front panel. Again, if a suitable clock is not present the setting of this switch is ignored. Once you know this (and it took me a while to work it out and then get it confirmed from the manual), it is actually terribly useful, as you find that you never get hit by unpleasant digital noises. And if you leave these switches set to Digital and External, as soon as you plug in a digital source it is sent straight into the Mac. Disconnect and the unit switches straight back to the analogue inputs and internal clock.
EASI Does It
So the operation of the EMI 2|6 under Sound Manager is almost entirely automatic. The price you pay for the convenience is, of course, that the unit only works in stereo, like all USB audio devices under OS9, and with a fixed and fairly unusable latency. Using Cubase's Audio System Setup, I measured the output latency as 93.515mS, which means that the input-to-output latency through Sound Manager is almost a fifth of a second (the figure that Cubase gives you needs to be doubled to get the total thoughput latency). Clearly, this makes overdubbing audio tracks in your sequencer difficult, unless you monitor the instrument you are playing at source, and playing virtual instruments is almost impossible.
To get around this, Emagic have produced both EASI and ASIO drivers. I was unable to test the EASI driver (included in Logic Audio 4.7.3 on the Volume 8 updater CD), as I still only have an ADB dongle. However, bearing in mind the excellent results I obtained with the ASIO driver in both Cubase and Nuendo, I can't imagine the EASI driver, Emagic's own standard, would perform any worse!
The ASIO Driver control panel for the EMI 2|6. With a fast Titanium PowerBook, the lowest latency setting (7mS output, 6mS input) is usable.
First I tried the ASIO driver on a 667MHz Titanium Powerbook and found its performance stunning. I was able to select the fastest of the three latency settings for 24-bit recording (you can only have 24-bit enabled for recording or playback at any one time), with all six USB outputs enabled. This sets up a 316-sample/7mS output buffer, and a 308-sample/6mS input buffer, for a total throughput latency of 13mS. Switching to 24-bit playback, I ran 24 tracks of 48kHz audio with the six outputs set to send a 5.1 mix, and they sounded great. The EMI 2|6 doesn't support 88.2/96kHz recording or playback, but then six outputs at 24/48 over USB is nothing short of a miracle.

Of course, the 667MHz Titanium is an extraordinarily fast computer, so I thought I should try a more average machine. Sticking with portables, I set up the EMI 2|6 on a Graphite 466MHz iBook, which has a G3 processor, running Cubase 5.01. As I suspected, the Fastest latency setting was too much for it; although playback never dropped out, it was full of glitches and noises. Things were no better at the Normal setting, which increases the output buffer to 900 samples (20mS) and the input buffer to 400 samples (9mS), for a total throughput of 29mS. Even at the Large setting, with a 2396-sample/54mS output buffer and a 435-sample/9mS input, for a total throughput of 63mS, I had to switch off six-channel and 24-bit operation before I could get faultless playback. However, as the EMI 2|6 and its driver are ASIO 2.0 compliant, you can monitor direct through the hardware, so the latency is not a problem for audio recording. I wouldn't recommend playing virtual instruments back through the EMI 2|6 using a computer with a G3 chip, nor would I expect to be able to use 24-bit recording or playback, six-channel output operation, or anything faster than the largest latency buffer, on a Mac without a G4 chip.
Sleep Disturbance
The one annoying thing that I noticed with both the Titanium and the iBook was that if the computer went to sleep, the USB audio connection would be lost when the computer awoke. However, this is not the fault of the EMI 2|6 but of the whole wretched business of energy-saving (I strongly suggest you turn off energy saving completely, or at least the processor sleep, when using any Mac for audio). Anyway, I found that disconnecting and reconnecting the USB cable brought everything back just fine.
Overall, I have to say that the EMI 2|6 is by far the best USB audio device I have tried on the Mac so far, and that it fully vindicates Gerhardt's claim of stereo input and six channels of output on the Mac. In defence of my own scepticism, though, it does take a pretty powerful G4 to make the most of all the emi2|6's facilities! I hope that we may see some OSX drivers soon, to allow the unit's six outputs to be driven by Core Audio (it already handles stereo output under OSX, but no input at the moment). Then the EMI 2|6 might just become the unit of choice for 5.1 surround output with the Apple DVD Player. After all, it is pretty enough to sell to all those people who buy Macs for the see-through appeal. ![]()