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ATPM 6.05
May 2000



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Digital Audio and the Mac

by David Ozab,



Last month we discussed software. Digital audio software can only reach its true potential, though, when combined with hardware. The G3 and G4 feature 16-bit 44.1 kHz audio input and output, and the new iMacs have a decent sound system when Harman Kardon’s iSub is added. But both serious hobbyists and budding professionals need a dedicated audio interface. The prices range from about $250 to over $13,000, depending on the system level desired.

Interface Basics

All audio interfaces consist of two parts: (1) a data converter comprising an ADC and a DAC (see Part One), and (2) a DAT I/O, which translates digital data to and from a specific format (e.g., S/PDIF, AES/EBU, or ADAT) to allow transfer between the computer and a digital storage medium. Traditionally, these interfaces connect to a Mac by way of a card slot (originally the NuBus card introduced with the Mac II, and more recently, the PCI slot standard on all Power Macs). The introduction of the iMac has forced new solutions. The current use of USB is inadequate, due to bandwidth limitations. FireWire offers the greatest promise, but one that is yet unfulfilled.

USB Audio Interfaces

USB has replaced the old serial ports once common on Macs. As such, it was only a matter of time before the same MIDI interfaces that previously converted data from Mac serial ports would be updated to, or replaced by, USB interfaces. To bring audio to computers without card slots, namely iMacs, a few USB audio interfaces have also been developed. USB is not an ideal solution for audio, though. The bandwidth is far too limited to carry the large amount of information required to represent multiple tracks of digital audio. For iMac owners, however, it’s the only solution at present; iMac DV owners can look forward to the day when FireWire interfaces arrive, but until then USB is the only option. Here are a couple of examples:

veryniceRoland UA-30 and UA-100 Audio Canvas


Price: $248 for UA-30; $448 for UA-100

Pros: Inexpensive, iMac compatible, UA-100 includes effects and two pairs of MIDI ports.
Cons: Limited data bandwidth, no mention of Mac support on Web site.

veryniceSwissSonic USB Studio D


Price: $849

Pros: XLR, 1/4", and RCA analog in and out, iMac compatible.
Cons: Expensive for a USB interface, limited data bandwidth.

Consumer PCI Audio Interfaces (Under $1000)

For owners of G3s, G4s, and older Power Macs, PCI is the way to go. A wide variety of consumer interfaces is available for under $1000 as Digidesign’s monopoly of years past has been broken by Mark of the Unicorn, Sonorus, and now MidiMan. Creative Labs will soon join the fray with a Mac version of their SoundBlaster Platinum card, which they debuted at the last Macworld Expo. You might consider:

excellentMidiMan Delta DIO 2496


Price: $300

Pros: 24 bit/96K, analog configurable to +4 or -10, built-in digital mixer.
Cons: System requirements (G4 or G3 with 128 MB of RAM), unproven Mac support.

veryniceDigidesign Toolbox XE


Price: $545

Pros: 24 bit, ProTools LE included, four ins and out with analog and digital combined.
Cons: 192 MB RAM recommended, more expensive than comparable Mac/PC cards.

excellentSonorus STUD/IO


Price: $849

Pros: 16 channels ADAT, plus S/PDIF and stereo analog, 24 bit/96K, compatible with third-party software.
Cons: No packaged software.

excellentMOTU 2408


Price: $995

Pros: 24 bit, 24 channels selectable between ADAT, TDIFF, and analog (eight only); expandable with add-on modules (takes price into $2000-$3000 range).
Cons: Included AudioSuite software is just stripped-down Digital Performer.

goodDigidesign Digi001


Price: $995

Pros: Numerous inputs and outputs (XLR, 1/4", S/PDIF, ADAT), two MIDI ports, ProTools LE included.
Cons: Not compatible with any third-party sequencers.

Professional PCI Audio Interfaces and Hardware ($7000-$13,000+)

Interfaces in this category are not for the hobbyist or starving musician. They are for the professional engineer willing to invest real money to build a state-of-the-art studio. As often said in the context of luxury cars, “If you have to ask how much it is, you probably can’t afford it.” This high-end market is still dominated by Digidesign. Consider:

excellentDigidesign ProTools


Price: $5,995 for ProTools|24; $7,995 for ProTools|24 MIX; $9,995 for ProTools|24 MIXplus.

Pros: 24 bit/96K, up to 64 tracks with effects and EQ, ProTools 5.0, TDM and AudioSuite Plugins.
Cons: Expensive, requires two PCI slots (except ProTools 24|MIX) and a Digidesign Audio Interface (888|24 I/O ($3,695), 882|20 IO ($1,245), 1622 ($1,595), or ADAT Bridge IO ($1,245)).


+4, -10: Two standard settings of amplitude in analog recording. Consumer devices are generally set to -10 while professional devices are set to +4.

1/4": A standard analog audio jack, either unbalanced (tip-sleeve) or balanced (tip, ring, sleeve). The balanced version reduces noise in the same way that an XLR cable does. Balanced 1/4" cables are also used to carry stereo signals.

ADAT: Alesis’s 8-track digital tape deck. Uses a proprietary optical format also known as Lightpipe.

S/PDIF: Sony Philips Digital Interface Format. A digital audio format most commonly found in consumer devices. Uses either RCA or optical connections.

TDIFF: Tascam Digital Interface File Format. The proprietary format used by Tacsam’s DA-88 digital 8-track tape deck.

XLR: A balanced audio line consisting of two wires carrying the same signal 180° out of phase and a third ground wire. When the signals are placed back in phase, any line noise is eliminated. (Note: XLR stands for “ground, left, right,” and these cables can also carry stereo signals.)

Next Month: Digital Audio and the Mac Part V: Digital Audio on the Internet.

appleCopyright © 2000 David Ozab ( David Ozab is a Ph.D student at the University of Oregon, where he teaches electronic music courses and assists in the day-to-day operation of The Future Music Oregon Studios.

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Reader Comments (1)

Srikanth Kailas · July 31, 2005 - 23:19 EST #1
Can you breafly explain different formats of audio interface and there functioning concepts

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