The minimum requirements...
...for a computer based hard drive recording system are a computer that is fast enough for what you want to do, a hard drive that is fast enough to keep up and has enough storage capacity, recording software and an interface that does Analog to Digital and Digital to Analog conversion (ADA). For this article, we are focusing primarily on interfaces that have at least four analog inputs and outputs that can be connected to an analog mixing console if desired. While you might get by with older, slower computers for stereo audio, for multi-channel use you need something a bit faster and newer. Luckily, computers are pretty cheap now. The first thing you'll need to decide is which platform to use, PC or Macintosh. If you already have a computer, this may be a moot point. Both have advantages. The PC is good because it's fast and cheap and there's a lot of good software and hardware available for PCs. The downside is that they're much more difficult to configure. Macs on the other hand are pricier and have less support and a smaller installed user base. At the top of the line, Macs are very fast and are easier to set up and use. Of the half a dozen people I spoke too while researching this article, the Mac vs. PC camp was split almost down the middle although there was a bias towards the Mac on the high end. Minimum suggested Mac Requirements are usually a G3 or better with 96- 128 MB of RAM, while on the PC side, you'll want a 250-300 mHz Pentium with 128 megs of RAM. The hard drive you record onto is especially crucial. I spoke with Bob Cacciatore at Xistor, a company that specializes in digital audio storage mediums, and he strongly recommends using a SCSI drive, because they're 'smarter' due to RAM caching. Ultra-wide is the best, if you can afford it and you'll want at least a 10 gig drive, preferably an external drive, with all of your applications and system on the internal drive. Crucial factors to address when buying a drive are seek times, density, rotational speed and data throughput.
Should you buy a Pro Tools system?
Pro Tools is the de facto standard for hard drive recording in most professional studios, much like two inch tape is for analog studios. Unlike most of the newer systems that use a PC for much of the processing and DSP, Pro Tools is an integrated and proprietary hardware and software system. With very few exceptions (See the MOTU section), you'll need Digidesign software and hardware to run Pro Tools. As this is a product with years of research and user feedback behind it, it works very well and has lots of support from third party manufacturers. So, if you want to be able to transport your tracks to other studios to work on them, for overdubs or mixing for example, Pro Tools compatibility is essential. On the other hand if you plan to be working primarily in your own studio and starting and finishing all your projects there, then Pro Tools is not essential. In fact, there are quite a few systems available for much less money and with even better specs that might work just as well or even better for you.
Do you need an expandable system?
Most, but not all, of the audio cards today are expandable. But, most of them will also require additional PCI slots, which can be a problem. (The work around is to get a PCI expansion board) Some systems like the MOTU will support up to three interfaces from one PCI Card. In many cases, it's a software issue. The Gadget Labs boards, for instance, support multiple units on PCs, but not Macs. This may change in the future and is mainly just an issue of driver development. This may also be the case with other units. This is something to look at on a case by case instance, as it's constantly evolving.
Will you need to sync to tape?
This is beyond the scope of this article, but be aware that if this is something you want to do then you need to make sure the system you assemble can reliably pull this off. Some of the options for sync are MIDI Time Code (MTC), SMPTE Time Code and word clock. Very few interfaces will read SMPTE directly which is how most analog recorders will need to sync up, so you'll need some kind of SMPTE reader/generator/sync box. According to several people I talked to, MTC isn't really reliable for digital audio; you should use word clock instead. If you're using MDMs like ADATs or DA88s, this is less of an issue since the ADAT BRC for example generates several types of sync tracks. Check the MOTU section below for more on this subject.
What Software And Computer Will You Be Using?
This will affect the audio card you'll need. Not all boards support all of the available recording software packages. Both PCs and Macs use the PCI slot, so in theory all boards should work on both platforms. But, you need driver software for your computer and your software. As new software is written and updated, this will constantly change. Make sure that the hardware and software in the system you assemble works well together.
