This was an article I saw the other day browsing around looking for something else. I felt there was enough basic FYI stuff to stickie it. Proper acknowledgment to the author over at Tweakheadz Lab.

Here is a link to the original article:
[="http://www.tweakheadz.com/audio_interfaces_1.htm"]The Best Audio Interfaces for your Home Studio by TweakHeadz Lab[/]="http://www.tweakhea…"]The Best Audio Interfaces for your Home Studio by TweakHeadz Lab[/]

Soundcard/Audio Interface FAQ

Questions and Answer Time

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Soundcards and Interfaces [[url=http://="http://www.tweakhea…"]1[/]="http://www.tweakhea…"]1[/] [="http://www.tweakheadz.com/audio_interfaces_2.htm"]2 [/]="http://www.tweakhea…"]2 [/] [[url=http://="http://www.tweakhea…"]3[/]="http://www.tweakhea…"]3[/] [="http://www.tweakheadz.com/audio_interface_pci_comparison_chart.htm"]4[/]="http://www.tweakhea…"]4[/] [[url=http://="http://www.tweakhea…"]5 [/]="http://www.tweakhea…"]5 [/] 6

Q) How many inputs and outputs should an audio interface have?
Tweak: The rule of thumb is that you need as many inputs as tracks that you will record simultaneously. Going to have 3 people over to jam and they all need their own track? Then you need 4 inputs. Simple, huh? Yep! Obviously, to do anything at all you need at least a stereo input and a stereo output. However, when recording music in a recording studio setting, even alone by yourself, two inputs can be at best inconvenient. You can work around this effectively by having a 4 bus (or 2+2 bus) mixer that can switch inputs of the mixer into the recording path and not affect playback of other tracks in the mixer. Regarding outputs, if you only have a single stereo out all your audio will go through it. If you have a mixer, and 8 outputs on your audio interface you can mix them at the board. However, it is certainly possible to do professional level work with just stereo i/o.
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Note the back panel of the [[url=http://="http://www.zzounds…"] MOTU 2408mk3[/]="http://www.zzounds…"] MOTU 2408mk3[/] with the full complement of analog, ADAT, TDIF, word clock and SMPTE ins and outs. A newbie certainly won't need all that digital connectivity, but you should know how things look on the professional end.
Q) Is a digital input/output (S/PDIF) necessary?
Tweak: No, but it helps to have the extra i/o, which can be used at the same time as the analog outputs in terms of playback. If you are recording to CDs or DATs in real time, it is very helpful. Also, you could connect it to a stereo system with Digital i/o and use the stereo to monitor your audio. If you can afford a card with an S/PDIF (digital) out in addition to analog outs, get it. By next year at this time you'll thank me. You can find out more about digital i/o and the different types in my [="http://www.tweakheadz.com/dat_recorders.htm"]Using a DAT recorder[/]="http://www.tweakhea…"]Using a DAT recorder[/] class.
Q) Is ADAT input/output necessary?
Tweak: If you have an Alesis ADAT multitrack you'd be mad not to get a card with an ADAT interface. But ADAT interfaces are found on more than multitracks. Most digital mixers have ADAT i/o. This interface connection allows the transmission and reception of 8 channels of audio in real time. So if you know a digital mixer is in your future you are wise to get an interface with ADAT i/o. If you plan to use an analog mixer you do not need ADAT i/o.

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The emu 1212m has both S/PDIF and ADAT on the card and has balanced audio connections, making it a great soundcard for the money.

Q) What is the difference between balanced and unbalanced audio connections?
Tweak: A) Balanced means it takes a 3 conductor plug like a headphone plug on each mono channel (as opposed to the little stereo jacks that carry both channels on a soundcard). Note that a balanced connection is NOT stereo even though they use the same "headphone style" TRS connector. (TRS stand for tip+ring+sleeve). Also note that to obtain the benefit of the balanced connection the output of the gear you connect must also be balanced.
The unbalanced connector is often called a TS connector. (TS has just a tip and sleeve, just like a guitar patch cable) These may come on 1/4" phone jacks or on RCA (home stereo) plugs.
Can you tell the difference? If the cable runs are short, it's hard to. If you turn the volume up all the way on your amp, you typically will find that unbalanced connections are noisier. The longer the cable run, the more noise in the signal. Unbalanced lines may pick up electrical interference or even act as an antenna for radio stations. But most of the time, in short runs, there are no problems.
Most soundcards that take balanced connectors will also take unbalanced, but the reverse is not true. If you are connecting unbalanced gear like a mixer with unbalanced outs, the balanced connections will not help.
Q) I heard that balanced connections are always +4 impedance wise and unbalanced are always -10. Does this make a difference?
Tweak: Good question. You are thinking! First, impedance is separate from the cable format. Its a newbie myth that impedance is tied to cable format. On better gear, balanced i/o can be set to -10 and unbalanced i/o can be set to +4. But usually, balanced outs tend to be +4. Impedance does make a difference. +4 gear will overload a -10 input and -10 gear will come into a +4 soundcard at a low level. If your recording levels are too low, see if you can drop the card's impedance to -10 to match the device you are recording. If you are always getting distortion, set the card to +4. Cards that have balanced i/o are more likely to be switchable between -10/+4. Those with unbalanced RCA connectors are usually fixed at -10. Getting a soundcard or audio interface with balanced connections and switchable impedance is, in my opinion, the best way to go.
Q) I don't want to mess with all this driver stuff, what can I do?
Tweak: A) Unfortunately, when you use computer-based recording applications you have to pay attention to drivers. You could go with a stand alone digital multi-track and sync it to MIDI time code so you could use all the great MIDI features of today's computers. With excellent MIDI synths and modules, a good midi sequencer, a hardware sampler and effects boxes you won't be missing much.
However, the intelligent thing to do is some research before you buy. Check on our forums for problems users are having with your motherboard and the device you want to buy. Avoid stuff that was just released last week. Wait a few months till you start reading about the card in discussion groups. Evaluate the horror stories you read. You don't want to be typing out the next one.
Q) What is the thing with Latency everyone makes such a big deal about?
Tweak: Latency refers to the amount of time it takes from when you press a key on your midi keyboard to when you hear the sound, when playing a softsynth. A few years ago there were big problems with soundcards that did not support ASIO. The windows MME drivers had terrible latency. Now with WDM and Asio drivers, on Windows, latency is at an all time low. The Mac's Core Audio has good latency out of the box. The improvements over the last few years in soundcard drivers actually make playing the faster soft synths a better experience than playing older slower MIDI synths.
Q: What does it mean when a driver says it is ASIO? MME? WDM? Direct Sound? Which is best...OOOPS, I mean what are the relative advantages of each?
A: Technically, the term "driver" refers to an API, or Application Programming Interface. The API sits between the hardware soundcard and the audio software. Your soundcard may install several drivers when you install it. These are "seen" by your music applications. In the application you have to choose which driver it will use. Remember, the drivers that come on installation CDs are probably outdated. Always go to the manufacturers website and download the latest set of drivers for your OS and soundcard or interface. Did I say always? Yes I did! You'll get us all irritated on the forums if you come complaining "my soundcard doesn't bleeping work (sob, whine, sob)" Then we have to start the routine...Did you update...(sigh).
Q: Where are these drivers on my system?
Your computer comes with audio drivers that are part of the operating system. Those are the ones you do NOT want to use (unless you have a Mac with OS X.) You install the drivers that come on CD from manufacturers and then update them at their sites. These end up in one of your Windows system directories and then are selected inside your software application. Note that simply installing the driver is not enough. You also have to select it inside of Sonar, Cubase, Fruity Loops or whatever. For Mac OS X the driver (Core Audio) is part of the operating system. Again, in the application you choose which core audio driver to use. You will see one for the onboard sound, and one for every audio device that has a driver.

Note the different ASIO drivers on my PC and where I can select them in the Ableton Live Sequencer. Only One of these drivers will work properly with my Emu 1820M audio interface. Can you guess which one? What if I want to use my Delta 1010? Of course I'd be crazy to select the Kore driver if I wanted the audio to go through my Emagic Emi 2/6 interface. But something you should know--don't use those "generic" asio drivers. On my systems those are the "Asio multimedia driver" and the "Asio direct X full duplex driver".

More on Drivers

So lets talk a little about types of drivers so you are a little more conversant.
MME stands for MultiMedia Extension that is a part of Windows that sets the rules for recording and playing back audio. It is typically used since the 1st Windows 3.0 systems as a default. It's slower because it is controlled by the operating system. Each soundcard maker had to write a .DLL file for the card to use the MME. These varied quite a bit in performance. Today, rule of thumb is not to us MME drivers in audio applications, unless the soundcard maker took the pains to develop and excellent driver. They usually don't.
Direct Sound came about around the time of Windows 95. It has the advantage of being able to playback softsynths with faster latency. However, Direct sound cannot record audio, it can only play it back, So if you plan to to audio recording, it is not a good choice. So, you dudes that write me and say "Can't (explicative) (explicative) RECORD!" Check to see if DS is ticked. Don't use it.
ASIO is short for Audio Streaming Input/Output This is an "open standard" developed by Steinberg for minimizing latency with virtual studio applications. where multiple streams of audio are processed. It has been adopted by most PC software makers. There are 2 versions. ASIO 1.0 and 2.0. 2.0 adds the ability to monitor several audio inputs at once. Cubase works best with asio drivers. Beware that there are drivers that call themselves ASIO drivers that are not. Most notorious are "asio multimedia" drivers. Don't use that one for music programs. Look in the driver list for a different ASIO driver that has the name of the interface in it. That is the true ASIO driver.
WDM stands for Windows Driver Model with Kernal Streaming This is a newer, lower latency driver that allows the application direct access to the "kernal" without going through the Windows OS. This results in latency figure that is fast like ASIO. It was introduced in Cakewalk's Sonar. So if you want to run Sonar, a card with a good WDM driver helps. However, today cakewalk does support asio drivers.
GSIF This is Gigasampler's driver model, optimized to work with their products, which require extremely tight latency with huge streams. If you plan to run Gigasampler, make sure your card has a GSIF driver. GSIF can only playback audio it cannot record. It is usually used in addition to another audio driver, such as ASIO.
Core Audio This is the main Mac OS X method of handling audio, developed by Apple. There is no Core Audio for windows. Mac OS9 used other methods including ASIO that are no longer supported in OS X.

Which is the right one to use? For the PC, only 2 main choices here: ASIO or WDM. Try them both if they are on your system. Use the one that seems the fastest. They should all be close. Typically, Cubase, use ASIO. Sonar use WDM.
Mac OS X users don't have much of a choice. It's Core Audio. However, there are some exceptions. MOTU has its own drivers available in Digital Performer as does Digidesign for its Digi 002 systems.

To finish up here, it's always best to go with the drivers that the soundcard/interface manufacturer recommends. You don't want to use Windows MME drivers in a card optimized for fast ASIO drivers. Yet it astounds me as to how many newbs fall into this hole in the rush to get their gear working.