Audio Interfaces

By in 56knobs, audio, podcast on May 12, 2010
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an Audio Interface is a box that allows you to capture audio signals from professional microphones, mixer boards, and musical instruments like guitars. you don’t need need and interface to capture audio. the built-in port on your Mac or PC will do a fine job. the KnowTech show is made using output from the Tape Out going to a 3.5mm jack. it works. but if you want to take your sound to the next level you need an audio interface.

why? the Analog-IN has some problems. the inside of a computer is a noisy place. there are very high frequencies all around the inside of computer. crystals that drive the processors a multiple gigahertz, power supplies with floating ground, and whatever else unshielded on the inside is not good for the low frequency of audio. the analog-IN port wasn’t made to be a professional input. it was really made for web cam mics and other low-fi things. you know how Mackie goes on an on about the Pre-Amplifiers on the board? not one computer vendor says anything about theirs. it can’t be awesome.

the best advantage of an interface is that it is not in the computer. meaning that audio can be shielded from potential noise and converted into digital long before it gets sent into your computer. Digital IN has the advantage that it cannot get distorted. well, unless there’s a bad cable. but then it simple won’t work.

we evaluated practically every single interface when we worked on the Gear Media Tech show (which seems like forever ago). here’s what we found:

nearly every interface worked without drivers. we just plugged the interface into USB or Firewire and it showed up. this was the case for both Mac and Windows. the few interfaces that needed drivers were weird and we didn’t recommend them back in 2007. today it seems that the weird things are gone or got upgraded to be less weird. or that product just isn’t sold anymore.

when we connected a dynamic microphone to an interface we found that it didn’t have headroom. that is, the gain had to be turned up the all the way. and there was no fader to adjust it further. this could be a problem for some mics. fortunately, you have some options: you can get a inexpensive mixer board or a Mic Preamp.

today not much as changed. the models that we looked at back then are the exact same models that are on the market today. although there are more speciality interfaces, more 4 and 8 input interfaces and mixer boards with interfaces built-in then there were back then.

one thing that hasn’t changed is that the Marketing Department still lies. they like big numbers and always have. so they like to count every single thing that is input or output and add them together to make a bigger number. never mind that usually the totally usable inputs is TWO. but TWO is not a big number. don’t be mislead. count carefully and don’t believe the number on the box.

and this is the thing to really watch out for — really! count your inputs. remember that 8 is not really 8. the Alesis Mastercontrol is a good example: it has TWO mic pre’s. so if you are expecting to hook up what they are claiming as inputs you might be surprise. always look at the picture(s) and always read the specs. so the Alesis might not make your cut but it looks cool though enough to temporally fool.

don’t over buy. there’s a saying that we call “reassuringly expensive.” it applies to wine usually but it also applies to audio gear. lots of people dismiss products because they are cheap or look cheap or don’t claim big numbers. for example the M-Audio FastTrack it has 1 mic and 1 line so it would work just fine for a blue grass band! those guys all sing around one mic moving in and out to make the solos louder on the PA. just because it’s black doesn’t make it better either. you have to consider the Mic Pre for example. so a plastic interface may actually be the better interface.

some audio interfaces make something we call table spiders. this where cables are attached on the front and the back for not apparent reason. it makes for a clutter on your work surface. the TASCAM 144 does this. it won’t be a problem for everyone but it something to look out for when you are deciding between two different models that are nearly identical.

this is possibly the biggest thing to consider: can you hook up headphones? because if you can’t you won’t know if you have good levels coming from your Mic or Instrument. but there’s another question and that is what are the headphone monitoring? post Mic Pre would be ideal.

there are lots features that seem important but turn out not to be important. one of those is the “over light” indicating when the input is being overdriven by the source. but you’d have to check this on your recording to be sure it’s really happening. the other problem is that light is so small and not in front of you that you’d almost never know you were over unless the setup included “sound guy” monitoring the lights. we also questioned the level meters that are made from three or four colored LEDs (green, yellow, red or green, green, green, red). maybe the thinking was better than nothing. but if you are worried about monitoring levels then maybe you need a different solution. and then there’s that sweet black metal case. do you really care that it’s black? does the black case make the sound better? is black somehow more professional? think about that before paying a hundred bucks more for black.

the next question is always FireWire or USB? my stupid Mac doesn’t have enough USB inputs. and one of them is weird. so I’m automatically looking at interfaces that are FireWire. FireWire has less issues with power and chaining. and it’s also always less CPU intense because of the way it’s handled at the chipset level. but it’s not cheap. USB tends to be cheaper and but don’t let cheapness throw you off. it’s every bit as capable. and there’s almost no difference in the speed of the interfaces. the major difference is that sample rates on FireWire tend to go higher.

speaking of sample rates just what are these numbers 16 24 44 48 96 192? the first two are the sample size. there are two that we hear about today:16 or 24 bit samples.16 is great and 24 is better. you can’t tell the difference. it takes a lot of training and a lifetime of ear protection to make it into your 30’s with ears able to tell the difference. if you had “audiophile guy” telling you what to listen for exactly then maybe you might hear something.

the next numbers 44 48 96 192 is the sample rate. the number indicates the number of 16 or 24 bit samples made in 1 second. in the case of the first one it’s sampling 44 thousand times a second. 48 would be sampleing 48 thousand times a second. once again you can’t tell the difference.

here’s the thing. anytime you have a choice about how big to sample pick the bigger number. it can’t hurt. but also realize that 44KHz 16 bit sound is a really, really good sample for 93% of the day to day.

so then there’s the question of when you should go with a mixer (aka board) that has FireWire or USB outputs to your computer. when considering between a board vs interface: when you need the features of a board don’t try to make an interface do the job. it usually makes things way harder then they need to be. use a board if you have more mics then are supported on an interface. in the case of a podcast you are likely mixing down to mono anyway so stereo left and right is good enough. also mixer is more the only way to got when you need to do sub mixes to support a phone patch or Skype. this is also known as “Mix Minus” but we are calling it sub mixing from here on! we decided that the old “radio term” doesn’t really describe how most documentation is written explain how to use the feature. finally mixers boards are always impressive. they have lots of knobs, lights and switches. one could argue the more knobs the better (ha!). it makes the whole works more impressive and professional looking. but if you don’t need the knobs skip them. it’s complexity you don’t need.

who makes what

    Alesis
    Apogee
    Duet (weird thing)
    CME
    DigiDesign (now Avid)
    Echo
    Focusrite
    Lexicon
    m-audio
    MOTU
    Presonus
    Tascam
    TC Electronic

BIG

    Digi 03
    M-Audio Project Mix
    NRV10
    Mackie Onyx
    MUTO
    Tascam 1884

bottom line
an interface is a good way to improve your overall sound quality
is better then the Analog IN on your Mac or PC
buy from a place with a 30 day return policy