What Does an Audio Interface Do

What Does an Audio Interface Do


Hey there podcast friends, Pod Sound School is
in session. Learning is the only thing the mind never exhausts, never fears and never
regrets. Let’s go. Hello again podcast-prenuers. How
are you feeling? I’m Studio Steve and this is Episode Five. Today we’re going to discuss
an exciting topic, Interfaces. So far we’ve covered acoustics and the treating of our
room and reduction and control of noise. Then last time we talked about microphones, dynamic
and condenser. Now that your room is treated and you’ve decided on a microphone we need
to record our voices into a computer and put together our podcast. The first stop after the microphone is our
interface. This is the piece of equipment that we plug our microphone into that then
connects to our computer or laptop, most commonly nowadays through a USB or Thunderbolt port.
What is an interface? What does it do? How does it work? What kind of brand do I need?
Like all the episodes on the first season we’ll be staying on the surface of how things
work. Next season we’re going to dive deeper into the technicalities. Once of the best ways to learn is to just
start doing it, start playing with your gear, pushing buttons, making practice recordings,
etc., but having a basic understanding will help you make an informed decision on what
gear to purchase and save you time in the fumbling around stage. Let’s quickly talk
about audio interfaces. The audio interface is really the boss of your computer recording
system. It performs many functions and has many key elements. For today’s discussion we’ll quickly talk
about the five basic aspects of an interface, preamps, converters, sample rate and bit depth,
MIDI and in and outs. If that sounds like a lot and maybe even a different language,
not to worry little pod-a-neers. It’s actually pretty simple once you break
it down. Number one, preamps. If you remember from
the microphone episode, we talked about how the microphone converts the vibrations in
the air into an electrical signal. Well, once it’s been converted into an electrical signal
that signal is then sent through a microphone cable and plugged into our interface. From
here the first place the signal comes in contact with is one of the interfaces built in preamplifiers.
What a preamp does is to boost the low mic level signal into a more powerful line level
signal. This line level is necessary for recording. The quality of the microphone and the quality
of the preamps are really the two biggest factors in how the recording turns out. A
good quality preamp is necessary to really hear the full potential of your microphone.
Many of the consumer brand interfaces are built with preamps that are not very high
quality. For this reason it’s popular to purchase a preamp separately from your interface and
simply use the line inputs on the interface instead of the mic inputs. If you’d like to
hear more about preamp recommendations, contrast and comparisons, check out our blog at PodSoundSchool.com/blog. Only a fraction of the couple hundred dollars
you’ll spend on an entry level interface is going toward that preamp. On the other hand,
if you spend a couple hundred dollars on just an entry level preamp, who’s only circuitry
is dedicated to boosting mic level, you’ll have much better results. A really expensive
microphone will sound like garbage ran through a garbage preamp and a cheap microphone can
sound really great being ran through an expensive preamp. Although that expression you get what you
pay for definitely applies to audio production, that doesn’t mean that you have to spend thousands
of dollars to achieve great sounding vocals on your podcast. If you’re on a super tight
budget, you can check out the Penny Pinchers Alternatives episode where we discuss the
cheapest and quickest ways to get going. The next most important factor is number two,
the converter. You’ll make this rather snappy, won’t you?
I have some very heavy thinking to do before 10:00. After the preamp has added power to our microphone,
the interface will send the signal to an AD converter, which stands for analog to digital
converter. This is where the interface converts the analog signal into digital data. A gigantic series of ones and zeros. The job of the AD converter is to make this
transformation as accurately as possible. Once the signal has become digitized, the
interface then sends the signal through the USB or Thunderbolt cable into the computer
to be recorded and manipulated by the recording and editing software, while performing this
magic task at almost the same moment that the interface also collects the sound coming
out of the computer through the same USB or Thunderbolt cable and brings it back through
another converter called the DA converter. Yep, digital to analog. This converter takes
the giant stream of numbers and transforms them back into an analog signal that can be
sent to speakers and headphones. Wow Rhonda, who designs this stuff? I know, right? Number three, sample rate and bit depth. The
terms sample rate and bit depth are selling points of interfaces. These terms are functions
of the converter. Sample rate is basically how many pictures the AD converter takes of
the sound per second. The measurement for this is in kilohertz. You’ll see this written
as kHz. Kilo stands for 1,000, so for every one kilohertz, the AD converter will take
1,000 pictures of the analog audio. Bit depth is basically the quality of each of these
pictures. The higher the quality of picture, the tastier the sound. The more pictures you take per second and
the higher quality of those pictures will give you a better and more real to life sound,
but it will also give you larger file sizes. The only thing you really need to understand
about sample rate and bit depth is that as the numbers get bigger, so does the audio
quality. With that being said, you don’t need the highest available numbers. Currently the
highest end interfaces offer 32 bits and 192 kilohertz. This creates much larger file sizes
and really isn’t necessary to achieve sweet sounds. A majority of podcast audio and music producers
do just fine with 24 bit and 96 kilohertz or 96K, and not that anybody exports their
music to CDs any more, but to put those numbers into perspective, the sample rate of a CD
is 44.1K and the bit depth is 16 bit. We’ll get into this more later when we talk about
exporting your MP3 for iTunes or for your web host. Number four, MIDI. MIDI stands for musical
instrument digital interface. This allows you to connect a MIDI keyboard or another
MIDI controller to your computer. There are countless digital instruments or virtual instruments
that can be controlled from this MIDI input. Lastly, number five, ins and outs. This is
what it sounds like, inputs and outputs. How many inputs and outputs an interface has varies
a lot. How many you need depends on your intentions. How many microphones will you be using? How
many hosts or cohosts do you have? Will you have guests? How many headphones do you need
to support? Are you also going to use the interface for music creation? All of these
considerations will let you know how many inputs and outputs you need. You really want
each voice or each instrument to have it’s own input and channel for optimum control
and quality. There are work arounds using mixers where
you can send multiple microphones through one or two inputs, but this won’t allow you
to adjust each voice separately later in mixing, so if you’re planning a round table podcast
with five friends and occasional guests you might want to get an interface with six to
eight inputs. If it’s just going to be you, or you and a cohost, then a two input interface
will probably be just fine. However, since you’re already making an investment into an
interface, it’s never a bad idea to leave yourself a little room to grow and that’s
our quick rundown on interfaces. What did we learn? One, we need a tasty preamp.
Two, AD and DA converters change the analog signal into a digital signal. Three, sample
rate and bit depth, referred to audio quality and file size. The bigger the number, the
higher quality and file size. Four, MIDI lets us plug a keyboard into our computer and play
and record virtual instruments. Five, ins and outs are how many inputs and outputs an
interface has. There you go. Always a pleasure getting with
you and chatting about audio toys. If you have any questions you can shoot me an email
directly at [email protected] and of course you can come along and find
us on our social medias @podsoundschool and if you really want to dive in head first and
make a dent in the world come get involved with the overachievers club over on our Patreon
page, Patreon.com/podsoundschool. Great job today everyone and I hope you’re not thinking
about giving up. I’m really excited to help you sound your best. Happy casting. Did you learn quite a bit? I know I did darlings.
Remember, success is walking from failure to failure with no loss of enthusiasm. Goodbye
for now.

4 thoughts on “What Does an Audio Interface Do

  1. The interface — The Boss of your computer recording setup. Have you purchased your interface already? Which one are you using? Do you want some recommendations?

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