Episode: 640
Title: HPR0640: About microphones
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr0640/hpr0640.mp3
Transcribed: 2025-10-08 00:16:48

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Hello and welcome to episode two of our hacker public radio series on an introduction
to audio and podcasting or aug casting.
I am Daniel Worth and this time we're going to be talking about how we capture sound.
First up I have a little bit of stuff to talk about about last time.
First of all I had some encoding issues because I'm using a Delta series card on my studio
machine and when I do the OS perspective show we use Skype and that requires 441 kilohertz
and then for the open source musician podcast we use 48 kilohertz and I did while I switched
the recording and arder I didn't switch it on the settings for the sound card so I had
some transcoding issues and I want to apologize for that.
I do understand there's quite a bit of irony in having a show about audio that messes
up like that so sorry about that.
Next I wanted to talk about accidentally called sample rate bit rate on the last show.
It's not bit rate, bit rate is how many kilobytes per second the audio streams off a disk when
it's compressed.
I was talking about sample rate, sorry about that.
I also threw in some links and people were hit me up on the mumble clients and I threw
in some info about the new recording information I'll link to that info on compiling mumble
from source to get the new recording feature before it's released and it's not very good
walk through but the information is in there on how to record mumble output using just
pulsario so not having to compile anything.
You wouldn't be able to do everybody in the room separately but you'd get the room total
and that would work.
And then for this episode I wanted to start out talking about a microphone and how a microphone
works.
A microphone's job is to take the sound in whatever is in front of it in this situation
your voice and turn it into an electronic signal that then could be passed through and
analog to digital converter which creates it in the bits and bytes and zeros and allows
you to send that over the internet to your listener.
So we have a few different kinds of basic microphones.
I'm going to cover the three main ones, actually four main ones and really you're probably
only going to be using one.
So the first one is a condenser microphone and this is generally what you see they're
rather large looking microphones that are generally side address, some are in address
but mostly side address they're what I use for my regular podcast and these microphones
use a diaphragm created of a membrane, PVC or mylar generally and they infuse the center
of the membrane with a metal, a lot of times it's gold, sometimes silver, platinum,
palladium are nickel and cheaper condenser microphones and then they attach a lead and they send
an electrical current through it and it creates a electromagnet field that as sound waves
bounce off of the diaphragm it creates a little bit of electrical signal very low and
that is what you're able to use to capture your voice.
So next we have a dynamic microphone which in contrast doesn't use a diaphragm with an
electromagnetic field as a fixed magnet like a speaker and then inside there's a diaphragm
and the diaphragm is free floating and moves in and out of the magnetic field creating the
electrical signal that captures your voice that way.
Last real quick I'll touch an Arriban microphone and Arriban microphone uses two permanent
field magnets and a piece of corrugated metal whether it's aluminum or gold kind of free
suspended and it's moving in and out of the field magnets is what creates the electronic
signal. You're not going to use a Arriban microphone. Generally a condenser microphone is going
to sound the best for recording a range of frequencies such as vocals when you're singing.
It can sound pretty darn good on recording your voice for voice over or for a podcast but it
does require phantom power so if your equipment doesn't support 40 volt phantom power you
won't be able to use a condenser microphone. Dynamic microphones don't require phantom
power but running phantom power through them doesn't hurt them however Arriban microphone
the modern ones won't but the older ones if you run 40 volt phantom power you blow them
up so keep that in mind. So we have a microphone and we created an electronic signal but it's
a really quiet signal and what we need to do is boost that signal and we do that through
a preamplifier. There's lots of different preamplifiers to choose from a million options
that cost anywhere from 20 or 30 bucks all the way to tens of thousands of dollars and
generally ideally I guess you would get a USB interface that would have built-in preamplifiers
and that should be probably good enough for a podcast. I know another type of microphone would
also be the back electric microphone. Back electric microphone uses a permanently charged
magnet inside of the condenser or a permanently charged element rather that doesn't require power
and these are generally the types of microphones you get in a USB headset for gaming or a plug-in
microphone because it doesn't require any power it can be used in a passive device and the issue
with these is that while there are high quality back electric mics they aren't in any of the
consumer level electronics generally though they're really good back electric mics are used in
like the little over-the-ear face mics you see dancers wearing or pop singers when they're singing
on stage and those are you know those microphones are for $500 and most of the elements below that
are cheap and crap and sound terrible and that's why it's really hard to find a decent USB headset
that sounds pretty good if that's all you have you know that's your starting point and that's
that's fine and for Hacker Public Radio I truly believe that content is king and the quality
of your audio isn't important as long as it meets some basics so you know I wouldn't beat yourself
up too much about it but doing the best you can to get quality audio definitely what you want to
do and remember there's all these things like oh we can fix it afterwards it's not true really
the best place to fix it is at the source get the best sound you can if you're limited by budget
or by the coming you have you know you're limited by that there's nothing you can do but you want
to put the best effort in that you can so back to the microphone preamble fire what it does is
it amplifies the signal up to line level and the higher end ones do this in the most transparent
way or they color the sound using tubes and such to give a nice effect on certain sources
generally you don't need a high end for just doing a hand microphone preamble fire just for doing
voiceover work or podcasting in fact they're bearinger and aren't makes a little
single channel portable ones that are pretty inexpensive and are you know they'll sound
just fine for doing a podcast next I want to talk about capture devices so we have a few different
options you can use the built-in card in your computer generally with those your only options are
using a back electric mic which we've said isn't going to sound very good like I said if that's
what you're stuck with try to find the best USB headset you can and go with that but you're
going to be really limited on the quality you're going to be able to get out of that next we have a
USB external device and these can be available for anywhere from generally they run bearinger makes
one that's about 30 bucks all the way to ones that run a couple hundred bucks the cheap bearing
or one doesn't include a microphone preamble fire it just has RCA inputs so you'll need an
external microphone amplifier they do make small mixing boards that are available for about
30 to 40 maybe 50 bucks you know 30 if you get them used that include preamble fires in them so
that coupled with one of those inexpensive USB headsets or an expensive USB audio interfaces
rather we'll get you some really good sounds I know task cam I think or at least this is making a
multi-mix device that is USB 1.0 and supported under Linux and has a mixer with like a single
microphone input and it's available I think for about 60 or 70 bucks so that actually
would be a pretty decent way to start also some of the inexpensive M audio
trying to remember the name of them fast track the fast track pro are supported under Linux you'll
have to double check because there's some different models of those devices those are supported
and they just have microphone preamps built in those are pretty handy little devices you want to
keep in mind that only USB 1.0 is supported under Linux because there is a standard audio spec
in the USB 1.0 specification and that is generally well implemented those devices if you want to
check compatibility will generally say they're usable on windows and Mac without a driver and that's
usually your clue if it says that and it's USB 1.0 standard spec device it'll work fine under Linux
USB 2.0 has a spec it hasn't been implemented by any manufacturers they chose to go with proprietary
specs and so we don't have any USB 2.0 devices that are supported so you want to stay away from those
we have quite a few PCI devices that are available on your Linux no stutably you want to look
up the M audio delta series that's a delta 44 66 1010 and 1010 light and also any of the other
NV24 based chipsets that are available on the market you can pick those up relatively inexpensive
but they do require a full PCI slot there's no PCIe devices so you'll have to watch that on your
motherboard then finally we have firewire devices those can be anywhere from a two channel setup up
you know eight channels it's kind of per device what's supported and they're supported through the
FFFADO project and you want to check out their website and their matrix for what devices are
supported for you pick one up you can get those used mostly they're not really manufacturing much
firewire devices anymore and for laptops a lot of laptops aren't coming with firewire devices
if you're going to be recording music with it too you want to keep in mind that certain laptops
share IRQs with other components in the in the laptop and that can prevent you from getting
low latency settings so you want to check around and try to get an idea of what that's going to look
like but firewire devices are out there if you have that on your laptop or your computer
might be worth a try a lot of the in fact most of those have preamplifiers built into them so
that's it that could be a good way to go for podcasting I think that pretty much covers the hardware
aspect of it the other one I wanted to talk about for USB 1.0 is there's a lot of microphones
such as the blue yeti there's also some adapters that allow you to plug it directly into a
microphone and use it as a USB 1.0 device these are fantastic they're almost always USB 1.0
and well supported under Linux and allow you to just directly plug a USB
any microphone and convert it to USB generally they don't support phantom power so you want to stay
away from condenser mics with those these are a really good option for getting a single channel
if you're going to be looking to do multiple channels it can be quite a pain in the butt to plug
into a lot of USB interfaces and try to get them all to work it is possible generally not recommended
my preferred recording application is still harder there's lots of complaints that
audacity is easier to use than harder and I really don't think for the basics it is
and I think you have a lot of power in using harder that you don't get with
audacity and so using a device like that single USB only gives you input there's no output
generally some of them do have a place you can plug in headphones but you do have to
keep in mind there's a little more additional jack configuration to use an input device that
doesn't support duplex or output I'm using my zoom h4 right now which is a USB 1.0 device
has two XLR inputs with microphone preamps has phantom power can run at 441 or 48 kHz
and works perfectly under Linux works great with jack so there's those kind of devices are an
option too the advantage of those is that you can take them with you without a computer and record
a podcast plug their card in to your computer pull the audio off and just edit it that way
and you get around a lot of problems with hardware settings doing it that way that you can just
just edit with really high latencies and not worry about a lot of jack configuration you can kind
of get up and running pretty quickly so keep that in mind that's a that's a good option too
zoom makes some lower end devices that don't have the pre amplifiers in them
don't support XLR inputs but they do have built-in microphones that are pretty decent
condenser microphones and those can be pretty handy too and I think I picked up my zoom for
I got it on sale for a pretty good deal and I think I paid 220 for it and then I'm right now
I'm using an SM 58 microphone which is almost always a hundred dollars and you know and then you
have a cable other than I don't have any more equipment that I'm using one thing that would be
strongly suggested and I don't actually have one on here as a pop screen what a pop screen is
going to do is prevent the plosives or popping like that that you get against the microphone and
those are available in a clamp on the clamp on to a microphone stand or you can clamp them on
to a desk and put them in front of the microphone or you can get the little like foam toppers that
go on a condenser mic and that'll do the same effect and those are indispensable I really recommend
everybody who's using a microphone uses a pop screen I don't think of other tips one thing to
remember is you generally want your microphone a little bit off center of the output of the
where a person's talking so you don't get as many plosives not as much air is actually hitting the
diaphragm of the microphone as far as finding a quiet room a lot of voiceover guys for video
for TV and stuff do stuff in hotel rooms when they're doing live recordings and they don't have
a studio so one trick is to just take a whole bunch of blankets pile them up on top of yourself
and sit with your laptop underneath the blankets or your computer screen and record under a bunch
of blankets it'll cut down a lot of your room noise and sounds amazing so if you're really looking
for a really good sound and a little bit of privacy maybe I won't cut out a lot of background noise
it'll cut out a lot of the echo of a room I know I got a little bit going on now because of
not in my studio so that's a good trick I've got a bit of covers it for this one if you have any
feedback you want to email me you can email me at d-worth at opensourcemusician.com
and give me feedback on the show let me know what you want up coming there also if you go to the
opensourcemusician.com website on the main page there's a link to my show notes for these shows
and you can help me edit it and add things that you want in there's a discussion page feel free
to throw stuff on the discussion page and I'll make sure I cover it in one of these episodes so
until next time podcast out
thank you for listening to Hack Republic Radio
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