Index:

Audio Quality
Ground Loops
Recording Telephone Conversations
Podcast Hosting on the cheap
XML
Microphones

Info for Pagan Podcasters.

On this page, I offer some tips and tricks for pagan podcasters. While I haven't been podcasting for that long, I have worked in radio and as a sound engineer for theatre groups. Some of the podcasts I've listened to have shown some common difficulties that I hope to offer some assistance with here.

1. Audio quality.

One of the most difficult things to understand when recording audio, especially in a digital format, is the concept of clipping. When you're recording audio into a computer, there is a maximum input level that the computer will be able to resolve. This is set by the highest voltage that the input is able to receive. Anything higher than that, and the computer will simply create its highest value. You can hear this in recordings that are very loud, but almost unintelligible.

To understand clipping, remember that a computer uses only 1s and 0s to reproduce information. Let's take an easy example. If our input had three digits to represent an audio signal, 000 would be the lowest number, and 111 the highest. (This isn't exactly how a computer does it in .mp3, but it will work for our example.) Let's say that the input board will take a maximum of 5 volts at the input. That would mean that 000 = 0 volts and 111 = 5 volts. But what happens if our input is 7 volts? The computer would assign 111 to 5 volts, 6 volts or 7 volts. We would lose information. This is called clipping. The computer chops everything off at its highest available level and the sound quality suffers.

When we're recording audio, it's important to keep the audio signal between the levels that the computer is able to decode. If we use audio levels higher than that, clipping results.

How do we do that? Most recording software has either a waveform display or a simulated VU meter. When recording, make sure that the waveform only rarely reaches its limits. If you're using a VU display, make sure that most of the audio is in the green and yellow, and only rarely touches the read, even in loud passages. If things stay in the red, you're clipping, and the quality will suffer.

It's ok to record at a lower volume (not too low though) and to use your recording software to amplify it afterward.

2. Ground loops What on earth is a ground loop?

Have you ever heard audio with a "hum" in the background? Something that sounds like what you hear when listening to a really old radio? Much of this is because of ground loops. It happens because multiple pieces of audio equipment might be being used, and they are not grounded together. They might be plugged into different circuits, perhaps in an older building with older wiring or faulty grounds.

When the grounding isn't correct and you connect (for example) a mixer to the input of the computer, current may be carried on the ground conductors between the computer and the mixer. When this happens, some of the AC signal in the ground conductor gets picked up by the signal conductors and applied to the recorded audio. This is called AC hum.

Good audio design will prevent this by insuring that the ground is sufficient on the equipment. All of the audio equipment should be plugged into the same outlet. If you have a cord with the ground pin removed, replace it with a good cord.

There are also isolation transformers available. These isolate the ground between various pieces of equipment, eliminating ground loops.

Also, using digital audio devices, like USB or FireWire mixers, or optical or digitial ports on the sound boards will help to eliminate ground loops and improve the sound quality.

3. Telephone recording.

A. Skype(r)

Skype(r) is often used to hold interviews on the Internet. It's cheaper than most phone calls, and with a program called Pamela, easy to record. But Pamela costs money ... not much, but many podcasters don't have much. Is there a way to record Skype(r) calls without Pamela?

If you're fortunate enough to have an audio mixer, there may be. Here is the setup I use. I have an Alto S-8 mixer. They're fairly inexpensive, and have a couple of important features. There is a control room output, and tape input and output. These are the key to recording Skype (r) without other software.

I connect the Control Room output of the mixer to the microphone input of the computer. This is what Skype will look for. I then connect the Main Output to my recorder (or line input if using Audacity). The audio out from the computer should go to the Tape In on the mixer. Make sure that the 2-track to Control Room is NOT SELECTED, and that 2-track to Mix IS SELECTED. This will feed the audio from both parts of the conversation are sent to the recorder.

You'll have to do a Skype (r) test call to get your microphone level set, but you'll have better control over your levels this way. Setting the Microphone and main-level mixes will give you great flexibility.

B. Standard telephone.

The best way to record an interview on a standard telephone is with a Hybrid. A Hybrid lets you split the phone line to the transmit and receive pairs, which you can connect to the microphone and recording equipment, setting levels individually. This is the best way to do things, but hybrids can be expensive.

An easier way to do things is with a telephone recording interface. These are available at Radio Shack for $20.00 or less. Connect the adapter to the phone line and connect a telephone to the adapter. The output from the adapter can go to your mixer or to the input of the computer. Make sure that the levels are set so that there is no clipping when recording.

If you find that either your voice, or that of the caller is significantly lower than the other, you ca go back with your recording software and amplify the low sections.

4. Hosting your podcast

This is probably the single greatest expense that podcasters run into. It's also the one that a resourceful person can save a great deal of money on. Many podhosting services charge a fair bit of money for that service. Is there a way to save some of that? Definitely.

What do you get with podhosting? Space. Editing tools. XML feed generation. Bandwidth.

Guess what ... One of the best editing tools is free. It's called Audacity. If you've got a web site, you have some space and bandwidth. If it's a free site, maybe not a great deal of space and bandwidth, but for what you pay a podhosting company, you can get unlimited space and bandwidth at Godaddy. Generating the XML feed is probably the part that will cause the most confusion. A good web hosting package will cover the space and bandwidth, so let's look at Audacity and XML

A is for Audacity. Audacity is a free tool for working with audio files. You can get it here.

You'll also need another program called an encoder. The encoder is the part that allows Audacity to create .mp3 files. Because of legal issues, they cannot be packaged together, but you can find a library called LAME which will allow Audacity to create .mp3 files here.

When you download LAME, you'll need to save it somewhere that you'll remember because the first time you try to save an mp3 file with Audacity, it will ask you where you put LAME. Point Audacity to the lame_enc.dll file and everything should work.

Spend some time with Audacity, getting to know how it works. It's a very powerful program with lots of features, and even more that can be plugged into Audacity.

5. XML

This was, for me, the most difficult part of getting things running, and is the most nit-picky part of the process. If there are errors in this file, nobody will be able to subscribe to your podcast.

So, what is XML, and what is your XML file?

XML stands for eXtensible Markup Language. Your podcast XML file is the file which describes your podcast and allows users to know when you've created a new episode, what's in it, and where to find it. It also lets people know how to get in touch with you. It lets Itunes know what category to place your podcast in. In short, it's like the library card-catalog file for your show.

There are three parts of the XML file. I'll highlight the actual XML file for my program in Blue, these are the parts that you'll change for your show. I'll keep the parts that shouldn't change in Red, and use black for descriptions.

First, there is the header. This merely tells the news reader some basic information about the type of file this is.

<?xml version="1.0" encoding="UTF-8"?>
<rss xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd" version="2.0">

Next is the Channel section. This section tells the news reader about your show, without specific information about the various episodes.
<channel>

<pubDate>21 Sep 2008 17:30:00 GMT</pubDate>
This is the initial publication date and time of your show.

<title>PaganFM!</title>
This is the name of your show.
<description>Podcast of PaganFM! from WSCA-LP, portsmouth, NH</description>
This is a short description of your program.
<link>http://www.paganfm.com</link>
This is a link to your web site.
<copyright>Copyright 2008</copyright>
Copyright info.
<docs>http://blogs.law.harvard.edu/tech/rss</docs>
A link to a document describing RSS (Really simple Syndication ... how podcasts work)
<language>en-us</language>
The language code for your podcast. You only need to change this if using another language.
<webMaster>dee@paganfm.com (Deirdre Hebert)</webMaster>
email address of the web master.
<itunes:subtitle>A live, on-air program for pagans and those interested in paganism</itunes:subtitle>
Short sub title of the program.
<itunes:summary>Music, talk, interviews, reviews ... anything of interest to the pagan community.</itunes:summary>
Summary for Itunes of your program.
<itunes:author>dee@paganfm.com(Deirdre Hebert) </itunes:author>
Email address of the podcast author.
<itunes:image href="http://www.deesigned.net/paganfm/albumcover.jpg"/>
Link to an image for your cover art.
<itunes:explicit>no</itunes:explicit>
Yes if the podcast contains explicit language, No if it does not.
<itunes:owner>
<itunes:name>Deirdre Hebert</itunes:name>
<itunes:email>deirdre@deesigned.net</itunes:email>
</itunes:owner>
Itunes specific owner information
<itunes:category text="Religion &amp; Spirituality">
<itunes:category text="Other"/>
</itunes:category>
Itunes Category information
<image>
<url>http://www.deesigned.net/paganfm/albumcover.jpg</url>
Location of the image displayed in the Itunes Store
<link>http://www.paganfm.com</link>
A link to your web site attached to the image.
<title>PaganFM!</title>
Title of the podcast.
</image>

The third part of the XML file is an entry for each individual episode. If you have only limited web space, you might want to make only one episode available. If so, only keep one episode listed. These are shown in the <item> sections. Each episode is an <item>

<item>
Starts the section
<title>PaganFM! 09-21-08</title>
Name of the EPISODE.
<description>Welcome to the show. It is September 21. PaganFM! has been around for about a year, and this is our very first podcast version.</description>
A description of the episode.
<pubDate>21 Sep 2008 17:30:00 GMT</pubDate>
Date of the publication of the episode.
<link>http://www.paganfm.com</link>
Web link associated with the episode
<author>dee@paganfm.com (Deirdre Hebert)</author>
Author of the feed or podcast.
<category>Religion &amp; Spirituality</category>
Podcast category.
<enclosure url="http://www.deesigned.net/paganfm/podcast/paganfm092108.mp3" length="115052177" type="audio/mpeg"/>
This is the EXACT location of the .mp3 file that is your show, followed by the size, in bytes of the file. If you've got a Windows computer, you can find the .mp3 file, right click on it, select "properties". What you are looking for is the "size on disk" parameter. Use this, without the commas.
<guid isPermaLink="false">http://deesigned.net/paganfm/podcast/paganfm092108.mp3</guid>
The guid is a Globally Unique IDentifier. Theoretically, there should be no two identical GUIDs anywhere. The unique web address of your podcast episode will work here. Some automated programs will generate a GUID based on random numbers generated with your MAC address as a key, but you don't have to worry about that. Just use the URL or Web address of the episode.
<itunes:subtitle>Welcome to the first podcast version of PaganFM! We hope that this
helps all those who have wished to listen but could not tune in during the live broadcast.</itunes:subtitle>
This is the episode sub title.
<itunes:summary>Welcome to the first podcast installment of Paganfm!</itunes:summary>
Summary of the episode
<itunes:author>dee@paganfm.com (Deirdre Hebert)</itunes:author>
name and email of the episode author.
<itunes:keywords>pagan, podcast, Wicca, Druidism, Eclectic, Deirdre Hebert, Heather Lowe</itunes:keywords>
Keywords for those searching for your episodes.
<itunes:duration>01:59:50</itunes:duration>
Length of the episode hh:mm:ss hours:minutes:seconds
<itunes:explicit>no</itunes:explicit>
Does this episode use explicit language?
</item>
End of the item.
</channel></rss>
End of the XML file

You then need to place the XML file on the web site where you host your podcast. I use the root of paganfm.com for mine. You can use whatever program you use to upload files to the site.

After creating the file, you'll need to test it. This can be done on the web with an XML feed validator such as http://feedvalidator.org/
In the feed box, type the URL of the XML file. If it finds errors, it will let you know. Some errors are not show-stoppers, such as a bad email address. But others, such as an incorrect location for your .mp3 file, bad tags (the items between < and > are.

Lastly, once the feed is correct, I go to one of my podcatchers or Itunes, and download the episode, listen to it, and make sure that everything is working, including having dowloaded the proper episode.

6. Microphones

There are 2 basic types of microphones that are used for recording today. These are the Dynamic and the Condenser microphones. While there have been others, such as the Carbon microphone, Dynamic and Condenser microphones are what we'll run across most often in recording today.

Dynamic Microphones.

The Dynamic Microphone is actually quite like a speaker, and speakers can, in fact, be used as microphones. The Dynamic Microphone operates by moving a coil of wire through a magnetic field in response to vibrations in the air. The coil of wire is attached to a diaphragm and suspended in a magnetic field. The diaphram is designed in such a way that it moves easily in response to sound. The coil, moving in the magnetic field, will generate a voltage that changes in response to the movement of the diaphragm, and that is the signal that is applied to the recording equipment.

Dynamic microphones of professional quality tend to be fairly rugged, and are epitomized by the Shure SM-58. This is the workhorse microphone for many artists and has been in production for quite a few years. It is the hand-held microphone with the ball over the front which protects the diaphragm. These microphones list for about $180, but can be had in many cases for around $120 or so. You can find them used for even less.

Dynamic microphones are easy to use because they don't require any external power, and are very good for close-up work.

Condenser Microphones.

Condenser Microphones work very differently than Dynamic Microphones. A condenser microphone is made of a conductive membrane (or diapharagm) suspended over another piece of metal, the stationary plate, but electrically isolated from it. Movement or vibrations in the air result in vibration of the membrane, causing the distance between the membrane and the stationary plate of the microphone to change in relation to sound. This results in a change in capacitance. (Condenser is another word for 'capacitor'.) This change in capacitance results in a charge across the device which can be amplified and used for recording purposes.

The microphone element of a condenser microphone is far simpler, and can be much smaller than a dynamic microphone. There is no magnet or moving coil involved, but the signal from the element is very weak, and needs to be amplified. Because of this, most condenser microphones need either an internal battery, or phantom power.

Phantom power is provided by mixers or other audio equipment, and supplies power to the microphone via the microphone cable. Most mixers will have a switch which is labeled "phantom", and an indicator to show that that power source is being used.

Phantom power does not interfere with the operation of dynamic microphones, but is necessary for most condenser microphones.

Condenser microphones tend to be more sensitive than Dynamic microphones, and can be used for a wide variety of applications. They are installed in many hand-held recorders and cameras, that are capable of recoding up close, or entire rooms.

Unidirectional Microphones

Unidirectional microphones are microphones that will respond to sound directed at the microphone, but much less to sound from other directions. These are useful in helping to eliminate background noise, or to reduce the chance of feedback in amplified systems. However, Unidirectional microphones are sensitive to position. If the speaker is moving in relation to the microphone, it will be noticed in the recording, as the volume will drop off as the speaker moves away from the sensitive region of the microphone.

Unidirectional Microphones may be labeled according to the pickup pattern. Common patterns are:

 

(c) 2008, Deirdre Hebert