As a former sound engineer, I completely agree with the need
for a preamp. I'm using a regular headset mic, and the sound is
very unprofessional. Not only is the quality of the voice so-so,
the amplifier of your typical sound card introduces all sorts of
hum, hiss, fan noise, ambient noise and other elements that are
distracting. Your average sound card has a poor microphone
amplifier.
The problem will be budget. A true, high quality microphone
will easily cost $200-400 and up. A good mic preamp can easily be
$1000 or much more.
So where does that leave us educators? Amazon.com carries the
Rolls MP13 Mini-Mic Preamp for $69.99. I haven't tested it, but it
looks pretty good for simple purposes. A condenser mic has lower
output and needs to be amplified, but it'll sound better than a
dynamic mic, which can have a "thuddy" sound. The audio technica
AT2020 is a good choice for around $100. Please also get a stand
and a high quality balanced XLR connector mic cable. You'll then
need an adapter cable to plug from the preamp to your sound card
input. In this case, a 1/4# phono to 1/8# mini (shielded). Make
this cable fairly short, no longer than 3 ft. Radio Shack should
carry them.
In any event, unless you also buy a pop screen, place the mic
a few inches from you, below your mouth pointing at your throat, or
angled down from above your head, pointing down towards your mouth.
The idea is to avoid having the mic where your breath can blow
across it. Test which one gives you the best sound quality. Don't
forget to turn the mic record volume down on your computer. For a
good article explaning home studio equipment, and good
recommendations, go to:
http://www.tweakheadz.com/microphones_for_the_home_studio.htm