microphone for PC

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Tomi Holger Engdahl

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May 5, 2003, 6:15:27 AM5/5/03
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ns...@email.com (Sophia) writes:

> I'm trying to figure out what type of microphone to use with my PC to
> create narration for an educational Flash presentation. Even though
> the narration will be compressed, I would like to avoid as much
> background noise as possible. I have an HP Pavilion with a SoundMax
> sound card.
>
> 1) Can I use a regular unidirectional Shure or do I need a pre-amp
> for that?

Generally all PC soundcards have microphone input. Soundcard mic
inputs are generally pretty crappy, meaning usually that they are
noisy and frequency response leaves much to be desired. Soundcard
microphone inputs are usually optimized only for telephone type voice
applications, not for any serious music recording.

The microphone input in soundcard is generally designed to be used
only with a "computer microphone" in mind. This category means those
cheap computer microphones you get sometimes with the computer
and can buy from the computer shop. This it to what use they
are designed for. And if you get this kind of microphone it will
work practically with any normal soundcard. If you connect some
other microphone type, then your resuls vary from card model to
another (some can take other microphone types better than some other).

Most sound card inputs require a minimum signal level of at least 10
millivolts. Many soundcard supply bias voltage on their outputs to
power the electret microphones

This discrepancy means that if a typical professional microphone is
connected to a sound card input, the user will have to shout into the
microphone or hold it just an inch or so away (or both) in order to
produce a strong enough signal for the sound card to "hear." Other
problem with dynamic professional microphones is that dynamic
microphones do not like DC current, but soundcards have 1-5V power
supply for feeding Electret mics on the 3,15mm-jack´s ring, which can
touch the tip of the connector when you plug your microphone in and if
you are unlycky it can damage your microphone.

There are two possible solutions for the low volume problem with
professional microphones connected to soundcard. First option is to
try to increase the sensitivity of the sound card input with the
control software which come with the soundcard (audio mixer
application or such). This might more or less help depending on
soundcard used. If the input sensitivity cannot be increased eough,
another option is to amplify the microphone signal before it goes into
the sound card input. This can be done by running the microphone
signal through a device called a mic preamplifier or mic-to-line
amplifier and feed that signal to the line level input in the
soundcard (this approach usually gives better sound quality also).

Soundcards with mic inputs on minijacks are usually low-quality
devices, which means that htey are not suitable for high quality
recording odf audio (they are still OK for general multimedia use or
internet telephony). Such sound cards are not designed for high
quality recording. Get a real soundcard and use a real audio
application if you want quality results. If you want to get good
quality microphone recording using computer the microphone wiring
should be balanced and the microphone preamplifier should be external
to the computer casing.

Usually you get quite acceptable results by using an external
microphone preamplifier that is connected to line input in the soundcard.
Genrally for a home recorder, I can recommend a small decent quality
mixing board connected to soundcard line input. With such mixer
betweenmicrophone and soundcard, you will get good results and have
freedom to select practically any microphone you want (anything you can
connect to that mixer).

> Id rather not spend the extra hundred dollars or so right now.

Spending extra dollars to buy for example a cheap small
mixer that has good microphone preamplifiers is a proven
to work solution.

> I understand from reading this group that there is a impedance
> problem with using some microphones with a PC.

Usually it is matter of signal level and impedance.

> Is it a trial and error thing?

If you try to connect anythign else than normal computer
multimedia microphone to soundcard microphone input it is
a trial and error thing.

> 2) Or are my options limited to PC microphones? I notice there are
> two different types -- ones that go into the sound card and ones that
> are USB? Is there much of a difference in quality?

I have never tested PC microphones that connect to USB, so it is
hard to say how good they are.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/

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