I’m not an engineer, so creating my DVD, “Depression What You Must Know,” and my Podcast, “Psychiatric Secrets Revealed with Dr. Mike” involved a lot a research and learning.  The information listed below is a compilation of that work.  I hope you find it helpful.  Mike Kuna

The Sound Card

Please note that many of these devices are no longer actual cards.  However I’m going to use this term throughout for simplicity sake.

The best way to think of the sound card is to think of it as an audio interface between the analog world of the microphone and the digital world of the computer.  The sound card is a complicated device that is composed of many separate modules.  Most on-board sound cards typically add between $5-7 to the total cost of the mother board.  At that low cost the sound card has to provide the following:

1. An interface (jacks) to connect the sound card to the outside world (speakers, microphones, etc.).

2. A mixer that controls the levels of various signals going into and out of the card.

3. A preamp to amplify the tiny signal from a microphone to a level that can be read by the sound card.

4. An Analog to Digital Converter (ADC) that slices the continuous analog microphone signal into thousands of snapshots per second (CD quality takes 41,000 snapshots per second) and converts these snapshots into digital data that can be stored as a computer file.

5. A Digital to Analog Converter (DAC) that converts the digital files back to a analog signal that can be understood by your headphones or speakers.

6. A Wave Table that contains little snippets of real sound samples that the DAC uses to interpret the digital file when it is making its conversion.

High quality cards use quality components.  Cheap cards cut corners wherever they can.  One easy place to save pennies is the mic jack and preamp.  After all, almost everyone listens to sound from their PCs but few people record sounds using the mic jack.  

The mic jack on most sounds cards isn’t designed for a typical microphone; it is designed for a computer microphone.  These microphones are typically of the ELECTRET CONDENSER type as these microphones provide a much higher output than a typical dynamic microphone.  In fact most sounds cards require a input level over 10 times the typical output of a dynamic microphone.  The way that you can directly use a dynamic mic is by over pushing the poor quality preamp on the sound card which usually results in hiss and distortion.  

Computer microphones usually require a small amount of voltage which is provided by the sound card.  That is why the plug of a typical computer microphone has three connectors on its plug instead of just two.  The third connector (often the ring) provides anywhere from +2 to +9 volts to a tiny microphone preamp that is typically build into the electret’s microphone capsule.  This preamp does two things: it changes the impedance of the microphone to match the requirements of the sound card and it amplifies the microphones signal making it easier for the sound card to hear it.  Strangely, there is no standardization for this function.  Some cards use the ring for voltage, some use the plug’s tip and some don’t provide any extra voltage at all.  This makes using a sound card’s microphone input an uncertain option, even when using a computer-type microphone.

I recently compared a number of sound cards.  Some were on the motherboard, some were add-on cards and some were USB external cards.  Although I had read endless debates on which was better it seemed that there were acceptable cards in each category.  By acceptable I mean that the card was capable of recording clear, noise free audio using the microphone jack and a computer type microphone (either a Labtech mic or a Logitech headset).  Unacceptable cards included the motherboard based soundcards of a Gateway desktop and laptop, and a Creative Soundblaster 16 USB card.  Acceptable cards included a Creative Extigy USB card, a Creative Audigy 2 sound card and a motherboard based card on a cheap E-Machine desktop.  With the exception of the E-Machine it seems that there is a direct correlation between the cost of the sound card and the usefulness of its mic jack.

I have read on many web sites that on-board cards are only good for playing back computer beeps; this is not absolutely true, in my opinion. If you record the same material using the on-board card and a quality card, both will sound good, but the quality card will sound much better. Think nice table radio’s sound versus a decent stereo’s sound and you will get an appreciation of the difference between a stock sound card vs. a quality add on.  The bottom line is that you can use a stock sound card, but a small investment may make a significant difference in the quality of your recordings.  Good internal cards include Creative Lab’s Audigy series and cards from M-Audio.  There are many good USB cards including the Griffin iMic and cards from Edirol and M-Audio.

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