PC Microphone Preamplifier
Posted on Oct 19, 2012 7989
Under: Microphone Circuits
Soundblaster soundcard series (SB16, SB32, AWE32 and AWE64) have all a microphone input designed to be used with the electret microphones which come with the soundcard package (some packages) or with separate microphone designed to be used with SoundBlaster soundcards (there are separate microphones and some monitors have built-in microphones like this). Because the microphone input needs very high input levels it is not suitable to be used with any other micophone type than elecret capsule microphones. If you connect a dynamic microphone (which gives typically few mV voltage) and try to record it you will get very low signal level with lots of noise.
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Dynamic microphones can be connected to SoundBlaster if a suitable microphone preamplifier is built which can amplify the signal levels from dynamic microphones so much that they give enough level for SoundBlaster. This circuit gives amplification of about 30-50 which is enough to make the signals from dynamic microphones enough high to be handled well by SoundBlaster. The circuit is very simple so the amplification is not accurately defined (depends on transistor parameters which can vary from transistor to transistor) and other performance figures are not the best possible. The circuit has a very nice feature that it does not need any external power supply because it uses the bias voltage (+5V) which SoundBlaster sends normally to the electric microphone as it's power source. I have used this circuit succesfully with AKG D 60 S dynamic microphone and Sound Blaster 16. Using this circuit you can add better microphones than those cheap multimedia microphones to your soundcards quite easily. With all SoundBlasters a better microphone is not yeat a guarantee for better sound quality because the poor frequency response of the microphone preamplifier in SB16 cards. If your want even better sound quality you might consider building by simple microphone preamplifier design and connect it to the line level input of your SoundBlaster. R1 1 kohm R2 220 kohm R3 4.7 kohm C1 15 uF 10V electrolytic (you use 10 uF or 22...