Written by
| Powered by phpBay Pro |
how to pre-amp an uni-directional electret microphone? I can't hear anything from it, HELP!!?
Hi, I wondering if you could help me. I am a struggling student who needs help, am using pre made components or kits that I have assembled.
My aim is to create an uni-directional electret microphone (off a 3.5mm jack) which works through a pre-amp and into some headphones. (pre-amp is powered by two 9v batteries)
All I am receiving is static and no real sounds.
I have tested all the components which a music device and they work, I am currently stuck and require some help, can anyone help me?
Josh.
Images:
http://picasaweb.google.com/joshal99/MyMobileBlog?authkey=xxbrFdS3Pws#5256413336059293522
http://picasaweb.google.com/joshal99/MyMobileBlog?authkey=xxbrFdS3Pws#5256413348978751058
http://picasaweb.google.com/joshal99/MyMobileBlog?authkey=xxbrFdS3Pws#5256413348151659682
http://picasaweb.google.com/joshal99/MyMobileBlog?authkey=xxbrFdS3Pws#5256413347655203634
A typical electret microphone capsule contains a preamp circuit that uses a common source FET as a buffer amplifier. The two or three-terminal electret capsule containing the common source buffer amplifier must be externally powered. An external resistor sets the gain and output impedance of the buffer amplifier . You will also require a coupling capacitor between the output of the buffer amplifier and the input of your preamp.
For a two-terminal electret microphone capsule:
Terminal 1 is the output of the buffer amplifier connect to it the positive plate of a 4.7 microfarad capacitor [ the negative plate of the capacitor connects to the signal input of your preamp ] and one end of a 1K ohm 1/4 Watt resistor.
Terminal 2 is the ground connection connect it to the input signal ground of your preamp and to the negative terminal of your external power supply or battery.
The other end of the 1K resistor is connected to the positive terminal of your external power supply or battery.
The power supply is usually 1.5V - 10V [ 4.5V for optimum performance ] and the current drain is < 0.5 mA.
If you have a three terminal electret microphone capsule:
Terminal 1 is the supply, connect one end of a 1K ohm 1/4 Watt resistor, connect the other end of the 1K resistor to the positive terminal of your external power supply or battery.
The power supply is usually 1.5V - 10V [ 4.5V for optimum performance ] and the current drain is < 0.5 mA.
Terminal 2 is the output of the buffer amplifier connect to it the positive plate of a 4.7 microfarad capacitor, the negative plate of the capacitor connects to the signal input of your preamp.
Terminal 3 is the ground, connect it to the input signal ground of your preamp and to the negative terminal of your external power supply or battery.
See the reference below for general information:
http://tinyurl.com/2o94xr
| Powered by phpBay Pro |
