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Attaching PA Microphone to PC (MIC IN) - Need help !

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learning

Member
When I put PA Microphone into computer MIC IN, I don't get any sound from it. Actually I want to record my voice in PC through a PA microphone. Can you tell me what is the reason behind it and how I can solve it ? Please help me !
 

Boncuk

New Member
Hi learning,

first off, what is a "PA" microphone?

Microphones are normally capacitive (Electret) or inductive (dynamic).

Most today's main boards with integrated AF-amplifier don't have a mic preamplifier. Using the windows voice recorder you get a very weak signal only when shouting into the microphone.

Here are schematic and PCB layout for a PC-Mic-Amplifier.

T1 must be a BC550C (hfe > 600)

AF-OUT connects to the outer pin of the 3.5mm stereo plug and Ground connects to the sleeve.

Boncuk
 

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learning

Member
Hi learning,

first off, what is a "PA" microphone?

Microphones are normally capacitive (Electret) or inductive (dynamic).

Most today's main boards with integrated AF-amplifier don't have a mic preamplifier. Using the windows voice recorder you get a very weak signal only when shouting into the microphone.

Here are schematic and PCB layout for a PC-Mic-Amplifier.

T1 must be a BC550C (hfe > 600)

AF-OUT connects to the outer pin of the 3.5mm stereo plug and Ground connects to the sleeve.

Boncuk
Thank you for your reply !
 

audioguru

Well-Known Member
Most Helpful Member
But an unknown type of mic was connected to the MIC IN, not to the LINE IN so it should work fine without adding a preamp.
 

learning

Member
But an unknown type of mic was connected to the MIC IN, not to the LINE IN so it should work fine without adding a preamp.
I have tried on both MIC IN and LINE IN but it does not working at all. S I decided to buy a M- Audio Audio Buddy Preamp for my purpose.
 

audioguru

Well-Known Member
Most Helpful Member
A dynamic mic is built like a tiny speaker with a cone driving a coil surrounding a magnet.
A computer MIC IN is made for an electret type of mic and powers the Jfet transistor inside the electret mic.
The power supplied might mess up a dynamic mic. A coupling capacitor between the dynamic mic and MIC IN might allow the dynamic mic to work.
 

audioguru

Well-Known Member
Most Helpful Member
It is not risky to attach a coupling capacitor since the MIC IN connector on a computer has a DC voltage of about only 5V at a very low current. Use a 2.2uF capacitor with its negative wire connected to the mic and its positive wirre connected to the audio input terminal.
 

learning

Member
It is not risky to attach a coupling capacitor since the MIC IN connector on a computer has a DC voltage of about only 5V at a very low current. Use a 2.2uF capacitor with its negative wire connected to the mic and its positive wirre connected to the audio input terminal.
PA Microphone has a 3-pin XLR connector with 1/4" TRS jack. Tell me how you can connect it !
 

audioguru

Well-Known Member
Most Helpful Member
Your mic has an XLR connector I guess it uses balanced wiring. Does the mic cable have an XLR jack connected to a stereo 1/4" TRS plug?
The MIC IN connector of a computer is unbalanced. So if the TRS plug is stereo then connect the ring wire to the sleeve terminal. Maybe the coupling capacitor can fit inside a TRS connector.
 

learning

Member
My connection to PC by PA microphone as PA Microphone -> PA Amplifier (MIC socket) -> PA Amplifier ( Speaker terminal) -> PC (MIC IN or LINE IN) Please tell me whether this combination will work without any problem !
 

audioguru

Well-Known Member
Most Helpful Member
My connection to PC by PA microphone as PA Microphone -> PA Amplifier (MIC socket) -> PA Amplifier ( Speaker terminal) -> PC (MIC IN or LINE IN) Please tell me whether this combination will work without any problem !
Yes, you will have a huge problem.
If the mic and the PA amplifier work probably then their voltage and current are much too high for the MIC IN or LINE IN on the computer and cause the computer to blow up!

If you connect your dynamic mic with a coupling capacitor to the MIC IN of the computer then it should work.
 

learning

Member
Yes, you will have a huge problem.
If the mic and the PA amplifier work probably then their voltage and current are much too high for the MIC IN or LINE IN on the computer and cause the computer to blow up!

If you connect your dynamic mic with a coupling capacitor to the MIC IN of the computer then it should work.
If I add a coupling capacitor in PA Amplifier ( Speaker terminal) then I hope that it will work ! What is your saying ?
 

davenn

Active Member
If I add a coupling capacitor in PA Amplifier ( Speaker terminal) then I hope that it will work ! What is your saying ?
NO, DO NOT connect the speaker output from the amplifier to the PC sound card it will kill the sound card and maybe the PC.
In an XLR connector for the microphone there are 3 wires going to the 3 pins

Pin 1 = Audio Shield (screen wire)
Pin 2 = Audio 'Hot' (signal line)
Pin 3 = Audio 'Cold'

connect audio shield and audio cold together now you have a 2 wire line from the mic.
let us assume for a start that the Mic In input is mono, audio hot goes to the Tip and the other 2 combined go to the Sleeve
there is a possibility that the Mic In input on the sound card is a stereo one ... then you have a Tip, Ring, and Sleeve connections on the 3.5mm plug ... audio hot can go to the tip and/or ring and the shield and sudio cold (connected together ) go again to the sleeve connection in the plug (thats the longest solder point with the small bits that cab folded over and clamped around the cable :)

Dave
 
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davenn

Active Member
Do you have any assembly picture of attaching coupling capacitor to MIC IN of PC ?
you shouldnt need an external capacitor wire up a patch cable as per my previous post to go between the microphone and the sound card mic input.

Again I repeat DO NOT use the amplifier

Dave
 

audioguru

Well-Known Member
Most Helpful Member
The MIC IN connector on a computer is made for an electret type of mic so it applies a DC current to operate the Jfet inside the mic.
The DC current might cause trouble with the dynamic type of mic he is using so I suggested adding a series coupling capacitor to block the DC current.
 
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