Microphone Help: Constant Amplitude w/ No Input

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The discussion centers on a circuit using an OPamp to amplify microphone input, which produces a constant amplitude output even without any input signal. The user suspects that the high gain of 500 might be causing this issue. Responses suggest that the constant output could be due to noise, specifically 100Hz or 120Hz from rectified AC mains, potentially influenced by nearby fluorescent lights. The conversation highlights the importance of considering environmental factors and circuit design when troubleshooting audio equipment. Understanding these elements is crucial for resolving the issue of unwanted output in microphone amplification circuits.
rama1001
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Hello,
I have a circuit that can take the input from microphone and amplify it with OPamp. I have connected everything correct and when i check the output whit no input at microphone still i get output with constant amplitude. I think that was due to gain of OPamp but not sure. The opamp gain is 500 and when if there is any input(song or sound) at microphone it just following the song. Please clear me why i am getting these constant amplutude when there is no input. Is this really due to gain. Please see the image when there is no input.
 

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rama1001 said:
Hello,
I have a circuit that can take the input from microphone and amplify it with OPamp. I have connected everything correct and when i check the output whit no input at microphone still i get output with constant amplitude. I think that was due to gain of OPamp but not sure. The opamp gain is 500 and when if there is any input(song or sound) at microphone it just following the song. Please clear me why i am getting these constant amplutude when there is no input. Is this really due to gain. Please see the image when there is no input.

Looks like 100Hz (or 120Hz) noise from rectified AC Mains noise. Are there flourescent lights nearby?
 
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