ghauri

I got A problem i Have a audio output from a speaker then it is recorded/tranmistted by a microphone
now i want to eliminate both Speaker and Mircophone i Coupled directry the wires of the speaker too the microphone but i got a big noise plz help mt and tell what king of a circuit i make in between that Speaker and Microphone that it should overcome the noise in between that
I m waiting plz help

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Muhammad Saeed
Department of Electrical Engineering
University of Engineering and Technology Taxila
Pakistan

Dr.EM

Really, it would be best to remove both the speakers power amplifier section and the mics pre amplifier section, then join the corresponding line level signals together. I've never actually seen a speaker to mic level convertor, but you might try searching for one, I know there are speaker to line level convertors (thy are quite simple), but the best way to go is removing the respective power and pre amps as they will only ever contribute noise.

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Nigel Goodwin

Your requirements aren't really very clear?, but ignoring earth loops and such things, all you need is a simple resistive attenuator - even a single high value resistor may well be enough, it depends on the input impedance of the microphone input and the output voltage of the power amp. Historically, the worlds first cassette recorders (Philips) only had mike inputs, in order to record line inputs you inserted a 1.5MOhm in the connecting lead. Speaker outputs are far higher than line outputs, but a similar value would be a good starting point.

But, as already suggested, the better way is to remove the power amp and mike preamp, and simply connect the line levels together.

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audioguru

I wonder why a big noise results when people try to cram a 10V (or more) speaker signal into a mic input designed for only 10mV?
The difference between levels and their background noise level is only 1000 times!

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Uncle $crooge