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Old 29th May 2004, 03:25 PM   #1
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Default a daring assault

this is a guess.
does a external noise reducting headphone even look like this?
well, i wanted the mic to create a negative version of the noise outside and well...silent it.
the mic amp feedback resistor's (R5), resistance can be changed with a screwdriver.
the chip is a opa4134, a quad version of opa134, for stereo input and 2 mics.

will it work?
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Old 29th May 2004, 04:03 PM   #2
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As I understand this technology, the microphone must be inside the earcup. The microphone amplifier must include an input from the headphone driver for cancellation of the sounds that you want to hear.

A microphone on the outside of the headphone would be ineffective because it would not have the ability to detect what your ear is hearing on the inside of the headphone.
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Old 29th May 2004, 06:40 PM   #3
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Default awsome!

ur great man!
now i get it!
i couldnt understand how to get the microphone in the speaker hull, but now its so clear!
hows this:
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Old 29th May 2004, 06:52 PM   #4
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You got it man!

Just one thing ... add a resistor between the output of the headphone driver and the pot that feeds the driver signal back into the system.
Make sure that the microphone is located very close to the headphone speaker.
Please let me know about your progress with this project.
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Old 29th May 2004, 06:56 PM   #5
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Quote:
Originally posted by Frank Berry
Just one thing ... add a resistor between the output of the headphone driver and the pot that feeds the driver signal back into the system.
is that meant to make sure the resistance at this point will never be 0?
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Old 29th May 2004, 06:57 PM   #6
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Yes.
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Old 29th May 2004, 07:10 PM   #7
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Default this is the latest version

but i have no clue as to what value is R7 and P2.
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