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about headphone amplifier using ad8132

Hi support,

now I’m using ad1832 as an unbalanced to balanced headphone amplifier.

although these usage is not recommended, I found this device reproduce

hi-end quality sound. (great!) but I can’t reject EMI. when I move smartphone close to it,

output heavy noise. (2.4GHz ,5GHz both)  almost all countermeasure are taken

such as grounding, shielding, decoupling.

is there any other countermeasure or is there any other full differential device to

recommend which has high EMRR and works arround 3.7V power supply voltage?

Parents
  • Hi YTohyama451,

    For any amplifier whose input or output is exposed to the "outside world", you should include filters to prevent out-of-band signals from causing problems. For an audio application, this would be anything below 20Hz (including DC offsets, a short circuit to ground, etc.) and above 20kHz. While 2.4 and 5GHz are causing problems for you now, note that there are plenty of EMI sources in the 50-100kHz range - offline switching power supplies, for example.

    This is not an exact science, there are lots of approaches that work, but this document does a pretty good explanation. 

    https://www.analog.com/media/en/training-seminars/tutorials/MT-096.pdf

    -Mark

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  • Hi YTohyama451,

    For any amplifier whose input or output is exposed to the "outside world", you should include filters to prevent out-of-band signals from causing problems. For an audio application, this would be anything below 20Hz (including DC offsets, a short circuit to ground, etc.) and above 20kHz. While 2.4 and 5GHz are causing problems for you now, note that there are plenty of EMI sources in the 50-100kHz range - offline switching power supplies, for example.

    This is not an exact science, there are lots of approaches that work, but this document does a pretty good explanation. 

    https://www.analog.com/media/en/training-seminars/tutorials/MT-096.pdf

    -Mark

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