Question Why does my Asus STX II sound card rapidly dip the volume of the mids and highs when the bass hits?

Sep 22, 2020
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Lately my Asus Essence STXII has been rapidly lowering the volume of the mids and highs when the bass hits, and then they bounce right back up in volume, with even maybe a bit of overshoot. I'm pretty sure it hasn't done this before, at least to the same degree. I'm using 4 year old ATH-M50x headphones and my card was bought new. Could this be an issue with the card, like maybe a bad capacitor, or is it due to some kind of degradation of my headphone's voice coils gaining resistance over the years?
 

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