For a systemwide EQ , Equalizer APO combined with the Peace interface is often used.
It works with Direct Sound/ WASAPI Shared mode
Download Equalizer APO for free. A system-wide equalizer for Windows 7 / 8 / 8.1 / 10 / 11. Equalizer APO is a parametric / graphic equalizer for Windows. It is implemented as an Audio Processing Object (APO) for the system effect infrastructure introduced with Windows Vista.
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As it is a APO, it works system wide hence one EQ for all apps.
Downside, it runs at the fixed sample rate as set in the audio panel. All audio not matching this rate, will be resampled. If the audio contains signal close to 0 dBFS this will introduce distortion.
This can be avoided by setting the pre-amp in EQ APO a notch down.
If a program uses WASAPI in Exclusive mode, it bypasses the win-audio stack. All output is send straight to the inputbuffer of the audio device. Obvious, EQ can only be done inside the app. As the app has a exclusive lock on the audio device, automatic sample rate switching is supported.
A nice overview of EQ software:
https://www.audiosciencereview.com/...ows-linux-macos-ios-ipados-and-android.18450/