razorbill If you're using (wired) headphones, here's an excellent solution:
https://neutronhifi.com/devices/dac/v1
Headphone amp with built-in DSP. Dongle, about half the size of a pack of gum. Tiny enough that you'll pretty much consider it as "part of the headphone termination".
EQ your brains out. It even does separate right/left EQ, if you need it. Settings are stored on-board, so you can just hook it up to a computer, or whatever USB audio device, and continue listening with equal (pun?) enjoyment there.
Best audio purchase I've made in years! I may not have the same needs as you, but all headphones benefit from FRC. Oh, and it does crossfeed too which is a must, in my opinion.
Been meaning to write a review on it in another thread, and will eventually get to it. Here's a professional review, at least:
https://www.audiosciencereview.com/forum/index.php?threads/neutron-hifi-dac-v1-review.56647/
There are YouTube reviews, also, where you can grasp it's size and scale. It really is tiny..!
Hope it helps! 👍