I am new to this/these forums, so I will just add my 2¢.
It is never a good idea to attempt to mitigate one problem by introducing an opposite coloration to balance the two. But you already knew that, right? 😉
The only path to success is to identify the problem, i.e. the source/cause of the brightness, then address that directly.
And contrary to other responses, as a degreed electrical engineer and an audiophile for 40+ years, a "cheap" fuse CAN alter the sound, but NEVER in a good way! Fuses only add another unwanted coloration - but you knew that already!
The very best way to tame brightness or any frequency-based colorations is to use an equalizer - either in the analog or digital domain - doesn't matter which. The proper/correct/judicious use of equalizers, in the hands of an expert, can and will fix essentially ALL frequency-related problems. Thank you.
Don Roderick, Tuxedo NY