Where has been your most effective placement for an aftermarket fuse?

So back to the subject matter.

My first experience with aftermarket fuses.

About 5 years ago I bought my first external dac, Exogal Comet Plus.
It so happened a long standing member had exactly same DAC.
He had just upgraded from SR black to SR blue fuse and offered to send me the SR black to try out and see what I thought.
Well nothing to lose so I did,I fitted it and sat back and..... nothing...maybe less than nothing.
I reported this back and his response was did I try flipping it for direction.
Say freaking what now??
But he was deadly serious so WTH, why not.
Sat back and slowly a big smile crept across my face as I could hear improvement in every area.
My first introduction to aftermarket fuse veracity and directionality all in one fell swoop.
My deep scepticism was washed away in minutes.
And that is the area I have found after maybe 4 more DAC to still have the most noticeable impact.
To my ears.
In my system.
Ymmv.

In my scenarios, fuse upgrades almost always made more improvement/change in the sound when placed in a preamp / source device.  In amplifiers, fuse upgrade still makes an improvement, but the amount of difference is not as much as a fuse upgrade in preamp / source.

Try wrapping PTFE around the glass part of a normal fuse. Ensure it doesn’t touch the metal endcaps. I have found a significant improvement in blackness and image solidity at no cost. Phono amp then amps.