Not sure what you have there then? Maybe these are time-delay fuses vs. fast fuses? Time delay elements look somewhat more complicated than the fast-blow types, they usually have a spring & some other stuff in there. They are intended for motor applications (refrigerators, washers, dryers, furnaces, etc) where the motor's startup current surge would fail a fast-blow element. I recall time delay fuses being called Fusetron's sometimes. I have not compared these to standard fuses when used for audio, but they might be OK.
An alternative approach when fusing a motor device is to overfuse it so the surge current won't fail the element, but this offers poor protection. Similarly, fusing a non-reactive load with a slow-blow fuse offers poor protection but it might, still just sound fine.
I only advise against glass body fuses because they sounded not that good in my own experience. Ceramic is definitely good (if you can find them anymore - please grab a couple boxes for me if you do find 20 amp ceramic fast fuses). Lately I've beenusing the nerw plastic body fuses but haven't yet made any hard comparisons against the one ceramic fuse that I still have left.
An alternative approach when fusing a motor device is to overfuse it so the surge current won't fail the element, but this offers poor protection. Similarly, fusing a non-reactive load with a slow-blow fuse offers poor protection but it might, still just sound fine.
I only advise against glass body fuses because they sounded not that good in my own experience. Ceramic is definitely good (if you can find them anymore - please grab a couple boxes for me if you do find 20 amp ceramic fast fuses). Lately I've beenusing the nerw plastic body fuses but haven't yet made any hard comparisons against the one ceramic fuse that I still have left.