My enquiries related to 13A fuses. In the UK they must be certified to be legal. Certification costs a lot of money. So QSA and SR relabel Bussmann. Otherwise the UK distributor would be breaking the law selling them. He told me they are not physically modified, but QSA say they have reduced resistance, which would require recertification. So they sell a $0.30 fuse that by law cannot be modified for $10,000. Just a massive scam as far as I am concerned.
The Zen Mk3 uses an uncertified 2A fuse. I tried a SR fuse in mine, as my once only fuse experiment. Innuos told me to use a 3.15A if I use SR, but that it should not make any difference. I can’t hear any difference.
There is no scientific reason why a stock fuse should under normal conditions have any impact at all. Its resistance is totally inconsequential. They are never on the signal path.
QSA seems to be a complete lie. No evidence he’s done any work for other companies. He’s a long time audio dealer called Lieder International. In 2015 he became distributor for Akiko, who do weird aftermarket fuse products, makes me wonder where he got the idea from for after-market fuses.