The Hi-Fi Tuning fuse made a difference. The first thing I noticed is Joshua Bell's violin was in better focus. More string and body sound to the violin. Highs are more extended and detailed. This was not subtle. I have to agree with the Stereophile reviewer that the Onkyo was a nice amp before but even better with the new fuse. Other than what I have read I have no idea why a fuse should make an improvement but it did.