You had no hum before simply for the same reason most don't notice, a combination of low level and solid construction. Lots of times there's background noise that can be there sometimes for a very long time, until something happens you notice and then OMG that noise is killing me! One person watching a movie is so engrossed they don't even notice the popcorn muncher beside them, while another can think of nothing else. Same noise. Completely different response.
The amp is the same way, you should know better than anyone, you had one that made no noise, then another same one that did, then the first one comes back makes noise but in between the other two. Perfect example.
Hum Buster is the name PSAudio sold theirs under. I forget the exact circuit, it ain't much. If they don't make it any more someone does. Just one of those names like Thermos people use even though a lot of insulated containers aren't actually Thermos name brand.
PSAudio may no longer make it. Here's another one called Hum Dinger. No idea if this is made either! I use a step-down transformer, which is another option.
https://avahifi.com/products/humdinger-dc-line-blocker
Another one
https://emotiva.com/products/cmx-2
Then you can get into stuff like this that will be more of an improvement
https://www.decware.com/newsite/ZLC.html
The amp is the same way, you should know better than anyone, you had one that made no noise, then another same one that did, then the first one comes back makes noise but in between the other two. Perfect example.
Hum Buster is the name PSAudio sold theirs under. I forget the exact circuit, it ain't much. If they don't make it any more someone does. Just one of those names like Thermos people use even though a lot of insulated containers aren't actually Thermos name brand.
PSAudio may no longer make it. Here's another one called Hum Dinger. No idea if this is made either! I use a step-down transformer, which is another option.
https://avahifi.com/products/humdinger-dc-line-blocker
Another one
https://emotiva.com/products/cmx-2
Then you can get into stuff like this that will be more of an improvement
https://www.decware.com/newsite/ZLC.html