It's unlikely it was the ground scheme. You yourself claim that the amp worked fine for over a year. You traced the hum to a specific point, and then chose to ignore that data and try something else based on some comments from a few people.
The only thing you really learned is that you changed something, and that seems to have solved your problem. You did too many things at one time to truly know what the actual problem was. That is fine...unless the problem crops up again.
You say you are a novice, so, if you want to actually learn stuff, I believe it's important for you to not draw the wrong conclusions from your process. With more patience, you could have found the specific thing that was causing the problem.
I disagree with the following quote. This technology is around 100 years old. There aren't really any "unknown variables".
But all of these questions are a reminder that there are so many extra unknown variables when putting theory into practice.
In my opinion, your tone is a bit arrogant.
Idon'tknowyou states that he/she is wanting to learn and so deserves better.
Anyways, what I see is that IDKY took the advice that it was likely a grounding problem and then followed advice for a proper grounding strategy. Maybe one of the connections was weak? Maybe there was cross-talk?? Regardless, changing a dodgy circuit to a known solid circuit is not a bad outcome. He's not a pro tech, but a hobbyist wanting to get the amp working again. Will it last? I do not know, but progress was made, eh?
