I performed many of the mods on Boyuurange A50 and left with an imbalance that eventual goes away.
Did every mod but the front end when my out of stock items get shipped.
I only have two things that come to mind are my coupling caps and bias. I am think my left cap is installed wrong as it was picking up noise. I did not fix that issue yet. I did not know about the shielding was performed by placing the cap to the first stage. I still feel that would only be a hum or other noise ingress issue. So last is something I have not gotten comfortable with yet but measuring the electrical circuits of my amp. I will get there. So I just need some recommendations or personal experiences that you may have had with same issue.