Trying to zero in on a tube for my Boothill 5F1. I originally stuck a 12W Tung Sol 6V6GT in there - it sounded really good but was red plating like a mother (see photo). After doing some calculations, I found the max plate dissipation % to be around 115%. So I swapped out the Tung Sol for a JJ 6V6S (rated at 14W), thinking it might get me closer to 100% max dissipation. The JJ tube got me to about 103%, but it doesn’t sound nearly as good. There are some abrasive high frequencies that occur once the tube starts to break; they’re really noticeable at about the 9 or 10 mark on the volume control. I’ve never used a JJ 6V6S before, so not sure if this is normal. Looking for some advice on what to do next. Should I put the Tung Sol back in and swap out the power tube resistor with a larger value? Would it help to add a resistor to lower the voltage between the rectifier and B+ connection? Should I try a different power tube? Different rectifier tube (currently using a JJ 5Y3S)? Maybe there is something wrong with the JJ 6V6S tube? I can post voltage readings for both the Tung Sol and JJ tube pins if that is helpful. Thanks for any advice!