Soldering is an indispensable work in the world of DIY audio. Good or bad of soldering is directly connected to sound quality. Especially in DIY amplifiers, I believe quality of soldering affects sound quality more than circuit design.
Here I will introduce my unique soldering technique.
It has durability that does not deteriorate semipermanently and good sound quality.
Note that it is a method not recommended by soldering iron manufacturers, and it might damage the iron's tip. Please be aware of this fact.
Please see this PDF for details.