Hello HeadPhoneAmp Enthusiasts

Hi, the other day sorting stuff on my old bookshelf I found my old Tietze&Schenk book, and it suddenly came to me that I want to rekindle my DIY life from like 40 years before...
I wanted to start small, so I started to look at headphone amplifiers, and after a couple days of research I was hooked... I found myself fascinated by the most simple circuits with one or two active components, in their wide varieties, and I want to build them all, and hear, compare their sounds with my own ears...
I have a gazillion questions, and I registered here to have an option to ask experts if (when) I cannot find answers through my own research.
Thank you!