Hello from Portugal

Hi, I am a Pysics professor, now retired.
By several years I made amplifiers from scratch, including pcb design, following several diagrams, includind the famous Quad 33/303. Usually friend wanted to buy these amplifiers, and no one failed...
This was a long time ago. I'm now almost 74 and my usual amplifier is now the Audiolab 8000A.
Regards.