Probably one of the best sites for beginners to join when I first started to dabble with amplifiers. The classic projects – P1, P1 eXtreme, H-Octane and SEL – are all very well documented. The Amp Maker SE-5a was very closely based on the P1 project, and the N5X is a development of the same, with useful features added.
The original forum has stopped but there is a lot of archived info with feedback and ideas about modifications and troubleshooting.
Original forum is here: click to open in a new window
The new forum is here: click here to open it in a new window