audioXpress is the only do-it-yourself audio magazine currently published in the USA. I’ve been a subscriber since the late 1970s and have a nice collection of back issues.
Their web site has plenty of free info so check it out… better yet, subscribe today and support DiY!
An example of a recent project is the Hybrid Valve MOSFET SE Amp by Stephen Moore, published in the Oct and Nov 2007 issues. They are online for free download: