On 21 March 2016 at 21:07, I wrote: > http://www.milton.arachsys.com/nj71/index.php?menu=2&submenu=2&subsubmenu=14 I've just added (completed) analysis of the Twin-T filter to illustrate how the Y matrix can help deal with parallel networks. Fortunately I get the right answer! Neil -- http://www.njohnson.co.uk