Where is the hum coming from? Don't automatically assume power supply. It could be some "ground loop" problem, including capacitive coupling through the wall wart. On Tue, Mar 3, 2015 at 10:42 PM, IVP wrote: > > Do you have any other filtering on the power supply input side > > to choke the 50Hz ? > > No, but I am trying to discover what is possible passively. Initially > I thought a choke would be rather large, in value and perhaps size > > IF a switcher was feasible, then I guess it would have to a buck- > boost to pick up the energy from both +ve and -ve peaks either > side of the DC > > Thanks > > Joe > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 2015.0.5751 / Virus Database: 4299/9220 - Release Date: 03/03/15 > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .