Typically, measure the power draw of each module with a DMM. You can just use the plus power as the - side is typically the same or less. Be carefull of the power rating of the supply. Is it rated for +500 mA and -500 mA or just 500 mA TOTAL (250/250 mA)? Regards, ___________________ John Blacet Blacet Research http://www.blacet.com