Quote: Originally Posted by ericj /img/forum/go_quote.gif I still don't understand what you're on about wrt the feedback resistor on the ground channel. TLE2426 output=virtual ground virtual ground -> op amp -> buffer -> output ground this time I ditched the three op amps and used sijosae's class ab "buf634" buffer instead. It needs to be kept in op amp control, in feedback loop or there will be dc offset. But now I understood, I don't need a resistor, I need only bare wire, right? hmm, I think I should start practicing using some schematic and simulation program (know any good and easy for Windows?), because I sometimes do things more complicated than is necessary.