>In the case of most circuits, the AB1 amps are AC coupled and the AB2 amps are >DC coupled to the grids - which permits current to flow. This is especially >clear in audio applications... Which may be the reason for this?. Practical?. > ** with AC coupling, grid-current flows into the grid bias supply. Anyway, with AC coupling it must have a DC return somewhere. Best regards Guillermo - LU8EYW.