Autotransformers are used in applications requiring a slight boost or reduction in voltage to a load. The alternative using a normal (isolated) transformer would be to either have just the right primary/secondary winding ratio made for the job or use a step-down configuration with the secondary winding connected in series-aiding (boosting) or series-opposing (bucking) fashion. In audio applications, tapped autotransformers are used in constant-voltage audio distribution systems or for impedance matching.