DAMPING FACTOR

摘要

This is the second headphone amp to come our way from Japan that includes deliberate manipulation of damping factor (DF) - the ratio of load resistance to output resistance. In driving loudspeakers it is normal for the amplifier output resistance to be low (DF high) in order to ensure effective electromagnetic damping, particularly of the loudspeaker's fundamental bass resonance. As this damping effect depends on current flow through the voice coil resistance in series with the amp's output resistance, though, it's arguable whether any practical benefit accrues when the latter is reduced below, say, 5% of the former (a damping factor of 20). Why a reduced DF should be of benefit to headphones, as Aurorasound's Mr Karaki suggests, is far from clear. But the audible effect, to judge from the variable DF control on the Teac HA-501, is obvious enough. As the damping factor is reduced, the sound becomes smoother, less 'etched', an effect unlikely to be explained simply by the changes in frequency response.