Impedance Bridging - Audio Amplifiers

Audio Amplifiers

In audio amplifer specifications, the value of the output impedance is sometimes described by the damping factor, DF, which is:

DF = \frac{Z_\mathrm{load}}{Z_\mathrm{source}} \,

Here, Zsource is the output impedance of the amplifer. Knowing the DF, one can easily calculate Zsource:

Z_\mathrm{source} = \frac{Z_\mathrm{load}}{DF} \,

Zload is the impedance of a loudspeaker, usually around 8Ω nominally. The output impedance of the amplifier is typically in the same order of magnitude as the impedance of the cables connecting it to the speaker (<0.1Ω), so DF can be rather high, ranging into the hundreds.

Read more about this topic:  Impedance Bridging