WM8904
Pre-Production
EXTERNAL COMPONENTS FOR GROUND REFERENCED OUTPUTS
It is recommended to connect a zobel network to the ground-referenced outputs HPOUTL, HPOUTR,
LINEOUTL and LINEOUTR in order to ensure best audio performance in all applications. The
components of the zobel network have the effect of dampening high frequency oscillations or
instabilities that can arise outside the audio band under certain conditions. Possible sources of these
instabilities include the inductive load of a headphone coil or an active load in the form of an external
line amplifier. The capacitance of lengthy cables or PCB tracks can also lead to amplifier instability.
The zobel network should comprise a 20 resistor and 100nF capacitor in series with each other, as
illustrated in Figure 38.
Note that the zobel network is recommended for best audio quality and amplifier stability in all cases.
Figure 38 Zobel Network Components for HPOUTL, HPOUTR, LINEOUTL and LINEOUTR
PP, Rev 3.3, September 2012
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
