amb
Member of the Trade: AMB Laboratories
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digger945, the passive filter found in the Wolfson PDF is for a DAC with unbalanced outputs. For WM874x you need to use the same filter on both the hot and cold outputs. To make it even simpler, you could connect each of the hot and cold outputs to the 470 ohm resistor as shown, but instead of running a 4.7nF capacitor to ground after that, just run a single 2.2nF cap across. The rest is the same -- coupling caps and drain resistors to ground.
Note that this passive filter design is 1st order (6dB/octave slope), whereas the active one implemented with the opamp is 2nd order (12dB/octave).
Note that this passive filter design is 1st order (6dB/octave slope), whereas the active one implemented with the opamp is 2nd order (12dB/octave).