The TAS576xM uses an external ac-coupling capacitor between DACx output and AMP INPx input and a capacitor from INNx to ground for minimum dc-offset and click & pop during power on/off. Shown as C13, C14, C19 & C20 in the drawing here.
The AMP INNPx and INNMx input stage is a fully differential input stage and the input impedance changes with the gain setting from 120 kΩ at 14 dB gain to 60 kΩ at 20 dB gain. The tolerance of the input resistor value is ±20%.
The input ac-coupling capacitor together with the input impedance forms a high-pass filter with the following cut-off frequency:
If a flat bass response is required down to 20Hz the recommended cut-off frequency is a tenth of that, 2 Hz.
Table 24 lists the recommended ac-coupling capacitors for the two gain step over a range of desired system high pass filter frequency.
|GAIN||INPUT IMPEDANCE||0.1 µF||0.22 µF||0.33 µF||0.47 µF||1 µF||2.2 µF|
|14 dB||120 kΩ||13 Hz||6 Hz||4 Hz||3 Hz||1.3 Hz||0.6 Hz|
|20 dB||60 kΩ||26 Hz||12 Hz||8 Hz||6 Hz||2.7 Hz||1.2 Hz|
The input capacitors used should be a type with low leakage, like film or quality ceramic X5R or X7R with high voltage rating. If a polarized type is used the negative connection should face the DACx output pins. INPx and INMx are biased at 3Vdc.