I have a question about power down my pcb (ADAU1446 and AD1939) in combination with a power amplifier and a loudspeaker. It crashes/crackles very very loud every time I turn off the power of the whole system!
I have the following structure on my pcb:
- analog input as on the ADAU1446 Evaluation board (except the OPamps has dual supply)
- digital conversion with AD1939 (at 96kHz, programmed over SPI with a PIC uC)
- signal processing with ADAU1446 (at 96kHz)
- analog conversion with AD1939 (...)
- analog output stage as recommended in the AD1939 Datasheet (except, there is a 10uF capacitor in the signal path directly before the output)
The power amplifier turns off at about 3 seconds after I turn off the power supply; the digital parts turn off earlier and cause the crashes/crackles/...!
1) Can I provide some simple changes in my analog design to avoid this problem?
2) Should I try to maintain the power supply of the pcb (e.g. with a goldCap or superCap)? (The power amplifier turns off very silently)