Purpose of resistor in amplifier circuit

[Fearsome]

I'm building a multi-message record/play unit based on a PIC, an ISD4002 record/playback device, an audio amplifier for the speaker, and a microphone. It's going to look something like the application example in the attached file (which is taken from the ISD4002 data sheet).

I've looked at the data sheet for the LM4860 amp and it's straightforward to connect. However, in the attached schematic there's a 1MOhm resistor (R2) between the audio out of the ISD4002 and ground. I can't figure out the purpose of this resistor. Does it have something to do with the line out jack? Any help is appreciated. It's probably very simple...

Fredrik

 

[Audioguru]

The resistor slowly charges the output capacitor C4 of the ISC4002 so when something is plugged into the line output jack the capacitor doesn't suddenly charge and cause a loud POP sound.

 

[E-design]

Also when something is plugged into line-out the input to the audio amp from point 4 would be left floating if not for R2. This could cause noise pickup to be amplified and passed onto the speaker. R2 prevents this by pulling the input to ground.

 

[Fearsome]

Thank you both. However, I don't understand Audioguru's reply. To me it seems the resistor discharges the capacitor since it connects to ground. Could you elaborate?

Fredrik

 

[shashipoddar]

It is used for biasing the circuit....and provide the actual ratings..

 

[Audioguru]

With nothing plugged into the Line Out jack, the 1M resistor charges C4.