PC audio to arduino ADC

Hi all,

I want to connect my pc audio to my arduino, I was using a freetronics crappy mic module, they have so much noise they are not much good for anything analytical.

I found a schematic in this thread: Connect audio signal  to arduino input - #6 by macegr - Troubleshooting - Arduino Forum

I'm unsure of what is V1 and V2 are, also is 1N4001 or 1N4004 suitable for D1 and D2.
Also, that op-amp was unavailable. I have an LM358, and I also bought an NE5534P today.

Cheers, Chris.

EDIT: small images switched with big.

V1 is the power supply for the op amp
V2 is the microphone or audio source.