This is going to sound awfully controvertial, so no offence Andy!
People try to help in their own way!, usually people respond with a solution that is un-tested. You responded with a typical "tried this, tried that!" And "it didn't work"! Then 'Gave Up'.
What didn't work?
How did you make the circuit I linked to ?
How did you power it?
How did you check it does'nt work?
Also, it's probably line-level needed for the DVR which we would have done in the next stage...
But without feedback, how can we help you?
Martin