To get back to the original question.......
If I use an op amp in an inverting config which moves the signal 180 degrees out of phase, does this cause a problem if both channels are inverted this way? I mean, should/must I use another inverting stage to correct this? If I don't what happens to the audio quality ?
I don't have the second stage right now and it seems fine....
Consider the actual recording and mixing processes and the equipment used to originate the music we all listen to:
Take the single most complex piece of equipment, the mixing console, and assume it is analogue. One important aspect of mixer design is that all inputs to, and outputs from, the mixer are in a coherant phase. Within any signal path between an input and an output there are often several phase inversions. A good example of this is a 4-band parametric equaliser, which will have 4 phase inversions through it: coherant phase is maintained.
In other circuits, inverting buffers will be added to maintain an in-phase signal between the input and output of a circuit block.
Phase inversions will only cause a problem if one channel is out-of-phase with respect to another channel. As long as both channels have the same number of phase inversions, I can see no reason to expect problems.
Regards,
Gareth.