If it can be avoided, then don't do it. Try to be separated by at least a foot if run in parallel and try to cross at 90 degrees.
If you are too close to the high voltage AC line, some interference may be heard, especially at lower volume and probably more noticeable with longer runs.
It doesn't take much to drill some new holes with a good bit.

I'll add something here.

Whether it can be avoided or not, do NOT run any of the audio wiring in the same holes as the electrical. It's not a matter of "some interference may be heard". It's a matter of a 60 cycle hum WILL be heard.

If you must run paralell, as stated above, separate by at least a foot, preferably more. And do cross at 90 degrees, that is absolutely correct.

As I tell my guys?

"Drill new holes you lazy ****" (said in fun of course).

By the way. Make sure the "stereo wire" that you install is actually meant for the purpose (16 gauge twisted as opposed to lamp cord/zip cord). Also ensure that it is rated for inwall use. That IS important.