when I’m working with one dedicated line the sound is better than two lines
the second line is for the monoblocks
with one line the sound is more relaxed and the timing is right
the two lines are from the same phase.
If using just the first dedicated line sounds better than using 2 lines, then I suspect the 2nd has issues. Like perhaps it's not really on the same leg/phase as you might think and/or perhaps there is a loose connection somewhere in the 2nd line and/or polarity is switched. There's no reason to ever trust electricians, no matter how highly they are recommended. IOW, you always need to double-check everything they do to confirm the work is to your satisfaction.
If the 2nd line is configured and as solidly constructed/assembled as well as the first line, then worst case the playback presentation should sound identical as using just one line. Best case, with a 2nd line dedicaated to the amps, the playback presentation should sound more dynamic, more alive. Particularly if your amps are high-current drawing.
To be fair, if anything on the 2nd line is new e.g. new circuit breaker, new romex, new outlet, etc. then these items need at least about 3 full days of burn-in to sound their best.
Otherwise, something ain't right with the 2nd line. You could get a polarity tester, trip the circuit and pull the outlet to ensure the lead and neutral connections at the outlet are tight. Beyond that, you might need to get an electrician out to confirm the phase and connections at the service panel.
