Dedicated circuits

Voltage drop allowances are not even a NEC requirement, I know I've had voltage drop with my system when I used a carver subwoofer for a short time, even with 20 amp dedicated circuits using 10awg wire.

If I recall, the Carver subs substituted power for size, so a ferocious amount of power was demanded.  Not that surprised.  :-)   A large diameter sub would fix that.

I believe in isolation of power to my audio system. I installed 3 dedicated lines for my system. I used 10ga romex for amp, 12 ga for preamp and another 12ga for digital.  I used 20amp breaker for the amp and 15 amp breakers for the other two lines. All my components have robust power supplies supplying the needs of the audio curcuits therin. I believe the current supplied is more than sufficient.  Also used hospital grade outlets for all lines. Lines are rum off a subpanel that, in addition, only serves  bedroom outlets and lights.

A 15A breaker for an electrical outlet is anything but a 'robust power supply'. It's code minimum, regardless of the wire gauge.

@builder3

 I think you misread.  He states that the components have robust power supplies. I would interpret that as the build of the transformer, rectifiers and filter caps. 

He's also stated his amp is on a different circuit. 15A for source components is plenty.