Voltage drop calculator.http://www.windsun.com/Hardware/Voltage_Calc.htm
Distance or Conductor Size: .... (Distance)
Single or Three phase: ........... (Single)
Conductor Type: .... (Copper)
Installation: ............. (Conduit) .... Same for Romex
Voltage: .................... (120V)
Maximum Voltage Drop: ... (Already set for 3%. You can change the percentage to what ever you want.)
3% of 120V = 3.6V VD
2% of 120V = 2.4V VD
Conductor size: ...... (14 gauge)
Current: ...................(12 amps)
Max length of branch circuit for a 3% VD (Voltage Drop) 55.97ft.
Max length of branch circuit for a 2% VD 37.32ft
Remember, up, down, and all around when figuring the entire length.
Dynamic Headroom: https://forum.audiogon.com/discussions/dynamic-headroom
Here’s a quote from a Pro Audio web site, old post.
Around 1984 when I bought my first QSC power amp I called QSC after reading that it has 3db of headroom. I was told that the 300 watt rms rated amp could produce 600 watts of peak power when needed. https://forums.prosoundweb.com/index.php?topic=139460.10
That means if I did a rim shot on the snare drum to make it louder or kick the bass drum harder when hitting a crash cymbal there would be enough power reserve for this and the amp would not clip. I remember the guy telling me its like snapping my fingers and then waiting a few seconds and snapping them again.
I guess if all you listen to is elevator music at a moderate listening level #14 wire is all you need.
When a load is known the NEC says the wire shall be sized at 125% of the connected load. Again when the load is known. Using #14awg copper wire, #14 has an ampacity rating of 15 amps. 80% of 15 = 12 amps.
(For a continuous load. Continuous load is defined by the NEC for a load lasting 3 hours or more.)
(ieales there’s your reserve you are looking for. )
That does not mean you can’t load a convenience receptacle outlet circuit to the 15 amp max until the 15 amp breaker trips..... If it trips..... With a receptacle convenience outlet circuit the loads are not known. The limiting factor is the circuit breaker.
In a dwelling unit there is no limit on the number of receptacle outlets that can be installed on a 15 or 20 amp branch circuit.