You mean dimming the lights is not a feature? :-)
Your main feed (200A?) is likely 2/0, so even if it is 500 feet to the pole, that 75 feet of 14A is doing way more damage. Some amplifiers have excellent power supply rejection and can tolerate this, some don’t. 6V or so at 15A, but that is only the fuse rating. Short term peaks could be higher depending on how far the capacitors have drooped and the saturation limit of the power supply transformer.
There are no issues with pigtails (connections always made in electrical boxes to meet code), as long as the connection is made properly. If you want a perfect connection, use a proper compression splice with a proper crimp tool (and make sure the conductors are clean of corrosion). Don’t use screw lugs and definitely don’t solder them together. A properly implemented compression crimp connection is pretty much like a continuous wire. Any impact of this connection will be orders of magnitude smaller than the connection of the power cord to the AC socket and to your equipment. The ground should connect direct to the junction box and not pigtailed to a thinner gauge. That is frowned upon.
If you do run multiple AC lines, I would encouraging terminating them at the receptacles in the same junction electrical box so that all the receptacles have the same ground connection and you don’t end up with any unintentional ground loops. As Cleed pointed out, the easiest time to do it is now and it sounds like you already have the 14 awg run, so unless you were planning to use that as a snake, just add the additional wire, even if you leave the 14 unconnected for now.
Running multiple AC lines is akin to bi-amping (not biwiring) speakers. Bi-amping allows you to prevent stresses in one range of frequencies (bass) from generating distortion in the higher frequencies, most prevalent obviously when run hard. Bi-wiring has limited (if any) value as the cross-over splits up the frequencies anyway. Running a separate AC line for power amps can prevent modulation of the AC line from impacting the more sensitive low power equipment. You are already accomplishing much of that by running heavy gauge and most low power equipment has better power supply "noise" rejection.
Interesting comment about large gauge being good for bass, and small gauge for treble. There is, unfortunately, with the way most amplifiers are designed, the potential for this. Almost as a rule amplifiers have good power supply noise rejection at low frequency (within limits as you have found out), and poor(er) power supply noise rejection at higher frequencies. Some low feedback designs can have pretty poor rejection at bass frequencies too. Reducing the resistance in the AC line can improve your bass, but it also means faster transitioning of the diodes (at higher peak currents) in the power supply which means more high frequency noise, something the amplifier doesn’t deal with as well.
Your main feed (200A?) is likely 2/0, so even if it is 500 feet to the pole, that 75 feet of 14A is doing way more damage. Some amplifiers have excellent power supply rejection and can tolerate this, some don’t. 6V or so at 15A, but that is only the fuse rating. Short term peaks could be higher depending on how far the capacitors have drooped and the saturation limit of the power supply transformer.
There are no issues with pigtails (connections always made in electrical boxes to meet code), as long as the connection is made properly. If you want a perfect connection, use a proper compression splice with a proper crimp tool (and make sure the conductors are clean of corrosion). Don’t use screw lugs and definitely don’t solder them together. A properly implemented compression crimp connection is pretty much like a continuous wire. Any impact of this connection will be orders of magnitude smaller than the connection of the power cord to the AC socket and to your equipment. The ground should connect direct to the junction box and not pigtailed to a thinner gauge. That is frowned upon.
If you do run multiple AC lines, I would encouraging terminating them at the receptacles in the same junction electrical box so that all the receptacles have the same ground connection and you don’t end up with any unintentional ground loops. As Cleed pointed out, the easiest time to do it is now and it sounds like you already have the 14 awg run, so unless you were planning to use that as a snake, just add the additional wire, even if you leave the 14 unconnected for now.
Running multiple AC lines is akin to bi-amping (not biwiring) speakers. Bi-amping allows you to prevent stresses in one range of frequencies (bass) from generating distortion in the higher frequencies, most prevalent obviously when run hard. Bi-wiring has limited (if any) value as the cross-over splits up the frequencies anyway. Running a separate AC line for power amps can prevent modulation of the AC line from impacting the more sensitive low power equipment. You are already accomplishing much of that by running heavy gauge and most low power equipment has better power supply "noise" rejection.
Interesting comment about large gauge being good for bass, and small gauge for treble. There is, unfortunately, with the way most amplifiers are designed, the potential for this. Almost as a rule amplifiers have good power supply noise rejection at low frequency (within limits as you have found out), and poor(er) power supply noise rejection at higher frequencies. Some low feedback designs can have pretty poor rejection at bass frequencies too. Reducing the resistance in the AC line can improve your bass, but it also means faster transitioning of the diodes (at higher peak currents) in the power supply which means more high frequency noise, something the amplifier doesn’t deal with as well.