By Bryan Geyer
I always wonder if anybody using esoteric “high end” AC power line cords has paused to consider the household wiring on the other side of their own listening room wall. That wire is ordinary AWG 12 Romex if it's for a 20 ampere circuit breaker, or (more likely) AWG 14 Romex if it’s for a 15 ampere circuit breaker. And what about that other ~ 10 miles of power line cable that extends back to the local distribution yard? Hey, can your AC power line purity really be improved by adding that last few feet of costly “audiophile grade” power cord?
The short answer is: Who cares? All of those alternating current pulses, however fine or fuzzy, are going to be converted into a smooth, flat stream of direct current. It's only this strained and purified DC, not any spurious AC, that will operate the ensuing electronic circuits. A modern solid state linear power supply utilizes full wave AC-to-DC rectification with very heavy filtering. Active components are added to enhance DC stability. Zener diodes clamp voltage levels and chop ripple. Precise series regulator stages are implemented where there’s justifiable merit, and high capacity electrolytic filter capacitors are used throughout, to assure good inter-stage isolation and smooth DC reserve. The consequent supply is scrubbed free of extraneous AC artifacts--it’s just plain/pure/smooth/steady direct current, and you can view and verify that flat DC waveform on an oscilloscope.
While every audio component has its own unique DC power supply, every supply draws its AC fuel from the same source, so it’s vital to provide enough AC current to run all the DC engines--refer paper “On Assuring Adequate AC Power.” The latter addresses cumulative AC line current drain.
AC power line cords serve as pipelines that route the required AC fuel to each DC engine. There’s no benefit served by making the pipe fatter than needed. Every DC engine has a basic design task, and it can’t store or utilize any excess AC fuel. Power line cord delivery capacity is defined by its conductor diameter. The original circuit designer selects a wire diameter gauge (AWG) that’s appropriate for the AC current required. If you have need for a shorter or longer cord, or perhaps one with an angled C13 connector (to reduce rear clearance—see photos), simply let the designer’s original AWG be your guide. Increase the diameter if you have to extend the cord (by some appreciable amount) beyond its original reach. Technically, there’s no harm incurred by moving to the next fatter gauge--I personally favor utilizing AWG 14 for a stereo power amplifier that was shipped with AWG 16 wire—but nothing whatever is gained by moving to grossly oversized cordage like AWG 10 or 12. Such cords serve no benefit, and become awkward handling and routing annoyances that invite problems.
With respect to AC line cord construction and insulation, the heavy-duty commercial standard for prime quality is type SJT, with molded construction. It’s quite excellent, and all that you’ll ever need.
Be aware that you can buy top quality SJT molded AC line cords, in AWG 14, 16, or 18, that’s made to any desired length--refer http://www.stayonline.com/molded-cord-configurator.aspx. The price for such custom cord will be quite low when compared to a high-end “audiophile grade” line cord, but it will be functionally equivalent and of optimum length, with no need to hide coiled excess. Do utilize AC surge protection at the feed socket; it might help if there’s some aberration on the power line.