On Assuring Adequate AC Power

How to assess your audio system’s full AC power line requirements, and how to determine whether your AC power line capacity is sufficient.

By Bryan Geyer

It’s important to confirm that you have an adequate AC current reserve to optimally power your audio system. This means more than just being confident that you can push the volume up without causing a circuit breaker to trip. The function of a circuit breaker relates to safety—not line quality or line stability. To assure that your AC supply is not plagued by load-induced voltage drops it’s desirable to verify that your audio system presents a drain that’s within the traditional guideline for power line current density. The conventional “good design” limits for this are as described here: http://www.powerstream.com/Wire_Size.htm.

You can generally determine your household’s wiring gauge by inspecting your circuit breaker. The current practice is to use AWG 14 Romex for a 15 ampere circuit, and AWG 12 Romex for a 20 ampere circuit. Because 20 ampere circuits are habitually routed only to kitchen, bath, and laundry areas, it’s likely that your listening room utilizes 15 amp circuits, hence AWG 14 wiring. By reference to the above, you can see that the classic (it’s ultra-conservative) design guide for AWG 14 wire is 5.9 amperes maximum. If it’s your intent to dedicate that specific circuit exclusively to audio system use, then 5.9 amps max. current drain should be your goal. If you exceed 5.9 amps you will potentially risk “modulating the line”, meaning you could induce brief AC line voltage fluctuations due to the inevitable load changes that your power amplifier imposes as its output shifts. Regardless, I feel that some 50% more current drain is both safe and acceptable if it truly reflects operation at full power output (with no other loads on same circuit). That makes 9 amperes my personal full power ceiling for AWG 14 in-wall wiring with 15 ampere AC circuit breakers.

To calculate your system’s maximum AC current drain, sum the net power (as stated in Watts*) consumed by your components, and divide the total by 120 Vac. That result will approximate the maximum AC operating current. Component power consumption is generally listed in the related performance specifications. Take care to assure that power drain listed for your main amplifier(s) refers to power consumed when operating at full power output into the applicable load impedance.

Better yet, directly measure the net current drain for yourself. Use a Kill-A-Watt P4400 meter; refer: https://shop.p3international.com/p/kill-a-watt.

A NOTE: You can buy top quality molded SJT-type power cords, AWG 14, 16, or 18, custom made to any length, at http://www.stayonline.com/molded-cord-configurator.aspx. The price for a custom SJT power cord is low when compared to the price for a high-end “audiophile-market” power cord, but it’s functionally identical, and it will be properly sized, without unwanted excess.

*Watts apply when considering most audio equipment, but not for AC motors, and not for Class D power amplifiers. (Most self-powered subwoofers use Class D power amps.) Use the Kill-A-Watt P4400 meter to measure the current drain or VA (Volt-Ampere) consumption of turntable/tape motors and Class D amps.

BG

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Meet the Staff

Meet the Staff
John J. Puccio, Editor, Publisher, Reviewer

Understand, I'm just an everyday guy reacting to something I love. And I've been doing it for a very long time, my appreciation for classical music starting with the musical excerpts on The Big John and Sparkie radio show in the early Fifties and the purchase of my first recording, The 101 Strings Play the Classics, around 1956. In the late Sixties I began teaching high school English and Film Studies as well as becoming interested in hi-fi, my audio ambitions graduating me from a pair of AR-3 speakers to the Fulton J's recommended by The Stereophile's J. Gordon Holt. In the early Seventies, I began writing for a number of audio magazines, including Audio Excellence, Audio Forum, The Boston Audio Society Speaker, The American Record Guide, and from 1976 until 2008, The $ensible Sound, for which I served as Classical Music Editor.

Today, I'm retired from teaching and use a pair of bi-amped VMPS RM40s loudspeakers for my listening. In addition to writing the Classical Candor blog, I served as the Movie Review Editor for the Web site Movie Metropolis (formerly DVDTown) from 1997-2013. Music and movies. Life couldn't be better.
Karl W. Nehring, Contributing Reviewer

For more than 20 years I was the editor ofThe $ensible Soundmagazine and a regular contributor to its classical review pages. I would not presume to present myself as some sort of expert on music, but I have a deep love for and appreciation of many types of music, "classical" especially, and have listened to thousands of recordings over the years, many of which still line the walls of my listening room (and occasionally spill onto the furniture and floor, much to the chagrin of my long-suffering wife). I have always taken the approach as a reviewer that what I am trying to do is simply to point out to readers that I have come across a recording that I have found of interest, a recording that I think they might appreciate my having pointed out to them. I suppose that sounds a bit simple-minded, but I know I appreciate reading reviews by others that do the same for me -- point out recordings that I think I might enjoy.

For readers who might be wondering about what kind of system I am using to do my listening, I should probably point out that I do a LOT of music listening and employ a variety of means to do so in a variety of environments, as I would imagine many music lovers also do. Starting at the more grandiose end of the scale, the system in which I do my most serious listening comprises an Onkyo C-7030 CD player, Legacy Audio StreamLine preamplifier, Legacy Audio PowerBloc2 amplifier, and a pair of Legacy Audio Focus SE speakers augmented by a Legacy Point One subwoofer. I also do a lot of listening while driving in my 2016 Acura RDX with its nice-sounding ELS Studio sound system through which I play CDs (the ones I especially like I rip to the Acura's hard drive so that I can listen to them whenever I want) or stream music through the system using my LG G7 ThinQ cell phone, which features surprisingly sophisticated audio circuitry. For more casual listening at home when I am not in my listening room, I often stream music through the phone into a Vizio soundbar system that has remarkably nice sound for such a diminutive physical presence. And finally, at the least grandiose end of the scale, I have an Ultimate Ears Wonderboom Bluetooth speaker for those occasions where I am somewhere by myself without a sound system but in desperate need of a musical fix. I just can't imagine life without music and I am humbly grateful for the technology that enables us to enjoy it in so many wonderful ways.
Bryan Geyer, Technical Analyst

I initially embraced classical music in 1954 when I mistuned my car radio and heard the Heifetz recording of Mendelssohn's Violin Concerto. That inspired me to board the new "hi-fi" DIY bandwagon. In 1957 I joined one of the pioneer semiconductor makers and spent the next 32 years marketing transistors and microcircuits to military contractors. Home audio DIY projects remained a personal passion until 1989 when we created our own new photography equipment company. I later (2012) revived my interest in two channel audio when we "downsized" our life and determined that mini-monitors + paired subwoofers were a great way to mate fine music with the space constraints of condo living.

Visitors that view my technical papers on this site may wonder why they appear here, rather than on a site that features audio equipment reviews. My reason is that I tried the latter, and prefer to publish for people who actually want to listen to music; not to equipment. My focus is in describing what's technically beneficial to assure that the sound of the system will accurately replicate the source input signal (i. e. exhibit high accuracy) without inordinate cost and complexity. Conversely, most of the audiophiles of today strive to achieve sound that's euphonic, i.e. be personally satisfying. In essence, audiophiles seek sound that's consistent with their desire; the music is simply a test signal.

Mission Statement

It is the goal of Classical Candor to promote the enjoyment of classical music. Other forms of music come and go--minuets, waltzes, ragtime, blues, jazz, bebop, country-western, rock-'n'-roll, heavy metal, rap, and the rest--but classical music has been around for hundreds of years and will continue to be around for hundreds more. It's no accident that every major city in the world has one or more symphony orchestras.

When I was young, I heard it said that only intellectuals could appreciate classical music, that it required dedicated concentration to appreciate. Nonsense. I'm no intellectual, and I've always loved classical music. Anyone who's ever seen and enjoyed Disney's Fantasia or a Looney Tunes cartoon playing Rossini's William Tell Overture or Liszt's Hungarian Rhapsody No. 2 can attest to the power and joy of classical music, and that's just about everybody.

So, if Classical Candor can expand one's awareness of classical music and bring more joy to one's life, more power to it. It's done its job. --John J. Puccio

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"Their Master's Voice" by Michael Sowa

"Their Master's Voice" by Michael Sowa