Equipment Review No. 3 July-August 2001
[This time we go beyond the basics and start discussing how to make the music in your home sound better. - Martin DeWulf]
The Ultimate Guide To Set-Up and Break-In:
AC Chassis-To-Ground Potential
I had to laugh when I saw Jonathan Skull at Stereophile talking about AC polarity, and the importance of polarity reversal in the proper cases. You would have thought this was some newly-discovered process, and he was at the leading edge of it. No way boys, BFS has been on top of this story since 1992. Of course, Enid Lumley beat us all to the AC thing, but I won't go there.
It's gratifying, however, to see the industry finally recognize the importance of correct AC polarization - it can make or break a system. Really. And we at BFS are trying to make the process of setup easier for you by stating the AC chassis to ground potential readings in our reviews whenever possible. My belief and motivation being that the more you know about a component, the better it will perform for you. And where the actual standard and reversed measurements are not available, we will endeavor to, at the very least, give the proper AC orientation for best sonic results. Again, I can't stress this aspect of set-up enough, and if you don't account for it, don't expect your system to perform at its best.
Because I feel so strongly about the issue of proper AC polarity, the following is a partial reprint of our original 1992 article on AC and system set-up. If you want to see the entire article, it can be viewed at www.boundforsound.com under the "Tweaks" page.
What You Need To Be An Objective Scientist: What you will be measuring is the amount of voltage running around in the chassis of your audio stuff. The preferred voltage is [usually] the lowest voltage, which will save you from making those dreadful subjective decisions such as "which polarity is more tuneful and in touch with the liquid euphony of my BAD SELF?" First thing you will need is an AC polarity testing plug which will set you back about $3.99. The second piece of test gear is a multimeter (VOM) which reads AC volts below 500; mine cost all of$35.00, but I went all the way by getting the IM, TM, ICBM, Crosstalk Spectral MELISA Cranial Analyzer which was a $10.00 add-on (only real experts like me need this latter option). The polarity testing plug can be purchased in almost any store that carries even the most meager line of home electronics. It's a 3-prong plug with three little lights on the back. You take the plug and insert it into each of your wall outlets, and the lights on the back will tell you if your outlets are wired properly in the wall. Many outlets, even in new digs and mobile homes, have the positive and neutral taps wired in reverse and grounds are oftentimes left open. The polarity plug will let you properly assess the orientation ofthe outlets that you use and make any necessary adjustments. This is the first step toward proper polarity....
THE BIG TEST: With your multimeter in hand proceed as directed. Each component to be tested must be totally isolated. Disconnect interconnects, antennas, power cords and grounds. If the component to be tested has a two-prong directional cord, plug it in. If the component to be tested has a three-prong cord, steal a "cheater plug" from the wife's mixer and use it to float (lift) the ground of the chosen piece of equipment. Set your multimeter to AC volts, connecting the probe to a true ground (I use a true earth ground consisting of an outdoor earth rod with a cable running from it into my listening room). You can also go to the ground connection of the outlet if you have three-prong outlets, or you can run to a drain pipe as I had to in my bedroom. NEVER connect to a pipe carrying electrical wiring or anything flammable like natural gas, and NEVER EVER connect to an antenna which can be struck by lightning.
Connect the red probe to the chassis ground terminal if it is a preamp you are testing, or to a sheet metal screw on the chassis on almost everything else. With the screws you may have to scrape a little paint off the screw to make good contact. Good contact is essential to an accurate volt reading from the chassis. Now plug the component in and turn it on. If you haven't been electrocuted yet, you should have
a voltage reading on your meter. Write it down. Turn the component off and reverse the AC power cord in the wall outlet. With a cheater plug, the neutral side of the plug is usually wider than the hot side and reversing can be difficult. In the past I have taken a pair of metal snips and cut the neutral side down so that it will fit into the hot side of the outlet. In my system today, I have the TG Audio Bybee-Sucker AC line conditioner. With it I ordered two outlets with reverse polarity so all that I have to do is go from a regular outlet with the Bybee-Sucker to one of the reversed outlets to reverse AC polarity to any component.
Once the polarity is reversed, turn the component back on and make a second reading. Choose the power orientation that reads the lowest. (Note: some equipment, especially power amplifiers, should be left off a few minutes before firing them back up with the AC polarity reversed.) Simple, ain't it? And with some experience you'll get to the point where you will be able to tell the proper AC orientation by simply listening to the equipment; the meter won't be necessary. At that point you will have earned your golden ear. (Some audiophiles, when reversing a power cord choose to leave the ground open or floating, alleging that the system sounds better that way. In some cases it is true; but remember, by fIoating the ground you may be defeating the UL rating for the device and maybe even voiding the warranty, which could be disastrous if for some reason a fire results. Play it safe.) YOU ARE DONE. The real trick here is to get each and every component in a system oriented properly. If your system has two components oriented wrong, the correction of one may not be enough to bring on earth shaking improvements - get the entire system right before passing judgment. Proper orientation makes one's system generally sound fuller in the midrange and more dimensional in the lower midrange. Clarity and depth of image will increase in good ways. Look for less strident and cleaner highs. If on the other hand you test everything and find all the plugs properly oriented already, you could consider the entire ordeal as time wasted, or, you might consider it an average day for an audio reviewer.
An Alternate View: After the above was written, a reader proposed that the lowest reading for every component in a system may not be the way to go. His theory is that what a person wants to do is average out the readings so that each component is relatively close to every other component in terns of measuring the voltage-to-ground potential. And I have seen occasions where the low reading off of one component was higher than the high reading off of another. According to this alternate theory then, one would leave the higher voltage reading in place even though that would be leaving the component in the wrong AC phase. I must admit that I haven't had the time to try out such a scheme, but there may be some validity to it. If you try it and have some definitive results, write me and we'll consider the matter further.
Another alternative for reversing AC polarity is to order power cords with the wiring reversed inside. A few years back Bob Crump at TG sent some cordage that came to be known as the Green Wienies. Named for their brilliant green exteriors, these power cords came with AC polarity reversed. Very effective, but you have to know for sure that you want the cords reversed; mistakes can be costly.
I don't care for the cheater-plug route. Trimming off the neutral prong can be a pain, and the cheaters don't generally fit in the outlet well after they have been operated on. This, more than anything, is a temp thing made to check voltage readings. Don't go there. What I do, and again Bob Crump taught me this one, is make a little reversing power cord that goes into the wall, then the regular cord which comes from the component goes into it. It's just a little extension cord about 8" long wherein the AC is reversed...
NOTICE: If you think this simple task is more than you want to handle, don't electrocute yourself by doing something stupid...trust me, 120 volts AC coursing through your members feels bad enough that you don't want to feel it even the first time.
- Martin DeWulf
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