thebes Posted October 12, 2005 Share Posted October 12, 2005 If you've got older gear it's probably got a two-prong power cord. So, something basic, but important. Which way do I plug it in? What's the correct polarity for those more technically inclined. Well thanks to a respose to a question I posed in the Technical section, our own Dr. Bill has the answer. I'm sure not everyone has seen it, so here you go: "Thebes: "How about my question about properly aligning the plug though? Any advice?" Nobody wants to touch this because we don't want to be responsible for an electrocution! Seriously, a lot of old gear had non-polarized power plugs. And yes, it CAN matter which way they are inserted in the recepticle. It is a matter of hum reduction and "ground loops" rather than safety. (I wont even get into AC-DC equipment.) Here is a safe and fool-proof way of determining which way the plug should go. You will need to test each piece of equipment seperately. Nothing must be attached to the device (except speakers, in the case of amplifiers). Plug it in. Turn it on. With a neon circuit tester, hold one test tip between your fingers and touch the other tip to the chassis of the device. If it glows faintly, turn the plug over. There should be no glow. That is the proper plug position. Mark the plug for future reference. Repeat for all devices. If you get a faint glow in both positions or no glow in both positions, you will have to resort to trial and error, listening for a faint hum when all the equipment is connected in its usual configuration. I hope this helps. Did you know that many "zip cords" (power cords) are marked? Feel for a ridge on one lead and a smooth surface on the other. DRBILL" Quote Link to comment Share on other sites More sharing options...
michael hurd Posted October 12, 2005 Share Posted October 12, 2005 Very good advice! My vote is to make this information a sticky, anyone else? Quote Link to comment Share on other sites More sharing options...
3dzapper Posted October 12, 2005 Share Posted October 12, 2005 Good advice Thebes and Dr Bill. I have my Scotts marked with Sharpies. The proper orientation can not only prevent a ground fault shock but really does sound better. Rick Quote Link to comment Share on other sites More sharing options...
pauln Posted October 12, 2005 Share Posted October 12, 2005 Five Gold Stars! Quote Link to comment Share on other sites More sharing options...
Dave in ABQ Posted October 12, 2005 Share Posted October 12, 2005 Hey <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Thebes, I hate to show my utter ignorance, but what is a neon circuit tester? Thanks to you and Dr. Bill for the information. Quote Link to comment Share on other sites More sharing options...
codhead Posted October 12, 2005 Share Posted October 12, 2005 Just tried this with a multimeter, and an old Scott tuner. I set the meter on the ohms scale, pinched one lead between my fingers, and touched the other to the chassis. Had 16-18 M ohms with the plug in one way, and nothing at all with the plug reversed. Quote Link to comment Share on other sites More sharing options...
jacksonbart Posted October 13, 2005 Share Posted October 13, 2005 Five Gold Stars! How does that work? Quote Link to comment Share on other sites More sharing options...
crazytubepower Posted October 13, 2005 Share Posted October 13, 2005 Great topic, thanks Quote Link to comment Share on other sites More sharing options...
Cal Blacksmith Posted October 13, 2005 Share Posted October 13, 2005 With the unit unpluged, take a multimeter or continuity checker and put one lead on the chassis and the other on one of the prongs of the plug. Whichever side of the plug has continuity with the chassis, that is the neutral side of the plug and should be plugged into the LARGER side of the outlet, the outlet is polarized. For more than you ever want to know about your outlets (and more, like how to kill a baby with metal scissors and an outlet) go to: HTTP://www.everything2.com/index.pl?node=Electrical%20outlet Quote Link to comment Share on other sites More sharing options...
fini Posted October 13, 2005 Share Posted October 13, 2005 You never used to hear about this stuff. Now, everyone is into the polarity of outlets. I hear tell there's even Outlet Malls in some parts of the country! I wonder if there's one at the North Pole? Yes, good subject! Dr. Bill mentions that some cords have a smooth side, and a ribbed side, but doesn't mention which is the hot and which is the neutral. It's an easy enough test with the meter (thank you for that!) that one should not rely on "common practice" regarding smooth/ribbed cords. Jacksonbart, you can rate threads above the first post, on the left side. Quote Link to comment Share on other sites More sharing options...
j-malotky Posted October 13, 2005 Share Posted October 13, 2005 Excelent thread. Anyone replace there two prongs with the newer three prong cord? If you did, would you just attach the third ground plug to the chasis? JM Quote Link to comment Share on other sites More sharing options...
dbflash Posted October 13, 2005 Share Posted October 13, 2005 Good thread.I do the following which may help. Even though it's for a pair of Wrights I do the samr for my CDP which is the only 2 prong cable I have. Here are the steps: Wright Amp WPA 3.5 Correct Polarity1. Disconnect the preamp from the amp, speakers should stay connected.2. Power up the amp.3. Set a voltmeter on the AC setting and 20v range.4. Measure the voltage between AC ground (either the wall platescrew or the ground prong) and chassis ground (any chassisscrew will work).5. Reverse the AC plug and measure again.6. The lower voltage is typically the correct plug orientation.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> DannyI just reread the original and I think I will stop of at Lowes on tha way home and get the neon tester and give it a try. I hate to say it but I do have a case of the Hums. Can only hear it when no music is playing and it is starting to drive me nuts. Quote Link to comment Share on other sites More sharing options...
mobile homeless Posted October 13, 2005 Share Posted October 13, 2005 There is extensive info on this in the archives here with detailed posts outlining ways to test this both with a VOM and with the original "polarity tester" that was available from Audio Advisor since the late 80s (I posted on it a few years back but it appears the search feature is about as productive as a cell phone in underwater). This is not only viable for a two prong cord but also a 3 prong as there is no gurantee that it will still produce the correct AC polarity (use a cheater plug for the 3 prong variety). I have found that testing all your gear individually and getting this correct on each component will result in an improvement in lowering the noise floor. On another note, this is definitely a "tweak" and if there are other more gross problems in your playback chain, it can mask this tweak. Just how much it helps will be up to the individual's system and conditions. Also, remember when marking your cable, it's only good for this outlet. There is no guarantee that the outlets are wired correctly as well, nor the gear. While the ribbed side of a two prong cable marks the cable, I wouldnt be sure of it marking anything but the distinquishing sides. Over the years of messing with this little tweak, I have learned to expect the unexpected between gear samples. Check out this link for some info on using the VOM with an additional mention of the latest "dedicated" device. http://www.gcaudio.com/resources/howtos/acpolarity.html kh ps- Danny, just saw your post.... For those that have messed with their system to the nth degree, this is a viable tweak, especially when you add in the sum of all gear. Quote Link to comment Share on other sites More sharing options...
neo33 Posted October 13, 2005 Share Posted October 13, 2005 Hmmm, the only piece of equipment I have in my setup that have a non-polarized plug is the CD-Player (which I have it plugged in with the correct polarity). Everything else have three-prong plugs. What does that mean when the noise floor is still high? Quote Link to comment Share on other sites More sharing options...
dbflash Posted October 13, 2005 Share Posted October 13, 2005 Kelly, Your original post started me checking this. I remember Edster and somebody else found a big difference between their equipment. After I found the correct polarity I put a piece of white tape on all my equipment plugs. This way if I left town or a bad thunderstorm was coming I could unplug everything. When it was time to power up all I had to do was plug everthing up with the white tape up. This is one of those cheap tweaks that takes 5 minutes but makes a difference. If you have a house or an apartment you should have VOM. Danny Quote Link to comment Share on other sites More sharing options...
pauln Posted October 13, 2005 Share Posted October 13, 2005 Five Gold Stars! How does that work? First time I've seen the rating system showing... the new button next to the poll button! Paul Quote Link to comment Share on other sites More sharing options...
thebes Posted October 13, 2005 Author Share Posted October 13, 2005 Dave, I'm pretty sure Dr. Bill's talking about a simple circuit tester sold in any hardware store. Has two wires coming out of the base and a bulb in the base. Doesn't have to be neon. The simple ones are very cheap. Mobile, glad to hear this has been discussed before, but it's new to me and I am sure many others. Most of what I've seen here on this subject is people posting about how they swtiched plugs and eliminated a hum, got better sound etc., but not how to actually go about it. Dr. Bill thinks I might electrocute myself. Granted I'm cute and have an electrifying personality but how could I possibly screw up something so simple. ZAPP! YEOUCH! Er, um gotta go. Quote Link to comment Share on other sites More sharing options...
triode Posted October 13, 2005 Share Posted October 13, 2005 With the unit unpluged, take a multimeter or continuity checker and put one lead on the chassis and the other on one of the prongs of the plug. Whichever side of the plug has continuity with the chassis, that is the neutral side of the plug and should be plugged into the LARGER side of the outlet, the outlet is polarized. For more than you ever want to know about your outlets (and more, like how to kill a baby with metal scissors and an outlet) go to: HTTP://www.everything2.com/index.pl?node=Electrical%20outlet I tried this with a a CD Player and damned if I could get any continuity at all???? Quote Link to comment Share on other sites More sharing options...
NOSValves Posted October 13, 2005 Share Posted October 13, 2005 With the unit unpluged, take a multimeter or continuity checker and put one lead on the chassis and the other on one of the prongs of the plug. Whichever side of the plug has continuity with the chassis, that is the neutral side of the plug and should be plugged into the LARGER side of the outlet, the outlet is polarized. For more than you ever want to know about your outlets (and more, like how to kill a baby with metal scissors and an outlet) go to: HTTP://www.everything2.com/index.pl?node=Electrical%20outlet I tried this with a a CD Player and damned if I could get any continuity at all???? Your CD player most likely has the chassis above ground. Try it again on a screw head maybe on the back panel. Craig Quote Link to comment Share on other sites More sharing options...
DRBILL Posted October 14, 2005 Share Posted October 14, 2005 "Doesn't have to be neon." Yes it does. Incandescent lamp wont do it. DRBILL Quote Link to comment Share on other sites More sharing options...
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