richieb Posted November 6, 2015 Share Posted November 6, 2015 Ok so I buy new Class A monblocks and a First Watt B1 buffered dual volume control. Initially the amps, through KHorns by the way, were very quiet which is a must for me. I started moving things around, installed new isolated duplex wall plugs and they started humming loud enough to irritate me. So now I'm changing everything, interconnects, power cords, old duplex's back in and still they hummed. I had just bought a few cheater plugs (3 prong female, two prong male into the wall). Quiet as a mouse. I thought if you used a three prong plug from a quality power cord into a three prong wall outlet you were golden. It seems like I'm working backwards inserting a $.69 adapter to the end a couple or three hundred $$ power cord to quiet things down. But it worked - why? Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted November 6, 2015 Share Posted November 6, 2015 (edited) You will have a very long thread by the time this is over. Basically, It is the way the system is ground. Normally, the system should have a common ground and you have an extra floating ground. Run a wire from the amp to the avr/preamp. You may also have a cable box causing the problem. I am sure someone much better with electrical circuits will chime in. Oh, that outlet is most likely not grounded correctly. Cheater plugs are a safety hazard. Nothing bad happens 99% of the time but, if that 1% is you or a family member in another part of the house, it goes up to a 100%. Edited November 6, 2015 by derrickdj1 Quote Link to comment Share on other sites More sharing options...
muel Posted November 6, 2015 Share Posted November 6, 2015 Ground loop. Running connected equipment on separate circuits can cause problems. Personally, except that I have everything on one circuit I do a similar thing for a dead quiet setup. My preamp is grounded but both mono blocks are on cheater plugs. Now hang on tight for the safety debate that will ensue. Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted November 6, 2015 Share Posted November 6, 2015 This is a case where someone died using a cheater plug: http://www.the-scientist.com/?articles.view/articleNo/23809/title/Ohio-cites-university-in-death/ Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted November 6, 2015 Share Posted November 6, 2015 (edited) The ironic thing about that article is the fact that most if not all fluorescent lights only use a two prong plug. Check out the first ad I came to on Ebay for example. Yep, two prong plug........go figure. http://www.ebay.com/itm/2-Fluorescent-4-ft-T5-Shop-Light-Fixtures-w-Connector-Power-Cord-Brackets-/181842451922?hash=item2a56a79dd2:g:rKUAAOSwMmBV2BVG Edited November 6, 2015 by JL Sargent Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted November 6, 2015 Share Posted November 6, 2015 The thing I don't like about the slight chance of something bad happening is that it can be in a place like the laundry room or some other room and a family member is injured. Quote Link to comment Share on other sites More sharing options...
wvu80 Posted November 6, 2015 Share Posted November 6, 2015 Nothing in West Virginia was grounded until a few years ago when they came up with these pesky "electrical codes." Every WV electrical contractor worth his salt building homes in the 70's knew that it was cheaper to put in wire that had two strands instead of three. It saves money since the homeowner doesn't know 2 wires from three. You just clip off the third prong on those appliances and you're good to go! Two prongs, three prongs, it's just jibber jabber, nobody can understand that stuff. I fail to see the problem. 1 Quote Link to comment Share on other sites More sharing options...
garyrc Posted November 7, 2015 Share Posted November 7, 2015 What exactly causes the cheater plug to be dangerous? I had hum, buzz, and hiss using a preamp/processor by NAD, even at very low volume (using Klipschorns), in a house that was wired in the '70s with three hole outlets. The NAD power amps made no noise at all, except for hiss very close to the Khorns. I now have a Marantz pre/pro in a rewired music room, with a new main and a new ground spike going into the earth. No hum, no buz, and only a tad of hiss (still using Klipschorns and NAD power amps). Because I changed everything at once, I don't know the cause. Quote Link to comment Share on other sites More sharing options...
babadono Posted November 7, 2015 Share Posted November 7, 2015 What exactly causes the cheater plug to be dangerous? If this is a serious question I will attempt an answer: The cheater plug disconnects the chassis of the equipment plugged into it from the ground in your house. If there is a 'fault' in the equipment (fault defined as a short circuit of the hot wire to the chassis) the chassis would then be energized to line voltage. If you then touch the chassis depending on how good of a conductor you are to ground you could be shocked or in the worst case electrocuted. Admittedly in home stereo equipment the chances of a 'fault' are minimal. Many pieces of stereo equipment don't even have a third prong. But a good rule to follow is: If it has a third prong it is there for a reason, do not defeat it on a permanent basis. Find the real cause of your ground loop hum and fix it. Quote Link to comment Share on other sites More sharing options...
richieb Posted November 7, 2015 Author Share Posted November 7, 2015 Agreed - the "blue fire" is mysteries stuff. Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted November 7, 2015 Share Posted November 7, 2015 (edited) I use something similar to 2 of these for the ground loops from my subs and amps. http://www.ebay.com/bhp/ground-loop-isolator . They are cheap at $7-10. Edited November 7, 2015 by derrickdj1 Quote Link to comment Share on other sites More sharing options...
djk Posted November 7, 2015 Share Posted November 7, 2015 The small car stereo transformers are too small, and have very poor performance. Get the 10K : 10K model. Quote Link to comment Share on other sites More sharing options...
djk Posted November 7, 2015 Share Posted November 7, 2015 This is a 3-prong ground lift with a diode bypass (so it lifts the ground, but is still safe). I can show what is inside if there is interest. 1 Quote Link to comment Share on other sites More sharing options...
mungkiman Posted November 7, 2015 Share Posted November 7, 2015 Every WV electrical contractor worth his salt building homes in the 70's knew that it was cheaper to put in wire that had two strands instead of three. It saves money since the homeowner doesn't know 2 wires from three. You just clip off the third prong on those appliances and you're good to go! A discerning client might choose to pay a premium for 2-strand wire, but with 3-prong outlets. Contractors... Quote Link to comment Share on other sites More sharing options...
westom Posted November 7, 2015 Share Posted November 7, 2015 Agreed - the "blue fire" is mysteries stuff. This is a hum in simple terms. A component A can connect to B which connects to C which connects to A via the safety ground. Use a cheater plug. Now that loop is broken - hum stopped. Anyone making conclusions only from observation would assume hum is created by C's safety ground. Or by a defect in C. Clearly not. A fault is in anything in that loop. Cheater plug only broke the loop - did not cure anything. Worse, a defect need not be in C or A as interconnected by the safety ground. A defect could be in B. Appreciate what a 'cheater plug' test reports Cheater plug only identified one part of that ground loop. Equivalent tests must be conducted to find other loop connection. Such as connections from B to C and from A to B. Then it gets complicated. That connection from B to C can be many wires. Each wire inside every cable might not or can be part of that loop. Disconnect one and another wire might still maintain that ground loop connection. IOW many disconnections must be tested to first identify what is in that ground loop. Fixing a defect in that loop comes later. This hopefully demonstrated is why ground loops can be difficult to first locate and later correct. Quote Link to comment Share on other sites More sharing options...
JohnA Posted November 8, 2015 Share Posted November 8, 2015 What exactly causes the cheater plug to be dangerous? The 3rd wire is a "Safety Ground". It is supposed to connected to the chassis of the device. The 3rd/safety ground wire is connected to the same bus as the white wire in most electrical boxes. So shound the white wire inside your device rub and make contact with the chassis, nothing happens. If the black wire contact the chassis, and the safety ground is connected, the current flows to ground, the breaker trips and you are safe. If the safety ground is not connected, the chassis is now elevated to 120 volts and your hand may turn into the return path to ground, to your great surprise. Quote Link to comment Share on other sites More sharing options...
Shiva Posted November 8, 2015 Share Posted November 8, 2015 (edited) http://www.lowes.com/pd_145257-33536-C629171___?productId=1135905&pl=1&Ntt=circuit+breaker+power+cord I had a similar issue with a power amp and adding a cheater plug also stopped the hum. Through some reading I bought the above power cord that I plugged the cheater plug into for some added safety. For those in the know does this not make the ungrounded amp safe from possible shocks. Edited November 8, 2015 by shiva Quote Link to comment Share on other sites More sharing options...
JohnA Posted November 8, 2015 Share Posted November 8, 2015 This is a 3-prong ground lift with a diode bypass (so it lifts the ground, but is still safe). I can show what is inside if there is interest. Yes, Please! I'd have 2 to buy. They are $51 on Amazon. Quote Link to comment Share on other sites More sharing options...
babadono Posted November 8, 2015 Share Posted November 8, 2015 http://www.lowes.com/pd_145257-33536-C629171___?productId=1135905&pl=1&Ntt=circuit+breaker+power+cord I had a similar issue with a power amp and adding a cheater plug also stopped the hum. Through some reading I bought the above power cord that I plugged the cheater plug into for some added safety. For those in the know does this not make the ungrounded amp safe from possible shocks. Nope. Quote Link to comment Share on other sites More sharing options...
westom Posted November 8, 2015 Share Posted November 8, 2015 Yes, Please! I'd have 2 to buy. They are $51 on Amazon. Based upon another's description, a HumX apparently connects the HumX safety ground receptacle (hole) to safety ground prong via diodes. $50 dollars for some $0.50 diodes. Diodes that violate human safety requirements. The only item that must connect is wire. Therefore a HumX could not obtain a UL Listing (for human safety). And only cures symptoms of hum; would leave a defect existing and unsolved. Quote Link to comment Share on other sites More sharing options...
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