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Cheater plug safety

So I recently decided to swap out my subwoofer amp for another one I had to see if it worked better with the driver. It did, but I have run into a slight problem. My old sub amplifier had a captive two prong cord. The new one has a 3 prong cord.

The subwoofer amp resides on a different AC circuit than the rest of the system. (Can’t be avoided)

Although the new amp is an upgrade for the sub, there seems to be a ground issue that is hazing up my transparency and sound stage. The system looses some air when the sub amps ground isn't lifted. There is no hum problem through any speaker per se, but just an overall sonic degradation when the ground is left in place. Using a cheater plug just on the sub amp brings back The transparency and it sounds absolutely beautiful.

I read that this can be dangerous, though. (Then why are these created plugs made?) anyway, I also read that as long as the amplifier with lifted ground is connected to the rest of the system via interconnect , and the other components are grounded, then the amp will use the ground from the other circuit that the other equipment is connected to and you are "safe", and only some very unlikely happenings, such as an internal ac wire becoming loose and touching the chassis and standing in a puddle of water should cause a concern. I even had a parasound 750 amp in my college dorm that even suggested using a cheater plug if needed for hum, sooooooo.........

At any rate I am addicted to the sound at the moment and going back without the cheater plug just sounds dull and fuzzy. The system is resolving and shows just about anything you do to it. Mind you, it’s not a night and day difference that would say that there is something wrong with any of the equipment, just a subtle but very tangible improvement that I definitely like and desire. The equipment is working 100% properly.....

It sounds so much better than the old amp and the transparency and air I’m getting right now are rediculous, but I don’t want to get shocked, but the chances seem to be very slim. Can anyone advise?
audiolover718
stringreen's avatar
stringreen
6,531 posts
 
safety is important....but also, using poor quality cheaters (all of them) brings grain and grunge into the system.  I use them only for detection of ground problems, but remove it after the test.  You should fix your ground problem, and use the original plugs as is intended.
jetter
3,127 posts
 
Thank you for the explanation jea48.  Actually I have been zapped once by the unit, but it was my error.  I was setting the bias, which of course you do with the unit running, and touched the wrong part of the amp (i.e. the exposed parts around the 7199 driver tubes).  Its one of those things you only want to do once.  
bpoletti
1,568 posts
 
The only way to safely use a cheater plus is to keep it sealed in it's original package.
erik_squires
16,909 posts
 
There is a little confusion in what "lifting a ground" means.

It’s perfectly safe to lift the signal ground. That is, the ground associated with RCA or XLR cables and plugs. Pro gear or devices with XLR inputs often provide this feature. It’s a very good thing and sometimes the most important reason to use XLR inputs.

The AC safety ground is not the same thing. It starts at the round middle pin on the AC plug and terminates at the metal chassis. Lifting, or removing the AC safety ground is NEVER a safe thing. Not all equipment requires it, but if they do, it should not be removed when present.

Cheater plugs originally had a good purpose. They were designed so you could screw the ground to the face plate screw on wall sockets without having to replace the entire receptacle. However, many of these receptacles weren’t grounded to begin with, so the screw was pointless, and no one uses it correctly anyway. :) So, effectively, @bpoletti is right. Leave them at the store. If you have 2 prong wall outlets then it is time to upgrade them anyway, as your wiring is probably 40-50 years old.

Best,


Erik
kijanki's avatar
kijanki
4,479 posts
 
erik_squires, +1, It is important distinction - chassis ground is different from the signal ground (in IBM computers system and chassis grounds is the same causing all sorts of problems).  It was mentioned here that IC might not provide adequate grounding thru other components because of the lower IC gage (they might burn).  Most of the time grounds are separated with small capacitor (0.01-0.1uF) and high value resistor (>100k) between them.  The only case I know where IC might serve as grounding is XLR IC with shield connected on both ends (assuming gear uses chassis ground for the shield). It is still dangerous since it can be disconnected causing possible electrocution.

Erik is right - I feel much safer with three prong wall outlets.
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