2. amps-preamps
  3. 126866-10110

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
erik_squires
15,875 posts
 
@cleeds

I in this case I believe you are mistaken. :) One 20A circuit may feed multpile 15A receptacles.

For those who don’t know, the 20 A receptacles look just like a 15A but with one leg T shaped, allowing for either 15A (normal) or 20A plugs.

More here:

http://diy.stackexchange.com/questions/12763/why-is-it-safe-to-use-15-a-receptacles-on-a-20-a-circui...

It’s perfectly safe to put a 15 A receptacle on a 20 A circuit, but it won’t have the T socket for 20A devices. In residential use these are actually pretty rare.
jea48
4,313 posts
 

cleeds said:

You can install a 15 amp receptacle on a 20 amp circuit, but you shouldn't and it violates NEC. A 15A device isn't rated to carry the 20A of current that a 20A branch circuit can deliver.

Cleeds,

Sorry, you are wrong. It is NEC Code compliant.

2014 NEC 210.21(B)(3) table. Receptacle Ratings for Various Size Circuits. 

.

Page 70-59



mmm

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cleeds
5,694 posts
 
erik_squires1m
... One 20A circuit may feed multpile 15A receptacles ...

It’s perfectly safe to put a 15 A receptacle on a 20 A circuit, but it won’t have the T socket for 20A devices.
Strictly speaking, it is not safe. It is against code. Consider an improperly functioning 15A appliance that is now trying to pull 20A of current through the 15A receptacle. The 20A breaker will not trip, and the 15A receptacle will overheat.
jea48
4,313 posts
 

Cleeds,

This may help you understand why it is safe and does meet NEC.

http://www.neca-neis.org/code-question-of-the-day/code-question/cqd-for-6-25-2002

Jim

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cleeds
5,694 posts
 
jea481m

Sorry, you are wrong. It is NEC Code compliant.

Perhaps you should read the code that you referenced:
" A single receptacle must have an ampere rating of not less than the overcurrent device protecting the branch circuit."

You cannot use 15A devices on a 20A circuit and be compliant with NEC.

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