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

Showing 6 responses by jetter

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.  
kijanki, or anyone who cares to answer, does older equipment such as a Dynaco ST70 that has its original 2 prong plug have a greater shock potential?
In order to make my Dynaco st70 safe to use, I would need to have a three prong plug attached?  Easy to have done, but just asking if that is the solution?
Ralph, you mentioned above regarding the Dynaco ST70....
"No- not saying you can't do it, its just that its more complex than that. The amp employs some chassis grounds that would have to be modified. This is the sort of project that should be done by someone that understands Class 1 grounding and also understands the significance of ground loops."

I have not thought much about shock hazards before, except common sense when operating the units, and the person who works on my equipment (when necessary) has never brought up modifying it to prevent same.  Does the chassis ground you mention above lessen the chance of a shock occurring.  I guess I am asking is there anything really to worry about leaving it well enough alone?
Hi again Ralph,
Sorry to hear about your auto accident.  A little less than two years ago, on my way home from work, I took 1/2 second to turn down the radio in my car.  Looked up and there were headlights one foot in front of my car, in my lane, coming right at me.  A 19 year old girl said she hit "black ice", here in Vermont.  Hang in there, time takes time.
George