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Another cheater plug thread

OK. So on a couple of other threads, opinions of cheater plugs to tame system hum range from "If it works use it" to "you're going to die in a fiery inferno." In my case, I used a cheater plug between my power supply and my pre-amp to finally get rid of a year-old hum problem. the power supply is a PS Audio Ultimate Outlet with only two outlets that supplies only my amp and pre-amp. Because the PS is still grounded - I think - all I did was break the ground circuit between the two components. So the question is, do I still have any grounding on my pre-amp here, just on the basis of being plugged into a grounded power supply? I wouldn't think so, but I'm not an engineer. Also, what is the benefit of being grounded vs. ungrounded in this situation?

Ready, set, fight!
grimace

Showing 3 responses by atmasphere

atmasphere's avatar
atmasphere
12,110 posts
 
Newbee, if you use your CDP normally, probably not much will come of it. But if it gets dropped or abused in such a way that the power switch or AC power is able to contact the chassis, then you may have a problem. If the chassis is ground, a fuse will blow and all is well. If not, it may be possible to start a fire or create a shock hazard in the system.
atmasphere's avatar
atmasphere
12,110 posts
 
Something not mentioned is the sonic issues related to lifting a ground.

The problem is a ground loop, you lift the ground and no more hum. This is caused by the fact that some part of the signal chain (amp, preamp) is improperly wired.

For example if the chassis and circuit ground are the same thing, that unit will be prone to ground loop issues. Now to pass UL and CE (in fact any electrical code worldwide) the chassis has to be grounded. The issue is how to deal with the circuit ground if the chassis is grounded, and not have a ground loop.

The solution is simple but you would be utterly amazed at how many companies have not sorted this out! All that is needed is the circuit ground 'float' within the chassis, with all ground points like RCA connectors and the like isolated from the chassis. Then a moderate resistance is used between the chassis and circuit ground. This floats the circuit ground at chassis potential (electrical ground).

The added benefit is that now the chassis shields the circuit without injecting noise, something that results in better sound due to 'blacker backgrounds'.

So, IMO/IME its worth it to get equipment with bugs like this fixed! If done, you never worry about grounds again, and you don't have to mess with exotic (kooky) grounding schemes like a rod in the garden or some messed up stuff that is a recipe for trouble.

I know that may draw some criticism but honestly, get the equipment fixed and you will find out what I am talking about.
atmasphere's avatar
atmasphere
12,110 posts
 
Removing a chassis ground might break a ground loop and sound good but it is deadly if you touch the unit's chassis, and any conductor to ground.

Amend to 'could be deadly'. Its that 'could' that is why there are things like UL and CE directives.

In the old days the RCA ground was the same thing as chassis ground in a lot of cases. IMO that is a bad move, and the better manufacturers even in the old days avoided the practice.

The funny thing is that proper grounding also results in better sound. You would think more manufacturers would want to be on board with this....
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