Bounce,

I didn't catch the omission in my train of thought till you brought it up...I had intended to say that it can have dire effects on the audio quality of the device in question (ground loops traditionally create popping and clicking noises in the audio path) but, in my haste I bungled it...However, the funny thing is, materially the statement remains correct - in certain circumstances high-end IC's can be damaged by a ground loop - particulary at vehicle startup (this is however, fairly rare). Thanks for pointing my error out - I hate when I misstate something...

A bit more on Ground Loops for those that are interested...What are Ground Loops and why are they bad?

The "ground loop" is one of the most hated, and pervasive, problems to deal with in electronics because it is formed pretty much whenever ground connections are made at more than one point. This could be inside the device, on its circuit board, or between two (or more) devices connected to a common power source, like a motorcycle battery. The classic example of this problem is whine showing up in a car audio system when outboard amplifiers are installed. The car stereo "head unit" is connected to ground on one point of the car while the amplifiers are connected to another point. No big deal until you consider that there is another ground connection between the head unit and the amplifiers: the shield of the patchcords. The shield and the car chassis form a loop that will act as an antenna for magnetic signals, but the chassis in between the two ground connections will also act like a resistor, producing a slight voltage drop along its length from currents flowing through it. This causes a problem because the amplifiers will treat voltage variations on the shield the same as those on the center conductor. This is why one is frequently advised to "lift the ground connection" from shield to plug on the amplifier side of the patchcord. That's easy enough to do if you are a professional car stereo installer, but the rest of us don't want to fool with making custom patchcords just to keep ignition and alternator noise out of our music! An alternate, and in some ways better, solution is to break the loop on the power side for one or more of the devices. This is done by using a transformer - just like for isolating the BTL amplifier from a ground-referred "load" - except that transformers don't transform DC, so the voltage from the 12V battery has to be rapidly chopped into AC, then applied to the transformer which breaks the ground connection, then converted back into DC for the circuits to use. This is what an isolating DC-DC converter does (there are types that don't isolated, by the way), and it's why we put one in the xma3.

-T