[BradJudy]

Quote:

Originally Posted by morsel Whether single or multiple inputs, my answer is the same. All signal grounds are tied together via the audio interconnects. Unbalanced equipment that ties AC ground to the case and/or signal ground is a liability as it may cause ground loop problems. The goal of quiet unbalanced equipment is in direct conflict with the goal of satisfying AC grounding regulations. In the USA most unbalanced equipment is 2 prong. Making a device as small and low power as a headphone amplifier 3 prong is just creating a giant nuisance for yourself.

Hmmm...I don't see how that answers my question, let me rephrase it.

If I have two sets of inputs, should the input ground of both sets be tied to each other and then the case, or only tied to the case when that particular input is selected? One way means I isolate the inputs and then tie the input ground coming from the switch (or at the PPA) to the case, the other way means I don't isolate the input jacks and both input grounds are tied to the case at the jacks.

 

[tangent]

Quote:

small and low power as a headphone amplifier

The power of the amplifier isn't at issue here. It's the power of the AC side of the power supply I'm concerned about.

The PAR Metals case has slots in the top. So someone drops something conductive through the slot, bridging AC hot to the case. Maybe Brad has kids, and they think the PPA is a piggy bank. Assuming the case isn't touching anything else and the case isn't safety grounded, it stays energized until Brad walks over and touches the pretty metal volume knob. Zot. --forum_members;

Quote:

should the input ground of both sets be tied to each other

That's a reasonable way to go. It should work. Switch the grounds shouldn't be necessary, but sometimes I do it when I have the extra switch poles, just because I can.

 

[BradJudy]

Quote:

Originally Posted by tangent That's a reasonable way to go. It should work. Switch the grounds shouldn't be necessary, but sometimes I do it when I have the extra switch poles, just because I can.

Okay. I was just concerned about potential problems with linking two different signal grounds from different sources. I'm not sure if there is potential for them to be different relative to each other and cause problems. Isolating the input jacks from the case and each other and simply grounding the chassis (via a resistor or otherwise) to the input ground on the PPA itself seems like a simple precaution, but I'm not sure if it will make any difference.

 

[jboehle]

Look at the back of most consumer-grade audio equipment...

For instance if I had multiple sources all plugged into my Denon home theatre receiver, all of the grounds are tied together on the Denon (the inputs are not insulated)....same applies to your PPA with switched inputs...(at least IMHO).

Now I need to go read the Rane article again...I read it a long time ago but have forgotten most of what I need to know!

-Jason