Ok, but my ears can hear the improvement and my brain can appreciate it. If it can't be measured it must not be? It reminds me of the age-old topic of power cords not making a difference.
I'm not contesting that. And I can easily measure why a power cord is audible in a system- they respond to Ohm's Law like anything else, but that's off topic. This:
Ralph is giving you a hint to fix the grounding issues at the source vs a series of relatively expensive band aids.
- is correct. It might not be as inexpensive as all that, since the manufacturer of the equipment that is causing you to need the grounding box might push back on the idea that they have a problem. Put another way, if the grounding box helps, its a useful tool to indicate that there is a grounding problem somewhere.
If that is the case, I use a DVM to check and see if the audio connection grounds are the same as the chassis and see how that relates to the ground pin of the IEC connection. You should be able to measure something between chassis and audio ground, but if its a short, that can be a problem. OTOH if you find that the chassis isn't grounded through the AC power cord that too is a problem! Grounding is a tricky thing and its not surprising if a designer gets it wrong- I've been there.
Now you might think 'hey, the box fixed it all' which is fine. No worries. But audiophiles often ask 'can it get better?' and the answer is often 'yes'. People have said to me many times that they can't imagine how it might get better, and then it does. There are almost always opportunities for improvement.
