If you're making a horror film the best gremlins are visible. Even the most terrifying invisible threats eventually make themselves known so viewers get their money's worth. But "seeing" audio problems isn't all that easy for designers.
In a practical sense we can see neither the good nor the bad that impacts audio. Music is invisible.
Perhaps it's more accurate to suggest there are the generally accepted causes that we metaphorically "see", and the less accepted we do not. We can't see germs with our eyes, but their impacts are felt none the less.
One gremlin is EMI (Electro Magnetic Interference). We take great pains to guard against this invisible enemy. Shielded wires, balanced cables, Mu metal, all exist to combat EMI's evil. It's easy to recognize when a hum or buzz has been eliminated by better shielding.
Far less noticeable is EMI's impact on digital audio, a subject our wizard, Ted Smith, has been schooling our team on.
It turns out that many of the improvements in sound quality attributed to lower jitter tweaks find their roots in EMI reduction.
Our research and learning curves march forward. As we learn more specifics I'll keep you posted.