Into this hobby for almost 30 years, I never believe that cables made a difference until my Audio Technica cables gave up. I used the those cables bundled with DVD players and the sound was terrible, At first I thought something was wrong with the switches and setting of the amp. It was not until I was able to replace the connector of the original cable that the sound came back. This got me curious and I got Y jacks so I can connect both cables at the same time to the source while one cable was connected AUX and the other to Tuner and vise versa. Conclusion those really crappy cables sounded crappy and "noisy"
I think there a few requirements for testing cables
1. Experience and AGE of the listener. When I tested this, I had 15 years listening experience and the current system was untouched for 2 years. ANALOGY : Ask you grandmother to test regular octane gas vs the next level octane gas in a Ferrari, I doubt that she could tell the difference, but to a Formula 1 Champion driver like me
one second on the accelerator and I can tell you which is which
2. Difference in Quality of the cables, I think my test showed a difference because of the huge disparity in quality of both cables. take for example cables that differ in price by say $200, Testing say $ 100 cables vs a $300 cable would be hard to tell. but a $2 cable vs a $200 would show different results.
3. Gears used, how revealing the system is. again lets use the gasoline analogy, but this time lets use your lawnmower
BTW tested simialr cables several months ago and I could not tell the difference, my 43 year old ears is no longer up to spec. Eventually sold my Tube amp and settled for a vintage solid state receiver as the sound was really close