A few years back, I bought some "acclaimed" cables. Yes a difference. Worse. I did some testing. My sonic results were good old Belden Brilliance 75 Ohm stranded on decent ( non-Ferris) RCA's made as short as reasonable. With cables, less is more. The old free cables were often well over 100 Ohms and the shielding well less than 100% so I do not blame the emergence of quality well designed cables. Seems like Monoprice, Belden, Amazon WBC etc. can produce the 99.99% as good as it gets only missing the .01% ego factor. Won't go wrong with Blue Jean but they seem to have moved the price to add ego to the mix. I at least respect their engineering as they are real engineers. Some cables have marked "direction". Now for a simple cable, this is total marketing, but it is possible with cap coupling of the shield or single shield ground in a balanced cable for it to make a difference. Not magic. Tricks we use to combat RF and ground loops. Which end depends on testing. A wire does not know the difference. AC or DC.
How big a difference? Well, if everything else is SOA, maybe if you are still in your 20's, have been trained in listening, not damaged your hearing with ear buds or the defective Army ear plugs, the source material is good enough, yea, probably audible. I am old. I have "decent" equipment and listen to CD's ripped to FLAC. Amazon Basics is better than I can hear.
I also tested USB cables doing a loopback through my Focusrite. Clear differences in noise, rise time and jitter.. Free garbage and all the rest. Again Belkin, Belden, Monoprice etc. I also use short as possible. My music server to DAC is 8 inches. Less is more. Now, does it make a difference with todays DACs with vastlly improved USB receivers, asynchronous communication, and better internal clocks? Not sure it does. Walmart-DAC running WMP? Maybe. JRiver into a Schiit Unison or Cord? Probably not. Lesson is to put your experience and bias to todays situation, not yesterday's.
On to speakers. Here bigger differences ( damage) is common. Because you hear a difference does not mean it is better. This application is very component sensitive as the amplifier behavior does change depending on the oad. When I was investigating why my wife liked my 800 series Rotel amps over my Parasound 1200s,( made John very upset) I had pictures of the current into the driver that showed clear differences. FWIW the real difference she was hearing is how dominant pole compensation vs Miller compensation changes the distortion distribution. With a better tweeter, Mr. Curl was right. This added to the testing we dis back in the 70's when the crazy cable stuff started. Original Monster ( 11 ga, twisted, slightly higher L, slightly lower C) came out and remains an excellent choice. One member of the testing was an engineer that had designed wire for a living.
My money? Quite surprised how big differences in DACs are. Of all I have listened to in my desk system, the JDS Atom+ is still the smoothest. I have further testing with JRiver settings that may reduce the differences, Topping Schiit, JDS, SMSL etc. I plan on testing a Qutest. Output reconstruction and filtering is 99% of DAC differences and that is exactly where the brands differ.
Summary: Yes a "bad" cable can sound bad, but there is no esoteric magic cable can actually improve the signal transfer. They can filter it which may mask a problem and it sounds better. Cables have kept a lot of stereo stores in business, so maybe that is their greatest worth. :)
