This question tends to provoke heated controversy.
However, I'm going to weigh in with the engineering perspective on the subject.
Cables are really rather simple and the physical laws that govern them are pretty well known.
And, unfortunately, there are an awful lot of claims being made lately that have... err... no basis in fact.
The reality is that most cables are perfectly adequate and, once a cable is adequate, most so-called improvements serve no purpose and produce no measurable or audible benefits.
The are a few notable exceptions:
1)
There are a few cables out there that are
NOT adequate.
Certain cables may actually be so poorly made that they don't make good contact, or have inadequate shielding, or are too thin (speaker cables).
(If you have one of those fifty-cent cables they throw in with your VCR, upgrading it to a good $10 one would probably be a good investment.)
2)
There are some "audiophile" cables out there that have really odd electrical characteristics... like very high capacitance or inductance... or very little shielding.
These cables may alter the sound in unexpected ways, cause noise or distortion, or even risk damaging your equipment.
(Normal equipment is designed to work with normal cables.... when you make a cable with unusual electrical characteristics you can expect problems.)
3)
Some cables may only be adequate over certain distances.
For example, a thin HDMI cable may work fine in six foot lengths, but not deliver a good picture in fifty foot lengths.
In that case, "upgrading" to a better cable would be a good diea - IF you plan to make long runs.
4)
You may have an
UNUSUAL circumstance......
For example, if you have a
VERY noisy environment, then you may need a cable with exceptionally good shielding to block all the noise.
That final example is one to be especially congizinant of.... and the one which is most abused by purveyors of snake oil.
What you have to watch out for is imaginary solutions to imaginary problems.
Yes, IF your DAC is picking up ground noise, then a fancy USB cable with isolation may eliminate it...
And, IF one of your components is generating power supply noise, and another component is picking it up, then shielded power cables may help.
And, IF you hear line noise intruding on the noise floor of one of your components, than a good line conditioner may help.
The important word there is
IF..... as in "IF you have a problem then it makes sense to look for a solution".
The snake oil contingent would like you to believe that, even if you don't hear any problems, "upgrading" to their product will deliver some subtle and barely perceptible benefit.
They want you to believe that, even though everything sounds fine already, there's some subtle problem you don't notice now... but, if you fix it, your sytem will sound better.
(And, if they do a thorough enough job of convincing you to expect to hear a diffeerence, ther's a good chance you will... or will imagine you do.)
The reality is that this is very rarely true.
Hum and noise are relatively obvious - when you have them.
If you notice "an inky black noise floor" after some upgrade, then why didn't you notice noise before you added the upgrade?
And, while some equipment may be especially sensitive to jitter... most modern DACs are not....
And, if that's the case, and it wasn't a problem to begin with, then reducing it isn't going to make much difference.
And, unless you're operating a microwave satellite, shielding your audio equipment against microwave interference is an interesting but pointless engineering exercise.
We humans have a tendency to believe that "anything can be improved" (and that, if we listen carefully enough, any improvement, no matter how subtle, will be audible).
The reality is that most "cable upgrades" don't actually deliver superior performance at all...
An that, once you pass the level of "adequate performance", superior performance usually won't be audible anyway.
I should also add another warning there...... (which applies to a remarkably widespread fallacy).
Most of the few real improvements realized by unusual technology are situational.
Because a certain upgrade improves your friend's system, or one belonging to a reviewer,
DO NOT assume that it will improve
YOUR system (or vice versa).
It's more likely that they've discovered an unusual solution to an unusual problem - and there's little chance it will do the same for your system.
Is that super-duper expensive cable, which helped eliminate the interference for that guy who lives next to the radio station,
REALLY going to help
YOU?
Probably not!
Note that I've avoided making an absolute statement... because,
OCCASIONALLY, an upgrade is significant and even useful.
However, to be brutally honest, unless you understand the engineering behind the claims, the odds are very much against any given upgrade being worthwhile.
