You could do that - sort of..... except.....
1)
It's really hard to measure jitter directly - since we're talking about variations in a clock frequency on the order of single-digit nanoseconds or less. This is something that requires specialized equipment to measure, and absolutely cannot be measured with a simple oscilloscope or meter. The normal way of detecting jitter is to look for the distortion sidebands that result from jitter being present when you send a digital audio signal through a DAC that is sensitive to it. (In other words, it's easy to measure how jitter affects a particular DAC, but quite difficult to measure jitter directly. The good news there is that the same measurements work for any type of input.)
2)
Assuming that Fidelizer functionally does what it claims, and turns off several unnecessary processes running in Windows, then it almost certainly will reduce jitter - on some computers - to some degree. However, confirming that won't tell you whether the improvement it makes is audible or not. (At best, it would tell you if there was no difference - which is actually pretty unlikely.)
The real, problem, however, is that the amount of improvement that Fidelizer makes will depend largely on the computer you try it with. It will probably make at least some difference on most computers, but how much difference will depend on the specific computer you try it with. And then, once you determine that it reduces the jitter on the computer's output, how much difference THAT will make, and whether it will be audible or not, will depend to a major extent on the DAC you try it with. Some DACs are very sensitive to jitter, while others are almost totally immune to it.... This means that your test is very unlikely to be a simple "yes it works or no it doesn't" and much more likely to be "does it work, and, if so, how well, with this or that particular DAC, when connected to this or that particular computer".
However, in the simplest case, measuring it on a "typical" computer, with a DAC that lacks any sort or ASRC or other jitter reduction mechanism, connected via a Coax connection, and playing a few simple test files and looking at the spectrum of the audio output, should be able to give you an idea of whether it actually does ANYTHING or not.
Quote:
So here's your cue
@WindowsX--KeithEmo has pointed out that a PC will generate significant amounts of jitter on its S/PDIF coax or optical outputs, and these can be read directly (as opposed to USB audio)--why not directly measure jitter on these with Fidelizer on and off instead?
