In my previous post, linked here, I noted that I was using a generic, very cheap variable Switch Mode Power Supply to power the DSC2 Converter temporarily. The supply is meant to help evaluate headphone amplifiers and their ability to power low impedance headphones, as it has up to a 5amp output at the lowest voltages. It is NOT by any means made for critical listening, and the XPower proves that. The changes in noise floor and digital 'hash' are clear when the XPower takes over duties from the generic switch mode power supply.
Now, the exact benchmark being sought at the time (jitter, IMD, SINAD, etc.) doesn't necessarily change, although the measured results CLEARLY show improvement when using the XPower. I have seen similar results from other clean power devices, especially PSU's and USB galvanic isolators. However....
Many an absolute objectivist, especially the most vocal, will point and say 'haha!', or 'gotcha!' because the jitter/IMD/SINAD etc. distortion measured result is the same. I find this to be extremely hypocritical and only self-serving. When faced with real evidence of a difference in the measurements, it is ignored and re-directed into excuses such as, 'you would never hear the difference anyway', or as mentioned before, 'the measurement you were seeking didn't change.' Ironically, they then sound exactly like the 'opposite' camp, who will point out that past a certain point, things like higher SINAD, or lower THD are meaningless because the differences are inaudible. These particular absolute objectivists seem to want their cake and eat it too, but they just can't have it both ways. One cannot laud "product Y" for its 125db SINAD, proclaiming it king of the hill, while at the same time say the obvious changes visible from "product X" are meaningless because they are 'obviously' inaudible.
The fact remains that something major DID change in the measurements, even if it is not the metric or metrics for which one searched. Perhaps what we see IS audible or contributes in some way that when combined with other metrics is audible. For all we think we know about audio reproduction, there are any number of things we don't fully know or understand. Why? Because ultimately what comes out of any audio product is judged inside an extremely complex neural network and bio-sensory system that we are only beginning to understand. If all we do is measure all day and don't listen, thinking our measurements tell us everything we need to know, this hobby is rubbish. Just as much rubbish as a half-million dollar RCA interconnect. (Yes, I find the truth to be likely found somewhere more in the middle. The fundamentalist absolutist objectivist 'know it all', and the 'used car salesman' in the store who calls amps 'class A' because he reads the Stereophile scriptures, not knowing that Class A actually IS a type of amp topology, are equally off-putting.)
Unfortunately the scientific method has been misused time and time again by closed minds to justify their 'position', or their 'ideology'. It is too bad there are not more researchers just interested in the truth, who will follow the data wherever it may lead, and entertain hypotheses in humility rather than dismiss them in arrogance, perhaps holding back and delaying progress.
Now getting off my soapbox, back to the changes the iFi xPower made in the DSC2 measurements. I will choose to focus on two in this blog entry. Intermodulation Distortion and Jitter.
With regards to the specific measurements being sought, the specific data didn't change. But many other things did. The noise floor, once full of spurious tones and quite frankly, a bit of a mess, cleaned up dramatically. And yes, listening tests performed BEFORE the measurements had already revealed a much more natural sound, with less sibilance and harshness than before.
We will start with IMD, 19khz+20khz. The first measurement is with the Generic PSU, the second is with the iFi XPower.