The tweaks I've made to this basic front end are, in chrono order: Added a Monarchy DIP 24/96 in between; fed everything balanced AC (from the Power Wedge Ultra that replaced the older, non-balanced PW I had been using); switched from taking the DIP output into the DAC on S/PDIF RCA to using AES/EBU XLR; switched analog output to preamp from single-ended to balanced XLR when I got new balanced preamp (and this was compared both ways using this new preamp); replaced all digital PC's with aftermarket upgrades. (I've been pretty casual so far about supports, just trying a couple different kinds of soft footers without really scrutinizing the results.) All the upgrades were extensively auditioned individually at the times I added each of them, and the experiment with the other DAC also ocassioned a lot of comparitive auditioning. I can't really say that any one of them stood out as being much more influential than the others, although some of them were more clear-cut as unqualified improvements (the balanced AC, the XLR IC's and digital IC), while the rest were easily heard to be different, but took more time to reveal themselves as definite improvements (the DIP, the PC's). Actually, I should modify that last statement: It was clear that they improved certain things right from the start, but they also (unlike the balanced connections or power) changed the 'color' of the sonics in different ways (especially the PC's), so there were aspects to those upgrades that demanded subjective preferences to be determined. I'm sure all the tweaks are probably additive, but I haven't had the heart to ever go back and pull them *all* out at once to see exactly where I came from vs. where I am now.
As far as the magnitude of the improvement wrought by PC replacements on the digital separates goes, that might well have seemed more revolutionary had they not been the last items in the upgrade sequence - but with balanced, conditioned power already in the mix, in addition to an anti-jitter box and balanced IC's all around, there probably wasn't as much susceptability to the kinds of problems introduced through stock cords as could have been the case otherwise. So the PC's do make a difference, no doubt, but as I say, it's one that brings with it a demand for some judgements to be made, because although all the ones I've tried so far do benefit the sound to various degrees vs. the OEM cords, they also display distinct personalities, ones which can be more- or less-complementary depending on which piece of gear in the chain they are used with. The auditioning can get pretty tiring in that regard, since the total effect changes when all three PC's (trans, jitterbox, DAC) are introduced together, after optimizing each choice in isolation. It's still an improvement no matter how you slice it though, and none of the cords I have on hand is over $150 used.
