I also use Duelund R and concur with Face. Duelund R sounds both cleaner and smoother in my Merlins than stock Caddock MP power resistors. At some point I will try Duelund C-- but not until I've attended to other mods to components that I believe have better price/performance ratio. Meanwhile, ClarityCap MR in Merlin tweeter is VERY good, and I will shortly be trying MR in Merlin woofer.
Volleyguy, I won't bother to compare the PIOs to each other, but only point out how tricky comparing caps can be, even to "well-educated" ears. Before I wired in the A/B switch to allow instant comparisons, I simply replaced the Mundorf Silver/Gold dry caps that I was accustomed to, with various PIO caps in sequence. In nearly every case I was inclined to say Wow! how impressive a change. But what was really happening is that my judgment was being carried off by the emotional content of the presence region. After installing the A/B switch, I was able to evaluate each cap carefully, and in the end came back to Mundorf. Once and awhile I need to switch in a PIO-- say to hear the last measure of stoic weathering in Johnny Cash's voice on Solitary Man. But there is fine detail that just goes missing with these PIOs, and a slurring of LF that becomes monotonous.
Volleyguy, I won't bother to compare the PIOs to each other, but only point out how tricky comparing caps can be, even to "well-educated" ears. Before I wired in the A/B switch to allow instant comparisons, I simply replaced the Mundorf Silver/Gold dry caps that I was accustomed to, with various PIO caps in sequence. In nearly every case I was inclined to say Wow! how impressive a change. But what was really happening is that my judgment was being carried off by the emotional content of the presence region. After installing the A/B switch, I was able to evaluate each cap carefully, and in the end came back to Mundorf. Once and awhile I need to switch in a PIO-- say to hear the last measure of stoic weathering in Johnny Cash's voice on Solitary Man. But there is fine detail that just goes missing with these PIOs, and a slurring of LF that becomes monotonous.