Jon L of Enjoy The Music: ... when the copper foil version of the AmpOhm PIO's became available, I had to give it a good listen and compare to the other versions. After the obligatory burn-in period, I directly compared the copper version with the tin foil version, changing back-and-forth.
I would say the difference in character between copper and tin is larger than between tin and aluminum, yet all three versions share similar presentations, which is no doubt due to the exactly identical construction except for the foil material. All share a well-balanced clarity with great detail resolution, at least for PIO's, and above all, music is well-served. This does not make it any easier to describe precisely how the copper and tin sound different, but I do have a few observations.
With the copper, there is a little more attention-grabbing presence or copper-glow, mainly in the midrange, which can be described as slightly rounder yet with a fraction more detailing of the texture. Both female and male voices step forward half a step closer while the high and low frequencies remain similar to the tin foil version. This "mien," if you will, is mildly reminiscent of the Jensen copper PIO, yet the AmpOhm copper seems to have better clarity and extension at both ends of the spectrum.
Jon L of Enjoy The Music: ...it came to me as a pleasant surprise when the AmpOhm Tin Foil PIO directly replaced Mundorf SIO and seemed to be sounding at least as good! AmpOhm really seems to hit the right balance among PIO's. In some circuits, the wonderful Jensen copper PIO can sometimes sound a bit too refined and buttery for my tastes, but AmpOhm avoids that while still remaining smooth. What it has over Mundorf is higher density of tone and richness while not sounding syrupy or slow.
I still remember the first time I played Bach Cello Suites via AmpOhm. The cello sounded so magnificent I almost fell off my chair! Every detail, texture came through with power and vigor.
If you are looking to PIO's as sort of a filter to hide system faults by rounding, glossing-over, or rolling-off, these AmpOhm Tin Foil PIO capacitors are not the way to go because they are incredibly detailed and revealing of the signal chain.
My initial impression is that the paper in oil aluminum foil cap is very smooth - the impact of the by-pass on the midrange was excellent - very solid sounding. In fact I got the impression that the soundstage was much better.
Jon L. Enjoy the Music: What I wrote about the tin foil PIO pretty much can be re-written here without significant changes, which is a very good thing. Invariably, someone will STILL ask which one they should get for their amp XYZ. If I had to give an answer, for no good demonstrable reason, I might say go for the tin if your amp is already on the slightly smooth, round side and go for the aluminum if one's looking for a touch more forgiving sound...
The overall sound of AmpOhm paper-in-wax was even and pleasant, with no part of the spectrum jumping out and biting off your ears. This is a great capacitor for tweaking an overly-bright or analytical system to more forgiving side, allowing one to enjoy a larger portion of poorly-recorded albums. The flipside was that great recordings could not reach the heights that tweaked Teflon caps can achieve; there just seemed to be a finite limit on how much resolution and transparency was available. It’s not really fair to compare any cap’s resolution to teflons, but that’s how it goes around here.