OK, got my 75 Ohm adaptor to try with the H100 and here's a quick summary of my findings using it directly with sources. In all cases here, I am using a flat EQ. Impedance of the H-100 is stated on its documentation as 32 Ohms and 101dB SNR, but as all of you will know with BA's, that impedance rating will be an average value at 1kHz and can rise and fall significantly above and below that during use:
Sansa Clip Zip (Rockbox) - The Clip is not an ideal partner for the H100 in the first place, as its clarity and neutrality of presentation, seems to accentuate the already sparkly trebles of the H100 and make them a little shrill. What the adaptor does when attached is soften the presentation from end to end, definitely takes the edge off the trebles and smoothing the whole frequency range. If you are after a significantly smoother and softer presentation, this may suit you. Mids are brought forward slightly, bass and treble remain where they were in the mix. However, it also means that playing music through an unamped Clip Zip, requires you to have the Zip at maximum volume for an acceptable listening experience and this obviously has implications for both user flexibility and battery drain.
Cowon C2 - again softens the presentation from from end to end and I think you lose a little of the bass punch. This being a Cowon however, you can tailor the sound to suit you again through its sound shaping technologies and EQ. The big issue with the Cowon is that again it requires max volume when listening for an adequate listening experience and unfortunately on the Cowan, this results in distortion and noise appearing in the sound, right across the spectrum. The Cowan with the adaptor and the H100 is not a setup that should be considered by anyone.
Colorfly C3 - The H100 on its own with the C3 is a lovely pairing that is only matched for me by the GR07 pairing with the C3. Some IEM's and sources just have great synergy and the C3 and the H100 are one of those. Adding the adaptor to this source adds absolutely nothing of any interest to the sound and in fact removes sparkle from the treble to such a degree the sound becomes dull. Again, max volume is required for an adequate listening experience. The adaptor with this combination is not something I can recommend to anyone.
iPod 5th Gen (Rockbox) - Cannot test this atm, as the logic board has failed on my iPod.
Next up will be to test the 75 Ohm adaptor with my Fiio E7 DAC/Amp, but I currently have that out on loan, so it might be a few weeks before I can do that.