I've come across several threads mentioning that older receivers and amps were designed for high-impedance headphones, making them not the greatest pairings for low-impedance headphones. I discussed the issue with my dad, who was a product designer for Onkyo, Marantz, and a few other companies. He theorized the signal would be clearer and truer to the original amplified signal if he removed the resistor between the amp section and the headphone output, and to prevent any catastrophic failure, he lowered the gain in the amp stage itself. With my non-existent knowledge of engineering, I was scared that a power source with too much wattage per channel would break the headphones, but he tried to explain to me in the most dumbed down language possible that if the gain were lowered, there wasn't really anything to worry about. The result? Not bad. Our first test case was a Scott R33AS receiver, with 15w per channel output. We tested the Scott with various headphones, and found it to be incredibly warm, and it had an unexpectedly large amount of treble roll-off. It sounded surprisingly like a tube-amp. Even with the treble knob turned to max, it wasn't enough to recover all of the missing treble. The mids were fairly balanced, but not the star of the show. The bass was almost overwhelming, even on headphones I would consider to be fairly neutral. We found, out of my collection, the Mr. Speakers Ether was able to show the largest difference between the Scott and my other headphone amps (V200, Vali 1, LP G103, Aune X7s). Certain songs with notes reaching deep into bass basically disappeared on my headphone amps, but were right in your face on the Scott. The coloration actually played pretty well with my TH900, but I couldn't stomach the combination unless my soul was crying to head bang. I was really impressed with the results, but it wasn't a perfect transition. On iems, I could hear a fuzzy static in the background, which apparently could be remedied by cleaning up the power supply. Additionally, there's a ground loop that makes the music slightly audible, even with the volume turned down all the way. Also apparently fixable, but we're on the search for a more neutral sound now. He had a spare Yamaha R9 lying around, which he just converted and awaits listening... He said the R9 was significantly better than the Scott, sound signature wise, after trying it himself, but we'll see. As someone with very limited exposure to "high end" headphone amps, I'd be interested to hear what other people think of the idea and the results. So this is also kind of an open invitation to try them out for yourselves, and/or give feed back on the idea.