I've been using the Quickie as a preamp for my Emotiva MiniX speaker amp to drive my Hifiman HE-500. Many people on head-fi have praised the pairing of the Emotiva with the HE-500, as planars need power, so the speaker amp works well. I wanted a warmer sound so I added the Quickie to the chain, and it has sounds great!
Recently, I acquired the Sennheiser HD800. It's known to be very analytical and lifeless sounding, but has technical superiorities in the sound, such as unmatched soundstaging and detailing. Most people agree that to give it some musicality, it's good to pair it with a tube amp, such as the Crack. I also have the Crack, and using it with the HD800, it does sound better than coming straight out of a solid state amp. However, even still I found the musicality of engagement of my HE-500 setup to sound better, especially for lively genres like rock or pop. For one, I found the soundstage of the HD800 to make the vocals a bit stretched out and not as engaging. Overall, it still had a very polite sound signature that was great for classical, but not edgy and exciting or lively enough for rock/pop.
For the heck of it I went ahead and connected it to my Quickie + Emotiva setup I was using for my HE-500. I expected it to sound pretty horrible, as the HD800 is very amp picky, and it doesn't need the power like planars do. At first there was a higher noise floor when nothing was playing, so it was starting look like my hunch was correct. But when I started playing the music, I was completely blown away. There was life to the music! Everything was more engaging, without losing the details or soundstage. The vocals especially, became much more coherent and intimate sounding. The HD800 now sounds as musical as any headphone I've heard! I removed the Quickie from the chain and tried it with just the Emotiva, and once again it started sounding too polite, with stretched out, thin vocals. So it's definitely the Quickie is contributing to this musicality.
Now that I think about it, I noticed there was quite a following on here on modding the Quickie into a headphone amp. At first, I thought it was just saving the $200 price difference between the Quickie and Crack, but after this experience, I'm wondering if there's something more to it. $200 isn't all that much in this hobby. Perhaps there's just something magical about the sound the Quickie gives, and that's why people want to make a headphone amp out of it? To me, the HD800 is sounding far better out of the Emotiva + Quickie than even the Crack!
