Finally getting around to posting a few thoughts on the wonderful C5.
Used with my Rockbox'd iPod Classic 160GB through the FiiO L3 LOD cable, with Phiaton PS210 earbuds and AKG K550s, it is noticeably better than either through the headphone jack. A bit of a "Duh..." moment, but that's where I started. Just going from memory, I'd say the sound was "cleaner." I always felt the iPod had trouble driving both, even they're 32 Ohms. I found the definition, esp. the lower frequencies, to be superb. Bass Boost was way too much for me, but I'm not a basshead. I prefer a flatter, more neutral sound. I can always EQ it up with Rockbox, if something sounds a bit thin.
Results are the same when using my laptop (Toshiba Qosmio Win7 Home Prem. with a Realtek HD ALC269, latest drivers). I used Winamp's DirectSound output, with playback in Windows set for 24-bit 96 KHz. I tested with the 24-bit 96 KHz version of "Clockwork Angels" by Rush. I mainly used the hard-driving, bombastic (I mean that in the best possible way!) "Headlong Flight" (excellent bass work), and the much more nuanced "The Garden" (strings, acoustic guitar parts; beautiful song). After listening once through, I picked a couple passages in each, then went back and forth between K550s directly into the headphone jack, and through the C5. The direct connection, while nicely defined, proved a tad harsh, and ultimately fatiguing. The C5 warmed up the sound nicely, adding noticeable oomph to the low end, and smoothing out the mids and highs, while not sacrificing definition. All that equals a far less fatiguing experience. Well, it wasn't fatiguing at all! Just a joy to listen to. I'd also say that the sound stage of the K550s benefited a lot from the C5's presentation. Whether or not that's due to the warmer, more relaxed sound, or just my imagination, I love what I hear. All this done with a cheap 3.5mm interconnect cable (at least it's gold tipped!). May have to invest in a better cable, as this is how I will listen to my 24-bit 96/192 KHz FLACs.
Now for the real revelation. In a previous post I asked about using the C5 with a car stereo. I'm happy to report that the C5 does wonders vs. going straight from the iPod's headphone jack or LOD cable. Road conditions, windows opened or closed, traffic, engine noise, etc., all factor into the overall sound. I have two cars with radically different sound systems and delivery methods. My "better" setup uses an old Pioneer DEH-P6400 with a CD-RB10 IP-Bus-RCA Interconnector for the AUX IN. My other car lacks an AUX IN, so I use an old iRiver FM transmitter that plugs into the 12-volt jack. Needless to say, that's a less-than-optimal delivery method, and it always showed when connecting to the iPod's headphone jack. Both systems definitely sound better with the C5 in the chain, but the sound through the FM transmitter is dramatically better. Gone is that harshness that I endured. Everything is so much smoother.
So, all in all, I couldn't be happier with my first amp. The anodized red is gorgeous and cleans off easily when it appears scratched. The FiiO L3 LOD cable makes it easy to access the volume control. And, LOL, I just realized I forgot about the push button gain control. Not sure what I've been using, but I'm also sure I never purposefully pressed it. Apparently it was on the higher setting. And apparently I prefer it that way But perhaps I'll play with that more now.
As far as marrying C5 to iPod, I opted to use what I had lying around, with a grateful nod to the poster who suggested using blue painters tape as a base. Ultimately, I might switch to the fancy 3M interlocking stuff. Also, I like the clear sticky feet on the top of the C5. They don't look awful, and they certainly are non-skid. Lastly, I put the "soft" side of the Velcro on the bottom of the C5, for those times it will be resting on a table, sans iPod.
Here are some pix.