Warning... Non audiophile evaluation here...
Colorfly C3 (Normal EQ setting, Vol 35/40 used for output to Amp)
beyerdynamic DT880 Pro 250 Ω
Ultrasone HFI-780 35 Ω
Koss Porta Pro Classic 60 Ω
FiiO E11 (Power High, Gain High, Bass EQ 1)
FiiO E17 (Gain 12db, Treble 0, Bass 0)
DIY 3.5mm IC
Wow, after wearing the DT880 for a while now the 780's felt hard and uncomfortable, but only for a little bit, just until the Bass kicked in.
The C3 has enough power to drive two of the three headphones from the HP out jack properly.
The Porta Pro's & 780's ran nicely with a volume between 20-30/40 and were driven quite easily, the 880's on the other hand had to be run at 40/40 on some tracks for a moderate listening level, obviously the C3 isn't meant to drive high impedance headphones.
The E11 provides a very nice level of amplification when using low ohm cans. I usually run it with Bass Boost either set to 0 or 1 depending on the music, also the volume will rarely go past 4/10 when driving the 780's or Porta Pro's from the C3.
Now the the DT880's are another story, they require a 8/10 setting to get a good listening volume, this also will depend greatly on the level of the source track used.
I find the E11 very flat so sound isn't altered unless you add Bass Boost to the equation.
Now the E17 is a great little unit a best bang for your buck kind of DAC, I mainly use it docked to my E09k driven by my computer.
I feel this unit also pairs very nicely when connected to the C3. It has more power that the E11, I only have to run the DT800's between 45-50/60 for a very adequate volume. The separate Bass and Treble controls gives a nice little control over the C3's sound. When connected to the DT880's I usually apply Bass +4 / Treble -2 to the Normal EQ setting on the C3.
If you don't need the E17's DAC capability then I would pass on it and look into possibly the C&C BH or C&C XO2 amplifiers. There is a good thread here on Head-Fi and a large following for the C&C Amp.
All the equipment listed can be found with Full Analytical Review in various places here on Head-Fi if you need Soundstage, Imaging, Attack, Decay, Sustain, Release, Dark vs Light factors etc...
Songs and Tracks tested:
Folk / Worldbeat
Paul Simon - Graceland: 25th Anniversary Edition
5. Diamonds On The Soles Of Her Shoes
10. That Was Your Mother
Infected Mushroom – Legend of the Black Shawarma
3. End of the Road
TRON - Legacy Soundtrack
10. Adagio for Tron
Well that is my take on the C3 / FiiO paring... Crisp and Clean with plenty of Bass when required.
When I have building maintenance to do, I put Infected Mushroom on the C3 with Bass EQ and E11 Bass +1 through the Ultrasones... it gives me all the ear vibrations I need. :D
My 3.5mm to 3.5mm IC
Is a 2” DIY cable with gold plated ends (repurposed from another cable) and wooden shells, regular copper wire as I am not a believer that silver, gold, unobtanium or Mongolian yak hair makes any difference in a 2” cable.
C3 is a $100 DAP and it does a great job, it has a few little quirks but they are easily overlooked.
E11 is a great little $60 Amp for lower ohm cans, that provides an nice Bass Boost if you want.
E17 is a $150 portable Amp / DAC that does 24/192 resolution, more inputs than you can use and docking capability.
Are there better? Yes Indeed, there will always be better.