I have a lot of headphones and none of them are perfect. Beats Studio Pro, Bose QC25 and QC35, Sony MDR1000X and new Philips SHP9500 open backs. All fully broken in and well used. They are all great in their own way and when I hear songs on the different phones, sometimes it's like hearing the song in a different way. Also, different phones for different uses, right? I don't take open backs on a plane. One thing is clear, if you want the music presented in all of the full-bodied glory that the artist and producers intended, you will not get it from your iPhone or android headphone jack, even on ANC powered phones like the new Sony or QCs. In order to get that, you need to boost that signal with an amp.I used to be like you and think, "Nah, I don't need an amp." But then I got a desk amp and plugged in my humble Philips open backs. Damn. They came to life with a depth and fullness that I didn't know that they had hidden in their cheap, $70 bodies. Next, I was on the hunt for a portable amp that I could plug into an old iPhone that I have turned into an iPod (iPhod). My research led me to the FiiO A5 in cool-looking, Sia-singing "Titanium."Once it arrived I gave it a cursory charge and put it to work. I lashed it to my "iPhod" and plugged in my Philips. Drum roll! Disappointing and dull. What? I paid $129 for this damn thing! I flipped the gain from L to H and...okay. Better.Then I flipped the Bass from Off to On and Boom! Hello happy ears! The Philips are not high end so I can only expect so much but they preformed well below high end cans but well beyond their $70 price tag. The FiiO does not make them sounds like Sennheisers but it does allow them to give you everything they have, which is rich clear sound with relatively good depth and a nice wide soundstage. I went straight to Lake Street Dive's "Call Off Your Dogs" and I could hear bad-ass bassist Bridget Kearney's (one of the best bassists on the planet) fingers actually plucking off of the strings! I heard bells and rims that were normally buried in the huge wall of sound. Lead singer Rachel Price's voice is huge in any speaker or headphone but amplified, it's unbelievable. Next was Walk Off The Earth "Sing It All Away" and the harmonies were fuller and more distinct. So far, I was happy but not totally blown way like some of the reviews I saw on YouTube.If the FiiO did helped my inexpensive Philips, what could they do for my Wife's Bose QC35? I plugged them into my iPhone and played Mutemath "Used To." Sounded good but with the famous Bose bass-less crystal clear highs. I switched to my iPhod-rigged FiiO, on high gain and bass on and BOOOOOM!! There is where the Bass has been hiding! WOW! I'm not a fan of the Bose sound profile but the FiiO really helps! "Use To" is an amazing song but amplified, it's like an avalanche of music hitting you in the face. I had to go back to "Call Off Your Dogs" and I was hearing the song presented with the precision and detail Bose is known for with a depth that I had never heard from those cans. I heard things that I had not heard before!On to the new Sony MDR1000X. These cans lack the precision of Bose but have a fullness that makes them better for listening to Pop, Country, Soundtracks and Indie Rock that I love. The FiiO gave them a richer sound and a deeper bottom end. It was not as dramatic as the QCs but it was noticeable. With the Bass ON the Sonys did suffer from a little muddiness that I didn't notice on the Philips nor the Bose but with it off, my ears yearned for a bigger sounds I kept if turned on. I could not help myself, I had to try "Finale" from Randy Eldelman's Dragonheart Soundtrack. Oh, I was in heaven! As a matter of fact, I'm listening to it right now as I type this.I always knew that amps helped passive and open back cans but I didn't know they would help powered ANC headphones. I had no idea! Well, I know now and I'm glad that I bought the FiiO. Now, how does it function...I lashed the FiiO to my iPhod using the small rubber bands but the bands covered the touch screen. See attached photos. So, I went to my Wife's Christmas bins and borrowed two 3M Command strips and used them to adhere the iPhod to the FiiO. I trimmed off the tabs and it looks pretty good. Also, showed in photos are the blue power-on light and the red charging light, both can get covered by the bands, as can the Bass On/Off switch or the USB charging port depending on how you position the bands. Another positive for the Command Strips.The bands do perform one good task, they keep the iPhod face or the FiiO back from getting scratched up when set on a solid surface. I solved that with little adhesive silicone feet, also stol...borrowed from my Wife's stash. Shown in photos.The volume knob is a bit of a pain in the butt. I would rather have side buttons or something as the knob is so close to the headphone port that it can make volume adjustments a little cumbersome. My solution is to put the volume mark straight up, pointing at the iPhod headphone jack (80%) and leave it. I adjust volume using the buttons on the iPhod. BUT, I do forget to turn the FiiO off all the time. Good news, when not in use the batter drains slowly, even when left on. Better to remember to turn it off though. I'm getting better at remembering.Do I love it? No. Do I really like it? Yes. Would I drop $129 for it again? Yeah, I would. It improves the sound enough that you hear details and nuances that are otherwise lost. This alone creates new discoveries in songs that you have heard over and over again and that is fun.I hope this review and some of my hacks helped. Thank you for reading it and if you don't have the Dragonheart Finale on your media player, get it!