Looking for a portable DAC to improve sound output on headphones, as opposed to just the headphone socket on a computer (mainly Mac, bit also the Bill Gates' offerings too) for field use.  Has to be portable, i.e no separate mains etc. power source, and ideally no batteries.  I could use my Zoom H1 as an audio interface, but it needs a battery and while somewhat compact, it could be smaller.  I quite like the look of the AudioQuest Dragonfly Red https://www.audioquest.com/page/aq-dragonfly-series.html  and it does seem to have good reviews. The Chord Mojo looks nice, but rather pricey to say the least, and has a rechargeable battery - the replaceable battery of a Zoom is better in the field, and the Dragonfly just runs on USB power.  So, I was wondering are there other gadgets people have used?  I'll be mainly using the Beyerdynamic DT100 16 Ohm version headphones, so should be easier to drive than some others.
Thoughts and comments most welcome.

Have you looked at the Cyrus Soundkey?

I have one, to improve sound quality output from a laptop, although I have never actually tried it so I can't guarantee it offers any improvement.

Chris.

I decided to get a Cyrus Soundkey in the end. 

https://www.cyrusaudio.com/products/soundkey/

Major influencing factor was Richer Sounds knocking them out at ?59, as opposed to the Audio Quest Dragonfly Red at ?169.  Cyrus are a good quality UK Hi-Fi maker, so I took a punt.  Sooo, does it sound better than just the headphone socket, output or is it just nicely made snake oil?

So in a highly subjective test I played a few tunes through the Cyrus and then just the headphone socket.  I was using a mid-2012 MacBook Pro and 16 Ohm Beyerdynamic DT100 studio monitor headphones. Stuff on computer iTunes is mainly 192k MP3s, and also whatever YouTube chucks out.  Not so much the Old Grey Whistle Test, more the Silvery Aluminium Mac Test.

To give a fair trial I tried a few tunes from different genres.  YouTube sound quality varies tremendously, but in all cases what I listened to was clearer, but if the source is really dire then there's only so much you can do.

I fed it Lady Gaga, Saxon, The Stranglers, Sisters of Mercy, Transvision Vamp, Pink Floyd, Tayor Swift, and Enya to start with.  Then for some orchestral stuff a bit of Ron Goodwin (633 Squadron, Where Eagles Dare). And then a bit of my standard testing speaker treble shredding when turned up to 11 Evanescence and Within Temptation.

For example, Wendy James' intro scream on Baby I Don't Care was more screamy in a nice way.  No clipping or buzzing with Within Temptation's Sharon Den Adel belting out Memories (no, not the Cats one, the metal one). Taylor Swift's Love Story was great, as was the definition of the drums and cymbals in the Stranglers's Hanging Around.

For those that like the cheerful pop-tastic stuff Leonard Cohen's Hallelujah came out very well.

It all seemed brighter and clearer than the headphone socket, and a bit more analytical.  Bass maybe a bit lighter, but in no way absent or detrimental.  I tend to like a balance that errs slightly on the bright side anyway, but that's just me.

For those that like the cheerful pop-tastic stuff Leonard Cohen's Hallelujah came out very well.

Also, when playing some of the material I recorded on a Zoom H1 sound recorder at various gigs I've videoed the sound playback was clearer.

So, yes it does sound better than the inbuilt circuitry of the computer, not that the computer audio is rubbish by any means. It adds another layer of clarity, detail, and texture that wasn't previously revealed.

Sound levels are OK, although I suspect it may struggle with high impedance headphones  (250-400 ohms or more) as output voltage is only 1.7v, and the Dragonfly Red's is 2.1v with similar reservations according to what I've read on line. It just won't go as loud.

To me it is great for the money, however, if your idea of music is a car with ill-fitting body panels belching out something that sounds like the unholy marriage of a bottle of Senokot and a few too many Jalfrezis then this probably isn't for you.

More money could get better results, but ?59 isn't bad for what it is for what I tested it on.