I had precisely the same requirement; a good, neutral sounding DAP on the cheap.
My solution was typical for me; geeky and awkward; but I happen to think it sounds great!
So... My kit is...
Raspberry PI B (version 2?) £35
IQaudio DAC+. £31 the latest specs seem to be :-
- Full-HD audio – up to 24-bit/192kHz playback
- Integrated hardware volume control (via ALSA), full 2v RMS
- Built in High quality audio headphone amplifier (TI TPA6133A)
- Class leading audio; 112db SNR, and -93db THD
- Audiophile TI Burr Brown 32-bit/384kHz DAC (TI PCM5122)
(http://www.iqaudio.co.uk/home/8-pi-dac-0712411999650.html)
16GB class 10 sd card £5. This is for the operating system.
Battery pack, 10400mAH, Three usb power outputs; 2.1AMP, 1.2 Amp and 1.0Amp £20
250GB SSD harddisk and case £60 But you could stick a couple of usb sticks in 32GB stick cost £5 from ebuyer
USB wifi card, £10
Lego to make a case. Free as I pillaged my sons...
So a total sum of parts is :-
With SSD hard disk £161, using usb sticks to give 96GB storage, £116
The operating system is Moode Audio :- http://moodeaudio.org/
Moode audio is fantastic, you get complete control of the system, both the raspberry pi and the DAC. You can take control of the digital interpolation filter, choosing high attenuation with de-emphasis, FIR interpolation with de-emphasis, low latency IIR with de-emphasis and ringing-less low latency FIR. You can stream Itunes music to it.You can have a UPnP renderer and a DLNA server. It can play music back from network shares.
What you get is a great sounding system able to play pretty much whatever file you give it; including DSD files. It can up-sample your music too. The sound I would describe as transparent, open and precise at least with my AKG K550s. I tried the Audeze EL8 open back at richer sounds and the system was able to drive them easily. I actually thought the sound had much the same open sounding, lean and clean signature as the AKG headphones, albeit with a lot more musicality and accuracy.
All this in a package you can *just* cram into the largest pocket in a north-face jacket; and will happily scatter itself across the geography if you drop it.
I'd post a picture, but the system won't let me until I have more posts...