I assume you mean a portable DAP? If you mean stand-alone DAP, the schematics for the Alien DAC and the y1 are free to use, and nothing is stopping you from wiring up the left and right channels to an amp.
As for DIY portable DAP's... This'll probably sound a bit rant-y, so here's the short version:
Quote:
| Has anyone attempted to build their own DAP complete with their own choice of DAC and amp? |
Yes. See below.
Quote:
| How difficult (and costly) would such a project be if building one's own board and ordering ICs individually? |
Difficult: 9 (0 being kindergarten and 10 being graduate school)
Cost: Probably around $300 all-told.
Long version:
The Daisy MP3 Player is available at the
MakerShed Store. However, it's limited to 48KHz output, and judging by the schematic... well, if you're going for sound quality, look elsewhere. If you're looking for hacking together your own MP3 player, sure.
EchoMp3 is fairly nice and comes in kit form. It probably sounds better than the Daisy, but I suspect the Daisy is much better documented.
The
MP3stick uses an Atmega128 instead of a PIC, however has no kit. That said, it shouldn't be too hard to build.
Finally, the
LyreProject aims to create a fully Rockbox compatible DAP, leveraging the existing firmware. This removes a significant amount of the effort, and seems to be fairly far along in development. However, who knows when it will be done, and how actively it's being worked on.
I suspect the reason complete portable DAP's are not very prevalent is the sheer complexity of them. It's not just a DAC and amp; there's some sort of CPU which lives on top of it all, decoding MP3's or whatever other formats, or alternatively piping data directly to an MP3 decoder chip. There's UI stuff, file access stuff (hard disk? SD card? etc.), and all sorts of other digital things. There's a world of computer architecture that happens before the analog circuit domain gets touched.
So I guess that's my answer to the difficulty question; if you're going from absolute scratch, and are aiming for iPod/D2/whomever type quality, you're going to have a long and arduous road ahead; this is speaking as an electrical/computer engineer who has a good idea of what's necessary to get there. If you want to leverage existing code like Rockbox, then I'd say it's an entirely doable project on weekends for a year. Finally, if you want to join a DIY project and push it along... well, I'd say join the LyreProject and make the damn thing pretty, as at the moment it's not so nice looking.
As far as cost goes, obviously the DAC and the amp can be as complicated as you please, and the cost will match the parts you put into it. I'd estimate $50 or so for decent amp components, and then probably some money for the enclosure. Don't forget milling the enclosure and making it pretty. As for the DAC, that probably will also run about $50. Then comes the other stuff... Screen, probably $30 for a Nokia cellphone screen clone or a nice shiny OLED dealio. General computer architecture stuff... without too much detail, and without cheating and going the route of an eval board (you want this pretty, right?) maybe $80 with some PCB's. Miscellaneous buttons, $10. You could get creative, get yourself some Cypress gear and have a PSoC doing capacitive sensing for those fun buttons, which would set you back further. Add in $30 for miscellaneous passive components, power supply stuff, and stuff I forgot from when I last popped open an MP3 player.
This isn't to say I'd discourage such an effort. Just the opposite; it's awesome, and lots of people on Head-Fi would probably get one if the sound quality was sufficiently good, or it was sufficiently hackable that people could just add whatever DAC/output stage they wanted. It could be called the TeDAP, and you would be heralded with the likes of Ti Kan and Pete Millett. It's just that you should know it ain't easy.
-- Rant end.
