audiophile diy DAP?

[Danielj]

OK folks...I know there are alot of electronic wizards here; building your own dacs, phone amps, etc. So what about a transportable true audiophile quality DAP? I know Vinnie is doing the imod thing with clean line out...which is what is missing from all these comsumer audio players. But he is working with microscopic size circuits. I am thinking of something larger: a bare bones unit; mains and battery powered, but smaller than the pixel magic and the like. something that outputs to a headphone amp and designed just for that. What would be needed to make a truly good DAP

easy stuff
2.5 harddrive, laptop type
small dac like monica
good quality lineout directly from dac no internal headphone amp
small ipod type screen

hard stuff?
firmware like rockbox?
the processor to operate the whole thing. Is this where the problem would be? The pixel magic type players are using a sigma processor and linux software.

so, is the technology abailable to gather all the parts for such a device? If it is, it seem s to me that all is needed is to have the knowledge to wire all of it together. I have a friend that is on headfi...I betcha he could do it.

thoughts and problems

thanks
Daniel

[pheonix991]

I don't think there is anything like this.

[threepointone]

not yet *hint hint*

sigmatel processors are uber-unobtainium in small quantities. However, the freescale MCF5250 (or scf, keep on getting confused) which is used in the iriver h3x0 series is more readily available.

The iriver h3x0 also happens to run rockbox *hint hint hint*

wiring together? surface mount, not quite as easy as you'd think. something goes wrong? debugging would require quite a bit of skill and tools.

[Sherwood]

I think if size is not an issue, most folks elect for a purpose-built silent PC. Really, what you're looking at is a music server. Perhaps something like the Olive Opus.

[Danielj]

So there are chips available i.e. as in iriver. that's encouraging About wiring...I dont know anything thats why its good to know people who do. But it seems to me that if the path of componant connection is known via all these consumer dap's diying on a larger scale should be possible. As you say tho, if something goes wrong, one would need alot of skill to track down the problem.

yes, the Olive opus minus the cd transport and of course diyable and much cheaper. I am a poor guy and as you all on headfi know - audiophil itis is quite expensive.

I am glad to hear so folks chipping in on thise...keep it up something good might come of it.

[Danielj]

Yes, I have looked into the small form silent pc vendors. I dont know if mounting a dac internally running directly off the motherboard is possible,or sonically advisable....or perhaps an internal soundcardwith digital out and use an external dac, then headphone amp?.

I see on ebay all the time these cheap multi media players where you put in your own hard drive. But everything I have read about them say the sound quality is really sub par

Just have been wondering if diyers have experimented with making their own DAPs
thanks all

[threepointone]

I personally don't like full-scale PCs for audio--there's just too much overhead from the software that isn't necessary and might mess up the audio without you realizing it (case in point: kmixer). Also, making a full-scale sound card is a whole lot harder than making a DAC. You have to deal with the PCI bus, all the digital noise inside a full-scale PC, and the drivers for the DAC. Quite a nightmare for any DIYer. I'm quite certain it's virtually impossible to do some crazy modification to the motherboard in order to accomplish this.

Either way, a 2Ghz CPU is about 10000x more processing power and complexity than you'd need to do this sort of stuff. It's probably easier to just design a DAP from scratch. The rockbox project actually has most of the schematics for the iriver on its site--it shouldn't be all that difficult to make a copy of the iriver using a bigger board and mostly thru-hole components, though it wouldn't be fun to solder/debug 100+ SMT processor pins. Most of the work would probably lie in the layout and modifying the rockbox firmware for the modified components (no li-ion power controller, different DAC, etc. . .). I've been planning to do this sort of DIY audiophile DAP this summer, although I was going to jump directly to an ultraportable design.

btw, the MCF5250 happens to come in a LQFP package, unlike some of the other coldfire chips I was looking at, which means it's accessible to a lot more than the 10 DIYers who have a toaster-oven-bga reflow system set up.

[gates_2]

To me, it would be absolutely amazing to see a high-quality DIY dap that has a SQ better than the standard Ipod

Amplifiers and Daps are two very different animals. I really wouldn't be surprised if we had some talented ECE people here who could pull this off.

With the cost of flash technology, you could easily stick a 4-8gb card in the player.

Big issues would still be on our(the DIyer side) Without a knowledge of how it actually works(those processors are much more complicated than an 8 socket opamp) one tiny mistake could cause huge amounts of frustration!

Heres a current offering, albeit not quite audiophile quality:http://www.techdesign.be/projects/020/020.htm

EDIT: more:http://www.teuthis.com/html/kits.html

[oicdn]

Well, maybe not just a home unit, but a portable unit. People are making portable amps....and as we all know, size can and will vary.

It would be sweet to see something flash based like a Shuffle (without a screen to make it easier on the developer, just buttons) with the 1/8th jack being a dedicated line out....i.e. useless without an amp, or can be used cans with an inline attenuator ala KSC 75s ampless.

I would buy one.

[Danielj]

I just did a search on the web and there are several diy mp3 players....but we are looking for somthing alot more high end.

3.1 I agree that a computer based system is way overkill. Please keep me posted on your progress this summer. thanks Dan

[jonnywolfet]

dammit, i cant find an old link i had for a diy product that was open source, hosted most hard drives, and output to coax digital. with various addon components.
does that not sound perfect?

[jonnywolfet]

i found this:
http://dma.elektroda.net/projects/mp...rm_player.html
not the link i was looking for but its interesting.

[balou]

firmware like rockbox?

why 'like'? rockbox is open source - you could use it as the main OS

I just did a search on the web and there are several diy mp3 players....but we are looking for somthing alot more high end

.
Makezine had one... it uses an all-integrated-chip. sd card interface, mp3 decoder, user interface, headphone amp... not really a good option.

It would be sweet to see something flash based like a Shuffle (without a screen to make it easier on the developer, just buttons) with the 1/8th jack being a dedicated line out....i.e. useless without an amp, or can be used cans with an inline attenuator ala KSC 75s ampless.

all that's really needed is something which accepts sd cards, and puts out an i2s or spdif signal. the rest can be borrowed from the alien dac or other usb-powered diy dacs. I'm interested in such a thing too. After my holidays, I'll try to find a chip which could one or more of the required things. Oh and why sd cards? 1. available everywhere 2. cheap 3. easy to adress from a hardware perspective 4. exchangeable. if you don't need multiple megabytes per second (320kbps mp3 equals just 40kb/sec), you can access sd cards with a simple serial protocol.
ti, maxim or ad surely have some mp3 decoders. maybe even with some extra stuff like spdif out... the other controling stuff could be done by an atmel microcontroller

edit: jonnywolfet: indeed interesting. seems like this guy wrote the mp3 decoder 100% in software, and used mm cards (sd cards are backwards compatible). but I don't think the on-chip dac could be considered audiophile.
edit2: looks like a software-emulated 1-bit dac. yep, maybe not audiophile...

[Sherwood]

Hypothetically, though, anything that could run slim client could also run linux and, through that, foobar or some foobar derivation. There are already existing DIY USB dacs that could be built into the housing of such a unit, bypassing kmixer and other internal processing. You could find parts for this, everything but the drive, for literally free at thrift stores. Sure, a modern computer is 50x overkill, but people are throwing away computers that are 1/50th of the power of a modern computer.

The biggest problem would be fan noise -- old computers are loud, and quiet computers are pricy.

[srobertson]

Hop on IRC and join the Neuros 3 design meeting:

http://open.neurostechnology.com/node/894

A full-featured DAP is being designed from the ground up, and as it stands the first run will have a case with a generous amount of room - it's conceivable that a digital out could be offered with test points that could be grabbed by a custom DAC and piped to a real line out.

Full disclosure: This device is going to be entirely community-designed, but manufactured by Neuros, the company I'm an intern with this summer. (Don't worry, they're great people.)