DIY iPod digital out

[joneeboi]

I'm dreaming of a white Christmas where DIY-ing iPod owners can enjoy digital I2S output from their iPods. From the little research I did, the Opus DAC can input I2S, but I'm wondering how to carry this signal to the DAC. I've searched and searched but couldn't find anything on DIY I2S cables anywhere. I gather that the wires can't be too long and need some sort of shielding. Should I just open up an old CD player and yank that I2S cable instead? My plan is to pull the signal from the Wolfson (funnest soldering job ever) and send them to the unused pins on the dock (funnest soldering job ever), which are pins 7, 14, and 17. I'll need a 4th one, so I'm guessing I can steal one from, say, pins, 8, 9, or 10. Apple iPod dock interface pinout and signals @ pinouts.ru tells me that these are used only on iPod photo, so I guess these are fair game too, right? From one of the many iPod-implemented Wolfson datasheets (see diyMod post 1), the data accepted are master clock, bit clock, DAC data, and DAC left/right audio interface. I think usually I2S has only 3 lines, but for some reason the iPod has 4. What does the Opus DAC take in for its I2S module? Essentially we're swapping the iPod's (4G in this case) Wolfson for the Opus Dac's. Has anyone else looked into the matter?

Any help is appreciated.

[OverlordXenu]

Cat5e cable.

You could also make a breakout box that makes it SPDIF or optical or something, if you wanted to use like an iBasso D1 on the go.

Here's my attempt at creating a digital out for an X5.

[Jambo]

I2S in my experience is four wires, but *I think* I2S links are sometimes three when your MCLK is a system clock coming from somewhere else, but I could well be wrong.

In this situation however you want all four. As the Opus uses Wolfson 8740/1s then I'm pretty sure it'll want those four.

[jinp6301]

I know that Audio Alchemy used basically S-video cables (or it seems) for its IS2 connection.

[stevenkelby]

You could put the I2S signal into a Pico. Would need more battery though. Unless you share the ipod battery.

No technical help here, sorry.

Good luck with it!

[jsmithepa]

Since THESE GUYS sell it for 2 grands, would u DIY it if it costs u say 1/2 as much?

[00940]

Originally Posted by joneeboi

Should I just open up an old CD player and yank that I2S cable instead? .... From one of the many iPod-implemented Wolfson datasheets (see diyMod post 1), the data accepted are master clock, bit clock, DAC data, and DAC left/right audio interface. I think usually I2S has only 3 lines, but for some reason the iPod has 4.

Don't open an old cdp... all you would find is some poor ribbon wire. I2S wire have to be kept short (less than 20cm is good) and if you're going outside of the box, I'd go shielded. CAT5 could be ok I guess.

Traditionnal I2S was 3 wires, for old DAC chips like the tda1543 (bck, data, lrck). Now that the DAC integrates digital filters and the like, you have to add the mck (ou sck) line. The WM8740 used in the opus certainly needs the 4 lines.

[MusicallySilent]

I guess Wadia does it too

Wadia iTransport iPod Dock Gets Bit-Perfect Digital from iPods!

This would be interesting to have, I imagine many users with portable DAC/AMP combos though it seems a limited amount have optical/coax in would appreciate this..

I might have to follow this thread :P

[joneeboi]

I must have closed Firefox before posting my response. =T

We could go the Wadia way, but as far as DIY goes, that's selling out. :P It's pricier than DIY, plus it isn't as personalized as we can make it. This guy from OverlordXenu's thread seems to have gotten it right. Serves our purpose, small footprint. One drawback is that it would have to draw power from the iPod. Then again, while we are fabricating our own iPod docks, we might also want to add charging capability to the iPod while the transceiver steals power from it. I can't imagine this kind of setup being portable, but some have carried T-amps and K1Ks around too. The biggest hurdle would be taking the signal from the iPod's Wolfson and sending it to the 30-pin dock. Further, internal layouts may restrict generation-compatibility. For instance, the 5G/5.5G iPods have that metal frame that screws into the front plate, for those of us who have seen the innards, so routing the wires to the dock would suck. I find it'd be easiest with 3G and 4G iPods, as it seems Apple hadn't shrunken that layout just then. There's plenty of room indoors for those iPods, so signal retrieval wouldn't be so bad. For future reference, I soldered some navships stranded SPC to the iPod dock before but only used 2 strands (documented in diyMod thread). After you get the hang of it, you feel like you can solder 100 Alien DAC PCM2702 chips with a 10W soldering gun in the dark. Anyone who'll try routing wire-wrap through that 5G/5.5G frame to the dock can report on the fit. Also, I don't suppose making this fit the Alien DAC for the ultimate in portability is viable either, is it?

[OverlordXenu]

Originally Posted by jsmithepa

Since THESE GUYS sell it for 2 grands, would u DIY it if it costs u say 1/2 as much?

The $2,000 is just for their silly dock. The iPod modification costs $200, so they probably just pull the I2S to the dock connector.