Opening an Ipod to get the I2S signal for a digital output

[gaetan8888]

Hello

I want to use a mp3 player to play wav or lossless files with a digital output to feed a TDA1541A non-os Dac.

The Iriver H100, H120, H140, did have a SPDIF digital output but those models are hard to find.

So, I would find an old Ipod like the G1, G2, G3 or G4, or the Mini 1, and open it to bypass the Wolfson Dac to have the I2S signal for a digital output to feed a TDA1541A non-os Dac.

The first and second generation iPods used the- WM8721; the third generation ysed the- WM8731L. The fourth generation - WM8975 CODEC; and the fifth generation - WM8758 Audio codec.

But looking at those Wolfson Dac data sheets, I am not sure which pin of the Wolfson Dac I need to bypass to get the I2S signal ??

Any hints ?

Thank

Bye

Gaetan

 

[gaetan8888]

Hello


Here is the links to the Wolson Dac


http://www.wolfsonmicro.com/uploads/documents/en/WM8731_Rev4.3.pdf



WM8971 it is same than the WM8975

http://www.wolfsonmicro.jp/uploads/documents/jp/WM8971.pdf



WM8978 it is same than the WM8758

http://www.wolfsonmicro.com/uploads/documents/WM8978.pdf

Bye

Gaetan

 

[amc184]

Most iPods use a PP5020 or PP5022 SoC by PortalPlayer (now defunct, adsorbed by nVidia). As far as I can tell they use I2S between the cotroller and the DAC, so should be OK to connect to a DIY TDA1541A DAC.

I think I2S should be taped like below:

WS: (DACLRC) WM8721(4) WM8731*(9) WM8975(7)
BCLK: (BCLK) WM8721(2) WM8731*(7) WM8975(5)
DATA: (DACDAT) WM8721(3) WM8731*(8) WM8975(6)

* 28 QFN package, which I think most iPods use.

Looks like a good project, good luck.

Anton

 

[amc184]

This site here shows which iPod models use which SoC and DAC. I would stick to the PP5020 and PP5022 models, the PP5002 may use AC'97 (but probably not).

 

[jcarr]

Rather than an iPod, I'd recommend field-recorders like the Roland R-01, R-09, Sony PCM-D50, or (at higher cost), Sound Devices' 744T.

Both the R-01 and 744T are equipped with CF slots (the R-09 uses SD while the Sony uses MemoryCards) and the 744T also is designed for a 2.5-inch IDE HD (which can be swapped for an SSD), so you can avoid rotating media.

I have modified iPods for CF/SSD operation and they work fine, but these will require more work than the Rolands, Sony and Sound Devices to achieve solid-state operation, and extracting SPDIF or I2S output will be considerably more difficult than on the Rolands and Sound Devices.

The Rolands have Toslink, and the 744T has coax SPDIF. Getting I2S out therefore should not be that difficult, although a service manual or schematic would be useful.

Sound quality is outstanding.

hth, jonathan carr

 

[EUVL]

Do they have built-in low jitter clocks ?

Patrick

 

[amc184]

I would still go for an iPod. They are much easier to find, and just because the Rolands etc. use S/P DIF doesn't mean you can access I2S directly in them (although you might be able to, I am not familiar with these devices), and a S/P DIF recovery circuit would add alot of complexity while being detrimental to performance.

I doubt iPods have low jitter clocks, just a standard grade crystal attached to an oscillator circuit onboard either the SoC or DAC. You may be able to install a low jitter clock, depending on what sort of clock layout the iPod uses.

I'd love to know what sample rates and bit depths the SoC is outputting. Unfortunately I can't find the datasheets for any of the iPod SoCs (PP5002, PP5020, PP5022), and the DACs used accept such a variety, so they don't help in narrowing it down.

 

[gaetan8888]

Hello


Jcarr

Those field-recorders like the Roland, Sony and Sound Devices cost too much money for me.

I would not buy a new Ipod but a used or refurbished one, or a refurbisher Sansa (easyer to find at low cost but it use another dac chip).


Amc184

Here is the only portal player chips data sheet that I found (PP5002, PP5020, PP5022) , they are short version data sheets;

http://web.tagus.ist.utl.pt/~rui.neves/se2005/basedoIpod_5002_brief_0108_Public.pdf


http://web.archive.org/web/20061202...products/documents/5020_Brief_0108_Public.pdf


http://web.archive.org/web/20060908...r.com/products/documents/5022_Brief_Mar05.pdf

Thank

Bye

Gaetan

 

[amc184]

Yeah, I've already seen the product briefings, but they don't even come close to having the info of a datasheet. Looks like the datasheets were distributed with an NDA, probably only to a few OEMs. I doubt they'll ever see the light of day.

 

[gaetan8888]

Hello

Btw, the player I will use will be stationnary and will be in a metal box on the top of my amp in my home.

Sansa player do not play wav, so no more Sansa. And Ipod do not play flac files.

But there is a very interesting player, the Rio Karma, it use a laptop hdd and it use the PP5003 and the WM8721.

And it play wav and flac files.

So I just need to find a used or refurbished Rio Karma.

About the dac;
(quote)
Rio Karma DAC

The DAC is fed with standard I2S signal. The pins are:
Pin 2 - I2S bit clock
Pin 3 - I2S data
Pin 4 - I2S left/right clock

However, there is no external 256fs master clock signal, which may be required to drive an external DAC setup. The Wolfson DAC is special in that it will accept a 272fs or 544fs master clock, which is great if you have a 12/24MHz clock kicking about (e.g., a USB clock) but not very standard for audio components. Also, the lines are not buffered and are at 3.3v levels - you may run into signal integrity problems over a cable run and the lines are not particularly protected against static discharges as they were never supposed to run outside the case.
(end quote)

But the PP5003 do seem to have a SPDIF output but I only have the short version of data sheet, so I do not know from which pins it goes out.


Here is somes web sites links about the Rio Karma;


The Portal Player chip product briefings file;

http://web.archive.org/web/20070218...products/documents/5003_brief_0108_Public.pdf


The Wolfson WM8721 dac;

http://www.wolfsonmicro.com/uploads/documents/en/WM8721.pdf


Others Rio Karma web sites;

http://www.rockbox.org/twiki/bin/view/Main/RioKarmaPort

http://www.dapreview.net/p/content/content.php?content.193

http://www.schenkzoola.com/karmaopen.htm

http://www.karmalimbo.com/

http://www.karmalimbo.com/dnna_karma_description.pdf

Thank

Bye

Gaetan

 

[xaudiox]

And Ipod do not play flac files.

If you install Rockbox into your Ipod, you can play Flac files...

 

[gaetan8888]

If you install Rockbox into your Ipod, you can play Flac files...

Hello

Interesting, but Ipod are so much popular that the used one are still quite often overpriced.

So I will look for both Ipod and Rio Karma

Thank

Bye

Gaetan

 

[gaetan8888]

Hello

Anybody would know which pin of the PP5003 chip do carry out the SPDIF signal ?

Thank

Bye

Gaetan

 

[giuliaudio1]

Hello, do you know how I can get an I2S signal out of the IPOD Touch?

 

[jkeny]

I know this thread has been dormant for a while but I have got my hands on a 5.5G ipod which uses the WM8758 DAC (same pinouts as WM8978, I believe).

Looking at this datasheet I identify the following pins (these are different WM8978 pins than on the first page):
Pin 7 = LRC - Left/Right alignment clock
Pin 8 = BCLK - Bit Clock
Pin 10 = DACDAT - DAC data input
pin 11 = MCLK - Master Clock Input

I'll be using this to feed I2S to a ESS DAC which doesn't need the MCLK signal so "in theory" the ipod clock jitter & the PLL sysnthesis of the audio clocks from it (more jitter?) is not of huge importance due to the ESS jitter reduction technology (I know this is not strictly true but anyway - worth a listen).

Has anybody identified the LOD pins that are unused & I could route the I2S signals to 3 spare pins?

 

[qusp]

19, 20 (+12vdc firewire power)
22 (firewire data TPA -)
24 (firewire data TPA +)
26 (firewire data TPB -)
28 (firewire data TPB +)

these are all related to firewire data and power and since firewire was discontinued before the ipod video these should be fine. there are others reserved, which actually are probably relating to the encoded i2s stream anyway. I will be very interested in your results as I am in planning stages for a portable ESS dac/amp which I will be feeding with a cowon X5L or iriver H120, but I have a 240gb ipod video I would love to tap for this. many before you have tried and failed though mate, it seems the integrity of the signal is not great, perhaps this lack of a need for the MCLOCK by the ESS dac will get around this though. i'm using asrc if needed but would rather avoid it.

there are also multiple pins tied to ground in the ipod so some of these could be commandeered if you lift the legs on the dock connection to the PCB

 

[jkeny]

19, 20 (+12vdc firewire power)
22 (firewire data TPA -)
24 (firewire data TPA +)
26 (firewire data TPB -)
28 (firewire data TPB +)

Thanks, qusp

these are all related to firewire data and power and since firewire was discontinued before the ipod video these should be fine. there are others reserved, which actually are probably relating to the encoded i2s stream anyway. I will be very interested in your results as I am in planning stages for a portable ESS dac/amp which I will be feeding with a cowon X5L or iriver H120, but I have a 240gb ipod video I would love to tap for this. many before you have tried and failed though mate, it seems the integrity of the signal is not great, perhaps this lack of a need for the MCLOCK by the ESS dac will get around this though. i'm using asrc if needed but would rather avoid it.

This is the trick I was hoping would help BUT I came across this post on Audiogon by Steve (audioengr) here AudiogoN Forums: Is iPod Digital Output Possible?
He says:

Johnmhuntbch - I took an iPod Video apart and mapped-out the signals. The problem in this particular unit is that the signals necessary for I2S are not present. The D/A chip is run from a 12MHz clock. It is a proprietary chip from Wolfsen, cannot find a datasheet. It also uses a half-speed bit-clock. With some effort and logic, I could generate S/PDIF from this externally, but it would be jittery.

The whole point of this was to get a low-jitter I2S out of the thing. Looks like maybe a different iPod is needed. The new ones evidently use the WM8741. This I have the data sheet for. This probably has I2S going in. Not sure which iPod to buy though. This is getting expensive. I managed to put the video iPod back together and I'm giving it to my wife for use when walking the dog...

The 5.5G ipod uses the WM8758 DAC (same pinouts as WM8978, I believe). So this looks like it might be doable - how good it will be is another matter I haven't looked into this yet but is the half-speed bit-clock standard or non-standard implementation?

there are also multiple pins tied to ground in the ipod so some of these could be commandeered if you lift the legs on the dock connection to the PCB

 

[qusp]

well there was never to my knowledge an ipod that used the WM8741, the ipod video, ipod touch 1g and iphone 3G were the last one to use a wolfston at all. they now use cyrus logic dacs. I could be wrong there, but i'm sure a fuss would have been made over an ipod using the WM874X dac over at head-fi and this would still be a very popular DAP if it ever did exist, which to my knowledge it never did.

 

[lampee]

Is there anybody here who actually did the mod? I would like to see pictures of the inside if it is possible and of cource how you did it? I really like to to this for my ipod.