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Old 11th April 2009, 04:57 AM   #1
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Default Opening an Ipod to get the I2S signal for a digital output

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
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Old 11th April 2009, 05:45 AM   #2
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Hello


Here is the links to the Wolson Dac


http://www.wolfsonmicro.com/uploads/...731_Rev4.3.pdf



WM8971 it is same than the WM8975

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



WM8978 it is same than the WM8758

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

Bye

Gaetan
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Old 11th April 2009, 12:15 PM   #3
amc184 is offline amc184  New Zealand
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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
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Old 11th April 2009, 12:23 PM   #4
amc184 is offline amc184  New Zealand
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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).
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Old 11th April 2009, 05:49 PM   #5
jcarr is offline jcarr  United States
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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
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Old 11th April 2009, 10:55 PM   #6
EUVL is offline EUVL  Europe
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Do they have built-in low jitter clocks ?

Patrick
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Old 11th April 2009, 11:20 PM   #7
amc184 is offline amc184  New Zealand
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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.
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Old 11th April 2009, 11:59 PM   #8
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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.nev...108_Public.pdf


http://web.archive.org/web/200612021...108_Public.pdf


http://web.archive.org/web/200609082...rief_Mar05.pdf

Thank

Bye

Gaetan
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Old 12th April 2009, 02:34 AM   #9
amc184 is offline amc184  New Zealand
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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.
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Old 12th April 2009, 06:37 AM   #10
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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/200702182...108_Public.pdf


The Wolfson WM8721 dac;

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


Others Rio Karma web sites;

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

http://www.dapreview.net/p/content/c...hp?content.193

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

http://www.karmalimbo.com/

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

Thank

Bye

Gaetan
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