Apple TV into miniDSP via I2S? - diyAudio
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Old 6th March 2013, 02:55 AM   #1
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Default Apple TV into miniDSP via I2S?

From what Iv'e read and discovered so far is that nobody has fed a minidsp I2S signal without a miniDIGI. I have been tempted to try a apple tv because it samples everything to 48kHz only and that is exactly what the minidsp needs. The only problem is that the clock rate needs to be devided in half for the miniDSP to 12.288mHz from the Apple TV's 24.576mHz clock.
I personally think this would be a very good mod and would keep components down to a minimum including costs this setup would cost $250 and be pretty flexible and great sounding. As everything is bottlenecked at 48Khz.

The Squeezbox Touch requires the 22.5792 MHz clock to generate data streams at 44.4 and 88.8 KHz sample rates, and the 24.576 MHz clock for 48 and 96 Khz sample rates. This complicates things compared to the apple TV running at 48k only.

I found a dual rate clock on our favourite auction site. Now all I need is a pinout or advice on how to locate the CLK sources.

With your help we can make it happen.

Last edited by damuffin; 7th March 2013 at 05:32 PM.
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Old 6th March 2013, 03:20 AM   #2
qusp is offline qusp  Australia
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off you go then ... make it happen

should be interesting, could do it with the minisharc, which I believe has onboard ASRC
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Old 6th March 2013, 01:55 PM   #3
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All that is really needed is a new external clock with dual output. There is no use in stacking a bunch of chips unless you want to introduce noise or spend more money.
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Old 6th March 2013, 03:30 PM   #4
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i'm afraid I have no idea what you mean. for starters, using an external clock and clock division will net you a bunch of jitter right there and I didnt suggest stacking anything; I suggested that you didnt need to send a different clock back to the apple TV if the board you are sending it to is async, as the minisharc is (minisharc is a new miniDSP product, no dacs, just hardcore DSP and i2s outputs). lots more powerful than the miniDSP too, it would not stack, rather replace.

I think you'll find there is a minimum inherent jitter in the miniDSP processor that swamps any tweaks you are thinking of, particularly ones that involve external improperly terminated clocks, which are IMO just a money sink and will not reduce jitter

Last edited by qusp; 6th March 2013 at 03:50 PM.
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Old 6th March 2013, 04:15 PM   #5
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The mini sharc has no dac and samples at 48k. Not that impressive.

Option 2- The miniDIGI will allow me to transmit toslink out of the Apple TV and into the miniDIGI at a cost, Both in price and sound quality. Any time you add a component to a circuit it will alter the sound. Up-sampling, down-sampling, cross talk.etc

There are proven sonic benefits when using a new source for MCLK.(Superclock)

The combo I am proposing is very basic and low cost. $250 for the components needed to stream airplay to a pair of analog amps with active crossovers.

This would be an impressive combo with minimal components. The Apple TV upsamples to 48kHz at the source then bypassing the spdif by pulling I2S and running into the miniDSP dac where it then adds the XO and sends them out in analog. (Keep It Simple Stupid.)

All that is needed is a low jitter curcuit with a 22.5792 clock and a flip-flop divided by 2. to output the 12.288 for the mini.

Last edited by damuffin; 6th March 2013 at 04:25 PM.
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Old 6th March 2013, 04:23 PM   #6
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minisharc will do 96khz when they get around to the plugins I believe, but what does it matter, you were talking about 48khz... its the DSP thats powerful (heres me thinking that was the important bit... but I can be stupid sometimes...), their most powerful DSP in any unit yet and no dac is the good bit. built for i2s in/out, with built in ASRC, also a good bit. pretty darn cheap and small.

but OK, youve got it all figured out, like I said, off you go, make it happen, dont call on others to make it happen with statements 'lets make it happen' nobody else has posted, so looks like its on you...

the miniDSP and apple TV PLL will limit jitter performance; dont bother with external clocking, just divide the clock if you need to.

Last edited by qusp; 6th March 2013 at 04:27 PM.
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Old 6th March 2013, 04:36 PM   #7
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Iv'e put in alot of time to get this far and am very excited to proceed further. I need help and am not afraid to ask. The "Lets make it happen" is implying that I am excited and eager to pursue this project as a team effort with a little help. You have misinterpreted it as "Make It Happen." and as a result made me out to be ........... If you cannot contribute productively to MY post on a DIY forum then by all means feel free not to.
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Old 7th March 2013, 05:33 PM   #8
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What is the best way to divide the clock?
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Old 24th March 2013, 03:54 PM   #9
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Default I2S

Is it possible to tap I2S from a Apple TV box ?

Or any other ways to use a laptop / smart-phone to play audio files wireless with I2S output ?

I am currently working on a DIYINHK ES9018 DAC, so a I2S wireless link would be a PERFECT match :-)
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Old 4th April 2013, 05:49 PM   #10
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So I've opened my ATV3 and realized that soldering any connections would be next to impossible. Also the ATV3 uses a 27.xx clock.

If someone has a broken ATV that they would like to donate to mad science I might proceed further.
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Last edited by damuffin; 4th April 2013 at 05:52 PM.
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