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Raspberry Pi -A New DIY'ers Digital Hub?
Raspberry Pi -A New DIY'ers Digital Hub?
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Old 29th October 2012, 09:25 PM   #91
linuxworks is offline linuxworks  United States
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if the test show that the i2s is actually competitive in quality to other ways of getting digital audio out, that's great. we'd all love to see it.

but just how likely is it that the $35 computing device is going to be a low jitter source? that's all I'm saying.
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Old 29th October 2012, 10:04 PM   #92
philpoole is offline philpoole  England
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Whether you suspect its low jitter or not, I suspect it's not too relevant as I intend to pass the signal through an oversampler before it gets to the DAC. The DAC needs to be clocked properly, the rest is less important. However, I do also intend to feed PCM_CLK with my own clock, and I plan to power the Pi with a linear PSU.

I also plan to locate the pi in the same case as the rest of the DAC (which normally receives I2S from a transport, and sounds great), so it's not exactly using I2S as an interconnect.

However, I2S is unusable in it's current state, for software reasons.
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Old 30th October 2012, 04:16 AM   #93
qusp is offline qusp  Australia
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happy for you yeah, but that seems like a lot of trouble to go to to use less....which is usually the case in these situations. With your only barometer being that 'it sounds great' with another random i2s source, i'm not convinced. . use the time and money where it maters, the dac. its a whole lot easier to clean up USB than it is i2s, same case who cares, if the PCB and termination is wrong for i2s, a whole world of pain can happen to i2s over a couple cm. you can bet even with an external clock you will be using the pi's PLL

Welcome to raspberry pi ground as audio ground in a single ended dac....

Last edited by qusp; 30th October 2012 at 04:20 AM.
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Old 30th October 2012, 08:34 AM   #94
philpoole is offline philpoole  England
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I have built several DACs before, using I2S. You say USB is easier to clean up, how? It ends up I2S (or some variant) when it enters your DAC chip. So clean up your USB, but if the chip converting to I2S is adding jitter, then surely you're wasting time? How are you tidying up your I2S? In fact, how is your DAC powered? USB power? Walwart?

I like to build my own stuff, this being DIY after all, I2S is more straightforward to deal with from that point of view.

Not entirely sure why I feel I should be justifying my decisions.
If you feel I've highjacked this thread by talking about using the Raspberry Pi to do audio, then I'm sorry, I'll start a new thread (I thought this was a digital source thread, not PC based?).
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Old 30th October 2012, 08:42 AM   #95
pinkmouse is offline pinkmouse  Europe
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Raspberry Pi -A New DIY'ers Digital Hub?
Phil, your project is exactly what I was thinking of when I opened this topic in the first place.
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Old 18th November 2012, 11:15 PM   #96
jij3 is offline jij3  United States
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Neither I2S or async USB are "better". For those of us who build our own DACs, using I2S makes more sense, since the DAC chip inputs needs I2S or something similar. Going through USB to get to the DAC is easier if you are using an off the shelf DAC, granted, since I2S is rarely available as an input. If you are using your own DAC with it's own master clock (and that is the key) then I2S is simpler, more direct, and less likely to add jitter. Yes, I2S has to be done right. I use differential signaling (LVDS) to send I2S data on twisted pair wires from my modified Squeezebox Touch to my DAC and to send master clock signals form my DAC to the Touch. Completely error-free up to 2 meters of cable, using master clocks of 22M and 24 MHz, Touch I2S-out and Clock-in mods.

Phil I am very appreciative of your work. I am interested in using the Pi as a Squeezebox player driving I2S outputs while receiving an exernal I2S clock from my Dac. My Squeezebox Touch does this very nicely up to 96K, but even the most recent DIY kernals, Async USB Dac Experiments - testers wanted..., can't get 176K or 192K on the I2S lines from the Touch. Also, the Pi is $35, while the entire Squeezebox line has been discontinued by Logitech.....
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Old 19th November 2012, 02:07 AM   #97
nathanjh13 is offline nathanjh13  United Kingdom
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Hiya, I have a RPi at work but I haven't fixed it up yet. Intention is to stream music to my external dac (from 3.5 jack to coax using an adaptor).

I think it is possible to install android etc and, with a tablet/android phone, it is possible to use these as touchscreen remotes.

This will be perfect if so as I don't want a pc monitor permanently in the room so once it is initially setup I can lose the monitor (and just leave the device on I suppose).

I'm talking sense here? Has anybody done this (or is looking to do this?).

Essentially, this device will be my "squeezebox touch".


Last edited by nathanjh13; 19th November 2012 at 02:12 AM.
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Old 19th November 2012, 10:01 AM   #98
nathanjh13 is offline nathanjh13  United Kingdom
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If i plug in a 'turtle beach audio advantage micro 2' adaptor to get a toslink option them Im a step closer? Come on don't make me the one that killed this thread.
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Old 30th November 2012, 12:33 PM   #99
trackstand is offline trackstand  United Kingdom
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I *think* you're talking sense but I'm no expert. I've read (somewhere) of a project that controlled the rpi with an app on an android phone. I've not seen any mention of Android on the rpi itself but then you don't need that? I'm following Raspberry Pi • View topic - I2S: Anyone got it running? for getting digital audio out of the rpi but it looks like it's hard. I'm happy to try USB too but I'm not clear whether that's working yet.

Is it possible to get a digital signal out of the 3.5mil jack? Do you have software to do that?
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Old 1st December 2012, 02:56 PM   #100
4est is offline 4est  United States
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I am following this thread with great interest. Although a linux newbie, I have been around audio for a long time. The concept of adding a great clock for the i2s feed and back clocking the rpi sounds like a sweet little deal. Even if it could never compete in the big leagues, it seems a worthy undertaking for a streaming device.
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