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Old 26th May 2012, 06:23 PM   #831
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Default The...

Quote:
Originally Posted by rsdio View Post
Sorry, but if it were possible to reconstruct a jitter-free clock in software, then this problem would have been solved long ago. What you're describing are data techniques, and there is no challenge to figuring out which header pattern is which. The final product must be a perfect clock, and the kinds of timing errors that produce jitter are way faster than can be corrected in software. Jitter is measured in nanoseconds and picoseconds, and you can't create a clock signal in software with that level of accuracy. It's basically the wrong solution set for the problem. Keep in mind that audio samples are timed in milliseconds and microseconds, which are a couple of orders of magnitude larger than clock signal timings.

In other words, the "compare and select" process in software would take longer time than the actual timing errors that already exist in the clock.
Approach I am trying to describe was proposed to be used in conjunction with a truly asynchronous buffer, where the samples would be clocked out with a fixed oscillator, and no PLL(s) necessary... Unfortunately, I am clearly not adequately describing this approach...
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Old 27th May 2012, 08:43 AM   #832
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Quote:
Originally Posted by Ryelands View Post
5. The last step was to restore the ADuM4160 isolator. Here there is a snag - I couldn't get it to work with the WaveIO even using a stock USB cable. I don't know why this is - there's nothing wrong with the isolator but the computer cannot see the WaveIO with the isolator in circuit. I repeated the test on a different computer with the same result. Any guidance would be appreciated.
I'm very interested in this thing. I'm waiting for a ADuM4160 isolator to be delivered and this incompatibility could be a problem, if confirmed. Is there anyone who have used ADuM4160+WaveIO successfully?
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Old 27th May 2012, 12:01 PM   #833
jrling is offline jrling  United Kingdom
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Originally Posted by Jogi View Post
Ryeland, if possible, try a Linux system, it is even possible to run it from USB stick or create a double boot system, so you can use both. I found especially XP very mediocre, to put it mildly, even with Asio and many tweaks.
I am running Windows 7/Foobar2000 with good results on a Tranquil PC T2E (Intel D510 dual core 1.6 GHz Atom); have just received my WaveIO and would like to try a Linux 'transport' driving it out to S/PDIF being my only choice with my Chord DAC64 MkII. Whilst I am proficient at getting around in Windows, Linux pretty much stops me in my tracks.
Are there any 'plug & play' Linux transport systems that one could boot from USB stick without the need for difficult and off-putting configuration? I just want to try it to see if it is materially better SQ than my tweaked WIndows 7 and Foobar2000.

Many thanks for any advice

Jonathan
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Old 27th May 2012, 04:35 PM   #834
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Default Jonathan...

What you will want to do is use voyage/mpd on linux for playback. This gives really great sound quality, and should be entirely compatible with the WaveIO.
Unfortunately, it is not "plug and play" easy, and if you are not fairly competant with computers, you may need some help setting it up. Do you have any local friends who are used to working with linux?
There are very detailed threads on voyage/mpd set up at the Audio Circle and Computer Audiophile forums. While set up can be tricky (I had a friend do mine, as I am not great with computers), it will be worth the effort for the sound quality which is possible, I highly recommend making the effort.
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Old 27th May 2012, 04:47 PM   #835
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Default Lorien...

Great to hear that you are considering putting the oscillators on the outside of the isolators for a "mk II" WaveIO project. I think this is a great idea, and will remove one small "compromise" in the current design. I would suggest that feeding the masterclock back to the XMOS side would best be done via a transformer rather than through an gmr or opto type device (according to Demian's words here).
Then perhaps you could provide a separate power supply input (which could be optional) for the oscillator power supply alone. Perhaps the oscillators could be mounted on a small daughter board to allow for easy clock rolling! A micro bnc for masterclcok output direct to the DAC would be great.
With this approach, the DAC would get the lowest possible MC jitter, and the output of the WaveIO could be isolated. This sounds like a win/win solution to me, and while I am sure it will add to the price, the additional expense should be well worth it to those looking to achieve the absolute highest possible level of performance.
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Old 27th May 2012, 05:01 PM   #836
Jogi is offline Jogi  Germany
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Jonathan,

Voyage should be the best solution, as Barrows stated, but I failed to get along with it, without help one can easily get lost in the Linux world.
Much easier would be downloading a USB installer like this one:
Universal USB Installer – Easy as 1 2 3 | USB Pen Drive Linux
and then creating a bootable stick with one normal Linux OS; Linux Mint 13 : The Linux Mint Blog Blog Archive Linux Mint 13 “Maya” released! or, smaller, Xubuntu :
Get Xubuntu Xubuntu.
They both should work out of the box. Windows 7 is a lot better than XP soundwise, so maybe there is no big difference unless you tweak the Linux with another Kernel and some scripts.
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Old 27th May 2012, 06:42 PM   #837
rsdio is offline rsdio  United States
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Quote:
Originally Posted by barrows View Post
Approach I am trying to describe was proposed to be used in conjunction with a truly asynchronous buffer, where the samples would be clocked out with a fixed oscillator, and no PLL(s) necessary... Unfortunately, I am clearly not adequately describing this approach...
I think you're missing something. If you have a fixed oscillator, then you either need flow control, which necessitates bidirectional communication that is missing from SPDIF, or you will suffer underflow / overflow eventually. You can have a really long buffer - enough to hold an entire CD - but then this becomes annoying to wait for the buffer to fill every time you select new media. The solution is flow control signaling so the DAC can tell the source to speed up or slow down to match the fixed oscillator.

Again, you seem to be talking about data techniques (buffering) when we were discussing the possibility of software techniques for synchronizing two clocks. You described a hypothetical software algorithm that would look at the actual SPDIF headers and somehow compare them to an ideal. But not only is that not possible to implement, but it doesn't make sense if you have a fixed oscillator (as you mentioned this time). Examining the SPDIF header timing only makes sense if you have a non-fixed oscillator that you want to adjust in frequency to match the incoming clock.

Perhaps we're having terminology issues in the discussion, or perhaps you need to study digital circuit design in detail to understand the challenges of creating a low-jitter clock in an actual circuit.
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Old 27th May 2012, 10:26 PM   #838
jrling is offline jrling  United Kingdom
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Quote:
Originally Posted by Jogi View Post
Jonathan,

Voyage should be the best solution, as Barrows stated, but I failed to get along with it, without help one can easily get lost in the Linux world.
Much easier would be downloading a USB installer like this one:
Universal USB Installer – Easy as 1 2 3 | USB Pen Drive Linux
and then creating a bootable stick with one normal Linux OS; Linux Mint 13 : The Linux Mint Blog Blog Archive Linux Mint 13 “Maya” released! or, smaller, Xubuntu :
Get Xubuntu Xubuntu.
They both should work out of the box. Windows 7 is a lot better than XP soundwise, so maybe there is no big difference unless you tweak the Linux with another Kernel and some scripts.
Thank you to both Barrows and Yogi.
I will give it a go.
I am good with Windows but need to learn Linux which is a useful skill to have anyhow.
Fortunately, I work for a computer software company, so have a number of 'friends' there who could help me!
I find W7/Foobar very good and even more so with minimising tweaking to only a fairly small degree. If Linux can better that, I will be very pleased.
Jonathan
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Old 27th May 2012, 11:16 PM   #839
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Default Not

missing anything:

"I think you're missing something. If you have a fixed oscillator, then you either need flow control, which necessitates bidirectional communication that is missing from SPDIF, or you will suffer underflow / overflow eventually. You can have a really long buffer - enough to hold an entire CD - but then this becomes annoying to wait for the buffer to fill every time you select new media. The solution is flow control signaling so the DAC can tell the source to speed up or slow down to match the fixed oscillator."

The Genesis digital lens did exactly this, back in the day when it was much more difficult (lack of memory, and not much in the way of DSP chips). You use a large memory cache, and control the loading of data into the memory using software without any changes to the fixed rate at which data is clocked out of the memory. The software keeps enough samples in the memory to insure that you never have "underflow". Of course, you cannot run this indefinitely, but even 8 Gb of memory is easy to have these days, and no, you do not have to wait for an entire album/playlist to load to begin playback either, you just let enough load to be sure that you will not "underflow", considering SPDIF is limited at 192 kHz, this will just be a very brief moment.
As long as one is not trying to playback many hours of gapless tracks the asynchronous, with fixed oscillator output, buffer can work without any problems (with adequate memory) without having to be bi-directional. This is the best solution for SPDIF, but as mentioned, I agree that async USB is a more elegant solution (with bi-directional control).
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Old 28th May 2012, 12:29 AM   #840
PET-240 is offline PET-240  Australia
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Jonathan,

I am still getting my Linux server going, looking at voyageMPD and MPDpup, pup has alot of wizards which makes setting up the compact flash card easy. If you run it off a USB drive to start, but long term get a headless pc board like an Alix or soekris and run off CF, keep the USB bus for just the dac. The soekris may have a SPDIF out, the Alix doesn't. Since the wave is XMOS, Linux sees it just fine. And it's USB.....Current ALSA drivers allow 24/192, this could change if you can configure OSS, then I'm not sure of max resolution of the WaveIO.
The Alix is $130 us from pc engines, the soekris I didn't look at. Not having excess Wchips and processes on the board does make foRr a server dedicated to serving off the network. Local disk is possible, but this may affect SQ.
Can post some links as required. I like the Linux option as it can be run as an appliance, turn it off when done, but it's such a low power device, may just stay on!
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