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Old 20th May 2012, 04:23 PM   #791
shoom is offline shoom  Europe
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Hi Hochopeper
Good info on the u fl checks
Thanks
Glad to hear that you have things sorted
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Old 21st May 2012, 01:49 PM   #792
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Quote:
Originally Posted by hochopeper View Post
These micro coax cables have a limited number of connect/disconnect cycles that they last for, saving any unnecessary activity on these is worthwhile.
Thank you for this valuable info. I completely missed it. 30 cycles are a very few indeed.
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Old 22nd May 2012, 04:20 PM   #793
Wolfsin is offline Wolfsin  United States
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Ryelands has helped me change my thinking about control for the Wolfson DACs. They need not allow external power so the following post was incorrect.

Quote:
Originally Posted by Wolfsin View Post
Let me add one more restriction on the USB to i2c converter -- I must be able to power it externally.
When using the WM8740, one needs SPI rather than i2c but the 8741 accepts either. The Diolan line of interfaces seem well suited, allowing either i2c or SPI together with enough GPIO to read WaveIO status and provide chip select for dual mono opus. ADum140x isolation for 12 bits between Diolan and WaveIO is better than USB isolation in this case but because of the added jitter, ADum4160 USB isolation is probably superior between PC and WaveIO.
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Old 23rd May 2012, 05:36 PM   #794
orpheus is offline orpheus  United States
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Default Measurements?

"Quote: (from Spencer)
How does the measurements compare to the XMOS reference design? I means at SPDIF out and I2S out? Any graph comparison is good especially on Jitter and noise figures. If possible, please show how the test is conducted and equipment used.

Thank you

reply: (from Lorien)
When I'll have the required informations I'll post them asap. For now, there are two members of this forum which could do noise and jitter tests and I'm still waiting an answer."

This was posted almost a year ago, in June 2011. Has anyone posted measurements? I have searched this thread and I haven't been able to find them. If they are available, could someone post a link? I am very interested in seeing the jitter measurements of the WaveI/O and the XMOS Reference Design. I found these measurements of the Reference Design, in case anyone is interested.

Thanks!
Aaron.
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Old 23rd May 2012, 05:45 PM   #795
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Quote:
Originally Posted by orpheus View Post
"Quote: (from Spencer)
How does the measurements compare to the XMOS reference design? I means at SPDIF out and I2S out? Any graph comparison is good especially on Jitter and noise figures. If possible, please show how the test is conducted and equipment used.

Thank you

reply: (from Lorien)
When I'll have the required informations I'll post them asap. For now, there are two members of this forum which could do noise and jitter tests and I'm still waiting an answer."

This was posted almost a year ago, in June 2011. Has anyone posted measurements? I have searched this thread and I haven't been able to find them. If they are available, could someone post a link? I am very interested in seeing the jitter measurements of the WaveI/O and the XMOS Reference Design. I found these measurements of the Reference Design, in case anyone is interested.

Thanks!
Aaron.
Measuring jitter is not a trivial matter. Very few people have the equipment and expertise to accurately measure jitter levels, and provide an actual jitter spectrum plot. Additionally, comparing jitter measurements can be a real problem: only measurements using the exact same equipment and methodology should be used for actual comparisons. Also, becuase the WaveIO is a DIY product, how it is implemented will also effect the output jitter levels (power supply, I2S wiring, perhaps even the USB cable and computer source), so jitter levels/spectrum and clock phase noise may all vary somewhat with different implementations.
I would love to see some measurements (hopefully on a WaveIO with the NDK oscillators), but the only comparisons which I would be willing to suggest coiuld be valid, were measurements taken with the exact same approach.
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Old 24th May 2012, 07:03 AM   #796
waltube is offline waltube  Italy
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I suppose that the only lab that can do this is Audioreview's lab ( it is an italian magazine where I have a collaboration)
In this lab there is an Audio Precision 5xxx family; Fabrizio Montanucci, the technical director, fix two specific tests: periodic jitter and stocastic jitter.
Very interesting!

Now I have ready a dac with Buffalo II dac , with Lorien board connected in I2s; the output is tube with a Sowter 3565 trafo from dac to output.
It will be measured in next days because I am trying to write an article on it

Bye

Walter
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Old 24th May 2012, 07:36 AM   #797
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Hi Walter,

Was wondering if you could make note of the XO installed on your waveio and include that with any published measurements please since these are not the same on all waveio.
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Old 24th May 2012, 11:15 AM   #798
Telstar is offline Telstar  Italy
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Quote:
Originally Posted by hochopeper View Post
Hi Walter,

Was wondering if you could make note of the XO installed on your waveio and include that with any published measurements please since these are not the same on all waveio.
+1
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Old 24th May 2012, 03:04 PM   #799
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Quote:
Originally Posted by waltube View Post
I suppose that the only lab that can do this is Audioreview's lab ( it is an italian magazine where I have a collaboration)
In this lab there is an Audio Precision 5xxx family; Fabrizio Montanucci, the technical director, fix two specific tests: periodic jitter and stocastic jitter.
Very interesting!

Now I have ready a dac with Buffalo II dac , with Lorien board connected in I2s; the output is tube with a Sowter 3565 trafo from dac to output.
It will be measured in next days because I am trying to write an article on it

Bye

Walter
Are you going to have the jitter measured as a product of the analog output of the entire DAC (how John Atkinson at Stereophile measures it?). If so, remember that the B-II has an onboard masterclock which re-clocks everything in the ASRC of the ESS chip, so this type of measurement will not be measuring the WaveIO, but instead, the B-II (unless you set your B-II up for synchronous operation by defeating the onboard oscillator and feeding it masterclock from the WaveIO).
It would be interesting to see jitter measurements of the direct I2S feed from the WaveIO, and to compare the isolated and non-isolated outputs. I believe the Wavecrest Analyzer is the right tool for this measurement (please those who know something about really measuring relevant aspects of jitter feel free to educate us)?
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Old 24th May 2012, 03:55 PM   #800
1audio is online now 1audio  United States
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The Wavecrest is a useful tool but not the best for this type of measurement. You are looking for the phase noise spectrum to get any real information. That is very closely related to the plots published in the Stereophile. The Wavecrest looks at the cycle to cycle spread of the master clock and essentially analyses its variations. It also measures across the entire hf spectrum. Its much less sensitive to low frequency variations however.

The most accepted way to measure the phase noise of the clock is using a phase locked reference clock and a double balanced mixer along with a low noise amplifier etc. into an audio spectrum analyzer. You need a really good reference clock, which can be difficult to find or really expensive. There are several tools for converting the measured phase noise into jitter. Phase noise above 2X the sample rate will not contribute to jitter in the output. There are a lot of questions about the audibility of low frequency phase noise since its contribution is attenuated by the process and peoples sensitivity to pitch modulation is well documented (from tape and disk studies) and way higher that anything from these processes.

The important thing to look for is deterministic jitter, the specific identifiable tones that come through. These can be much higher than the random jitter and may be audible at much lower levels.

While its interesting to see what jitter is in the clock its more meaningful to see what comes through to the output of the system, since this is the cumulative effects of all the jitter mechanisms upstream. ASRC's can remove some jitter problems but they will also permanently imbed others into the stream.
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