miguelito Posted October 1, 2019 Share Posted October 1, 2019 I have a budget digital scope (Rigol DS1054Z - upgraded to 100MHz bandwidth). I was thinking of a way to produce an eye diagram with it. I only care about 16/44 at the moment, so we are talking a bit rate of 1.44 MHz which isn’t all that much. The few articles/videos I found use more sophisticated digital scopes with clock recovery features, but I am thinking there might be a way to do this regardless: If I trigger on a transition and then look at transitions, say, ten bit-lengths later, I should be able to see something akin to an eye diagram. I don’t really care about absolute measures as much as I care to see, for example, what mods/cables/connectors/cable lengths reduce jitter. And more specifically I am looking at simple mods to a CD transport (Cambridge CXC) to reduce such jitter. So two basic questions: 1- Does this make sense? 2- What signal would you play on the transport to get the maximum number of transitions? White noise should not be such a bad choice. Thx. NUC10i7 + Roon ROCK > dCS Rossini APEX DAC + dCS Rossini Master Clock SME 20/3 + SME V + Dynavector XV-1s or ANUK IO Gold > vdH The Grail or Kondo KSL-SFz + ANK L3 Phono Audio Note Kondo Ongaku > Avantgarde Duo Mezzo Signal cables: Kondo Silver, Crystal Cable phono Power cables: Kondo, Shunyata, van den Hul system pics Link to comment
mansr Posted October 1, 2019 Share Posted October 1, 2019 Have you seen this application note? https://www.sitime.com/api/gated/AN10007-Jitter-and-measurement.pdf Link to comment
miguelito Posted October 1, 2019 Author Share Posted October 1, 2019 31 minutes ago, mansr said: Have you seen this application note? https://www.sitime.com/api/gated/AN10007-Jitter-and-measurement.pdf This is fabulous. Thx @mansr NUC10i7 + Roon ROCK > dCS Rossini APEX DAC + dCS Rossini Master Clock SME 20/3 + SME V + Dynavector XV-1s or ANUK IO Gold > vdH The Grail or Kondo KSL-SFz + ANK L3 Phono Audio Note Kondo Ongaku > Avantgarde Duo Mezzo Signal cables: Kondo Silver, Crystal Cable phono Power cables: Kondo, Shunyata, van den Hul system pics Link to comment
miguelito Posted October 4, 2019 Author Share Posted October 4, 2019 On 10/1/2019 at 5:32 PM, mansr said: Have you seen this application note? https://www.sitime.com/api/gated/AN10007-Jitter-and-measurement.pdf @mansr I got this working although the math part not yet - scope config unclear, would like to do the math on the persisted data in the scope. I could also capture and move the data to the computer and use python to analyze. Thank you. Question: Is the SPDIF input supposed to be terminated? I do have one pass-through BNC 50 Ohm terminator, but not a 75 Ohm. Closer to 75 than 1M obviously. But is it supposed to be terminated? I would have guessed yes... Thx. NUC10i7 + Roon ROCK > dCS Rossini APEX DAC + dCS Rossini Master Clock SME 20/3 + SME V + Dynavector XV-1s or ANUK IO Gold > vdH The Grail or Kondo KSL-SFz + ANK L3 Phono Audio Note Kondo Ongaku > Avantgarde Duo Mezzo Signal cables: Kondo Silver, Crystal Cable phono Power cables: Kondo, Shunyata, van den Hul system pics Link to comment
mansr Posted October 4, 2019 Share Posted October 4, 2019 4 hours ago, miguelito said: Question: Is the SPDIF input supposed to be terminated? I do have one pass-through BNC 50 Ohm terminator, but not a 75 Ohm. Closer to 75 than 1M obviously. But is it supposed to be terminated? What are you measuring? If you have an S/PDIF output simply connected to the scope, you should set the scope input to 75 Ω termination. Link to comment
miguelito Posted October 4, 2019 Author Share Posted October 4, 2019 1 hour ago, mansr said: What are you measuring? If you have an S/PDIF output simply connected to the scope, you should set the scope input to 75 Ω termination. That was my question, thx. My scope cannot be set to anything but the 1M Ohm impedance termination. I have 50 Ohm terminators but no 75 Ohm terminators (easy enough to make one). NUC10i7 + Roon ROCK > dCS Rossini APEX DAC + dCS Rossini Master Clock SME 20/3 + SME V + Dynavector XV-1s or ANUK IO Gold > vdH The Grail or Kondo KSL-SFz + ANK L3 Phono Audio Note Kondo Ongaku > Avantgarde Duo Mezzo Signal cables: Kondo Silver, Crystal Cable phono Power cables: Kondo, Shunyata, van den Hul system pics Link to comment
miguelito Posted October 4, 2019 Author Share Posted October 4, 2019 I am trying to measure jitter by triggering on an edge and then measuring n-th edge std dev. That's all I really care about. NUC10i7 + Roon ROCK > dCS Rossini APEX DAC + dCS Rossini Master Clock SME 20/3 + SME V + Dynavector XV-1s or ANUK IO Gold > vdH The Grail or Kondo KSL-SFz + ANK L3 Phono Audio Note Kondo Ongaku > Avantgarde Duo Mezzo Signal cables: Kondo Silver, Crystal Cable phono Power cables: Kondo, Shunyata, van den Hul system pics Link to comment
mansr Posted October 4, 2019 Share Posted October 4, 2019 1 hour ago, miguelito said: That was my question, thx. My scope cannot be set to anything but the 1M Ohm impedance termination. How odd. It's a pretty basic feature. Link to comment
miguelito Posted October 4, 2019 Author Share Posted October 4, 2019 10 hours ago, mansr said: How odd. It's a pretty basic feature. It's a $349 scope... Frankly it is such a simple feature to replicate with external terminators... Plus it is so easy to blow out a terminator with such a little voltage (eg shouldn't put a voltage higher than 10V on a 1W terminator) that I rather use an external termination than internal... For example: https://www.amazon.com/gp/product/B06XHFGVXM/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 and https://www.amazon.com/gp/product/B01ASF5UHY/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 Easy and safe. NUC10i7 + Roon ROCK > dCS Rossini APEX DAC + dCS Rossini Master Clock SME 20/3 + SME V + Dynavector XV-1s or ANUK IO Gold > vdH The Grail or Kondo KSL-SFz + ANK L3 Phono Audio Note Kondo Ongaku > Avantgarde Duo Mezzo Signal cables: Kondo Silver, Crystal Cable phono Power cables: Kondo, Shunyata, van den Hul system pics Link to comment
miguelito Posted October 5, 2019 Author Share Posted October 5, 2019 Interesting simple measurement: I see a rise time of about 8ns with a Blue Jeans coax cable ($18) vs 12.6ns with an Audioquest Cinnamon ($69). All properly terminated. Thoughts? NUC10i7 + Roon ROCK > dCS Rossini APEX DAC + dCS Rossini Master Clock SME 20/3 + SME V + Dynavector XV-1s or ANUK IO Gold > vdH The Grail or Kondo KSL-SFz + ANK L3 Phono Audio Note Kondo Ongaku > Avantgarde Duo Mezzo Signal cables: Kondo Silver, Crystal Cable phono Power cables: Kondo, Shunyata, van den Hul system pics Link to comment
mansr Posted October 5, 2019 Share Posted October 5, 2019 10 minutes ago, miguelito said: Interesting simple measurement: I see a rise time of about 8ns with a Blue Jeans coax cable ($18) vs 12.6ns with an Audioquest Cinnamon ($69). All properly terminated. Thoughts? The AQ cable has higher capacitance and/or inductance. Both figures are well within spec. Link to comment
miguelito Posted October 6, 2019 Author Share Posted October 6, 2019 15 hours ago, mansr said: The AQ cable has higher capacitance and/or inductance. Both figures are well within spec. Yes, I get that. Now consider the 5ns slope difference, and consider a crossing voltage noise of ~1mV (in the source or the receiver, just back of the envelope). So give or take this means the AQ cable could inherently have jitter that is higher by 5ps. I guess this is not much... NUC10i7 + Roon ROCK > dCS Rossini APEX DAC + dCS Rossini Master Clock SME 20/3 + SME V + Dynavector XV-1s or ANUK IO Gold > vdH The Grail or Kondo KSL-SFz + ANK L3 Phono Audio Note Kondo Ongaku > Avantgarde Duo Mezzo Signal cables: Kondo Silver, Crystal Cable phono Power cables: Kondo, Shunyata, van den Hul system pics Link to comment
mansr Posted October 6, 2019 Share Posted October 6, 2019 56 minutes ago, miguelito said: Yes, I get that. Now consider the 5ns slope difference, and consider a crossing voltage noise of ~1mV (in the source or the receiver, just back of the envelope). So give or take this means the AQ cable could inherently have jitter that is higher by 5ps. I guess this is not much... The clock recovered by typical S/PDIF receivers has much higher jitter anyway, the best specs I've seen being 50 ps rms. Link to comment
miguelito Posted October 6, 2019 Author Share Posted October 6, 2019 2 hours ago, mansr said: The clock recovered by typical S/PDIF receivers has much higher jitter anyway, the best specs I've seen being 50 ps rms. Ok... Compared to specs from high end DACs this looks awful! NUC10i7 + Roon ROCK > dCS Rossini APEX DAC + dCS Rossini Master Clock SME 20/3 + SME V + Dynavector XV-1s or ANUK IO Gold > vdH The Grail or Kondo KSL-SFz + ANK L3 Phono Audio Note Kondo Ongaku > Avantgarde Duo Mezzo Signal cables: Kondo Silver, Crystal Cable phono Power cables: Kondo, Shunyata, van den Hul system pics Link to comment
Arpiben Posted October 7, 2019 Share Posted October 7, 2019 In case you don't have it already this J.Dunn document may help you: http://www2.electron.frba.utn.edu.ar/~jcecconi/Bibliografia/13 - Medicion de Amplificadores/Documentos/AudioPrecision_AN5_DigitalAudioMeasurement.pdf Jud 1 Link to comment
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