Chord Electronics - Blu Mk. 2 - The Official Thread

Discussion in 'High-end Audio Forum' started by ChordElectronics, Jan 5, 2017.
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  1. rayl
    An extreme thought:

    Has anyone tried an RF isolation box? It is an expensive experiment and may be too awkward for normal use (Few 100 off eBay though you can resell the box).... but that will give definitive data on the role of environmental rf entering via the coaxes. Even basic boxes are 50 dB up to a few GHz. Good ones are around 80 dB.
     
  2. Jawed
    Two cheap cables long enough to hold 30 or 40 ferrites each is the experiment I'm suggesting. I'm certainly not suggesting you buy longer Clearer Audio cables!!!!

    In my experience, once you've travelled far enough with RF filtering, you get beyond questions of tonality. Rob has described changes in sound stage rather than tonality (associated with the "2.5GHz" Wurth ferrites).

    As I said earlier, the fact that you can hear differences amongst your 3 sources is proof that you haven't got enough RF filtering. It's a bit of a conundrum for Blu 2 users if it's this difficult to stop RF noise getting into DAVE...

    Now playing: Milla - Clock
     
  3. Triode User
    As we are discussing this in the Blu2 thread I think the issue is not external RF or EMI noise but is noise generated as part of the MScaler processing. This then gets directly into the dual bnc cables. Shielding of the cables as cited for the Clearer Audio cables is therefore not relevant to this discussion. The need is to filter out the noise that is already in the cable and not to try to shield it from noise. I don’t think your idea of trying an RF isolation box would bring anything to the party.
     
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  4. Triode User
    I’m with you on the thought to try the longer cheap cables. I have 2m cables and I feel the need to try a few more ferrite options on these. Basically adding more and of various sorts until no more change is noticed. I have 8 or nine Wurth ones on each from memory at the moment.
     
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  5. rayl
    I missed that subtlety.

    But why would noise from the Mscaler be common mode noise (i.e. be identical on both signal and ground lines)?

    It seems more likely to be differential mode noise which would require something different on the signal vs the ground line. [I edited this line of my comment to more accurately cover the different possibilities.]

    My unit is still some wks (months?) away, but want to get a leg up on best practices.
     
    Last edited: Jan 1, 2018
  6. adyc
    Where do you get the info that the EMI is a byproduct of Mscalar processing? Has Rob confirmed this?
     
  7. Triode User
    Yes, and that is why he suggested a particular frequency of ferrite. If you search you should find his posts regard this.

    Please bear in mind through all this that Rob has also said that we are only talking about fine tuning here of something that works very very well already without any ferrites. In other words it is not a fix for something that is fundamentally broken.
     
  8. rayl
    I am thinking of the comments in:

    https://www.head-fi.org/threads/cho...-official-thread.831343/page-98#post-13705284

    which is indeed about RF noise:

    "The issue here is not so much RF noise per se but when it is correlated with the wanted music signal. What the ferrites do is reduce common mode RF currents from entering Dave's ground plane. My thinking is that the correlated RF gets directly demodulated into a distorted audio signal, and this is responsible for the improvement in depth that I have heard with this treatment. "
     
  9. Jawed
    UELong and rayl like this.
  10. rayl
    Thx for the ref. I did miss this distinction bec I assumed RF meant from the air instead of a reference to the frequency range.

    For education, I am still curious as to why this effect would not lead to differential mode noise needing isolation (as is typical to reduce other switching noise).
     
  11. rayl
    To guess at an answer to my own question, we are speculating that the FPGA action is inducing the noise by proximity instead of by direct conduction into the wires.... I see...
     
  12. Triode User
    See below for the bit that counts and which was supplemented in the post noted by Jawed above.
    “I believe that the issue we have here is not RF from the source (the galvanic isolation should eliminate that) but the actual 768 kHz data signal itself. I plan to prove that with some future listening tests”
     
  13. marcmccalmont
    Isn’t it possible that the cable performance is improving external emi/rfi reduction and the ferrites are dealing with both the external and the Blu2 generated ground noise? Doesn’t really mater the system is sounding great and I believe Dave has excellent jitter rejection but is still somewhat suseptable to phase noise. If you get a chance to hear the ProJect do so it is really special and a great cost effective drive for Hugo2. Now to get my Spectral DMC20 headphone amp to drive the utopias balanced. Dave is an order of magnitude lower in distortion but the high current/damping factor output of the DMC20 did a better job driving my HD800’s let’s see (hear)
     
  14. marcmccalmont
    Oh when I first tried different cables I tried them all with a ferrite on each end since the ferrites on the clearer Audio cables can’t be removed
     
  15. marcmccalmont
    I hear no difference with the MSB, N10 and internal drive all have various levels of jitter but I do hear a difference with the ProJect drive that has astonishingly low phase noise? For what ever reason it is "scraping more details out of the noise floor" than the other sources.
     
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