Chord Electronics - Blu Mk. 2 - The Official Thread

Discussion in 'High-end Audio Forum' started by ChordElectronics, Jan 5, 2017.
  1. Jawed
    Yes. But the only noise that affects DAVE is common-mode noise. So the ferrites filter that. If you use enough ferrites, then the construction/materials of the cable make no difference.

    Unfortunately all you've proven so far is that common mode noise is still spoiling DAVE's sound in your system. If the ProJect sounds different, it's because of common-mode noise.

    What's phase noise? Sounds like you're talking about noise that causes jitter:

    Variation in the precise timing of the rising and falling edges of a digital signal are what's traditionally called jitter and "phase noise" is the crud that appears in an eye diagram and which leads to the rising and falling edges moving around and changing slope, which is the cause of jitter.

    Rob says that jitter has the effect of increasing noise in the pulse array, but it's not signal correlated noise. Rob hasn't said how loud that noise could be and whether it has any effect on sound quality. It might have an effect on sound quality, given that DAVE is affected by ultra-sonic noise that's typically part of the "music" (in high resolution recordings), and which is why DAVE has the HF Filter.

    The jitter that Rob's referring to may be systemic jitter within DAVE, rather than jitter originating in the digital source input, as it appears DAVE doesn't use rising/falling edges to decode the digital input.

    Now playing: Transient Waves - Blackjack
  2. marcmccalmont
    The ferrites are to reduce ground plane noise in Dave generated by Blu2’s fpga after a calculation. (PM with Rob) the ferrites also help reduce noise on the signal and so does good multilayer shielding. The longer the cable the more the ground plane noise is attenuated but the greater the exposure to emi/rfi I agree a cheep long cable will solve the first issue but good shielding will solve the second issue that is present in all systems not just Blu2/Dave I’ll put it to the test when I have time
  3. Whazzzup
    really, new to me.
  4. marcmccalmont
    All digital transmissions are suseptable to noise that’s why cable manufacturers go to great lengths to shield their coax. I admit hi-end audio cables are overpriced and don’t necessarily perform to their price point but I have built many cables and if it is done manually it takes time and I have not built one yet that performs like the Clearer Audio coax. For me I don’t have room to lay out a pair of 1.5m to 2m cheep cables lined with bulky ferrites so instead I’m trying to find an optimum balance between a well shielded cable with the best performing ferrites at a reasonable length (between Blu2 and Dave). The coax between my sources and Blu2 is another issue. USB is another issue I wish I could get the usb input to Blu2 to sound as good as the coax but not yet and I wish Blu2 had a tos input the lifatec tos cable works really well with Hugo2
  5. Whazzzup
    antipodes to TT your good to go course it isn't blu2 to dave.... I use a 3 ft oyaide continental cause my 1.5 ft audio quest diamond isn't long enough. But both worked fine as an FYI
  6. Triode User
    With a Zenith SE the USB input to the Blu2 sounds at least as good as the CD played on the Blu2. I don't think (unless shown otherwise) that any USB cable can make up for the quality of a quiet source such as the Zenith SE.
  7. marcmccalmont
    Yes of course but let’s not ignore emi/rfi in your environment WiFi wall warts tv etc
  8. marcmccalmont
    And I was thinking ferrites probably need to be sized correctly on the outside of your cable so the magnetic field permeates the ferrite symmetrically and as close to the shield as possible
  9. marcmccalmont
    So we have
    1. noise generated by the source
    1a. Jitter/phase noise from the source
    2. noise in the environment
    3. Blu2 fpga ground plane noise
    Let’s try to minimize all of these to the point Blu2/Dave sounds it’s best.
    I think I’m getting close because my system has never sounded so good!
  10. marcmccalmont
    Have you compared the zenith to the Aurender N10? The Aurender sounds and measures very well ovenized clock etc I have not had a chance to hear the zenith
  11. Triode User
    Not sure that is the case. None of the manufacturers specs suggest that is necessary. Indeed often a range of cable diameters is quoted as being suitable and is more likely based on just on physical size constraints than what you mention. If one looks at ferrites with multiple turns of wire through them then there seems little to support your hypothesis. However, I have no technical expertise here!
  12. marcmccalmont
    I discussed it with a Fair Rite application engineer. The more the ferrite is emersed in the magnetic field (physically closer) and the better the 90 degree alignment (right hand rule cylindrical shape) the more effective the ferrite. He also was tactful when he stated “ I think you will find the Fair Rite 61 ferrites are more effective at your frequency of concern (2GHz) than other manufactures” this aligned with my recent observation. Remember I started this journey thinking a ferrite is a ferrite (just iron oxide cintered into a cylinder) and the low cost ones are fine. Once again I’ve proven myself wrong it’s not so simple! Years ago when I was designing loudspeakers a Bell Labs engineer gave me the advice “try to prove yourself wrong if you can’t then you are correct it is easy to prove yourself correct most people do” I started off favoring simple crossover networks, ridged cone materials transmition line/ported bass, tube amplifiers. By proving myself wrong I’m now a polypropylene cone, steep-slope xover, sealed box,fast solid state amp .... Chord DAC person!
    Last edited: Jan 2, 2018
  13. Jawed
    Yes I can see how a pair of 1.5m cables hung with say 30 ferrites each is awkward! Especially if you've got a BluDAVE stack on the Chord stand.

    Because you have so many sources I suppose you have, at least, the best chance of determining whether it's possible to negate all the differences amongst them by using cheap BNCs with 30 or more ferrites...

    A tighter fit is definitely better. But once you have used 10s of ferrites (so that you're in the target range of 4000+ ohms, if possible) it's probably moot.

    Winding a cable multiple times through a ferrite (not the clip-on style of ferrite, but a solid cylinder or ring) will substantially increase the impedance (similar to string multiple clip-on ferrites along a cable), but will also substantially reduce the resonant frequency and shorten the range of frequencies that are most strongly filtered. Using multiple clip-on ferrites doesn't result in the resonant frequency shifting.

    I can't remember if you were active in this thread back at the end of summer:

    There's lots of other posts back then, other PDFs to read. And some very educational videos. Some of this stuff is on the DAVE thread from around the same time.

    Now playing: Julianna Barwick - Choose
  14. etnt
    I'm using Belden 7731a with canare bnc to connect the blu and dave. This is a RG11 cable with extremely low loss.

    The connection is stable compared to stock which have a tendency to drop-out if touched (and the d.bnc will blink). Soundstage seems wider than stock.

    Have some TDK ferrite cores on hand (without specs, they are found in a basket at a local hardware store) but have not tried them yet as the sound is really great now, and I don't have the urge to further mess with it.
  15. Jawed
    This is a valuable report because ferrites have been a solution for this problem up until now and this seems to indicate that it's possible to find extremely well constructed cables that also help. Presumably each cable was very cheap, less than £20?

    I suppose you still have to deal with the RF noise that Blu 2 is making, so it seems ferrites are unavoidable.

    Now playing: Dire Straits - Private Investigations

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