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Discussion in 'High-end Audio Forum' started by magiccabbage, May 14, 2015.
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  1. Rob Watts
    Yes it is grounded - via a wire to chassis aluminium block, then each spacer from chassis to the PCB's ground planes.
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  2. romaz
    Here is what Rob had to say about the USB VBUS +5V issue that you believe is a problem:
    "No don't worry about the USB VBUS +5v, as it too is isolated from Dave."
    Recently, having purchased my LPS-1, I also purchased a W4S Recovery (a USB regenerator that combined with the LPS-1 provides a very clean +5V VBUS that is devoid of leakage current).  I bought this mainly for a USB hard drive to see if it would improve SQ (and it didn't and so I sent it back).  While I had it, I connected it to DAVE and it made absolutely no difference.  Zero.
    There has been much talk about the deficiencies of USB compared to other modes of transmission (SPDIF, AES, AOIP, etc) and it's true that USB has problems but they can be overcome and you don't need to add a dozen trinkets to your USB chain to overcome them if you have a DAVE.  Very rarely will you see DAC manufacturers boast of their USB input over their other inputs.  It's often the opposite and so USB is often added more for convenience's sake.  If you pour through the AOIP or RedNet threads here on Head-Fi and other forums, it seems the consensus is that USB is dead in the water.  "Long live AOIP."  That may one day happen, especially if Rob decides to one day incorporate an ethernet input into the DAVE but as of right now, the best source I have heard is a USB source.
    LIke so many others, I understand you have not had good experiences with USB in your system but what I would suggest is that you spend some time with the DAVE and decide for yourself if Rob has overcome these issues that you talk about because I believe he has.  Of course, you will also want to make sure you have a good low-impedance music server paired with a good low-impedance PSU and lastly, a proper USB cable that meets spec.  That's all I use.  My setup is fairly simple.
    As for a proper USB cable, as you know, there are literally dozens out there and I'm sure everyone has their opinion on which one sounds best.  Here's the thing, most audiophile USB cables regardless of price don't even meet proper USB 2.0 spec.  Most companies seem to focus on expensive conductors and shielding.  Some will separate the power and data lines.  These are all good things but ask these manufacturers what the measured differential impedance of their cables are and whether they take individual measurements of every USB cable they make since there will be variances from cable to cable as well as variances among cables of different lengths.  The answer will likely be that most manufacturers don't take individual measurements because it isn't an easy thing to do.  The assumption that most manufacturers make is that if a signal is being passed without interruption, the impedance must be where it needs to be.  This logic is fine for laser printers but not for high-end audio.  There are even some boutique USB cable manufacturers who don't believe in taking measurements because they tune their cables "by ear."  There's a reason why a coax SPDIF cable should measure 75 ohms impedance and why an AES/EBU cable should measure 110 ohms impedance, otherwise, you get reflections that will have a negative impact on SQ.  Same thing applies for USB cables.  
    According to Gordon Rankin, an electrical engineer who was the first to implement asynchronous USB in a consumer DAC and is regarded by many as one of the world's best authorities on USB tested about 30 audiophile USB cables and surprisingly, most did NOT meet USB 2.0 spec which means that a cable must have a differential impedance of 90 ohms.  He says that unless this parameter is met, the USB feedback mechanism doesn't work because reflections get the signal confused on the computer end. Without it, there's no way for the computer to know that it's sending the data at the proper rate and bits get dropped. Since USB receivers have no error correction, a dropped bit gets interpolated at the DAC, and distortion increases. 
    Exactly which companies measure the impedance of each USB cable they manufacture to make sure their cables meet spec?  I know of quite a few who don't (and I intentionally won't publically name them) but I can verify that Clarity Cables based in Wichita, Kansas does.  This is a small outfit run by a husband and wife.  Chris Owens (the husband) is an electrical engineer and he makes each USB cable he sells by hand and measures each cable to make sure they meet full USB 2.0 spec.  Aside from applying heavy shielding and separating his data and power lines, there's no real magic ingredients used (he uses only standard oxygen-free copper).  Thus far, this is the finest USB cable I have heard.
    Here is a recent interview with Gordon Rankin on John Darko's website.  I believe you will find it to be an informative read:
  3. analogmusic
    Ok so what is the most reliable cable for bit perfect data to Dave?
    Optical, Coax or USB?
  4. romaz
    Rob can capably defend himself but I suspect he'll choose not to.  Personally, Rob has taught me quite a bit about how to listen critically for differences.  If you haven't read his piece on "listening," you should.  It's a marvelous read:
    I don't think it's a secret to anyone that Rob is a one man show.  He doesn't have a giant development team that helps him tune the sound of his DACs.  He uses only his ears and as DAVE is a product of those ears, I would say his hearing is fine.  It's easy for many who have never spent quality time with the DAVE to dismiss it based on its small size, small price tag (relative to other TOTL DACs) and because it uses a switching PSU but those that dismiss it based on such pre-conceived biases will miss out on a wonderfully transformational experience.
    x RELIC x likes this.
  5. romaz
    They each have their problems but with care, they can all sound good.  Ultimately, I would love to see a DAVE or an outboard scaler for the DAVE with an ethernet input that bypasses all of the above similar to MSB's Network Renderer or dCS's Vivaldi Upsampler.
  6. halloweenman
    Just to follow up on this. I tried Pure Music and hated it. It sounded very good, when it worked! The user experience is horrible and the software and remote app are littered with bugs. It is also dependent on iTunes.
    The good news though is that I also tried a free trial of Roon. Here's what I said in the TT forum:
    "Wow, just had a play and listened to free trial of Roon. Absolutely head and shoulders above anything else I have tried for user experience and at least as good if not better for sound quality. Very impressed. Shame it costs so much!
    One thing that is great - you can setup so that it outputs true bit perfect 44/16 output to TT when playing 44/16 ALAC files. Audirvana and iTunes apply conversion to 32 bit with TT. It also has internet radio (Hi Def 6 Music here I come!) and a great ios/andriod remote app. All in all perfect for my needs."
  7. Hubert H
    Hi halloweenman,
    You can listen to all the BBC channels at 320kbps already with the following links, courtesy of Steve Seear;
    http://steveseear.org/high-quality-bbc-radio-streams/ - I use either Foobar or JRMC for this content.
    I listen to 6 Music occasionally via the 320kbps stream and it is noticeably better, unfortunately I have a slow internet connection so need to use DAB more often than not.
    It seems that iPlayer radio also outputs at 320kbps
  8. gnomen

    Ha, ha!  Yes, the user experience is challenging once you go off piste, that's for sure.  Out of the box defaults are pretty good, though, and I am not aware of any bugs.  The main design strength of Pure Music IMHO is that it DOES work very well with iTunes: it completely takes over the sound production while allowing iTunes to do all the file management as usual.  So if your library is in iTunes already, you can get audiophile sound without making any other changes.  And you get the bit perfect file delivery you describe with Roon.  How did you find the SQ compared to your previous software?
    Roon looks very tempting, but as you say expensive as well.   Would you need to move your music files from iTunes to Roon if you adopted it?
  9. halloweenman
    Thanks, good to know.
    I use the official BBC stream :
  10. halloweenman
    Hi Gnomen, both Roon and Audirvana automatically read and playback the itunes library, you don't have to do anything - keep using iTunes as your library.
    I'll give you one bug example, the PM remote app kept failing to control the music correctly, all sorts of weird things happened.
    As far as sound quality goes, it was difficult to assess as I did not listen for very long after experiencing issues. It did not sound any worse.
  11. Arpiben
    With all due respect, I would like to add the following regarding USB 2.0 cable's caracteristics & impedance:
    - cable impedance accuracy matters only if you are matching impedances at both cable ends.
    USB 2.0 specs are something like 90 Ohms +/- 15% differential for USB cables/PCB lines/Ins & Outs.
    Using a perfect USB 2.0 90 Ohms +/- 1% is, IMHO, a non sense if you have no idea or control of digital player / DAC output/input  impedance tolerances.
    Using an USB 2.0 really compliant with specs is important.
    - Rare are the cable manufacturers providing relevant data. By relevant data I am meaning eye pattern at usage bit rates.
    But again, if they provide it will be in the best possible conditions: ex load of 90 Ohms +/- 1% at Input & Output
    - You may have a cable in between the USB termination with excellent specs but usually this is spoiled by impedance matching or even cable diameter matching when reaching the USB or micro USB connector....
  12. rkt31
    i am not expert but as far as I know in asynchronous data transfer there is little chance of fault in transferring the data . if impedance accuracy has an effect then such cable should not copy the file correctly.
  13. Arpiben

    Regarding data integrity, impedance accuracy is having a greater role when increasing bit rates or cable lengths.
    Dealing with short USB2.0 compliant cables you shouldn't have issues.

    Pay attention that asynchronous transfer doesn't mean that data is resent after error detection at DAC level...Chord DACs do request the erroneous paquet to be resent when using ASIO Chord driver.

    Bad impedance matching increases Jitter even when not altering data integrity.

    My point was when looking at impedances matching one should look not only at cable level but also at DAP & DAC.
  14. JaZZ Contributor
    After almost one year of ownership I'm still in love with my DAVE. Fantastic sound quality and ultimate reliability. But a few minutes ago it was doing something strange: it reduced the volume continuously by 6 dB, from –15 to –21, within about three seconds, as if somebody was turning the volume knob. I was listening with eyes closed, so couldn't see anybody/anything (I'm definitely alone in my apartement, and the door is locked). BTW, it was around 18:18 CET, and I was listening to Peter Hammill's «Golden Promises» (from «The Storm after the Calm»). Maybe somebody has an explanation?
  15. romaz
    Yes, I agree with you.  I would love to have an eye diagram of my cable in my system at Redbook rates and beyond.  While some things matter more than others, it would seem that everything matters nonetheless and so I have come to value simplicity.  The less moving parts, the better and the shorter the signal path, the better.  I also believe that unless you find and address your bottlenecks, your system will be limited to its weakest link which is often something as simple as a USB cable.  I think Gordon Rankin's point is that if manufacturers aren't abiding by a spec that they're supposed to abide by, then you get unnecessary variances which is why some cables can sound better than others.
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