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How to stop USB noise in my DAC from my Laptop (mac)

Discussion in 'Sound Science' started by indigo bob, Jan 27, 2017.
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  1. Indigo Bob

    That's a good question...
    1.  There is definite static that occurs as a result of the Rig being next to the laptop with the wifi is on.  That's 100% of the time and correlates completely with the wifi being on or off.  The background high-pitched hum does seem to arise significantly when the rig is on or next to the mac.  This I would want to make sure to test more, but i can say yes to that.  It is more substantial when the HVA DAC is plugged into the USB port.  But this has only been after 2 trials.
    2. The headphone jack sounds normal.  There is still some static interference, but no background noise problem with the high pitch sound.
    3.  Yes, when I face the HVA DAC rigged to the X3ii face down to the keyboard, the static interference is much worse, but the background noise doesn't seem to take a hit..  The background noise seems more directly related to the usb to be honest.
    Thank you for the link.  I will look into that.  I know I am not the only one with the HVA DAC to have this problem, but it was hearsay about others with similar problems so I could directly contact the people.
  2. spruce music
    kiseido got me to thinking.   I haven't followed the entire thread.  Try wrapping aluminum foil around the open window just to see if it kills or reduces the interference.  Or if you have a way to ground a piece of aluminum foil just slide it between the Mac and HVA to see if it blocks the interference.  I have seen tubes with similar openings around them effected by wifi, switching supplies etc.  They just need a shield or faraday cage as already mentioned. 
  3. kiseido
    Spruce is going down exactly what I was thinking of, you could try making a DYI faraday cage out of aluminum foil, so long as you are careful not to get it into your usb port and short anything. From what I have read, 3 layers thick should block 70-90% of the signal.
    As well, I believe the HVA sells with a tin, if you still have it, that may work as a testing apparatus for this purpose, even if you can't actually close the lid thanks to cords sticking out.

    Indigo Bob, as you say the USB gives it's own symptoms, I recall you mentioning having a jitterbug that didn't fix the other symptoms you're now relating to the WIFI. If the faraday cage idea works, you may be inclined to try the usb with jitterbug again while under the protection of the cage.
    I do not have personal experience with this amp, or tube amps in general, I understand some can get quite hot. Please be careful about temperature in any testing you may do involving placing this DAC/AMP unit in a wrapping or confined placed.
  4. Indigo Bob
    OK, so to start today's trials I will first try the shielded USB cable to see it that works....
    That offers no help.
    Farady shield....
    No improvement.
    It's just a loud USB.  
    When I hook it up to the Line Out on my DAP it's beautiful
    I can conclude that the USB detracts from the background noise substantially for the FiiO x3ii DAP/DAC and the Martin IMS HVA AMP/DAC.
    Luckily the two pair beautifully with each other on Line Out 

    If you guys have any suggestions that don't cost money, I might be game, but for now I am satisfied and will be returning the jitterbug and the shielded USB cable.
  5. pinnahertz
    1. Try the rig on a different computer
    2. Shield the DAC/Amp, not the computer.  Wrap it well, any hole will compromise the shield.  Of course, you can't actually use it that way.
    3. If that helps, ditch the DAC/Amp and find one that's designed better (this should NOT be a problem!)
    4. If that doesn't help, ditch the DAC/Amp and find one that's designed better (this should NOT be a problem!)
    3 and 4 could be cost free if you consider divesting the old gear to reinvest in new.
  6. Indigo Bob

    It's honestly hard to say it's the DAC/Amp since I had the same problem with the FiiO x3ii DAP.
  7. spruce music

    Nevertheless shield the DAC amp. See if it helps. Also the way you wrapped the foil may not have been grounded anyway.
  8. pinnahertz
    These devices all have something in common, which I suspect is lack of RF shielding.  But, that's also why my #1 suggestion is there.  Take your rig to another computer and try it.  In fact, if you have an Apple Store near you that would be a good choice.  If the problem exists on other computers, and the devices lack any visible RF shielding (which is true), then they're not suited to your application.  
  9. Arpiben

    In principle the foil acting as a faraday's cage or better said a reflector/attenuator should be grounded. In practice,due to the low electromagnetic (E) power involved a no grounded foil or can/candy box should be more than sufficient.
    The foil will act as an almost perfect mirror for the E fields.

    If the EMI source is the MAC's WiFi, the interfering waves will propagate and bounce depending on various parameters -> foil/box has to surround the affected device.

    According to poster's description, I am not expecting the amp tubes to be interfering.
    AFAIK, poster didn't try another USB port, let s say MAC left side.
    AFAIK, poster didn't verify (tester) if the USB cable he received was having a common ground at both ends.
    AFAIK, poster didn't try putting the No Noise configurations nearby his MAC when WiFi is active.
    Therefore, I am still wondering how is the interference propagating?

    As an end user point of view, what matters? Do I need to use MAC Wifi while listening to music? If no, the work around is found.
    If, yes, can I withstand to have a box/foil around my devices? If no, change computer/ use Toslink/ bring the DAP as far as possible from my MAC / etc...
  10. U-3C

    Watch the video at around 5:00.

    That's the basic idea of the shield. Maybe you can mimic it?
    spruce music and kiseido like this.
  11. spruce music

    That demonstrates why I said you need to ground the foil. Same experience I've had. The foil is marginally effective without ground since it isn't offering complete coverage.
    U-3C and kiseido like this.
  12. Arpiben

    The video was showing Radio Frequency interferers (LED light/ ballasts/CRT displays/etc). By RFI I mean an interferer in the Radio spectrum range. For such a grounded foil will probably be more efficient.
    Pay attention that the foil/protector's thickness is also important. Keep in mind that a DIY grounded foil may also act as an antenna...
    Ideally the best EMI/RFI protection is achieved with a common and proper grounding and earthing(casing/cables/...) added with some basic rules such as keeping well known interferers at distance.
    In Consumer Electronics the most efficient protection will be to keep EMI/RFI away when possible.
    Bring an old motorcycle without spark plug protection in front of your home or any Telecom center and you will have a large spectrum interferer.
    Some cases are unavoidable therefore Earth Satellite Stations for instance do tend to be located far away from industrial/human activities.
  13. pinnahertz
    Just a reality check: the foil thing is really just a diagnostic tool.  If you wrap it up in foil and ground the file, and it works great, what are you going to do?  Use it that way?  Not me.  I don't want my DAC sitting on my desk looking like a baked potato.  I'd seriously look for something designed properly and upgrade. 
    sonitus mirus likes this.
  14. pinnahertz
    Well yes, of course, distance from the RFI source is great.  It's usually impossible too unless you're really starting from scratch.  That doesn't mean audio stuff can't work in a high RF field. Audio gear works just fine at a 50kW AM radio station with the tower 1000' away and the transmitter in the same building.  That takes a bit of care and a lot of proper design, but that does work.  
    There are thousands of satellite receive installations in metro downtown areas, BTW.  They work just fine too.  Again, proper design and consideration of what the surround spectrum actually is.  Just think of it: a satellite dish picking up a miniscule signal from 23000 miles up surrounded by 30 high power FM and TV stations.  And yet, that works.  
    Which is why I'm saying the little DACs without shielding (and likely no RF bypassing either) are just bad designs.  There are good ones out there, including the "one that shall not be named here".
    I also find my self wondering why the DAC in the first place? Something wrong with what's built in?
  15. Arpiben
    [3] I am not an expert at all regarding EMI/RFI and have short experience with those issues when dealing with audio devices. I am more familiar with EMI/RFI when dealing with microwaves and data transmission. I just found the case we are dealing with quite interesting and I am also wondering about something wrong built in. I am conscious that it will be hard to have a definitive root cause.
    [1]By distance I was having in mind common sense rules such has for instance:
    1. do not  run USB/Analog cables along power cables or AC power supplies
    2. do not stack DAP/AMP on top or very close to EMI/RFI interferers.
    3. etc...
    Fully agreeing with your Short/Long Wave's Transmiter case. Proper design is also applied when dealing with higher power & frequencies ( TV broadcasting /Earth Satellite Stations/Military or Civil EMI test centers). That said I would not like to have a house in the vicinity of such Tx station [​IMG] since I will probably be able to listen to BBC International just with an unplugged headphone.
    [2] True for the majority of them. Nevertheless, big diameter parabolic antennae when having a low site/elevation are more prone to catch urban interferences in their side lobes even if extremely rare.
    Microwave transmission (TV included) spectrum is not interleaving with Satellite transmission bands. Electromagnetic fields are orthogonal in radio transmission ( Horizontal & Vertical) and rotating in Satellite. That said the Transmitted (Tx) power involved in some Earth Satellite dishes is enough to saturate some radio transmission receiver amplifier stages located nearby under certain circumstances.
    Telecommunication backbones following traffic roads were facing more errors in transmission during traffic hours (in some countries) due to unproctected spark plugs used in motorbikes....nowadays such motorbikes are more rare.
    Just for saying that it may happen more often than you may think.
    Luckily, when dealing with Audio devices the interferers are less numerous, still annoying and as you mentionned mainly due to poor or cheap design.
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