USB 3.0 issues on recent iMacs? (not able to select 48khz)

  • Hi,


    this really is a follow on post from my post on SPDIF issues - which seem like a red herring now - as they were just USB issues.
    (Distortion thru SPDIF and USB out , if 48khz)


    Ive got a iMac Late 2012 27" 2.9Ghz i5 mac running 10.8.5


    Ive noticed even if I remove ALL USB devices from my iMac (including keyboard!), and connect the Virus TI to ANY of the 4 USB ports - you cannot select 48khz only 44.1khz.
    There are no errors reported Virus Control Centre report ALL is ok, and Ive used the TI without any issues at 44.1khz - Just you cannot select 48khz.


    However, If I plug the TI into my cheap (Trust 4 port) USB 2.0 hub OR even my Mac keyboard, then I am able to select 48Khz (and everything in VCC is still ok)


    my assumption, therefore is the TI driver or USB hardware (1.1), is having issues with USB 3.0 hubs, and putting a USB 2.0 hub in, means the USB 3.0 coverts to 2.0, and then it uses the TT of the USB 2.0 hub to convert down to 1.1, successfully.


    my questions are:
    - Have others found the same?


    to Access
    - is this a general problem with the TI and USB 3.0 on Macs? (if so all current Macs will be affected)
    - is the 44/48 switch not allowed, because it cannot allocate enough bandwidth? and why is there no error message to alert the user? (VCC could make this test, even if not the driver)
    - I wonder, if you are unable to switch to 48khz... if this is a likely indication you may have other potential performance issues (e.g higher chance of audio glitches, of which ive had a few)



    If this is the case, then I think Access should include some kind of release information to this affect, as its an issue that will affect more in the future,
    and is very time consuming to figure - also the published 'wisdom' of don't plug the TI into a hub is rather too simple, and keeps people from finding a true solution.
    (i assume is due to people plugging multi 1.1/0 devices into a single TT hub)


    anyway, good news is there is a solution to these issues - so I thought it might be useful to highlight to others, so they dont waste as much time on it as i have!


    Mark

  • I am working on USB 3.0 (not Audio related) and have low knowledge about MAC's Hardware but what I would say that this should not be a problem of the hardware layer.


    Anyway I was interesting to know if you have any similar difficulties with your USB running different devices? USB 3.0 is very vulnerable regarding bad cables for instance.

  • Ive plugged many other devices into USB 3.0 devices in the mac with no problems (not at the same time as the Virus of course!)
    only the virus has an issue, and as my post said it is only the not being able to select 48khz - its quite obvious the Virus driver has detected some problem, but is silent on it.


    plugging in the Virus into a USB 2.0 hub, and then the usb 2.0 into the usb 3.0 of the mac cures the problem.


    i suspect perhaps that the Virus software tries to reserve more bandwidth for 48khz, and is possibly refused this - why? i have no idea, as the source code is not open source, so I cannot check, and the logs are completely silent.


    (note: my audio interface is perfectly capable of being used in 48khz mode)



    "but what I would say that this should not be a problem of the hardware layer. " ... i never said it was, to me its very likely to be a problem in the audio driver written my ploytec, but I cannot diagnose with so little info to go on, its seems strange to me that the driver refuses to carry out a request, but does not log any error message (into the console logs) as to why it was unable to achieve this.


    anyway, no issue for me, as
    a) i plug into a usb 2.0 hub
    b) i now dont use the virus as a sound card, I have a dedicated audio interface, and connect the virus via analog outs, and spdif
    c) due to (b) i rarely use USB with the virus any more.