• Mac OS X 10.5.6 Update & 24/88.2 USB Problem Resolved?

    This year at Rocky Mountain Audiofest I received a call from a manufacturer having trouble playing some newly acquired 24/88.2 files. He was using a MacBook with OS X Leopard 10.5.5 and a 24-bit USB interface. Every twenty to thirty seconds during playback there was an audible glitch. I offered my MacBook Air with OS X 10.5.5 and we heard the exact same problem. After about forty-five minutes of testing every configuration known to man we could not get 24/88.2 material to playback on OS X without audible errors. PC users will be happy to know Windows XP played the files flawlessly. I talked to the usual suspects around the show and sent a couple emails searching for answers. No solid information could be found.
     


    As I mentioned earlier we tried for forty-five minutes to get the 24/88.2 material playing without errors. Interestingly enough we did get this material to playback perfectly if we used OS X core Audio to upsample to 24/96 and we succeeded in playing back a 24/96 track downsampled to 24/88.2. To be absolutely sure there wasn't anything wrong with the file we had someone in another location play the same source file on his system. Everything worked perfect. The difference between the working and non-working systems was the interface. Using a Lynx AES16e card the 88.2 material played perfect. Unfortunately there was no 24-bit USB interface available for the offsite person to test.


    When I arrived back home in Minneapolis I used the same 24/88.2 music with different interfaces on my Mac Pro. I was able to reproduce the same playback errors using my Benchmark DAC1 Pre via USB. Some commonalities between the systems were Mac OS X, USB interfaces, and CEntrance chips. After a few days it was determined that the Mac OS X USB driver was the culprit. Apple was said to be working on the issue and a couple weeks ago I was told the issue had been resolved by Apple but the release date of the patch was unknown. Last night when OS X version 10.5.6 was released the first thing I did was test the USB interface with 24/88.2 material and voila (vwä-?lä) everything was perfect. I could not get the system to hiccup no matter how long I played 24/88.2 material.

    If anyone has OS X version 10.5.5, some 24/88.2 material, and a 24-bit USB DAC it would be great if you could reproduce the playback problem. Then update to OS X 10.5.6 and let us know if the problem has been resolved in your system.
    Comments 25 Comments
    1. The Computer Audiophile's Avatar
      The Computer Audiophile -
      Hi Gordon - I was hoping you would post something about this! I remember asking you at the show if your DACs had any issues with 88.2 and of course they did not have any problems. I am able to reproduce this problem on several Macs every time I play 88.2 material. Even Apple agreed something was wrong. With the update all is well.<br />
      <br />
      This is a weird one and I hope some readers have a chance to test it themselves. Thanks for the post Gordon!
    1. Wavelength's Avatar
      Wavelength -
      Chris,<br />
      <br />
      Really the only two machines I use all the time is my superMini and my 2.4GHZ SSD MacBook. But I would think these would use the same USB Host controller as the models you are using.<br />
      <br />
      Thanks<br />
      Gordon
    1. hubsand's Avatar
      hubsand -
      Here's a weird, similar (but probably not related) problem: I'm running three Macs at this location: two Minis and a MacBook, all the same OS. One of the Mini's creates a glitchy noise every 20 seconds when I convert from ALAC to AIFF. Every time: same iTunes settings, same iTunes version; same library files. The other Mini doesn't do it. What's that about? I'm wondering if anyone else can reproduce the gremlin on their machine?<br />
      <br />
      The reason to do this, incidentally, is that AIFFs sound better than Apple Lossless, I discovered recently.
    1. The Computer Audiophile's Avatar
      The Computer Audiophile -
      Hi hubsand - Thanks for the post. What DACs are you using? I would try a different USB port during playback on the Mini that has the problem. Also, try disconnecting the keyboard and mouse and any other connected devices as a test. More than one item on a USB bus can cause problems.<br />
      <br />
      Let me know what happens.
    1. hubsand's Avatar
      hubsand -
      No: that's the weird thing: it's not a playback issue: I even viewed the converted file in Soundbooth: it ENCODES a glitch at around 20 seconds when converting from ALAC to AIFF, every time: just on the one machine. Really odd.
    1. The Computer Audiophile's Avatar
      The Computer Audiophile -
      Wow, that's a good one. I suppose you could look at the versions of everything such as iTunes, OS X, the ALAC encoder etc... You've likely done this already. There may be a problem with the disc drive. You could swap them if you really want. Or, just wipe the Mini clean and start over :=(
    1. cfmsp's Avatar
      cfmsp -
      <br />
      what software are you using to do the 'conversion'?<br />
      <br />
      Is it a trial software issue perhaps?<br />
      <br />
    1. hubsand's Avatar
      hubsand -
      And the files are all written to the same NAS, regardless of the iTunes client, which makes it all the more enigmatic. In an attempt not to hijack the topic, I can confirm that upgrading to 10.5.6 hasn't fixed the problem!
    1. stanh's Avatar
      stanh -
      I have no problem outputting 24 bit/88.2 kHz files from either the MacBookPro's digital out or via a USB soundcard. I am running an early '08 MBP OS X 10.5.5; the USB card is an M-Audio transit and the 88.2 recording I used is Debussy Preludes (on Surrounded by), Joan Rowland on piano.<br />
      I am afraid your problem is not the OS X operating system.<br />
      <br />
      Stan H<br />
      <br />
      PS: You do know that you have to go into "Audio Midi Setup" and set the output to 24 bit/96k?
    1. The Computer Audiophile's Avatar
      The Computer Audiophile -
      Hi Stan H - <br />
      <br />
      <br />
      <i>"I am afraid your problem is not the OS X operating system. ... PS: You do know that you have to go into "Audio Midi Setup" and set the output to 24 bit/96k?"</i><br />
      <br />
      Interesting comments to say the least. Apple itself said it was a problem with OS X. I'm completely satisfied with Apple's answer and I'll assume Apple knows what it's doing in this area.<br />
      <br />
      You're comment about Audio Midi Setup is purely in jest right? Otherwise it seems like you skimmed the article and jumped to posting a comment :-)
    1. stanh's Avatar
      stanh -
      Depends on who you talk to at Apple. An Apple engineer I would trust but first line support staff - not so much. <br />
      <br />
      Didn't mean to insult you with the Audio Midi setup note but sometimes even knowledgeable people forget to check obvious things (myself included). Actually I find that I have to check that setting each time I plug in the USB audio device as it is often back at the system default of 44.1k. I also have to check the settings of the M-Audio Transit to make sure it is set to outputs 1&2 otherwise I wouldn't get 24-bit output as it is not a full duplex device. And just so there is no misunderstanding, I also locked the core audio setting to 88.2 so there was no upsampling to 96k and still no problem. <br />
      <br />
    1. The Computer Audiophile's Avatar
      The Computer Audiophile -
      Hi Stan - No offense taken, it was a little early here when I read your post. Also, since it was your first post I wasn't sure what background or knowledge level you had etc... Anyway, I think I figured out why you can't reproduce the problem. The m-Audio Transit requires its own device drivers and does not use the OS X USB driver. Since the OS X USB driver was the questionable driver, when playing 88.2 you were totally immune to the issue because you have the M-Audio device.<br />
      <br />
      That's my theory on this one :-)
    1. cfmsp's Avatar
      cfmsp -
      <br />
      <br />
      When you say 'lock in CoreAUdio settings', what exactly do you mean?<br />
      <br />
      Is there something other than AUdioMidi Setup which allows this?<br />
      <br />
      I only heard yesterday that there are various possible SRC algorithms in CoreAUdio and that programs like iTunes do not use the most sophisticated.<br />
      <br />
      Are there other ways to access CoreAudio than AudioMidi Setup?<br />
      thanks<br />
      clay<br />
    1. stanh's Avatar
      stanh -
      Yes, the M-Audio has its own drivers and apparently avoids the problem for that reason. However, I did have a concern whether the M-Audio USB device was bit transparent after reading this tech note on the Benchmark site (http://www.benchmarkmedia.com/wiki/index.php/USB_audio_interfaces). But I tested the Transit using an HDCD file (Alan Broadbent's "Round Midnight" - gorgeous BTW) and it played perfectly through the HDCD decoder so I take that as a sign that it is bit transparent (at least to 16 bits). You were using the Benchmark USB DAC, right, and since it doesn't require a USB driver I presume it relies on the native MAC one, right? So, yes, you are probably correct about the MAC USB driver. Funny, that Benchmark doesn't have anything on their site about it. <br />
    1. stanh's Avatar
      stanh -
      No, I was just referring the AudioMidi settings where you can specifically select 88.2. I don't know of any other settings. <br />
      <br />
      Can you expound a little more on the SRC algorithms in Core Audio and iTunes? As far as I know, iTunes uses whatever sample rate/bit depth you set in Core Audio and there aren't that may choices - 16, 20 and 24 bit at 44.1, 48 and 96k, right, in addition to digital gain settings. What else can Core Audio do? (Tell me it can really do 192k - that would be sweet! Ha!).
    1. stanh's Avatar
      stanh -
      [deleted duplicate post]
    1. cfmsp's Avatar
      cfmsp -
      I don't know much more about the various SRC algorithms, other than what was suggested on a pro audio forum I read, where it was stated that neither iTunes nor Logic use the full SRC capabilities of CoreAudio.<br />
      <br />
      As I understand it, the most sophisticated real-time SRC processing can take longer (in time) than it takes to play the song, therefore compromise SRC algorithms are used due to time and processor constraints, which makes sense when you stop to think about it. These compromises hardly matter in iTunes, given the target audience and their use of compressed audio.<br />
      <br />
      This provides insight into why something like Amarra would provide a dedicated box of high power DSP capabilities as part of it's solution.<br />
      <br />
      OTOH, everything I"ve read recently says - forget about real-time SRC, it's better if you convert prior to playing, at which point the playback software is NOT as critical. Not as convenient as Amarra, but not as costly by several orders of magnitude.<br />
      <br />
      YMMV,<br />
      clay<br />
      <br />
      <br />
      <br />
      <br />
      <br />
      <br />
    1. The Computer Audiophile's Avatar
      The Computer Audiophile -
      Hi Stan - You're in luck. Core Audio will handle 24/192! With the right DAC and interface there are no problems at this resolution. I listen to 24/192 quite often :-)
    1. stanh's Avatar
      stanh -
      Chris,<br />
      <br />
      I honestly didn't know that Core Audio could do 192k! Not that I have much at that resolution but still I have my eye on a few of those new RR Hrx recordings. I do have an outboard DAC that is capable but what interface? Another USB or Firewire audio card that will pass through 192K; got any recommendations?
    1. The Computer Audiophile's Avatar
      The Computer Audiophile -
      Hi Stan - There are a couple ways to get 192. With a desktop you can use the Lynx AES16e card that outputs an AES/EBU digital signal to your DAC. On a laptop FireWire is the best route. Weiss Engineering's Vesta is a FireWire to AES or coaxial (I believe) converter that will handle 192. The Weiss Minerva is a FireWire DAC that handles 192. I reviewed that unit a few months ago and it's really good. I placed it on the <a href="http://www.computeraudiophile.com/computer-audiophile-suggested-hardware-list">CASH List</a>.<br />
      <br />
      None of these options are cheap, but they'll give you unbelievable sound quality for the RR HRx material. I have all the HRx albums and use them as my reference. I don't review a single piece of gear without listening to HRx material (provided the gear can handle 24/176.4).