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

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!

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

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.

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.

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.

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 :=(

<br />

what software are you using to do the 'conversion'?<br />

<br />

Is it a trial software issue perhaps?<br />

<br />

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!

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?

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 :-)

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 />

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 :-)

<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 />

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 />

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!).

[deleted duplicate post]

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 />

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 :-)

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?

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).

Chris,<br />

<br />

On the MBP in AudioMidi setup will the 192k option appear when I plug-in, say, the Weiss FireWire device? Right now, with nothing external plugged in, the only options that pop-up are 24-bit/96k and below.<br />

<br />

There may be another, cheaper, option. Play the discs through the HDMI output of my Oppo 980H to my surround sound receiver which is my only 192k D/A (I also have the Benchmark DAC1 [96k]). I know the RR site tech notes say that you can't play their disc (DVD-R) on DVD audio players but the Oppo will read DVD-R discs and can output 192k over HDMI. RR may have been thinking only of the SPDIF output which may not handle anything beyond 96k, but HDMI can. You think that might work?

I had exactly the same problem with a MacBook and the Benchmark DAC when playing 88.2khz files and I was able to reproduce it with an iMac and a MacMini. I am glad to say that after months of waiting the problem has finally been resolved with the update to OS X 10.5.6. However, I could not find anything about this in Apple's support documents.

Excuse me jumping in here as a newbie but I was given this web site as a possible source of help for this very problem : hiccups at random intervals which seem to have increased markedly in recent weeks, possibly since upgrading to 10.5.6. These tiny dropouts have been around and noticeable on more than one PPC Mac here for a while and I had thought they were a processing problem, related to the dynamic of the track in question. I have tried a few ideas for fixing but to no avail.<br />

<br />

However, unusually in the context of this posting, I am on the bottom rung of this improvement ladder and I am still working in iTunes and 16/44.1... I am also just using the internal DACs on the G5 and on the CD deck. From the G5 I am plumbed in with a high quality cable from the minijack to the RCA/Phono input on my Musical Fidelity PreAmp ( with monitoring running back into the mic input ). I also have the CD deck and turntable running into the PreAmp and the split line out goes to a REL sub bass and a pair of bridged Electrocompaniet power amps and thence to the main speakers.<br />

<br />

The glitches only occur on playback from the G5 and I am tempted to think that the severity or frequency is diminished when playing from CD but I am not putting money on that one just yet, more comparative tests to do.<br />

<br />

The G5 is a 2.3 Dual with 4GB of RAM and while I am playing music I am sometimes doing other things but not processor-hungry stuff as a rule.<br />

<br />

If anyone has any good ideas about how to deal with this I am very keen to hear as it is spoiling my listening enjoyment considerably.<br />

<br />

I would also like to know if there is a place I can go to read up on how to progressively tweak and upgrade on a limited budget. As far as I can tell, iTunes will always downsample to 16/44.1, so I am not sure how to get around this.<br />

<br />

I also rip favourite irreplaceable vinyl and would like to know if there is a resource herein where there is a guidance on set ups and configuration of Macs for musical playback at sonically superior levels.<br />

<br />

Thanks.<br />

<br />

Drew

Now there is some terrible marketing for you , well it is no wonder they made mistakes like this before , can you imagine if some <a rel="follow" href="http://www.paretologic.com/products/drivercure/index.aspx">update drivers windows</a> would have some errors how it would destroy your PC.

It's good to see there are people trying to fix any error that can occur on a MacBook with OS X. I'm using Windows and I hope I won't encounter this problem while I'm doing a couple of <a rel="follow" href="http://www.truecommerce.com/">edi</a> operations with the audio files. I would be happy to know if the problem has been solved. <br />

<br />