Computer Audio Asylum

Music servers and other computer based digital audio technologies.

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Original Message

Follow up on Leopard

Posted by Charles Hansen on July 10, 2012 at 14:09:56:
I spoke with Gordon Rankin, developer of the Streamlength asynchronous USB audio connection we license from Wavelength. He said that the problem with Leopard was actually in the feedback pipeline for the asynchronous operation, and not the 192 kHz capability per se.

This was confirmed by our lead technician, Ryan, who has a much better memory than I do. This is what e-mailed to me regarding Leopard operating at 192 kHz:

"When we were developing the QB-9 192kHz, we did have a 10.5.8 computer
that we were using here at Ayre in the form of the Mac Mini. As Gordon
said, it works (displays 192kHz and even plays at 192kHz), but it was
getting occasional popping. This same behavior was also present with
10.6.3. I unfortunately have upgraded the computer to 10.6.4 since
then, so I can't go back to do it now, but I remember very
clearly that it did it then. I also am pretty confident saying that I
doubt Apple had the 10.6.4 fix in 10.5.8, as 10.5.8 was released August
5, 2009 while 10.6.3, which definitely has the problem was released
March 29, 2010 and 10.6.4 didn't come about until June 15, 2010.

"The pop issue we heard wasn't a constant popping, like you'd hear from a
dirty vinyl, but it was definitely there when you listened for an
extended period of time, probably showing up now and again every 3-10
minutes. So it's very possible he thinks it works, when in reality,
he's shorting himself some quality."

So we will leave our recommendation for 10.6.4 or newer on our website setup page. Leopard may work at 192 kHz with an adaptive USB DAC (if such a thing exists, as most people making adaptive USB DACs use the Burr-Brown devices that are limited to 48/16), but not reliably for asynchronous USB at sample rates above 96 kHz. If you own a QB-9 I would recommend either upgrading to Lion or waiting a few months for the next OS that is in the works, Mountain Lion.

The upgrade from either Snow Leopard or Lion appears to only be $20. Mountain Lion will only work with the newer Mac computers. I'm not sure how to upgrade from Leopard to Mountain Lion. It may require an intermediate upgrade to Snow Leopard first. But the general consensus has been that there have been improvements in audio quality in each of the recent releases of the new Mac OS's.