1. Although I don't own a NOS1a, it does greatly interest me as a clever design that I'd like to audition eventually.

2. I've been a Mac user for 24 years, and I've developed AppleScripts, etc for managing my music library, so I like to do what I can to facilitate the Mac as a platform for computer audio.



Bombich "Carbon Copy Cloner" is the backup program I use.  It is the highest regarded program for carefully preserving all the hidden files, permissions, Bootcamp partition, recovery partition, etc.  It has a fully functioning 30-day free trial.

http://bombich.com

The help in the Help menu is the same as the online help, so it probably is easier to view the instructions online.  I believe there are instructions in Nederlandse, too.

http://bombich.com/kb/ccc4/how-set-up-your-first-backup

When you replace an extension by simple Finder copy (drag-and-drop) rather than running the Apple Installer program, I do not believe OS X cares whether the new extension is a higher or lower version number.  (Although I have to admit that I am not using Yosemite.) 

The usual cause of an extension update being ignored is that the old extension remains in cache.  OS X does not notice that you installed a different version of an extension if you merely copied it in the Finder instead of using the Apple Installer program.

The solution is to clear the extensions cache in one of two ways:

1. The "touch" command in my previous reply #36.  However, I made a mistake: I specified the Extensions folder for OS X 10.8 and earlier, not the new one for Mavericks and Yosemite.  The "touch" command for the latter is:
sudo touch /Library/Extensions/

2. A completely foolproof method, although extra steps, is to restart the Mac in "Safe" mode by holding down the Shift key after you hear the startup chime until you see a horizontal thermometer icon (representing the progress of the fsck operation).  Login in Safe mode, then restart again normally.



GUID versus AFS is a property of the entire hard drive, not of an individual partition.  To convert a drive to GUID you must completely erase the drive, recreate the desired partitions, then restore the data from a backup.  Instructions at:

http://support.apple.com/HT201723
or
http://bombich.com/kb/ccc4/preparing-your-backup-disk-backup-os-x

It has prevented dropouts with certain audio device (DAC) drivers.  I do not know whether it will help with Peter's driver, but it is worth trying, and I do not believe it can make anything worse.

As stated in the ComputerAudiophile posting I referenced, you can revert to normal OS X defaults using:
sudo nvram -d boot-args

You must restart the Mac for any of these changes to take effect.

Another tip:
When installing an updated version of a device driver, the following command, followed by a restart, clears the cache to ensure that the new driver is used rather than the old driver:
sudo touch /System/Library/Extensions/

Coen, you might try the following Terminal command:
sudo nvram boot-args="dart=0x0 kext-dev-mode=1"

as discussed in posts 201 and 203 here:
http://www.computeraudiophile.com/f11-software/official-os-x-yosemite-thread-22030/index6.html#post368663

Peter, I believe you can speed up the beta testing if some users are willing to disable Yosemite's "kernel extension signing" by storing the "kext-dev-mode=1" parameter in nvram as described in the first Step 5 here:
http://www.cindori.org/trim-enabler-and-yosemite/

It's in the US online catalog:
http://www.ikea.com/us/en/catalog/products/90201532/

Not to be confused with this larger cushion:
http://www.ikea.com/us/en/catalog/products/S29874242/

I didn't realize that you created a separate business division for Phasure that has its own management (in addition to yourself, presumably).  Is this just for USA distribution?

Anyway, please post an update here if you receive any more information about Phasure's activities at the show.  Thanks!

Peter, XXHighEnd is listed as an exhibitor at this show near San Francisco.  Will you actually be there, or does this merely mean a dealer is including the Phasure DAC in his system?

Thanks, Peter.

Regarding even one resistor of the highest quality killing the sound, my power amplifier has a few resistors, so I guess the sound is close to death by the time it reaches the loudspeakers

I apologize that my question was unclear.  I was not referring to the software-implemented low-pass filtering in the digital domain.  I was referring to the absence of any analog low-pass filter after the D/A conversion.

The analog signal produced by the D/A conversion stage will not be smoothly continuous, but will look like a staircase, with sudden steps between each sample.  Therefore, pulses at the sample rate (not the Nyquist rate which is half the sample rate) will be superimposed on the audio signal.  In other words, the analog signal will look sort of like a pulse train at the sample rate that is amplitude-modulated by the audio signal.

I don't understand why the Phasure DAC, or any other DAC without low pass filtering, does not damage tweeters.

It seems to me that the DAC would output a pulse train whose frequency equals the sample rate and whose amplitude is only a few dB lower than the amplitude of the audio signal.

Music normally has treble content that is a small fraction of the total music power, so tweeters do not have to be designed to handle as much power as woofers.  It seems that continuously outputting 192 or 384 KHz pulses at a 10 watt power level would risk burning out a tweeter.

Am I overlooking something?

On the other hand, it's possible that one of the reasons the Phasure DAC sounds good is that superimposing an ultrasonic signal on the music reduces tweeter distortion due to hysteresis near the zero crossing, sort of like the ultrasonic bias signal used in magnetic tape recording.