Hi Daniel, Thanks for the quick reply. I am able to set the clock on my Mac, though I do need to do further tests and make sure that the sync is actually reliable there. The setting is available from the built-in, standard OS X audio setup application "Audio MIDI Setup".

There should be a S/PDIF clock signal going to the digital inputs on the device. Some of the other controls such as per-channel mute also appear to work. I've also attached the lsusb output (attachment stripped for the mailing list).

There are some other details that may be relevant, but I didn't want to make my initial post too long/confusing because these extra details may end up just being a red herring: Each mixer element name (as seen in amixer) is prefixed with "AudioBox 1818 VSL Clock Selector" even if it is not a clock selector. I am confident though that the control I've been playing with is the clock selector because it lists the different clock types as options. I also see this when I plug the device in or load the ALSA driver:

ALSA sound/usb/mixer.c:342 cannot get ctl value: req = 0x83, wValue = 0x201, wIndex = 0xa00, type = 4 ALSA sound/usb/mixer.c:846 10:0: cannot get min/max values for control 2 (id 10) ALSA sound/usb/mixer.c:342 cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0xa00, type = 4 ALSA sound/usb/mixer.c:846 10:0: cannot get min/max values for control 2 (id 10) ALSA sound/usb/mixer.c:342 cannot get ctl value: req = 0x83, wValue = 0x201, wIndex = 0xb00, type = 4 ALSA sound/usb/mixer.c:846 11:0: cannot get min/max values for control 2 (id 11) ALSA sound/usb/mixer.c:342 cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0xb00, type = 4 ALSA sound/usb/mixer.c:846 11:0: cannot get min/max values for control 2 (id 11)

Amixer reports the control at numid=2 to be a boolean, but because of the naming bug I can't see what the control really is. I'm assuming this isn't relevant, but I'm including it here anyway.

Louis

On 06.09.2012 22:20, louis@museresearch.com wrote:

...

Hi! I'm attempting to get the "Clock Selector" mixer control to work with the PreSonus AudioBox 1818VSL (a UAC2 device).

The control shows up in amixer as an enumerated value, but I don't seem to be able to set it (I've tried amixer, alsactl, and setting it programmatically). The possible values are correct (listing Internal

Clock, S/PDIF Clock, and ADAT Clock as possible options); It just doesn't

...

appear to take my setting, by which I mean amixer doesn't update the

settings, I still have the occasional click when the sampling rates match

...

over S/PDIF and I attempt to use external sync. No error is returned.

After digging around USB specs and ALSA's usb/mixer.c and being unfamiliar with both the USB audio spec and the inner workings of ALSA, I thought

it'd be best to ask the list about this: How would I check to see if ALSA

...

is asking the device to change clock source at all?

Hmm. A clock selector is handled like any other control entity on the

hardware. Some thoughts:

• Are you able to control other settings like the volume?

• It's fairly common for devices to not accept a new clock source

setting if they can't lock to the external source within some time. Did you connect anything to the digital inputs?

• Are you able to control that setting with the native Mac OS X driver?

(IOW, without installing a 3rd-party driver)

Also, please send the output of "lsusb -v" for that device.

Daniel