Anyone using the Focusrite beta version 1.9b12 of Mix Control with Windows 10 and Sonar?

Yes. It's working okay with Sonar on Windows 10 with a couple of exceptions. 1) I noticed a slight increase in my CPU usage since switching over the the beta driver. Not a show stopper but I thought I'd get better performance. 2) I do not like the choices to change buffer settings with the beta driver. I liked the control features much better with 1.8 which also worked well with Win7 and Win10. I only upgraded to the beta drivers because I wanted to stay with the most recent drivers. I can't say I regret it but had I known I would've just stayed with 1.8. Your mileage may vary. One thing I noticed when talking with Focusrite support is they seem unsure as to when the official drivers will be released. I've been using 1.9b12 for almost a year now. I hope they release the official drivers soon.

No issues with 1.8 on Windows 10.

Is it not possible to go back to 1.8?  I re-read the description of 1.9b12 and it sounds like you can't use the 1.8 Mix Control with the beta drivers, but it doesn't say you can't go back to 1.8.  It does say you can't roll back the firmware.

I opened a support ticket at Focusrite, so I'll let you know what they advise.  I did find these instructions for completely removing the Focusrite drivers over at the Avid forum.  They are from a Focusrite support tech:
 
1) With the Scarlett connected please open the Control Panel > System > Device Manager. Locate the Scarlett under Sound, Video and Game Controllers section.
 2) Right click the Scarlett and choose Uninstall. Make sure to check the box to remove software for the device.
 3) You will see the unit disappear from the list. Unplug the unit and plug it back in. It should reappear in the list.
 4) Repeat steps 2 and 3 until the Scarlett appears with a yellow exclamation mark, and/or the properties says Code 10. The Properties > Driver tab will likely say a Microsoft driver is in use. This means all the drivers are removed.
 5) Next go to Control Panel > Uninstall a Program. Uninstall any Focusrite USB Audio Driver, Scarlett Family Audio Drivers or Scarlett MixControl you find here.
 6) All Focusrite drivers are now removed. Please reinstall the MixControl software and/or driver for the unit.

aspenleaf
I opened a support ticket at Focusrite, so I'll let you know what they advise.  I did find these instructions for completely removing the Focusrite drivers over at the Avid forum.  They are from a Focusrite support tech:
 
1) With the Scarlett connected please open the Control Panel > System > Device Manager. Locate the Scarlett under Sound, Video and Game Controllers section.
 2) Right click the Scarlett and choose Uninstall. Make sure to check the box to remove software for the device.
 3) You will see the unit disappear from the list. Unplug the unit and plug it back in. It should reappear in the list.
 4) Repeat steps 2 and 3 until the Scarlett appears with a yellow exclamation mark, and/or the properties says Code 10. The Properties > Driver tab will likely say a Microsoft driver is in use. This means all the drivers are removed.
 5) Next go to Control Panel > Uninstall a Program. Uninstall any Focusrite USB Audio Driver, Scarlett Family Audio Drivers or Scarlett MixControl you find here.
 6) All Focusrite drivers are now removed. Please reinstall the MixControl software and/or driver for the unit.

Thanks. One thing I can say is support is excellent. Sometimes it takes a little while for them to reply but they really are excellent.

Just came across this and now I'm really confused. Why would Focusrite recommend connecting my Scarlett 18i20 to a USB 3.0 port when the device is USB 2.0? Anyway it looks like there's some good info included to help troubleshoot some issues.
https://support.focusrite...t-has-an-AMD-processor

Do you happen to leave Mix Control open all the time?  After much experimentation, I discovered with my 18i20 and Mix Control 1.8 (and corresponding driver/firmware) that leaving Mix Control open all the time causes similar stability problems as you described.  Basically, the 18i20 seems to lock up and stop responding to the PC after some time and needs to be power cycled to get it back up.  The simple solution is that I only open Mix Control as needed to change settings and then close it immediately.  Haven't had the hardware crash on me since.  This isn't a SONAR issue as I've been able to replicate it with other DAWs.  
 
I did try a recent beta version (pre-b12) to see if it would help with the hardware crash but I hated it due to the latency changes.  None of the settings had sufficiently low latency compared to 1.8 and the lowest latency setting produced audible clicks.  They definitely seemed "beta" quality and not ready for prime time. 
 
I haven't bothered with 1.9b12 because of the warning that the 18i20's firmware will be irreversibly updated.  The other beta drivers I tried were so bad that I don't want to risk that.  
 
 

aspenleaf
Focusrite advised using a USB 3.0 port?  I've been using USB 2.0 ports because when I first got the unit, that's what they advised.  I'll try a USB 3.0 to see if that helps.

Yes. They advised using a 3.0 port if you are having issues with an AMD processor. I clearly remember reading at one point where they recommended "NOT" using a USB 3.0 port. My 18i20 is connected to USB 2.0 and other than the slight increase in CPU everything else seems to be okay. 

Soundwise - are you finding the lack of buffer settings in Mix Control to be an issue?

This is timely for me, as I was just wondering the same thing.  Two days ago, I wrote to Focusrite Support to ask whether I should consider moving up to the 1.92 beta. 
 
With 1.8, I have a 'pop' that occurs at the start of playback, though everything else works fine.  Once in awhile, I do need to power cycle the 18i20, which I leave on all the time.  Same for the MixControl software -  I leave that on all the time, and it is in my Startup folder.
 
I concur wit the comment that their support is excellent and fast. 
 
I went through much the same situation when I upgraded to Windows 10 over a year ago and then discovered their beta driver site.  The beta driver at that time caused pops, clicks and stutters despite everything I tried, so Support gave me those steps to uninstall everything and reinstall 1.8, which I am still using a year later. 
 
I too am very concerned by that warning that the firmware will be updated which cannot be reversed.
 
I will share any answer I receive.
 

NO!  Do not assume that.  Let me try to me more clear:
 
When I first updated to the beta drivers (a version earlier than the newest one), there was no mention of firmware.  It was just a beta driver.  From that, I could roll back using Support's instructions, and did so, to 1.8.
 
Now, however, it appears from the minimal description that using the 1.92 driver ALSO upgrades firmware, which cannot be rolled back.
 
That's how I read it.  The instructions are far from clear.

Dave76

Soundwise
Not at all. You can set the buffer from a special dialog, which is a lot more convenient.

Hmm, can you clarify where to find this special dialog?  All I got was a popup with a couple of inadequate options the last time I tried the beta drivers.  

Update.  For my initial click problem, Focusrite Support just advised me to first try NOT the firmware update, but just a newer driver.  I had been using a 2.5.x driver.  They sent me a link to a 3.2.1 beta driver.  They speculated I was hearing a change in sample rates.  Since I have heard that sound before, I tend to agree even though there is nothing on my system that should be trying to change the rate.
 
I have to say, so far, after installing just the driver, I'm not hearing the initial click.  I need to live with it awhile.
 
Once again, I have to compliment Focusrite on quick and thorough service.

I've been in contact with Focusrite Support and thought I would give an update.  They had me install the 1.9b10 version of Mix Control (which doesn't require a firmware update) and the 3.2.2 beta drivers.  After doing so, I couldn't get any files to play through Sonar.  Even projects with a single track would not play.  I would just get an audio dropout message before playback even started.  Earlier in the day I was working on a complicated mix with lots of plugins using the 1.8 Mix Control and the 2.5.1 drivers and it played back perfectly at 3 ms buffer.  I work at 24/96.
 
I also attempted to install Mix Control 1.9b12, but the firmware update failed.

aspenleaf
riojazz - are you using the 1.9 Mix Control with those new drivers, or the 1.8 Mix Control?

No, I still have 1.8.128.0.
 
The bad news is, I just discovered I cannot open the MixControl mixer!  It says "No Hardware Connected".  Of course, it is connected, and the unit is working, presumably with my prior settings.  I tried reinstalling with no effect.  I am awaiting another answer from Support.
 
This is not good.