I have always kept my main interface for the exclusive use of my DAW and video editing software. In the early days this was essential as sound cards could not handle multiple sample rates and any system  sounds would reset the sample rate of entire projects - the 'not so goid' old days that I don' t miss at all (anyone remember Cubase 1.0 and the Audiomedia 3 card before Cakewalk had audio capabilities? OMG!).
 
Now days I find it doesnt matter at all what settings  I have in control panel for multiple sound cards - I simply choose only the drivers I wish to use in Sonar preferences. On my live rig I use a VST DMX controller called DMXIS. Interestingly, it will only take its timing from the internal sound card, so I must have  both it and the Yamaha 01x  active within Sonar. Even this causes  no issues whatsoever.
 
I'm sure I  carry many habits such as disabling particular drivers and features from a time when both windows and DAW's were far less stable. I guess it is someting to do with old dogs and new tricks:)

I use two devices on my main set up. A Roland Sonic Cell that I use as the Windows default device and an Allen & Heath ZED-R16 for Sonar. I haven't a clue about the settings in Windows though as I don't think I've ever touched them apart from making the Sonic Cell the default. I'll check when I fire the studio up.
 
For anyone wondering why two devices are helpful.......
 
For my video work I need to be able to record the output of Sonar into Camtasia while screen capturing. Two devices is the only way I seem to be able to do that.

CakeAlexS
> I deliberately have on-board sounds for Windows.  as the default audio device
 
You mean you assign your motherboard's sound chip for this?
 
Cheers Bob..

Yup - I feed the speaker output from the computer audio jack into a couple of inputs on my interface.  This allows me to run multiple audio applications with Sonar having exclusive control of the audio interface in ASIO driver mode.  
 
I run a lot of audio separately, as I frequently am analyzing and transcribing various progressive/fusion tunes and sequencing them up.  The above arrangement works well for those needs.
 
Bob Bone
 

Its funny how most of the older hands here tend to set things up much the same way. I wonder why that is. LOL

The only thing "required" is to be sure the device used for SONAR is not set as default in Windows. However, I am not sure if this is even required with the Saffire as it has ASIO aggregation. I use the onboard audio to drive a near-field 5.1 system and the Saffire to drive far-field amps. My Saffire (24) accepts ASIO input from everything at the same time (even in exclusive modes), so I would assume the 40 is the same.

Yes my Saffire accepts ASIO from everywhere all at once (best ASIO drivers in the world) so possibility of conflict is small, however I'm hoping zero now as the Traktor is going to be the default interface for (almost) everything else.
 
Saffire is set to be disabled in Windows sound, so cannot be default and seems to work good so far.

Thanks for all your comments.
 
 

rule of thumb normally with asio.. 1 device is supported.. BUT there are a few exceptions
 
yamaha sw1000/dsp factory... delta 1010 etc can be chained.. but in both their cases the drivers support multiple devices of the same maker at least. I'm sure there are more, but you lot never bought me em :)
 
wdm , or chaining 1 device into another . but in the past that has caused me issue with the spdif clock going out of sync..
 

While ASIO devices only address one driver at a time multiple software can access this driver simultaneously. This is nothing special about the Sapphire drivers in this regard.

It's the use of multiple devices that causes the problems.

When using windows there's 2 things to consider.

Windows can't use ASIO drivers.
Windows sounds are restricted to 16bit 44.1 kHz so I if you do share another driver wbetween your DAW and windows it will always be changing your sample rates if you use different settings for your Daw.

mudgel
Windows can't use ASIO drivers.
Windows sounds are restricted to 16bit 44.1 kHz so I if you do share another driver between your DAW and windows it will always be changing your sample rates if you use different settings for your DAW.

Mike hit the nail on the head here!! The "issue" is really keeping Windows' "grubby paws" off any interface that you want to use ASIO drivers with. The only way I have found to do this is power everything on, and specifically tell Windows "use X as default." If X already is default, I found that I need to set something else as default first, and then set X as default explicitly. Without that being done, Windows can errantly nab whatever interface it "happens to choose" and if it does nab your preferred ASIO interface, it just wreaks havoc.

OK slap me if you want. Say all kinds of tart remarks. Etc., etc.  But what I do is run Sonar thru an outboard ASIO interface (MOTU) and let Windows use the onboard sound device.
 
Then (and here's where you might feel inclined to bring out the slapping apparati), if for some reason I want to pipe another sound source to Sonar -OR- I want to hear another sound source thru my speakers/headphones while using Sonar, I run a cord from the computer's headphone jack to an input on my mixer.
 
However, this is not advisable for recording those sounds as you will get some computer noise with it.