I'm needing a reliable AD/DA interface.   The Focusrite 8i6 is unreliable; keeps flaking out, disconnecting from Sonar.  Have you a recommendation?

RME Fireface UFX (http://www.rme-audio.de/en_products_fireface_ufx.php)

Well you can start picking up some reasonable ones from about $150-$200 on up, and other than making there are stable drivers available for your OS (Win 7/8), it comes down to needed/desired features and the quality of pre-amps and converters.
 
There is also the manner in which the interface will connect to the computer.  Some folks like Fire Wire, some like USB, etc.  Some need more inputs and outputs than others (using separate mics for every drum kit piece, for example, or just one mic for vocals and another input for a guitar or keyboard).  Some mics require phantom power, and some folks don't even need mic inputs or pre-amps.
 
I am not trying to be as as flaky with my comments as the above appears, it's just that once you figure out which interfaces are both stable and have the appropriate drivers for your OS, it's all about what YOUR needs and YOUR wants are, and all of that affects price.
 
I happen to use and like the Presonus AudioBox 1818 VSL interface.  It has a number of mic/line/instrument inputs, a number of outputs, decent pre-amps and converters, and connects through a USB 2.0 port to my computer.  I have several mics that I routinely have plugged in, as well as a couple of synthesizers, and a couple of guitars.  I truthfully do not need the number of inputs I have - it is mostly vocal mics that get plugged in at the same time, and that does not happen that often.
 
I would suggest looking at a couple of the larger retail music equipment companies online, and sort their lists of available interfaces by price.  Then, begin looking at the available features in the different price breaks, and after deciding which features you really want for your interface, then take that set of results and do some digging to make sure drivers are available, that the connection mechanism is one you are comfortable with (and is stable), and look at multiple reviews online for each potential interface you are considering.
 
You can also get to the point of the 'short list' and post that list here and get additional feedback from the forum on experiences folks here have had with the ones you are considering.
 
The above is just an off the top of the head stab at methodically coming up with a small number of interfaces that are stable and fit your needs, and then based on your comfort level from reviews of those, most likely more than one will be quite suitable.
 
I hope that helps, 
 
Bob Bone
 

marvinglenn - I think you should figure out what's going on with your PC. You might have challenges with other audio interfaces otherwise.

Focusrite stuff is pretty rock solid. You might have a conflict going on. Have you been in touch with Focusrite support?

I would recommend you post this message in the Hardware section of this forum - or pick up on another thread there. Plenty of discussion about the choices in that section.

Imo it´s a good advice of lawajava (above).
There are tons of good interfaces, but the focusrite is a good one.
If you have issues with the focusrite, you will probabbly have also with others.
You can also give here in this thread info´s about your box, driver ,issues aso.
Have fun
Pragi

Good advice to check out whats causing your problems before spending more money.
 
If the Interface is damaged and need is to be replaced add the Roland Capture series to any short list. The Quad Capture appears to be the closest to your existing interface but also check out the Duo Capture EX if you do not require digital ins and outs and the Octacapture if you need more channels.

Glyn Barnes
Good advice to check out whats causing your problems before spending more money.
 
If the Interface is damaged and need is to be replaced add the Roland Capture series to any short list. The Quad Capture appears to be the closest to your existing interface but also check out the Duo Capture EX if you do not require digital ins and outs and the Octacapture if you need more channels.

I have to fully agree. I used to have focusrite interface and it was definitely O.K. But since I have Quad Capture I am really happy with it. I have to confirm, that Quad Capture driver is really stable and VS preams are just the best.
 
But before buying the new interface, increase the Focusrite 8i6 audio buffer size to maximum and check if it is stable. And if it is stable, then slowly decrease the buffer size. I assume, that you use ASIO driver.

marvinglenn
I'm needing a reliable AD/DA interface.   The Focusrite 8i6 is unreliable; keeps flaking out, disconnecting from Sonar.  Have you a recommendation?

Is it possible that your Windows Power Settings are allowing Windows to disconnect your Focusrite 8i6, after a certain amount of time?  For USB-connected audio interfaces, such as yours, Windows will disconnect what it determines to be 'idle' devices after a certain time limit.  This functionality can be adjusted in your Power Plan settings, and it is recommended that folks with audio interfaces that connect via USB ports that they change default Windows behavior to make it so USB-connected devices are NOT allowed to be selectively turned off or disconnected.  (for that matter, a lot of folks completely disable all turning off of devices on PC's that run Sonar, as not every device wakes up on the right side of the bed).
 
My original answer was simply based on your initial question, and it never dawned on me until now (after reading the other responses), to suggest that you look to addressing whatever is causing you grief with the interface you already have.  Doh!  :)
 
Another place to look is to look at the type of port you are plugged into.  My Presonus AudioBox 1818 VSL interface FLIPS OUT if it is plugged into a USB 3.0 port, and some other folks have reported cases where simply moving from one USB 2 port to another USB 2 port 'fixes' issues they are having.  SOOOOO, check out making sure you are using a USB 2.0 port, and if that doesn't work then try a different USB 2.0 port (you may need to move and install the drivers again after moving to different USB ports).
 
Hopefully your issues can be addressed with your current interface, as that would be expedient and cost-effective.
 
Bob Bone
 

PapaBear
RME Fireface UFX (http://www.rme-audio.de/en_products_fireface_ufx.php)

+2, if you MUST get a different interface.

marvinglenn
I'm needing a reliable AD/DA interface.   The Focusrite 8i6 is unreliable; keeps flaking out, disconnecting from Sonar.  Have you a recommendation?

 
Hi Marvin,
 
Assuming the Focusrite is in proper working order, it's not the source of the problem.
Are you connecting via a USB-3 port?  Unless you're running one of the later Z series motherboards, your USB-3 ports are provided via 3rd-party add-on controllers.
This opens the door to compatibility issues (similar to using a non-TI chipset Firewire controller).  The solution is to use native (integrated into the Intel chipset) USB-2 ports.
There's absolutely no advantage to connecting a USB-2 audio interface to a USB3 port.
 
I agree with the advice that you need to figure out what's going on with the (current) system.
As great as the Fireface UFX is... connecting it to a problematic system will still result in issues.
 
Provide more details on your system... and we can provide more detailed assistance.