I recently got a Focusrite Scarlett 2i4 gen2 (USB audio interface).  I haven't used it much with Sonar yet, but have been listening to music on it as a test.
 
I am currently having dropouts while listening to music.  Every few minutes, the sound will cut out for a fraction of a second and then resume.  It's distracting and annoying, and makes me question whether the Scarlett can handle what I'd like it to do with Sonar, which is: multi-track audio recording, playback, and MIDI at the same time.
 
Playback dropouts like this never happen with my PCI sound cards, so I suspect it might be a USB (or Scarlett) issue.  DPC latency is fine (I just checked).
 
I have disabled USB power saving (in both the device manager and power management) as suggested in another thread.  That may have helped, as the interruptions as less frequent, but they still happen. I have also confirmed that the USB port is indeed 2.0 (by using a USB port viewing tool).
 
What else can I try as far as finding and eliminating the cause of the dropouts (USB interruptions)?
 
The Scarlett's current ASIO settings are:  44.1 hHz sample rate with 128 buffer size.
 
It appears that the 2nd gen Scarlett 2i4 only has one driver, and that's the ASIO driver I'm using:
https://global.focusrite.com/downloads?product=Scarlett+2i4


Normally I use WDM with my Delta 44 PCI card.  It's not a big deal to switch over to ASIO, but I'm wondering if there are ASIO-specific troubleshooting steps I should be taking (to deal with the dropouts).
 
And finally, are there ways of improving the performance and stability of the Scarlett (or any USB audio interface) by somehow increasing the power to it?  For example, should I connect it to a powered USB hub, which is then connected to the PC's USB2 port?
 
Thanks a bunch!
 

You system looks like it should handle lower buffer settings, Mine will produce drop outs if I lower my buffers  too far. I work with them in the middle @ 256. You could try a higher setting but this should not have any effect on playing music outside Sonar.
Those settings don't effect playback from Media player or movies, The drivers will automatically switch to what ever the file playing was set for. This sometimes caused issues if you have Sonar open and tried to play in other software.
I've never had this problem with my Scarlett. I use it for everything and I often have multiple programs open.
 
Try disconnecting from the internet if you haven't already done so.
Windows can be updating and all sorts of stuff.
 
Open the task manager and keep it open while you listen to playback.
See if anything is hogging CPU etc.
 
Video card audio drivers are known to cause problems. Disable them in Device manager.
 
 
 
Dropouts are almost always caused by your computer multi tasking.
 
Question, did you remove the Delta from your MOBO?
I found you can't have a PCI card installed and use a USB audio interface together. The PCI card with conflict.
 
 

Thanks for the response!
 
I actually have 3 audio cards connected to the PC at the moment:
 
1) ASUS Xonar DX (PCI card)
2) M-Audio Delta-44 (PCI card)
3) Focusrite Scarlett 2i4 (USB)
 
I haven't removed the PCI cards yet because I don't trust the Scarlett to handle all my audio needs.  And since I listen to music all day, it would be a pain to yank the PCI cards out, listen to the Scarlett until I hear drop-outs, and then put the PCI card(s) back in.  Would disabling a PCI card or two via Device Manager be worth testing, or is it not as effective as physically removing the PCI cards?
 
I don't see any video card audio drivers enabled in the Device Manager.
 
I can't disconnect from the Internet because I work from home, and am always online.
 
I didn't notice anything hogging the CPU, besides the normal games, programming apps, etc.  Note that I am not trying to use Sonar; I'm simply trying to play music in the background (using foobar2000) like I've done for years with PCI cards.  It's very common for me to be playing a demanding game, ripping a CD, and listening to music all at the same time, with no problems.  I've never had dropouts listening to music until today, with the Scarlett.
 
Are USB audio interfaces more easily interrupted than PCI cards?  Are they not as capable of handling multitasking?

I've had a Scarlett 2i4 for about a year now, and apart from it occasionally getting 'missed' by the PC's fast start-up (unplug and replug sorts that), it's been rock solid with W10. Really like the unit.

Well you are doing lots of stuff I avoid with my DAW. I think that the Scarlett is a device made for working with Audio inside professional software and was never intended to be used for PC chores. 
I don't have any issues with my set up but as I said, I have no other audio device available so Windows seems happy to use my Scarlett. 
The audio buffer setting are the key here and those in my case are set in Mix Control. 
Most people in your situation, only one computer, will use their PC audio via the on board sound card and run just their DAW through the audio interface and monitors. Of course this requires a second set of speakers for the on board audio. You could share speakers via a small mixer or dedicated device. 
 
Disabling the PCI cards in device manager may work fine for testing what's up. 
In my case it was a Sound Blaster which required total removal. 
I have an old PCI card made by Card Deluxe which co-existed with my USB interfaces just fine. It still working happily away in my old backup DAW. To bad PCI has become obsolete. Seems those interfaces were all rock solid ( other than Creative)  
 
Another issue found with the 2i4 is it runs on USB power. I have read lots of posts where this was the issue. So make sure to try your best USB ports. Not much juice from USB , in my opinion it's a very bad design. The should have allowed for the option of wall power like the Tascam us2x2, same price point. 

Tripecac
Normally I use WDM with my Delta 44 PCI card.  It's not a big deal to switch over to ASIO, but I'm wondering if there are ASIO-specific troubleshooting steps I should be taking (to deal with the dropouts).
 
And finally, are there ways of improving the performance and stability of the Scarlett (or any USB audio interface) by somehow increasing the power to it? 

You definitely want ASIO.  It's rare that a modern card works better under WDM  (Not surprised the Delta card does, but that's ancient).
 
Make sure the interface is plugged into a USB2 port (not USB3).  Also, USB ports can share resources with other devices, meaning you can have different bandwidth amounts available on each USB port -- in short, they're not created equal, so try different ports.  (This also addresses the USB2 power issue mentioned by Cactus above).

I have found that if I am just listening to music and playing games, the drop-outs are about once every 20 minutes.
 
When I am uploading files to my web site, however, I get drop-outs every minute or so.
 
Does this help isolate the possible cause of the drop-outs?

Research seems to indicate that connecting the Scarlett to a dedicated USB PCI card might help stabilize it.  If I buy a USB PCI card (or find one in my closet), then do any of the following choices matter in terms of the minimizing the likelihood of dropouts when using the Scarlett with Sonar?
 
a) PCI vs PCI-E
b) USB 2.0 vs USB 3.0
c) Price - I see some of them on eBay for less than $10

Also, I noticed that my Device Manager already shows 19 items under "Universal Serial Bus Controllers:

- 8 are "USB Root Hub"
- 6 are "Intel(R) ICH10 Family USB Universal Host Controler - [hexidecimal]"
- 2 are "Intel(R) ICH10 Family USB EnhancedHost Controler - [hexidecimal]"
- 1 is "Generic USB Hub"
- 1 is "NEC Electronics USB 3.0 Host Controller"
- 1 is "NEC Electronics USB 3.0 Root Hub"

If I add yet another USB controller/hub (in the form of a USB PCI card), should I disable some of the other USB hubs and controllers?  Or will there presence have no influence on the performance of a device attached to a USB PCI card?

Just to chime in.. I use my Scarlett for both DAW use and windows general use. I'm under the impression that ASIO is used only within the DAW and other drivers are used for regular windows sounds

FWIW, I've always used a PCI/PCIe add-on card (Firewire and USB 2) for my audio interfaces, and I believe it's the reason I've never had any of the problems others complain about.
 
So do I think it's a good idea?  Yes... but only if you've tried all of the other USB2 ports and gotten the same results.
 
The intermittent dropout timing does suggest some task polling in the background... But didn't you say you ran Latency Monitor and found nothing?
 
You should also check if you have any unnecessary utilities in Startup (Task Manager-Startup tab).