Switching sound devices causes distortion/repeated sound

Hey guys,

I'm having a weird issue with switching between my onboard audio and my Sound Blaster Z. Whenever I set the latter to be the default device, I get what sounds like a sound repeated over and over, echoing endlessly. The reason I switch between the two is to use my headset when I'm playing a game that requires voice.

My setup is as follows -

MSI Z97 Gaming 5 - onboard audio connected to Logitech X-540 5.1 speakers

Sound Blaster Z - PCI-EX card connected to Roccat Kave 5.1 headset

I can set the Sound Blaster to be the default communications device and use the microphone with no problem - also setting the playback device to be this card in Teamspeak lets me hear sound through the headset as well.

I have no problems with switching to the onboard audio, it's just with the headset. Any help would be greatly appreciated - I have a tournament on Saturday and I'd really like to be able to get this sorted in time.

Specs -

i5 4690K
16GB DDR3
Radeon R9 390X
Windows 10 Pro x64

Yep, that was it. It's always something small! Thanks Ken :)