Low FPS when mic is inactive

I got a nVIDIA GeForce 9500 GT video card several months back, and when it worked fine for all of my games exept for garrysmod. Now when I join a Dedicated server in gmod, I have low framerate (10-20, should be 60-100)and very crackly and poor sound unless I’m holding my microphone button down. I did not have this issue when I was using my computer’s old and shitty integrated graphics. Now, I bought a much better chip (nVIDIA GeForce 250) and it works flawlessly, except I have the same problem in Gmod. It’s not the microphone, as I’ve unplugged it and used a different mic, and I’ve updated to the latest sound and video drivers. Also, when I’m playing sound through the mic from a file (Like with HLSS/HLDJ) the FPS and sound are just fine and dandy. Obviously I don’t want to have to lean on my mic button to play, and I can’t do much with the low FPS doing otherwise gets me. What I think is that this has alot to do with the card drivers, some other software, and Garrysmod, and the way sound is output through the microphone in gmod as this is the only game this happens in. I’m running windows 7 64 bit by the way.

Has anyone encountered this problem? Know of any causes? Fixes?

lol i have exactly same characteristics of the pc and i can say you fail. my fps is like 260 and it works like charm. open taskman.exe (Task Manager) and find hl2.exe in processes category (whilst running gmod). press right click on it and select the third function from downside of the context menu. put ticks in all boxes. lulz press ok

All boxes are already set.