I've recently had similar issues Lusche.
I used a Logitek usb headset for years, but decided upgrading to a razer, which has an analog
microphone. My in game voice went to crap...all other applications, I came through loud and clear.
Part of the problem with the razer mic, apart from being analog, is that it does not reach around to
the front of my mouth, it's only 2 inches long and so sits mid-cheek. I found that if I took
the headset off and spoke directly into the mic (in AH) that my transmissions were clear
or I had to almost yell to get my voice through in AH.
So I purchased a plantronics headset online (it has analog jacks with a mini usb adapter for the jacks)
and while the sound in the ears didn't compare with the razer, the microphone, routed through a usb port
was crystal clear and loud.
Ultimately, I took the usb adapter from the plantronics and used it to convert the microphone jack on the razer and
plugged the rest of the razer jacks into their normal analog slots (audiology 7.1)...and it works perfect.
That's a long winded way of saying, try and get your hands on a analog to usb adapter for the mic only...
worked for me.