At first launching OBS makes your microphone volume disappear completely.
At first launching OBS makes your microphone volume disappear completely.
I then need to increase the mic level by around four to five times, which causes a lot of background noise and hissing. The modmic was there for a reason—to reduce those unwanted sounds! When I'm not streaming or using Skype or a sound recorder, it works fine without the boost. Why did I share this in the periphery?
Are you adjusting the volume through OBS or via Windows settings? If your microphone works fine elsewhere but not in OBS, it might be better to rely on OBS's built-in enhancement. Also, consider if your game or desktop audio is affecting the microphone output—you may need to lower the game audio to 50% or less in OBS so the mic is audible.
Occasionally a program using your microphone in Windows 7 makes the system assume you're in a communication app such as Skype and reduces the volume of other apps. You can verify this by right-clicking the volume mixer in the taskbar and selecting "Playback Devices." Once in that window, go to the "Communications" tab and switch it off. Try it and observe the effect.